Currently, up to 215 million metric tons of harvestable straw are available in Europe, 50% of the crops come from wheat, 25% from barley and 25% from maize. More than half of the production remains undeveloped. The overproduction of straw in the world means that the current methods of its management are insufficient. The article describes the production method and characterization of natural rubber biocomposites containing cereal straw powder modified with functional nano-additives in the form of carbon black, silica and halloysite nanotubes. The use of cereal straw in the elastomer matrix should contribute to obtaining a product with good mechanical properties while ensuring a low cost of the composite. In turn, the application of the mechanical modification process will allow the combination of specific properties of raw materials to obtain new, advanced elastomeric materials. As part of the work, hybrid fillers based on mechanically modified cereal straw were produced. The impact of hybrid fillers on mechanical, rheometric and damping properties was assessed. The flammability and susceptibility of the obtained biocomposites to aging processes were determined. The use of hybrid fillers based on mechanically modified straw allowed us to obtain a higher cross-linking density of vulcanizates (even up to 40% compared to the reference sample), and thus higher values of the rheometric moment during the vulcanization process of rubber mixtures (from approx. 10% (10 phr of filler) up to 50% (30 phr of filler) in relation to the unfilled system) and higher hardness of vulcanizates (by about 30–70%). The curing time of the blends was slightly longer, but the obtained composites were characterized by significantly higher tensile strength. The use of fillers in the elastomer matrix increased the modulus at 100, 200 and 300% and the elongation at break. Moreover, greater resistance of vulcanizates to the combustion process was confirmed. In recent years, discussions on natural resource prevention and recycling have led to a special interest in biomaterials. Due to growing environmental awareness, limited petrochemical resources, government regulations and changes in company policy, the use of traditional composites based on epoxy resins, unsaturated polyesters, glass , carbon A primary factor in the correct approach to biocomposite production is knowledge of the structure and properties and functions of the matrix material, as well as how it connects and interacts with other additives in biocomposite formation . The shaThe second and most important factor determining the properties of biocomposites is the selection of appropriate natural fibers as a reinforcement of biocomposites. Their low density and cost, stiffness and relatively high strength make natural fibers materials that strengthen the structure of natural fiber polymer composites (NFPCs). The properties of natural fibers may differ significantly from conventional carbon, glass or aramid fibers . Their cStraw consists of the leaves and stems of mature, dried crops: rape, poppy, flax, cereals and legumes . The dryAlthough the chemical composition of natural fibers is very diverse, almost all of them are hydrophilic . The conHybridization is a modification method that combines individual, seemingly different properties of additives. This is a particularly fascinating technique used in fillers for polymer composites. It consists in creating new materials from substrates that appear physically and chemically different. As a result, this creates a synergistic effect, a combination of properties affecting the entire material at the same time.Recent years have seen rapid development in the manufacture of a new group of polymeric materials, namely polymer nanocomposites ,40,41. R2(OH)4Si2O5·nH2O [Halloysite nanotubes were first described by Berthier in 1826 as a dioctahedral 1:1 clay mineral of the kaolin group. The multilayer tubular structure of halloysite results from the wrapping of the 1:1 clay mineral layers under favorable geological conditions, driven by a mismatch in the oxygen-sharing tetrahedral and octahedral sheets in the 1:1 layer. Halloysite has a structural formula of Al2O5·nH2O . The lenNanoscale carbon black is one of the widely used nanofillers because of its abundant source, low density, permanent conductivity and low cost . The pri2. The silica molecule is in the form of a tetrahedron with a silicon atom in the center, surrounded by four oxygen atoms in the corners of this geometrical structure [2/g and a porous structure [Nanosilica is silicon dioxide SiOtructure . Chemicatructure , which ptructure . Silanoltructure . The surtructure .The work aimed to produce natural rubber biocomposites containing grain straw powder modified with nanotubes. Composites containing various types of plant fillers are already produced on an industrial scale and continuous research results in the continuous expansion of the area of their application. The use of cereal straw in the elastomer matrix should contribute to obtaining a product with good mechanical properties while ensuring a low cost of the composite, as this raw material is characterized by easy availability and a low unit price. Straw is considered a common and cheap raw material, the purchase price is on average EUR 25 per ton, but many farmers are willing to give this valuable material for free due to the large overproduction and the lack of generally available management methods. Additionally, to eliminate the negative properties of cereal straw as a bio-additive of natural rubber, modifiers were used: carbon black, silica and halloysite. The mechanical modification should allow for the production of advanced materials that will combine the specific properties of the components used.® VN 3  with a specific surface area of 180 m2/g;Industrially precipitated silica ULTRASIL2/g;The carbon black, HAF N-339  with a specific surface area of 91 m2/g, the material was supplied by Sigma-Aldrich .The halloysite was applied in the form of nanotubes with a specific surface of 64 mThree different types of straw-based fillers were used in the study. The materials were prepared by hybridizing wheat straw  with nano-additives. Silica, halloysite and carbon black were proposed as functional agents:Natural rubber (NR)  in the form of ribbed smoked sheets (RSS 1) was used as the elastomer matrix. The elastomeric composites were cross-linked with the use of a sulfur system containing : 2 partsThe reference sample was a filler-free natural rubber composition with a cross-linking system. The remaining blends additionally contained hybrid fillers in amounts of 10, 20 and 30 phr. Hybrid fillers were mixtures of cereal straw with functional nano-additives, i.e., carbon black, silica or halloysite, in which the weight ratios were, respectively, straw:nano-additive 2:1 and 5:1.Previously, the straw was ground with a Pulverisette 5 Classic Line planetary ball mill   and dried at 70 °C until a constant mass was obtained (approx. 2 days). To obtain two-component fillers, straw with each individual nano-additive was hybridized. Mechanical modification of the biofiller was carried out with the use of a Pulverisette 5 planetary mill . Hybridization was performed for 15 min at 300 rpm. Each of the straw:nano-additive systems were prepared in two weight ratios: 5:1 and 2:1 . The comThermal analysis of hybrid fillers was carried out in a range of temperature of 25–700 °C. Up to 600 °C, measurements were made in argon atmosphere (55 mL/min), while from 600 °C to 700 °C, the pyrolysis residue was burnt in air (55 mL/min). The heating rate of both steps was 20 °C/min. Measurements were recorded using a TGA analyzer .The oil absorption parameter (DBPA) was determined using a Brabender Absorptometer C . The test was based on the measurement of the torque while mixing the filler (20 g) with simultaneous dosing of n-dibutyl phthalate (DBP). Titrant was dosed at a constant rate of 4 mL/min. The result (DBPA) is the amount of absorbed titrant (per 100 g of filler) corresponding to the maximum torque. The test was performed according to the ASTM D2414 standard.Measurement of the contact angle of the straw materials with water was carried out on pressed filler discs. An OCA 15EC goniometer  was used to place a drop of distilled water (10 µL) on the smooth surface of the pressed fillers. Then, just after the water drop was deposited, a picture was taken. Based on the drop shape analysis using the software, the value of the contact angle was determined.Samples of hybrid fillers were analyzed using an LEO 1530 Gemini scanning electron microscope .The process of making rubber mixtures was in two stages. In the first one, NR was plasticized (4 min) and mixed with the filler (4 min). Mixing was carried out using a laboratory blender  at 50 °C with a rotational speed of 40 rpm. In the second stage, the system of vulcanizing components was mixed in using laboratory rolling mills.90) and rheometric parameters of elastomeric composites, vulcanization curves were recorded using an Alpha Technologies rheometer .In order to determine the optimal cross-linking time , V0—the molar volume of solvent (toluene: 106.7 cm3/mol). µ—the Huggins parameter of the polymer–solvent interaction—was calculated from Equation (2) [tion (2) :(2)μ=μ00—the parameter determinant of non-crosslinked polymer/solvent relations, β—the parameter determinant of cross-linked polymer/solvent relations , Vr—the volume fraction of elastomer in the swollen gel (Equation (3)) [µion (3)) .(3)Vr=1r—natural rubber density (0.99 g/cm3), ρs—solvent density (toluene: 0.86 g/cm3), Qw—the weight of equilibrium swelling:ρsw—the weight of the swollen sample; ms—the weight of the dry sample; 100—the elastomer content in the sample; x—the filler content in the sample.m100,200,300), tensile strength (TS) and elongation at break (Eb), were determined using a universal tensile strength tester . The testing machine was equipped with an extensometer measuring elongation during deformation. Dumbbell-shaped samples with a width (on the measuring section) of 4 mm and a thickness of 1 mm were used for the tensile strength test. The crosshead speed was 500 mm/min. The measurement was performed in accordance with ISO 37 [Mechanical properties of vulcanizates, including stress at 100, 200 and 300% elongation  was applied for determining the hardness of rubber vulcanizates to ISO 48  HardnessThe Payne effect (ΔG’) was determined on the basis of the decrease in the storage modulus during dynamic mechanical analysis. A rotational rheometer ARES-G2  was used to carry out measurements. The dynamic rheological measurements were at a frequency of 10 rad/s by varying strain amplitude from 0.1 to 100%. The ΔG’ value was determined from Equation (5).min(lim 10−1)—a composite storage modulus determined under a deformation of 0.1%;G’max(∞)—a composite storage modulus determined under the max deformation.G’2 incident heat flux.The flammability of natural rubber composites was tested using a cone calorimeter . Vulcanizate samples with dimensions of 100 mm × 100 mm × 2 mm were tested in a horizontal position using a 35 kW/m−1.The analyzer Jupiter STA 449F3  was used to determine the thermal properties of elastomer composites. The measurement was carried out in air atmosphere, in a temperature range of 25–700 °C at a heating rate of 10 °C minThe study of the absorption of n-dibutyl phthalate by hybrid fillers consisting of mixtures of straw with carbon black, silica and halloysite was carried out. The measurements aimed to determine the DBPA parameter, which characterizes the porosity of fillers and the ability of the fillers to form the so-called “own structure”. The highest recorded value of n-dibutyl phthalate absorption was observed for the mixture of straw and carbon black in a weight ratio of 5:1, which may indicate the highest porosity and a greater dimension of voids between the formed aggregates of particles. The 2:1 straw to carbon black filler mixture was 19% lower. The more complex the structure, the greater the tensile strength, lower the elongation at break and the better the tear resistance of vulcanizates. On