Wood Polymer Composites Research Articles

Properties of core-half wrapped shell structure wood-polymer composites containing glass fiber-reinforced shells

Glass fiber (GF) is commonly applied as a filler in the preparation of polymer composites. Due to the presence of GF, composite mechanical performance, flame resistance, and thermal performance could be greatly improved. The influence of a GF-filled polymer shell layer was investigated relative to the morphology, mechanical, thermal, and fire flammability performance of the core-half wrapped shell structured wood high-density polyethylene (HDPE) composites prepared via co-extrusion. The use of the relatively less-stiff pure HDPE with high linear coefficients of thermal expansion (LCTEs) lowered the general thermal stability and modulus of the wood polymer composites (WPCs). Flexural and thermal expansion properties were improved for the GF-filled HDPE shells in comparison to the unmodified material, enabling a well-balanced performance of this novel core–shell material. Implementation of GF-modified HDPE or unmodified HDPE layers as a shell for WPC core remarkably improved the impact resistance of the co-extruded WPCs. In comparison with composites possessing unmodified HDPE shell, the flame resistance performance of the shell layer was slightly improved in case that the GF content was below 25 wt%. A slight decrease in composite general heat release and rate was discovered in case that the GF content was greater than 25 wt%.

A Review of Wood Polymer Composites Rheology and Its Implications for Processing.

Despite the fact that wood polymer composites are interesting materials for many different reasons, they are quite difficult to shape through standard polymer processing techniques, such as extrusion or injection molding. Rheological characterization can be very helpful for understanding the role played by the many variables that are involved in manufacturing and to achieve a good quality final product through an optimized mix of formulation and processing parameters. The main methods that have been used for the rheological characterization of these materials are capillary and parallel plate rheometry. Both are very useful: rotational rheometry is particularly convenient to investigate the compounding phase and obtain structural information on the material, while capillary viscometry is well suited to understand final manufacturing. The results available in the literature at the moment are indeed very interesting and are mostly aimed at investigating the influence of the material formulation, the additives in particular, on the structural, mechanical, and morphological properties of the composite: despite a good number of papers, though, it is difficult to draw general conclusions, as many issues are still debated. The purpose of this article was to overview the state of the art and to highlight the issues that deserve further investigation.

Insights into modification of lignocellulosic fillers with isophorone diisocyanate: structure, thermal stability and volatile organic compounds emission assessment

This study presents an analysis of the structure and properties of different types of lignocellulosic fillers modified by isophorone diisocyanate (IPDI) to provide insights into the possibility of their application to the manufacturing of wood polymer composites (WPCs). Moreover, it deals with the environmental aspects of modified fillers, by assessment of volatile organic compounds (VOCs) emitted during modification, as well as from final products. Three types of commercially available lignocellulosic fillers were modified with different content of IPDI (from 1 to 15 wt%) using the internal mixer. The main compounds detected in the air during modifications were terpenes and terpenoids. No IPDI was detected, which is very beneficial considering its toxicity. On the other hand, IPDI was emitted from modified fillers at a slightly elevated temperature of 40 °C, which was associated with a significant rise in its vapor pressure. Successful modification of fillers was confirmed by FTIR spectroscopy and thermogravimetric analysis. Performed modifications of lignocellulosic fillers with IPDI had a relatively small impact on their particle size and color properties. Such an effect can be considered beneficial for the mechanical performance and appearance of WPCs, which could be potentially manufactured using IPDI-modified lignocellulosic fillers.

A new approach to the design of street furniture in Krasnoyarsk

The article describes the trends in the field of small architectural forms and outdoor furniture in the public environment of Krasnoyarsk. The objects of study are outdoor furniture located in central and popular public places that shape the image of the urban environment. The article contains a study of street improvement in the city of Krasnoyarsk, which made it possible to assess the current state of furniture used in the city. The research methodology consists in conducting an Internet survey of respondents in the social network “VKontakte”. The survey showed the advantages and disadvantages of existing furniture objects according to ergonomic, artistic, aesthetic, environmental and economic criteria. The collected material made it possible to determine changes in the approach to the design of outdoor furniture for public urban spaces, made it clear the feasibility of an integrated solution for environmental objects. The article demonstrates the design concepts of products with progressive design and improved qualities. The authors-developers propose a modern approach to the organization of public spaces and the design of products, taking into account the anthropometric and physiological characteristics of the population. They explain the use of modern materials in terms of ergonomics and ecology, such as wood-polymer composites, plywood, modified wood. The recommendations of the expert in the person of the chief architect of the city, in the design and implementation of such objects, were taken into account. The results of the analysis have both theoretical and practical significance and will be used in the improvement of urban spaces within the framework of the “Comfortable Urban Environment” program in Krasnoyarsk.