the other hand, the increased agglomeration of fillers in the elastomer matrix, resulting from the weak interaction between the rubber and the filler, causes the deterioration of properties.In the case of hybrid straw fillers with silica, no significant change in the absorption of n-dibutyl phthalate was shown depending on the weight ratio used. The DBPA value was on average 10% lower than the highest recorded during the test (sample Straw:Carbon black_5:1).The lowest amounts of absorbed dibutyl phthalate were recorded for mixtures of straw with halloysite nanotubes. The DBPA value was the lowest for the sample with the lower content of halloysite nanotubes, amounting to 85.7 mL/100 g .In this case, the influence of the architecture of filler particles on the tested properties of biocomposites should be taken into account, as carbon black and silica particles have a spherical shape, and halloysite has a tubular structure. Moreover, the specific surface area and aspect ratio also affect the varying degree of “packing” of the particles.Measuring the wettability of powders is a difficult task due to liquid absorption during the experiment. Nevertheless, the method of measuring the contact angle (CA) on a compressed powder is widely used and acceptable . ContactThe morphology of the obtained straw fillers was assessed based on the SEM images presented in Generally, in the case of hybrid fillers containing halloysite c, nanome3+ ion and the formation of a “metalloysite” took place [ok place . In the 5 temperature value when entrained from pure straw, for which the value was 146 °C. Straw:nano-additive 5:1 materials showed values of the initial decomposition temperature oscillating around 200–222 °C. On the other hand, for the samples of straw:nano-additive in a weight ratio of 2:1, the T5 parameters were higher by 84, 59 and 96 °C, respectively, for silica, carbon black and halloysite compared to pure straw. In the case of the temperature at which 50% weight loss was registered, the same relationship was observed as for the T5 parameter. The T50 value for pure straw was the lowest at 327 °C. For hybrid fillers (straw:nano-additive 5:1) the values were slightly higher and were between 338 and 349 °C. On the other hand, for straw:nano-additive 2:1 materials, higher temperatures of 50% weight loss (by about 100 °C) were observed compared to the pure straw sample. Summing up, the thermal stability of two-component fillers was significantly improved by the hybridization of straw with the addition of silica, carbon black and halloysite, which were thermally resistant and did not decompose in the discussed temperature range.700) for pure straw was 13%. This residue consists mainly of inorganic compounds present in straw, such as compounds of silicon, calcium, magnesium, etc.After the pyrolysis process from 600 °C to 700 °C, the sample was burnt in an oxygen atmosphere. The solid residue after combustion  and maximum (Mmax) torque and its increase ΔM during vulcanization are presented in 90) are presented in The influence of the type and content of the hybrid fillers used on the rheometric parameters of the obtained elastomer blends was investigated. On their basis, a comparison was made with the reference mixture, which is unfilled natural rubber. The results of the minimum . The results presented in The effect of the type and content of the hybrid fillers used on the efficiency of the cross-linking process was determined by the density of network nodes using the equilibrium swelling method , halloysite resulted in obtaining a high density of network nodes even at low filling (10 phr). For samples containing straw with added silica, the cross-linking density initially increased and then decreased sharply at 30 phr (Straw:Silica_5:1)  . This efIn the prepared samples of biocomposites, the Payne effect values were determined as a change in the value of the storage module under conditions of the increasing amplitude of shear strains. The results of the calculations are presented in Analyzing the results, it can be concluded that the use of filling at the level of 30 phr caused a significant agglomeration of all tested hybrids, hence high values of the Payne effect were observed. These observations correlated with the results of the tensile strength measurements, where the deterioration of the mechanical strength was also noted when the rubber mixtures were highly filled (30 phr), probably due to premature rupture of the sample as a result of stress concentration in the agglomerates. Silica vulcanizates showed the greatest tendency to agglomerate in the elastomer matrix, and the smallest samples were prepared with the use of halloysite. The obtained results confirmed the previously discussed results of the rheometric properties and determination of the concentration of nodes in the biocomposite network.Taking into account the results of tensile strength measurements and dynamic mechanical analysis, it can be concluded that the most favorable reinforcing effect resulting from the extensive secondary structure of fillers, in which the agglomerates are not large enough to propagate an unfavorable stress concentration and, consequently, deterioration of the composite strength, was obtained at 10–20 phr of filler in the composition .The main factor determining the mechanical properties of rubber composites is the mechanism of stress transfer by the filler particles dispersed in the elastomer matrix. Thus, surface functional groups that determine the strength of the interaction between the components, the shape of the particles and the amount of added filler and other properties, e.g., the ability to create its own structure, i.e., a three-dimensional lattice, are important.100, SE200 and SE300). The recorded results are presented in The influence of the type and content of hybrid fillers on the mechanical properties under static conditions was assessed based on the results of the measurements of the tensile strength (TS), relative elongation at break (Eb) and stress at 100, 200 and 300% elongation . The samples with the addition of carbon black in the case of both considered weight ratios of fillers and their content in the mixtures showed higher values compared to the compositions containing silica or halloysite. As a consequence, the straw:carbon black hybrid filler was characterized by the greatest reinforcing effect (in the case of low deformation), which correlated with the obtained results of the DPBA  analysis.The addition of fillers increased the relative modules SEAnalyzing the data presented in The use of hybrid fillers increased the relative elongation at break (Eb). The higher straw content in the compositions resulted in less flexibility of the samples (5:1 weight ratio). Regardless of the type of the analyzed hybrid filler, along with the increase in its content in the composition, the stiffness of vulcanizates increased, which in turn resulted in a reduction of Eb. Halloysite vulcanizates showed the greatest flexibility (Eb is even over 700%). This may be because, during stretching, the oblong particles of the halloysite oriented towards the acting force, which favored a greater elongation of the samples .The determination of the mechanical properties also included the measurement of the hardness of vulcanizates, and the results are presented in The thermal decomposition of cross-linked natural rubber took place in the temperature range ΔT = 310–465 °C, which was manifested in the exothermic peak recorded on the DSC  curve . This tr5 parameter decreased, but both the T50 and TRMAX values increased significantly, which indicated a positive effect of the straw:carbon black filler on the thermal stability of composites containing it  increase the amount of carbon layer formed. They act as insulators that hinder the diffusion of gaseous products of thermal decomposition into the flame, and at the same time constitute a barrier for oxygen diffusion into its interior . In the case of the straw:silica filler, its positive effect on the value of T50 and TRMAX parameters was observed (MAX), time to maximum heat release rate (tHRRMAX), effective heat of combustion (EHC) or maximum average heat release rate (MARHE)  , Table 7MAX parameter by 21.1%. The total heat release (THR) parameter was reduced by 46.3%, while the EHC and MARHE parameters by 50.2 and 27.4%, respectively (The straw:carbon black filler in the amount of 30 phr (Straw:Carbon black_2:1_30phr) reduced the HRR parameter value by 28.45% for the unfilled NR vulcanizate (unfilled NR), and the HRRectively .The limited flammability of the tested composites was due to several reasons. First of all, there are graphite layers on the carbon black surface. It is known that polymer chains are easily trapped by the edges of these structures. The increase in the immobilization of macromolecules on the surface of the carbon black filler reduces the amplitude of the thermal vibrations of the polymer and, consequently, inhibits its thermal decomposition. It should also be taken into account that there are paramagnetic centers on the surface of carbon black particles, which are stable radicals . This coThe data in The flammability of the natural filler, i.e., lignocellulosic fibers, depends on their chemical composition and degree of polymerization and crystallization, as well as the orientation of microfibers, i.e., fibrils. The literature review shows that even a small amount of lignin (10%) increases the resistance of natural fibers to fire ,74. DuriThe orientation of the fibrils primarily controls the amount of oxygen that diffuses into the fiber. The greater the orientation of the fiber, the lower its gas permeability. Given the above, it should be stated that natural fibers with a low degree of crystallinity and a high degree of polymerization and fibril orientation are an excellent filler of polymeric materials from the point of view of reducing their flammability. The sample containing the straw:carbon black filler in the amount of 30 phr (Straw:Carbon black_5:1_30phr) was characterized by the lowest flammability of all tested samples containing straw:carbon black filler, which was confirmed by the high fire suppression potential of the natural filler used .A significant degree of reduction in the flammability of the tested composites was also achieved with the use of the straw:halloysite nanotubes filler. The anti-pyrenic effect of halloysite, in addition to the abovementioned barrier effect, was associated with its endothermic dehydration and dehydroxylation processes occurring in the temperature range ΔT = 120–560 °C. The water released as a result of endothermic transformations of halloysite diluted the gaseous, combustible products of the composite destruction. Moreover, halloysite in the temperature range ΔT = 885–1000 °C transformed into mullite, a refractory material, significantly limiting the heat flow between the sample and the flame. The iron compounds contained in halloysite were also important. Despite the low concentration of iron oxides in the halloysite (in most cases it does not exceed 0.3% by mass), iron ions acted effectively as “scavenger” acceptors of free radicals that are formed in the processes of thermal degradation of the tested composites, thus increasing their thermal stability (parameter dm/dt) and fire resistance. Furthermore, the flammability of the tested composites was also reduced in the case of the straw:silica filler.It should be clearly emphasized that for all tested fillers, the reduction in the flammability of composites containing them was the result of the reduced intensity of free radical reactions taking place in the gas phase as well as the mass and energy exchange between the sample and the flame (channel effect). In the case of the tested composites, the construction of the boundary layer was of secondary importance. In the combustion process of the tested vulcanizates, filler islands formed more often than a homogeneous, uniform boundary layer.The flammability of a composite differs from the properties of its constituent materials. Factors such as the structure of the composite, adhesion between the fibers and the matrix, the type of polymer constituting the matrix and the type of fiber play key roles in determining the flammability of the biocomposite. There are a number of current articles and literature reviews that provide in-depth information on the state of research and solutions in the field of using mineral fillers for flame-retardant polymers, for example, on phosphorus-based flame retardants  and halomax and ΔM values during the vulcanization process of rubber mixtures and greater hardness of vulcanizates. The vulcanization time of the blends was slightly longer, but the obtained composites were characterized by a significantly higher tensile strength.The use of hybrid fillers based on mechanically modified straw allowed us to obtain a higher cross-linking density of vulcanizates, because, in addition to cross-links between the polymer chains, chemical and physical interactions with functional groups present on the fillers’ surface were created. The consequence of increasing the network node density was greater stiffness of the composition, and thus higher Mmin and ΔM during the vulcanization process, especially with higher filler content. Since the increase in torque is an indirect measure of the cross-linking density, the efficiency of the vulcanization process in silica biocomposites was probably lower and was related to the phenomenon of absorption of the components of the cross-linking unit. On the other hand, higher values of the minimum torque during cross-linking could be caused by the insufficient dispersion of fillers in the elastomer matrix. Vulcanizates containing halloysite were characterized by shorter vulcanization times and lower hardness. However, unlike the other tested cereal straw modifiers, they caused the greatest strengthening effect even at low contents (10 and 20 phr in the rubber mixture). Besides, the use of a straw-based filler with halloysite, due to good barrier properties, played an important role in limiting the speed of thermal decomposition of composites. The use of carbon black resulted in obtaining vulcanizates with the highest hardness (even 55°Sh) and good mechanical strength, which was the result of the high cross-linking density and probably the formation of its own structure in the elastomer matrix. Moreover, these vulcanizates were characterized by a satisfactory resistance to the burning process.By analyzing the effect of the type of additive on the tested properties, it was observed that the use of silica as a modifying agent for cereal straw with the other tested functional additives resulted in lower M90, an increase in the flexibility of vulcanizates and a reduction in the thermal stability of composites.It is difficult to determine the most effective content of hybrid fillers, however, the results of the experiments confirm the negative influence of agglomeration on the properties of natural rubber biocomposites. The experimental rubber mixtures were prepared based on hybrid fillers, in which different weight fractions of individual components were used, i.e., straw and functional nano-additive. The analysis of the results of the conducted research suggested that increasing the weight fractions of straw in hybrid fillers resulted in the extension of the vulcanization time tTo sum up, natural rubber biocomposites containing hybrid fillers based on cereal straw powder constitute an alternative method of managing its surplus. The manufactured products were characterized by good mechanical properties and, at the same time, their cost was low due to the availability and low unit price of straw. The mechanical modification allowed us to obtain materials with specific properties, which translated into the extension of the scope of their application.


The mechanical properties of wood, respectively the elastic, plastic, and strength properties, depend on a large number of factors, due both to its structural and physical characteristics, as well as to the size, direction, nature, and speed of application of forces. Wood, generally considered to be a viscous-elastic material, has creep deformations over time under the effect of a constant load. In this study the behavior of pine wood samples was investigated due to its large utilization in different finished products, such as roof construction, furniture, outdoor applications, garden furniture, and toys. The paper aims to analyze the viscoelastic behavior of pine wood subjected to cyclically loading to traction-compression with different loads , applied at different speeds . It was observed that, at low speeds (1 mm/min) and low intensities of the applied force, it was possible to distinguish the three creep regions specific to wood: the primary area (primary flow), the secondary area, and finally the tertiary creep. As the force increases, the law of variation of the wood flow changes. The degradation of longitudinal elasticity modulus occurs with the increase of the number of cycles, so after 20 alternating symmetrical cycles of traction-compression of the pine wood samples, there is a decrease of its values by 35%. Wood, due to its polymeric and layered structure, is considered a natural composite material. Thus, the late wood and early wood can be considered composite layers ,2. TheirTaking into account the structural changes produced by cyclic stresses as well as the modification of the tensile breaking section of wooden samples, Christoforo et al.  present However, the cyclic stresses of wooden structures lead to a constant reduction of wood strength by accumulating deformation energy and producing plastic deformations at the cell walls. Studies have shown that, to predict the behavior of wood over time, the design and construction of structural elements must take into account not only the values of allowable stresses, but also the ability to load wood under cyclic load, respectively the creep and relaxation function of wood ,10,11. GPinus sylvestris) as control samples and thermally modified subjected to cyclic bending, Sharapov et al. [Konstantinov et al.  analyzedv et al.  performev et al.  considerv et al.  and Andrv et al.  developev et al. ,17 invesv et al.  and natuPinus sylvestris). The novelty of the paper consists of better understanding of the mechanical behavior of softwood and determination of the hysteresis loops to tensile and compression. Also, the structural modifications of wood cells are presented by means of optical microscope.While numerous studies have presented failure analyses of wood subjected to axial stresses (or tensile or compression) or flexural stresses, little information is available about the structural and mechanical degradation of wood (softwood) subjected to symmetric axial cyclic tension, obtaining the Bauschinger effect. Wooden constructions, new or heritage, are subject to variable loading, such as precipitation (snow), wind, or dynamic loads from earthquakes, which requires a knowledge of the mechanical properties of wooden components, behavior over time, along with a description detailed defects or their degradation (resistance reduction factors). Pine wood, along with spruce wood, and fir wood, is very widely used in making construction/building elements that are subjected to loads in different directions and with different intensities and duration. So, the objective of the current study is to analyze the degradation of mechanical properties and structural failure produces by symmetric axial cyclic loading of Scots pine samples (Pinus sylvestris) with 12% moisture contents (provided by the norm EN 384: 2004) [The wood species analyzed in this research was Scots pine samples (4: 2004) . In the L = 150 mm, width b = 15 mm, thickness h = 5 mm ; at 10 cycles (sample P2) and at 20 cycles (sample P3). The next set of samples (B1) was subjected to symmetrical cyclic stresses with a speed of 1 mm/min with the force intensity of ±1500 N in the same manner as previous samples: at 1 cycle (sample P4); at 10 cycles (sample P5) and at 20 cycles (sample P6). The C1 group of samples was subjected to cyclic stress at a load intensity of ±2000 N, the loading speed of 1 mm/min, at 1 cycle (sample P7), at 10 cycles (sample P8), and at 20 cycles, (sample P9). The second category of pine specimens denoted with A10; B10; C10 was subjected at a speed of 10 mm/min, having similarly to the first category, three sets of samples tested at different intensities of the applied load. The input data of tested samples are presented in The samples were subjected to symmetric cyclic loading tensile-compression test using the universal testing machine type LS100 Lloyd’s Instrument belonging to the Mechanical Engineering Department of Transilvania University of Brasov, in order to study the degradation of mechanical properties of a Scots pine wood. The specimens were loading with a constant speed of 1 mm/min and then 10 mm/min, being subjected successive to 1 cycle, 10 cycles and 20 cycles. The tensile and compression displacements were measured simultaneously with applied loading b,c. For During the experimental investigations, numerous primary data were obtained that required processing so that the viscous-elastic behavior of pine wood can be characterized. Thus, in e (the strains from A to D points) represents the recovery strain after a complete cycle and total true plastic strain range Δεp (the strains from D to 0 points) is the permanent strain after a complete loading cycle. The tensile recovered elastic strain from point B to point 0 can be observed in The most important mechanical degradations occur in the first stress cycles as seen on the creep curve, specifically the first area . Thus, aThe stress values are independent of the number of stress cycles and the stress rate. These have the same values both in traction and compression. The difference between the categories of values is given by the intensity of the applied loading. Thus, for the force of ±1 kN, the average value of the maximum stress ranges between 13 and 14 MPa, for the force of ±1.5 kN, the average value of the maximum stress is between 19 and 20 MPa, and for the force of ±2 k, the average value of the maximum stress is between 26 and 27 MPa, as can be seen in The values obtained give us an image of the quality class of the Scots pine samples studied, namely that they are part of quality class C45 according to wood standard. As the study was performed on small samples, it can be improved by additional studies on larger length samples to correlate the obtained results with the inhomogeneity and anisotropy of the material. In The microscopic structure of pine wood before loading can be seen in However, due to the anisotropic characteristics of wood and the different strength of late wood and early wood layers, the fracturing mechanism does not occur in one direction . TherefoDegradation of mechanical properties of wood samples subjected to symmetrical cyclic stresses accompanied by microstructure degradation of wood. If the structural damage in tension does not affect the stiffness degradation or the strength of the wood when a reversed load is applied in compression (stiffness recovery) as was shown in In this study, axially symmetrical cyclic loads (traction-compression) samples of pine wood in the direction parallel to the grain were tested. The degradation of the mechanical properties begins by the degradation of the wood structure as a result of the different resistance of the early wood and late wood layers, as well as the different viscous elastic responses to the traction and compression of the wood. Thus, after 20 alternately symmetrical cycles, the longitudinal modulus of elasticity decreases by approximately 28%, and with the increase of the loading speed, for some cases, there was even destruction of the samples. Also, the way of breaking the wood that occurs at an angle of approximately 30 degrees is noticed, which implies the appearance of shear stresses during the axially symmetrical cyclic stress. This study reveals that, in the strength calculations and in the design norms, it is necessary to introduce some coefficients that take into account the speed of wood degradation at cyclical stresses.


The selective layer of these membranes is made of highly permeable hydrophobic poly(trimethyl-1-silylpropine) (PTMSP) and hydrophilic chitosan-ionic liquid (IL-CS) hybrid matrices, respectively, filled with hydrophilic zeolite 4A particles in the first case and HKUST-1 nanoparticles in the second, coated over compatible supports. The effect of water vapor in the feed or using a commercial hydrophobic PDMSXA-10 HF membrane has also been studied for comparison. Mixed gas separation experiments were performed at values of 0 and 50% relative humidity (RH) in the feed and varying CO2 concentration in N2 and CH4, respectively. The performance has been validated by a simple mathematical model considering the effect of temperature and relative humidity on membrane permeability.In this work, the performance of new robust mixed matrix composite hollow fiber (MMCHF) membranes with a different selective layer composition is evaluated in the absence and presence of water vapor in CO This agrees with the observations reported for thermally arranged HF membranes on the separation of simulated flue gas mixtures [In fact, the hydrophilic IL-CS/PSf CHF shows a slight increase of COlsewhere . Fam et lsewhere . In our affinity ,45. Thusaffinity , the IL affinity  with themixtures , and it mixtures .2 separation performance through our HKUST-1-IL.CS/PSf MMCHF membranes are plotted in 2 permeance through the HKUST-1/IL-CS MMCHF membrane in 2 permeance decreased slightly in wet CO2/N2 separation, compared to dry conditions, the values of these membranes were the highest obtained for all the membranes reported in this work.The experimental results of the CO2:N2 and CO2:CH4 mixture separation, and thereby attributed to the competitive sorption between CH4 and CO2.The selectivity of the membranes is increased from 10–20 for the polymer IL-CS/PSf CHF in 2 permeance and selectivity of Zeolite A/PTMSP MMMs in the presence of water vapor [2 permeance in wet conditions. The N2 and CH4 permeance were less influenced by water vapor presence than they were for the hydrophobic PTMSP/P84 CHF and PDMSXA-10 HF membranes, and so the CO2/N2 and CO2/CH4 selectivity increased around 34% and 46%, respectively, from dry to humid conditions.Hydrophilic zeolite fillers and hydrophilic glassy polymers usually have to be surface-modified to increase their compatibility. The combination of hydrophilic zeolite fillers and hydrophobic polymer matrices in the selective layer influenced the COer vapor , and is er vapor , by simu2 concentration in the feed. Especially, the constant value of CO2 permeance at high CO2 concentration reached in CO2/CH4 separation, may be correlated to the robustness of the 20 wt.% Zeolite A-PTMSP/P84 MMCHF membrane, attributed to the compatibility of the membrane materials components [In the feed. The combination of hydrophilic Zeolite A and PTMSP in the selective layer of the composite membrane provided a stable performance at 25 wt.% COmponents  without mponents .2 concentration in the feed. There, the deviations can be attributed to the plasticizing effect by CO2 and the competing and synergistic interaction between the penetrants and the polymer matrix that is the base component of the selective layer of a composite membrane, causing a decrease in slow gas permeance at increasing CO2 concentration [The agreement with the model used in this work is a function of the type of selective membrane material. For the commercial PDMSXA-10, it was acceptable, except at high COntration ,49.The calculated permeance of the MMCHF takes into account the consideration of the presence of water vapor in the feed, by introducing the Equation (4) obtained in a previous work , into thThe model prediction for this work CHF membranes is more accurate than in the case of the commercial PDMSXA-10 HF membrane, probably because it has been easier to consider the resistance in series of the different layers by Equation (3) and the effect of plasticization is not as significant as that of water vapor ,50,51, g2/N2 performance in dry conditions better, with an error below 20%  and (4) to account for the change of geometry and the effect of humidity in the feed. The parity plots in lines in , while ttuned up .2 [2 permeance through the IL-CS/PSf membrane increased in the presence of water vapor, with increasing CO2 concentration in the feed, which may be attributed to the increasing hydrophilic character of the selective layer [The influence of water vapor in the feed stream on the permeation flux depends on the hydrophobic or hydrophilic character of the selective layer of the membrane, as this facilitates the affinity towards CO2 . On the ve layer .2 solubility has been observed to alter the performance of other glassy polymer based MMMs [The influence of water on COsed MMMs . Thus thsed MMMs , as well2 permeance and selectivity on the separation of CO2/N2 and CO2/CH4 mixtures, using several hollow fiber membranes, was measured in the absence and presence of water vapor in the feed. On the one hand, the permeance through the PDMSXA-10 HF and the PTMSP CHF membranes decreased in wet conditions in response to the competitive sorption and transport through the hydrophobic membranes. On the other hand, the CO2 permeance through the IL-CS/PSf membrane increased in the presence of water vapor, with increasing CO2 concentration in the feed. This was also observed for the HKUST-1-IL-CS/PSf and the zeolite A-PTMSP/P84 MMCHF membranes, which accounts for the possibility to tune up the CO2 separation by altering the hydrophilicity of the selective layer material in composite membranes. The experimental results have been validated by a simple mathematical model, adding the effect of the hollow fiber geometry and the influence of water activity in the gas feed, with a global error generally lower than 20%.The experimental CO2 separation processes with non-ideal mixtures, to fill in the existing gap from laboratory to bench scale in the presence of impurities. Further characterization of the CO2 separation performance at higher pressures and in the presence of other impurities such as hydrocarbons in the absence and presence of water vapor conditions [This work provides scope for the evaluation of novel CHF membranes in COnditions , both ex


As a result, the diffusion overpotential of 9 cm2 MEA was worse than 1 cm2 MEA. The generated condensate was multiplied and moved to the downstream side, and thereafter it caused the flooding/plugging phenomena.In this study, we investigated the influence of the Catalyst-Layer (CL) structure on Polymer Electrolyte Fuel Cell (PEFC) performance using an inkjet coating printer, and we especially focused on the CL thickness and the electrode area. In order to evaluate the influence of CL thickness, we prepared four Membrane Electrode Assemblies (MEAs), which have one, four, five and six CLs, respectively, and evaluated it by an overpotential analysis. As a result, the overpotentials of an activation and a diffusion increased with the increase of thickness of CL. From Energy Dispersive X-ray spectroscopy (EDX) analysis, because platinum twines most ionomers and precipitates, the CL separates into a layer of platinum with a big grain aggregate ionomer and the mixing layer of platinum and ionomer during the catalyst ink drying process. Consequently, the activation overpotential increased because the three-phase interface was not able to be formed sufficiently. The gas diffusivity of the multilayer catalyst electrode was worse than that of a single layer MEA. The influence of the electrode area was examined by two MEAs with 1 and 9 cm Our society has faced various environmental issues represented by the global-warming phenomenon, and we need to reduce the emission of greenhouse gas to mitigate such issues. However, because the consumption of fossil fuels has accelerated due to rapid development of developing countries, advanced countries have the obligation to accelerate technology development for everyone to be able to obtain affordable power by clean energy. In this situation, hydrogen energy is focused on as an alternative energy, and the popularization of polymer electrolyte fuel cells (PEFCs) was begun. By 2019, 200,000 units, or more, of Ene-farm were sold as a domestic cogeneration system, and about 2926 fuel cell vehicles (FCVs) were sold in Japan [However, the coverage of PEFC is quite different from the road map of the Ministry of Economy, Trade and Industry. This principal factor is that the system cost is too high. For example, the payback time of Ene-farms is five years or more, and the price difference between an FCV and a hybrid vehicle is about 30,000 dollars . Therefo2 electrodes in the prior work, the influence of an electrode area on MEA performance using IJC method has not been examined yet. It is necessary to elucidate these effects to manufacture a CL with complex structure. Therefore, in this study, we aimed to elucidate the influence of the CL thickness and the influence of an electrode area on cell performance using the IJC method.As one of the methods, applying Ink Jet Coating method (IJC method) has been studied recently ,21,22. TWe used a Microjet Labojet-500, a piezo-electric type inkjet printer, and the nozzle head was for high-viscosity and high-surface tension . The droplet condition was adjusted by the nozzle head driving parameter as shown in The catalyst ink was a blend of 0.50 g of platinum catalyst , 7.0 g of purified water, 2.75 g of ethanol and 1.53 g of Nafion solution  using a screw vial, and stirred by a rotor for 12 h. Finally, as for the catalyst ink, distributed processing was applied for 180 s by the homogenizer at power of 20 W, and the defoaming processing was also applied for 3 min by the vacuum stirring mill.x-axis and y-axis by in-line arrangement as shown on 2 and 9 cm2 of electrode area. Here, the catalyst layer was one layer as shown in The catalyst ink was exhaled on a Micro Porous Layer (MPL) side of a Gas Diffusion Layer (GDL)  every 100 μm according to 2 MEA and 9 cm2 MEA is different, all MEAs were evaluated using a common single cell with 3 × 3 cm2 electrode area. The gas channel was a single serpentine channel which had 1.8 mmW × 1.2 mmD, and the width of a rib was 1 mm. Here, because 1 cm2 of MEA contacted with 3 gas channels and 4 ribs, its contact area between MEA and rib was only 0.4 cm2 though that of the 9 cm2 MEA was 2.88 cm2. Because 1 cm2 of MEA only had the membrane in the parts besides the 1 cm2 part of the midrange, the gas seal was applied by supplementing the thickness of GDL in the part which had this film with PTFE sheet.Although an effective electrode area of the 1 cmfuel/Uox = 70%/40% @0.4 A/cm2 defined as the 9 cm2 of the single cell.Cell performance was evaluated by I-V characteristics curve and Cole–Cole plot using a fuel cell impedance meter . Generally, the deterioration factors of cell voltage on PEFC are classified as overpotentials of resistance, an activation and a diffusion. In this study, we referred to the protocol conducted by Vielstich et al. as the overpotential analysis .(1)thV is the theoretical open circuit voltage in the PEFC (1.23 V), actV is an activation over potential, irV is a resistance overpotential, diffV is a diffusion over potential and cellV is a cell voltage, respectively.We assumed the relationship as Equation (1): (2)irV is derived using Equation (2) from the resistance R measured by the measurement of I-V performance: i A/cm2 is the current density, r Ωcm2 is an area resistance, I A is a current, eA cm2 is an electrode area, R Ω is a measured resistance and cA cm2 is a contact area, respectively.The resistance over potential (3)actV) was derived by the difference between the regression curve of the voltage of the Tafel plot and the theoretical voltage in the low current density region.I-V performance was converted to an IR-free curve, thereafter the I-V curve was rearranged to Tafel plot. Here, an activation overpotential ((4)diffV) was defined by the value in which the above-mentioned regression curve of voltage and IR-free are subtracted from the theoretical open circuit voltage.A diffusion overpotential  and the influence of electrode area on the cell performance.In the influence of the thickness of CL on the cell performance, we confirmed that the activation overpotential and the diffusion overpotential were increased with the increase of thickness of CL (number of CLs) from the overpotential analysis. From the EDX analysis and SEM image, we understood that platinum twines about 23 wt.% of ionomers and precipitated, and the platinum and the ionomer that were not able to be the precipitated became a big grain aggregate by cohesion and were scattered in the CL during the catalyst ink drying process. Moreover, the crack on the surface of CL grows noticeably as the thickness of CL increases. We understood that because the oxygen diffusion was disturbed with water generated by the cell reaction that was accumulated by these cracks, the diffusion overpotential rose, and consequently cell deterioration was caused. Therefore, the dispersion of ionomer should be improved when the CL is applied by IJC.In the influence of the electrode area on the cell performance, we confirmed that the activation and the resistance overpotentials are hardly influenced by the increase of electrode area. However, because the distance in which the generation steam is multiplied becomes longer with the increase of the electrode area, the diffusion overpotential deteriorates by the plugging phenomena. That is, the condensate is accumulated toward the gas outlet, and causes the plugging by which the condensate blockades the gas passage in the vicinity of the gas outlet. Consequently, the diffusion overpotential of the cell with a large electrode increases.From these study results, although the effectiveness of IJC was able to be confirmed, improvement of the homogeneous dispersion of ionomer and platinum in catalyst ink and the crack prevention at dryness are necessary.


The conditions of adhesive connections testing can significantly affect the recorded findings. The standards, under which the investigations are conducted, do not take into account numerous factors that can greatly influence the outcome of the tests. Moreover, the research parameters in the standards are not specified. It is not defined in what manner their change, or any failure to comply with the standards, will affect test results. This article presents the results of experimental research, completed with numerical simulations, designed to test to what extent the recorded impact strength of adhesive connections is affected by the stiffness of the test stand, and the speed and energy of the impactor. In the experimental research, the authors used block samples whose substrates were made of an aluminum alloy. The elements of the samples were bonded by means of three different epoxy adhesives. The models used in numerical calculations were built on the basis of the real dimensions of the specimens used in this experimental research. As a result of the performed tests and conducted calculations, it was found that the use of test stands of lesser stiffness resulted in an increased registered impact strength due to an increased energy value of elastic deformations. Examinations of impact strength of adhesive connections are becoming increasingly popular and necessary due to the constantly rising overall use of this type of connection in contemporary design, and due to the fact that glued structures may undergo an impact load. Dynamic, single, or multiple loads often occur during the operation of means of transport ,2,3,4 orOne of the most popular methods of impact strength testing of glued connections is the standard method ,12,13. TIn order to test the impact strength of the samples, the authors prepared batches of adhesively bonded block samples , whose aThe adhesive materials were Epidian 57 with Z1 hardener, as well as construction adhesives Loctite 3421 and 3430, selected due to their significant difference in the Young’s modulus . The thicknesses of the joints were the same and measured 0.1 mm.Prior to bonding, the metal parts were cleaned and their surface was given proper structure and roughness through abrasive blasting ,15,16, wAfter curing the joints, the authors performed a visual inspection of the quality of the obtained connections and removed excess glue and threads outside the bonded surfaces. Removing the threads soaked in glue was particularly relevant, since they may be caught up during an impact strength test by a torn upper element and consequently slow down the dropping tool, which would translate into a higher value of impact strength of the connection. The excess glue may result in raising the strength of the joint  , in which it is possible to use two pendulums of different maximum energy of 10 J or 25 J. The pendulum of 10 J has a smaller flexural stiffness (arm diameter of 12 mm), whereas the pendulum of 25 J has higher bending stiffness (arm diameter of 20 mm). Moreover, the testing device allows for the modification of the initial energy of the impactor through moving the angle of the pendulum, which is also associated with changing the speed of the impact. The maximum shifting of the pendulum loads the examined sample at a speed of 3.81 m/s. In order to check whether the eleven-piece batch of samples is sufficiently large to conduct impact strength tests, for all the examined adhesives the authors conducted testing of two eleven-piece batches in the same conditions and then compared their results . The invIn In order to evaluate the influence of the pendulum stiffness upon the impact strength of block connections, batches of identical specimens were loaded by a pendulum of 10 J and 25 J, at a speed of 3.81 m/s. The findings of the tests are presented in The registered lesser impact strength of samples loaded with the pendulum of 25 J may be explained by a smaller value of the deformation energy of the stiffer pendulum arm “25 J” (Φ = 20 mm) than of the “10 J” (Φ = 12 mm). This might indicate a considerable impact of the test stand stiffness upon the recorded findings. Additionally, investigations were conducted in which identical samples were loaded with the energy of 10 J using different pendulums (“10 J” and “J 25”). The pendulum “10 J” struck the sample at a speed of 3.81 m/s, whereas the pendulum “25 J” struck at a speed of 2.42 m/s. The findings of these tests are presented in The obtained results suggest that reducing the impact speed increases the recorded impact strength of adhesive connections. However, taking into consideration greater stiffness of the pendulum “25 J”, the result requires a more in-depth analysis.The calculations were conducted in the software ANSYS 16.2, using the Explicit Dynamics module. A numerical model of the tested samples was built .The impactor was modelled with two elements, in which the striking piece that directly struck the upper element of the sample had a stiffness equal to steel (E = 200 GPa); the stiffness of the other element was higher by one row in value (E = 2000 GPa) in order to ensure adequate stiffness of the impactor . The mat−4, and at the speed of 3.81 m/s and the time of 8 × 10−5. For these times, it was possible to estimate the force of the impactor striking the spacer during the time of the occurrence of the stresses in the joint, being close to the destructive ones, based on stresses σx The recorded energy of impact damage of adhesively bonded connections is a sum of the energy of the joint’s destruction and the elastic deformations of the test stand.(2)The use of research stands of lesser stiffness resulted in increasing the registered impact strength due to a higher energy value of elastic deformations.(3)Reducing the speed of impact loading in research investigations led to an extended time of the research stand, and thus an increase in the elastic strain energy. Therefore, it caused an increase in the recorded impact strength.(4)The comparative study of the impact strength of adhesive connections should be executed on test devices, whose stiffness and speed of load application has been explicitly specified.


The aim of the study was to evaluate the impact of the coronavirus pandemic on the willingness, anxiety and concerns of Italian people on undergoing dental appointments. An anonymous survey was posted online on social media on 11 May 2020 and was completed by 1003 respondents in one week. Multiple correspondence analysis and multiple logistic regression were used to evaluate the association between socio-demographic characteristics, dental care access, contagion fear of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), trust in dentists regarding sanitization procedures and perception of the impact of the risk of contagion on dental care. Subjects with a high level of education, attending public dental offices and that are used to go to dental offices for urgent care would not feel comfortable in undergoing a dental appointment and would prefer to postpone or cancel dental visits, waiting for a decrease in the number of the contagions. Moreover, the risk of canceling or postponing the appointment at the dentist was 1.59 times greater in those who claimed to be strongly influenced by SARS-CoV-2. Fear of coronavirus disease (COVID-19), new cases decrease and the not urgent nature of dental visits influenced more than the lowered income household on upcoming or resuming dental appointments. In the next months, despite the forecasted economic crisis caused by coronavirus pandemic, fear and anxiety generated by the spread of the virus will impact more than the lowered familiar income with regards to access to dental care.  Coronavirus disease COVID-19) is an infectious disease caused by a novel coronavirus: SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) [9 is an iAccording to the Italian Health Ministry, to date more than 248,000 cases were diagnosed with COVID-19 and more than 35,000 deaths due to such infection were recorded [The coronavirus pandemic has rapidly changed health conditions, social relationships, economic prospects and daily routine life around the world. Lucchese and Pianta  forecastEven though Italian dental offices have never stopped working, they limited their practice ensuring just urgent and emergency dental care treatments. Droplet production and blood and saliva exposure put dental practitioners at high risk of contagion during their routine procedures ,10,11. Ahttps://forms.gle/sAP8E5D3pWgs9pn46). Data collection took place in the time period between May 11th and May 18th, 2020. The questionnaire was submitted in the very early moments of Phase 2 in order to describe feelings and concerns of Italian people during Phase 1 of pandemic and to assess the impact these could have on scheduling or resuming dental visits during and after the period of quarantine imposed by the Sars-CoV-2 pandemic.A questionnaire was created using the free-access platform powered by Google . Facebook was chosen as a preferred social media for the purposes of the research because of its increasing relevance as a social network, as a communication tool for the users and also for the significant amount of time that users spend on the platform . A snowbThe questionnaire, in Italian, was composed of 43 questions, divided into three sections . The firA descriptive analysis was performed to evaluate the main characteristics of the participants in the study. Absolute and percentage frequencies were calculated to summarize the characteristics collected. Multiple correspondence analysis (MCA) was used to explore the association between socio- demographic characteristics, dental care access, the fear of SARS-CoV-2 contagion during Phase 1, the approach with dental care visit during Phase 2, the perception of the impact of the risk of contagion on dental care and trust in dentists regarding sanitization procedures, were considered altogether. MCA enables the identification of associations among variables when considered simultaneously. The modalities of the categorical variables are organized in a multiple contingency table, and a low-dimensional explanation for the interaction or the dependence between rows and columns of the table is provided. This analysis allows a geometrical representation of the results by locating each variable modality as a point on the Cartesian axes according to the frequency of the modalities: closer points indicate that the corresponding modalities are shared by the subjects, and modalities are considered associated. Results are interpreted according to the relative position of the points and consist of looking for groupings of variables modalities as those with the closer distance between points. The association between variables can be described by several identified dimensions and the number of the axes depends on the variability explained by each dimension.A multiple logistic regression was carried out to estimate the independent effect of the fear related to the pandemic and the behavior individuals would have during Phase 2 in approaching new or scheduled dental visits on the probability of the perceived impact of COVID-19 pandemic on modifying the behavior on the upcoming dentist appointments. The analysis was adjusted for socio-demographic characteristics of the individuals.All statistical analyses were performed with R statistical software  and the Overall, 1003 respondents completed the survey within the 7 days of the publication of the questionnaire. Out of the total of respondents, 60.7% was female and 39.3% was male. The largest share of respondents, 32.4%, belonged to the age group 25–34, followed by those aged between 45 and 54, who made up the 18.1% of the sample; furthermore, 17.6% was aged 18–24, 15.7% was between 35 and 44 years old, 12.2% was between 55 and 64 years old, 2.6% was between 65 and 74 years old and 1.4% was more than 75 years old. Most of the respondents came from Central Italy , with a total share 48.0%, 38.1% from South Italy , and 11.9% from North Italy . n = 27) indicated that they had never been to a dentist. Among those participants who were used to accessing dental care (n = 976), 93.2% of them declared they attend private dental offices. Only 6.8% of the sample declared to attend either public dental structures or low-cost dental offices or private dental offices affiliated to the national public health system. In total, 71.6% of the respondents declared to have attended the same dentist for at least three years, 16% for two or three years, and 12.4% for less or equal than one year.n = 94) of the respondents underwent dental treatment during the Italian lockdown period. Among those who underwent dental treatment, all considered, 82.8% reported a positive experience, 10.8% did not know how to judge the treatment and 4.2% reported a negative experience. The second part of the third section of the survey was dedicated to those who needed dental treatments during the period from 9th March 2020 to 4th May 2020, the so-called Phase 1, when access to dental visits was only allowed for emergency reasons. In total, 9.4% , while 17.6% reported a low level of trust . Among the participants of the present survey, a share of 44.1% was informed about all the procedures that were followed in order to sanitize the dental office, mostly through a phone call (33.5%), followed by a talk with the dentist (13.6%) and social media communication (9.1%). In total, 51.1% of the respondents declared they would call the dental office or the dentist directly in order to receive further information, while 37.3% of the participants would not ask for supplemental details.The group on the top right (G1) was characterized by subjects living in North Italy, whose income was reduced over 50% due to the pandemic. They feel comfortable going out of their home, are not afraid of a new spread of the virus and would postpone the dental visit for economic reasonsThe group placed on the top left of the graph (G2) identified subjects with a high level of education, attending public dental offices and that are used to go to dental offices for urgent care. During Phase 2 they would not feel comfortable in undergoing a dental appointment and would prefer to postpone or cancel dental visits, waiting for a decrease in the number of the contagions. Moreover, they did not receive all the information on dentist’s sanitization procedures, had a low level of trust with regard to these procedures and had the perception that the risk of contagion would have an impact on their upcoming dental visitsThe group on the bottom left (G3) referred to subjects living in South Italy, mostly females, with a reduction in income due to the pandemic of less than 50%. They fear SARS-CoV-2 contagion, do not feel comfortable getting out of their home and fear a new spread of the virus. They fear dental visits during Phase 2 and would postpone because of fear of getting infectedThe last group on the bottom right of the graph (G4) mostly included men with low or medium levels of education, living in regions of Central Italy, usually attending private dental offices for regular visits. They do not fear contagion and would not have any problem with and would feel comfortable in undergoing a dental appointment during Phase 2; moreover, they would postpone dental visits in case of non-urgent need for treatment. They had received information on all the procedures that were followed in order to sanitize the dental office, having a high sense of trust in the dentist and having the perception that SARS-CoV-2 would have no impact on their dental visits.Results of the MCA are shown in Several surveys have been proposed since the spread of SARS-CoV-2 pandemic in order to assess the impact of coronavirus on dental activities, highlighting the great psychological distress among dental staff ,18,19,20Natural pandemics, principally those with high rates of infection and mortality, are often responsible of the onset of fear and anxiety. Considering previous similar infectious diseases outbreaks, such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS), several studies have shown their role in the occurrence of psychological implication, apprehension and distress both in healthcare workers and in patients ,23,24.Italian healthcare is mostly provided by public providers with some private or private-public entities. General taxation finances healthcare system . The LEAAccording to Cotrin et al. , in BrazThe present study has two major limitations. On the one hand, the use of a non-probabilistic sampling technique may limit the representativeness of the sample. However, the snowball sampling has proven to be an efficient tool for data collection on social media, and in particular on Facebook. Baltar and Brunet, Scott and Vigar-Eliis and Kang et al. have demonstrated that snowball sampling adopted on Facebook manages to provide higher response rates than traditional snowball sampling, because of the strong personal links that exist on the social network between the researcher and the respondents ,36,37. MLimits notwithstanding, the present study allowed to assess the impact of the coronavirus pandemic on the willingness of people from different Italian Regions to undergo and to resume dental appointments. Moreover, it was possible to define patients’ profiles on the basis of their socio-demographic and behavioral characteristics.Natural pandemics such as Sars-CoV-2 one are responsible of the onset of anxiety and fear but also awareness among the population. Especially in patients from Southern Italy and in those with high educational level Sars-CoV-2, fear could be the main reason to postpone dental appointments. The latter may lead to an increase in the incidence of diseases that could occur in the next months, due to the lack in prevention. Despite the forecasted economic crisis caused by coronavirus pandemic, feelings of fear and anxiety generated by the spread of the virus will impact more than the lowered familiar income in the access in dental care. Further studies are needed in order to assess the real impact of the SARS-CoV-2 pandemic on oral health, dental care access and dental offices.


The test-retest was performed and indicated moderate to strong correlations. Convergent validity demonstrated a positive correlation between the Presence of Symptoms and the sadness (r=0.443) and anxiety (r=0.464) variables. Weak negative correlations were observed between the PDI – Br domains and functionality, spiritual well-being and quality of life.composed of three domains and 25 items, the PDI – Br instrument presented satisfactory psychometric properties for its use in our environment, through the evidence of validity and reliability. According to the Brazilian Institute of Geography and Statistics , in 2050 the population over 60 will be 2 billion people and 25% of them will be over 65. Neoplasms also represent a public health problem and Brazil is expected to have 625,000 new cases per year from 2020 to 2022.The progressive aging of the population shows that people are living longer, but with a high prevalence of chronic diseases, neoplasms or dementia-2; co over 65. Neopla to 2022..However, the increase in life expectancy has not been accompanied by a better quality of life in the phenomenon of aging and illness. Technological advances and the variety of therapies available lead to a constant search for the cure of diseases, leaving interventions that focus on the dignified end of life in a second place..Differentiating itself from curative medicine, the palliative care approach is a type of assistance that proposes multifaceted care, with the management of physical, social, emotional, and spiritual symptoms for patients facing advanced life-threatening diseases..In the context of palliative care, patients can experience situations that affect their perception or sense of dignity, which can be defined as a value, from which the person is perceived by the world and by himself/herself as a valuable and respectful human being who keeps its essence intact, even when facing the physical degradation caused by different circumstances.. Thus, the investigation of the sense or perception of dignity in the scope of palliative care has been gaining prominence in the health area.The literature shows that the sensation of loss of dignity has been associated with an absence of the will to live, indicating a strong connection with depression, lack of hope, and expression of an interest in anticipating death. Thus, .A Brazilian study investigated the concept of dignity of patients in palliative care and showed that both health professionals and caregivers can influence self-perception of dignity. Being a “correct” person, maintaining autonomy and being cared for with respect were the elements that positively influenced the perception of dignity; on the other hand, urban violence and the lack of public accessibility policies had negative influences.(-). For Chochinov, maintaining dignity allows patients in palliative care to continue performing their usual roles(-).Physician Harvey Max Chochinov from Canada is one of the main researchers in this area and proposed the Dignity Model, with the purpose of establishing the association between dignity and psychosocial factors in patients in an advanced stage of an incurable disease-10. Fal roles-10.(-).Based on the Theoretical Dignity Model, Chochinov proposed an instrument composed of 25 items distributed in five domains, called the Patient Dignity Inventory (PDI), in order to identify the problems associated with the loss of dignity-10.(-). So far, in Brazil there is still no single questionnaire that identifies the problems related to dignity for patients in palliative care, but there is a growing demand for this type of care.The Dignity Inventory proposed by Chochinov was translated, adapted and validated in Germany, Spain, Italy, Portugal and Greece-15. S.Investigating the concept of dignity in patients in palliative care can contribute to direct the focus of care, in addition to allowing for the evaluation of interventions with the potential to improve the sense of dignity of these patients.Thus, the aim of this study was to perform the psychometric validation of the Brazilian version of the Patient Dignity Inventory (PDI – Br) in patients with advanced diseases in palliative care.A methodological study to verify the psychometric properties of the Patient Dignity Inventory (PDI – Br) instrument, based on validity and reliability tests of the measurement instrument.Instituto do Câncer do Estado de São Paulo, ICESP, in Portuguese) and at the Clinical Hospital of the Medical School of the University of São Paulo .The study was set up in outpatient clinics in Palliative Care at the Cancer Institute of the State of São Paulo  - Brazil, Code 001. The psychometric validation process of the Patient Dignity Inventory was authorized by Canadian psychiatrist Harvey Max Chochinov, author of the original instrument.The data collection process was approved by the Ethics Committees of the Nursing School at the University of São Paulo and of co-participating institutions, under opinion No. 2,490,660. In addition, the study was carried out with the assistance of the Coordination for the Improvement of Higher Level Personnel  and preserved verbal communication were included in the study.The data collection process was carried out from April to June 2018. The active search for patients occurred between consultations with the palliative care team. The patients who accepted the approach signed the Free and Informed Consent Form and answered a questionnaire to identify the sociodemographic and clinical situation.. The Brazilian version of the Edmonton Symptom Assessment System (ESAS - Br) was used to assess the intensity of the symptoms: pain, fatigue, nausea, depression, anxiety, drowsiness, appetite, well-being, dyspnea and sleep. Each symptom was assessed from 0 to 10.Scales were also applied to assess symptoms and quality of life. The Brazilian version of the Hospital Anxiety and Depression Scale (HADS) was used to assess anxiety and depression. The HADS scale has 14 items divided into two subscales, with scores varying from 0 to 21; scores between 0 and 10 in each subscale indicate absence of symptoms or mild changes and scores between 11 and 21 indicate moderate to severe changes. The Br 0 to 10..Two items from the Brazilian version of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC-QLQ-C30) scale were used to assess overall self-perception of health and quality of life. The scores of these items vary from 1 to 7, with 1 being very poor health and quality of life and 7, excellent..The Brazilian version of the Functional Assessment of Chronic Illness Therapy-Spiritual Well-Being (FACIT-sp 12) scale was used to assess spiritual well-being by means of two subscales: “meaning/peace” and “faith”, in which the higher score, the higher the patients› spiritual well-being., in addition to the translated and adapted version of the Patient Dignity Inventory (PDI – Br).The Karnofsky Performance Scale (KPS) was used to assess the functional capacity of the patients, with a score of 100 to 0, with 100 being preserved functional capacity and 0 representing a patient in the process of death, in add(-). For the adequacy of the data in the factor analysis, the Kaiser-Meyer-Olkin (KMO) coefficient was used, for which the literature indicates that values above 0.80 are acceptable.Construct validity was performed by exploratory factor analysis, which verifies correlations between several variables, grouping them into a set of common latent dimensions, the factors, domains or dimensions-24. F.The exploratory factor analysis was performed with the Statistical Package for Social Science (SPSS) statistical software, version 20.0 for Windows, through the latent structure of the relations, by the main components. The factor extraction technique was the latent root, for which eigenvalues greater than 1 are significant. The method of oblique rotation (oblimin) of the correlation matrix was used to achieve theoretically significant factors or constructs.. Concurrent validity was analyzed using Pearson’s correlation coefficient, a numerical measure that verifies the relationship between two variables. It ranges from 0 to 1, either positive or negative and the closer to 1, the stronger the correlation.By means of concurrent validity, the accuracy of an instrument is verified, contrasting it with a gold standard or an external criterion. This type of verification is divided into two types: convergent (when there is a correlation with the criterion) and divergent (when there is no correlation with the criterion). Concurrelation.(-) and according to the literature recommendation, other scales were applied to the patients in association with the Patient Dignity Inventory (PDI), for the analysis of the correspondence of the phenomenon of dignity with external criteria.In Brazil, until now, there is no model of instrument that quantifies self-perception of dignity. Based on the PDI validation carried out in Germany, Italy, Canada, and Spain-14 an and the Hospital Anxiety and Depression Scale (HADS) were used. The established assumption was that the loss of dignity has a positive correlation with depression, anxiety, and physical symptoms.For the test of association between dignity and physical symptoms, the Edmonton Symptom Assessment System (ESAS-Br) and thee (HADS) were us, the FACIT-sp 12 scale and the two items on quality of life of the QLQ-C30 were used.The assumption was also made that the loss of dignity is negatively correlated with functional capacity, spirituality, and quality of life. In order to assess the association between loss of dignity and decreased functional capacity, the Karnofsky Performance Scale, the FA12 scale and theere used.. The analysis of the α value also contributes to the conformation of the items, to the resolution of sustaining their permanence or the removal.The internal consistency tools were used to assess reliability, using Cronbach’s α and test-retest. Internal consistency estimates the isonomy of the items, indicating whether the items on the scale measure the same characteristic and, when they do, they are inclined to demonstrate a good correlation with each other. The an removal.(-). In the study, the PDI – Br was used for patients in the consultation following the first approach.The conjecture of reliability by the test-retest is based on establishing the association of the scores achieved on the same instrument by the same people at two different times and the expectation is that the scores achieved show an association-24. Ith consultation; their mean age was 65 years old, with a mean schooling of 5.9 years, and most of them were retired (68.2%).In total, 135 patients were analyzed, followed-up at the ICESP (61.5%) and at the HC-FMUSP (38.5%) and were approached on average in the 4Neoplasms were predominant, accounting for 68.2% of the presentations, followed by diseases of the respiratory system (11.8%), cardiovascular diseases (6.7%), and neurological diseases (4.4%), as shown in The Kaiser-Meyer-Olkin (KMO) coefficient was 0.84, showing an adequate conformation of the sample to perform factor analysis. Only items 11, 16 and 17 had lower factor loads than those indicated in the literature.The results of the exploratory factor analysis were organized in a solution of 3 factors, or domains, for the PDI – Br. The eigenvalues found for the domains were 3.70 (A1), 3.33 (A2), and 3.19 (A3). The three factors together are responsible for explaining 40.9% of the total variance .To validate the composition of the PDI – Br in three factors/domains, correlations between the domains were performed, in pairs. The correlations between the A1 and A2 domains (r=0.433) and between A1 and A3 (0.430) were classified as moderate. The correlation between the A2 and A3 domains was weak (0.285).To obtain the reliability of the PDI – Br, a test-retest was performed with 32 patients approached at two different times, with a mean time span of 31.6 days (SD 11.3). In addition, in the analysis of internal consistency the correlations between items in the three domains detected in the exploratory factor analysis were identified for the reliability of the instrument, described in All the items in the A1 domain presented moderate to strong correlations, as well as the items in the A2 domain. The increase provided in α by the removal of item 18 from the A2 domain was 0.871 to 0.874. Removing item 17 from the A3 domain increased α from 0.759 to 0.762 .The correlation analysis of the retest for items 2, 5, 13, 14, 15, 16, 17, and 18 was strong and significant. Items 1, 3, 4, 6, 7, 8, 9, 10, 11, 19, 20, 23, 24, and 25 showed moderate and significant correlations with the answers of the first interview.Regarding the first interview, item 22 showed perfect linear correlation , while item 12 showed a weak correlation with the answers of the first interview, as shown in ; although items 11, 16 and 17 presented factorial loads below 0.30 , they remained in the instrument. Only the removal of item 17 would increase the value of Cronbach’s α by 0.003, an increase considered insignificant. The analysis of the internal consistency in association with the factorial loads is the basis for the composition of the PDI – Br in 25 items, gathered in 3 domains/factors/dimensions .The exploratory factor analysis of the PDI – Br showed that all the items were loaded in the data correlation matrix. For the decision to remove or keep the items in the final instrument, the factorial loads were evaluated together with observation of the internal consistency, using the value of Cronbach’s αIn the A1 domain, there are items related to physical and emotional symptoms, so it was named “Presence of Symptoms” (PS), as well as in the Canadian instrument. The A2 domain received the nomenclature of “Dependence” (D), since its conformation is identical to the Chochinov instrument. The A3 domain was named “Existential Suffering”, as it contemplates 3 of the items in the Canadian instrument domain, items 12, 13, and 14.Moderate, positive, and significant correlations were noticed between the PS domain and the symptoms of sadness and anxiety, measured by the ESAS and anxiety, as measured by the HADS, in the observation of convergent validity. Among the other symptoms measured by the ESAS and HADS scales and the PDI – Br, the correlations were weak or very weak .For the PDI – Br Dependence (D) and Spiritual Suffering (SS) domains, weak and very weak correlations were found with the scales that measure symptoms. The evaluation of the hypothesis of negative correlation between the PDI – Br domains and the KPS, FACIT-sp 12 and EORTC-QLQ-C30 instruments showed negative and weak associations, as detailed in . 135 patients were interviewed in this study, which guaranteed a mean of 5.4 observations for each item of the PDI – Br.For psychometric validation studies, the literature suggests samplings over 50 individuals, recommending at least 100 people; these recommendations are necessary to guarantee more solid conclusions, from the mean of 5 or more observations per item. 135 pa. The correlation matrix of the exploratory factor analysis resulted in a three-factor solution for the PDI – Br; in this analysis, items 11, 16, and 17 showed factor loads lower than the recommended ones. However, the 25 items of the instrument were organized only once in each of the three domains.Evidence from the literature also shows that values greater than 0.30 are admissible for factor loads. The co, a value which is higher than the one observed in this study (40.9%). In the Italian research the three factors were named as follows: existential suffering, psychological suffering, and physical suffering. In the present study, the three factors were named presence of symptoms, dependence and existential suffering.An Italian study that examined the factorial structure of the PDI applied exploratory factor analysis and also found three factors, with an explained variance of 64.4%, a valuuffering. In the. According to the recommendations in the literature, the following elements were considered for the definition of maintenance or removal of items from the PDI – Br: factorial loads greater than 0.30, correlation between the PDI – Br domains, reliability through internal consistency , and assessment of the domain’s α value after the removal of each item.The definition for the final organization of an instrument should not be based only on one criterion. Accord.For a population of 135 patients, a Cronbach’s α value of 0.90 is greater than the recommended one. This indicates that the items really measure the dignity construct, indicating that there is an interconnection between them.), Germany (n=112 and α=0.96), Spain (n=124 and α=0.89), Italy (n=266 and α=0.96) and Greece (n=120 and α=0.71 to 0.9).The values found for Cronbach’s α in this study are similar to those evidenced in other PDI validation studies, such as in Canada (n=149 and α=0.93), Germad α=0.89), Italy1 to 0.9).. The data corroborate for a three-factor solution with adequate internal consistency.The values of the Cronbach’s α coefficient for the domains were α=0.859 (A1), α=0.871 (A2) and α=0.759 (A3), considered above what is acceptable in the literature . The da. In the PDI – Br all the items were loaded into the data correlation matrix after exploratory factor analysis.In the Canadian instrument, validated in 2008, items 10, 19, 23, and 24 were not loaded in any domain after performing the exploratory factor analysis, but were kept in the instrument, because they were highly related to a loss of sense of dignity, according to the Chochinov’s Theory. In the.For the test-retest analysis, 32 patients were approached at two different times, with a mean interval of 31 days between consultations. In the validation surveys of the Patient Dignity Inventory (PDI), the retest was performed at different intervals, 24 hours in Canada, 48 hours in Spain, 1 week in Greece, and 2 weeks in Italy,-15.. This factor may explain the lower correlation of this study, given the 31-day interval.Evidence from the literature demonstrates that the reliability of the test-retest assessment can change due to approaches taken over very distant periods of time,24. TPalliative care patients have different stages of the disease and may progress in different proportions over the course of a month. Associated with this, there is a decrease in functionality and an increase in the number and intensity of symptoms, which may have interfered with different perceptions of dignity between the first and second approach of patients..A research study dealt with the theme of dignity under the scrutiny of autonomy and the sense of control in patients in the final stages of an advanced disease, through a systematic review. The studies compiled by the review showed that aspects such as loss of functionality were directly related to the reduction of dignity, as the loss of body control and the development of daily activities represented a great impact for these patients.In this study, positive, moderate, and significant correlations were evidenced for the symptoms of sadness and anxiety measured by ESAS and the PDI – Br, in addition to a positive correlation between the HADS scale and the PDI – Br.. In studies conducted in Germany  and Spain (-), the findings were also similar to those found in this research.The data found for the correlation of the PDI with the symptoms of anxiety and depression were similar to those evidenced by other studies. The psychometric validation of the Canadian inventory showed a significant correlation between these elements, being moderate with anxiety  and weak with depression . In stup<0.001)-13, t. An Italian study found weak to moderate positive correlations  between the PDI and symptoms of depression.A validation study developed in Greece also found moderate and strong positive correlations between some domains of the PDI and the symptoms of anxiety , and weak to moderate correlations with the symptoms of depression . An Itapression..Evidence from the literature corroborates to explain that the loss of dignity is directly related to worse levels of anxiety and depression. A recent systematic review study found that, by raising patients’ sense of dignity, the anxiety and depression levels also improved significantly.(-) regarding the pain variable, for which the correlation was positive, weak, and significant.For the symptoms evaluated by the ESAS scale, positive, weak and significant correlations were found between the symptoms of pain and tiredness, and very weak and few significant correlations between the PDI – Br and nausea, appetite, well-being, and shortness of breath. The findings are similar to those found in other validation studies conducted in Canada and Germany-12 re.The convergent validity tests also showed negative correlations between the inventory and the KPS, FACIT-sp 12 and EORTC-QLQ-C30 instruments, deferring the hypothesis established at first. The PDI – Br domains showed a significant although weak correlation with the functionality measured by the KPS. In the investigation carried out in Spain, the findings between the two instruments were the same..For the FACIT-sp 12 scale, the Meaning/Peace and Faith domains showed weak and significant negative correlations with the PDI – Br domains. Compared to other validation studies, in Canada the correlation found was negative, weak, and significant between the peace of mind domain of FACIT-sp 12  and the dignity inventory; in Spain, the correlation was moderate and negative , the same as observed in Italy ,-14..For the items on the EORT-QLQ-C30 scale, weak and significant correlations were found between the domains of the PDI – Br and the questions of general health and general health quality. In Germany, the same instrument to measure quality of life was used and the correlation found was significantly moderate and negative .. A previous study conducted in Canada in 2002 highlighted a directly proportional relationship between better quality of life rates and a greater sense of dignity.A research study carried out in 2015 in Spain showed that the sense of dignity was heightened by the application of the dignity therapy, which also brought significant beneficial effects on spiritual well-being (p<0.001) and on quality of life (p=0.011). A prev dignity.This research corroborates with studies carried out in other countries regarding the connection between the phenomenon of dignity and the questions of anxiety, depression, pain, functionality, spirituality and quality of life. In addition, the psychometric validation data in this study are also similar to other studies of the same nature for PDI – Br..Evidence shows that reduced samplings influence the value of Pearson’s correlation, forcing this coefficient to present a high magnitude to be significant, with values close to 1. Psychometric research studies of the PDI in larger samples should be encouraged, especially to perform the correlation hypothesis test, researching the strength of correlation between dignity and the variables measured by the other scales.The results obtained by construct validity through exploratory factor analysis, concurrent validity through convergent validity and reliability through the internal consistency and test-retest of the PDI – Br indicate satisfactory psychometric properties for its use as a measurement tool for problems related to loss of dignity.This study has strengths and limitations, which can be transposed in new investigations. The great aspect highlighted as a strong point is the provision of a valid and reliable instrument to estimate the dignity of patients, especially those in palliative care. On the other hand, its limitation was the fact that the sample includes patients with low schooling and low socioeconomic status, which represents a portion of the population, but the results may be different in other population stratum.The tests performed demonstrate evidence of validity and reliability of the PDI – Br instrument, composed of three domains and 25 items, confirming its psychometric properties for its use in our country. This instrument offers the health professionals the possibility to assess the perception of dignity of patients in palliative care, contributing to the study of this phenomenon in the national context.