Elements of bases of mechanics of wood-polymer composites

s. Disclosed is a solution of a particular case of a problem of polycomponent motion within a poly speed model, which is reduced to setting conditions of joint motion of components and determining intercomponent thermal-force interaction. The study of construction of the basis of mechanics of wood-polymer composites from phenomenological positions of mechanics of heterogeneous media is presented by construction of equations of laws of mass and momentum preservation for two component media and their closure by a viscous-elastic-plastic rheological model of the composite material for development of the basis of mechanics of wood-polymer composites from phenomenological positions of mechanics of heterogeneous media, Contributing to improvement of production of structured composite for FDM - printing technologies due to production of composites on the basis of thermopolymers with filling of them with ground wood. Raw materials can be wastes of logging and wood processing industries, the product is a composite with high filling of wood with a wide field of application in different sectors of national economy and industry. The equations are closed by a viscous-elastic-plastic rheological model of the composite material and by matching the equations of inseparability and the displacement strain vector.

Influence of aggressive media on mechanical properties of wood-polymer composites

Mechanical properties of two samples of decking boards were measured after exposure in rain and chlorinated water, in ice, and in a mixture of gasoline and water in different concentrations from 1 to 7%. Samples consisting of 60% wood flour, 30% polyvinyl chloride and 10% additives were used for measurements. Additives are flame retardants, stabilizers, modifiers and dyes. The mineral filler CaCO3 was used as modifiers. For sample №1, the CaCO3 content was 42% and the wood content was 18%. For sample №2, the CaCO3 content was 24% and the wood content was 36%. As a result of measurements after exposure for 150 days, it was found that the specific impact strength increases by 120%, the bending strength decreases by 60%, and the Shore D hardness decreases by a maximum of 10%. Consequently, decking boards can be confidently used for a long time, since a number of properties almost do not change, but even increase, and some decrease in strength remains within acceptable values.

Development of wood polymer composites with thermosetting resin from soybean oil cross-linked with rosin derivative

Wood polymer composites (WPCs) were prepared via compression molding technique using wood flour and methacrylic anhydride modified epoxidized soybean oil (MAESO) copolymerized with triallyl maleopimarate (TMPA). Various percentages of TMPA were incorporated into the composite system to compare the properties of the final WPCs. TMPA was synthesized from rosin acid and the chemical structure was characterized by 1H-nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. The interaction between wood flour, MAESO and TMPA were revealed by FTIR and scanning electron microscope (SEM) study. Results demonstrated that TMPA was effective in enhancing the mechanical and thermal properties of the composites. Flame retardancy, biodegradability, chemical resistance, and dimensional stability significantly improved after the incorporation of TMPA into the composites. Wood polymer composites loaded with 30 wt% of TMPA exhibited maximum improvement in properties compared to other systems.

A computational approach to design moisture-resistant wood polymer composites

This work computationally predicts the onset of moisture-induced damage for different wood polymer composite (WPC) formulations using an experimentally validated micromechanical model. For model validation, the flexural mechanical properties of a commercially available WPC were experimentally obtained after exposure to either moisture or combined moisture and freezing conditions. As expected, exposure caused a loss in mechanical properties, which was primarily attributed moisture-induced damage and not further exacerbated by freezing. Once validated, the model was used to predict that the WPC would incur damage when placed in a commonplace 40–45 % relative humidity environment. This work demonstrates that computational simulations can be used to design moisture-resistant WPC formulations given specific environmental conditions (i.e., relative humidity, temperature) of the intended target application.

Research of Wood-Polymer Compositions of DMTA Methods

The article presents the results of polymer-wood composites, as well as the excretion of tritium woods and leaves. The base of the composite was made of thermoplastic polypropylene. Three composites prepared by the volume of filling content (25, 50 and 70%) and the various fractions of the used slags were prepared for research. The test is prepared with the use of spray technology. One of the methods of thermal DMTA analysis is used for research. Accompanied studies of dynamic mechanical properties have been chosen to determine the effect of filling and the size of the traces on the properties of the cured composites. The obtained results were invited to determine the design of these materials, as well as the determination of the amount and the alternative level for materials applied to large-scale elements made of polymeric materials.

Preparation, characterization and performance evaluation of wood flour/HDPE foamed composites reinforced with graphene nanoplatelets

This research explores the effects of nanographene on the cell morphology, mechanical strength, and water uptake behavior in the extrusion foaming of wood polymer composites. Composite materials containing high-density polyethylene, wood flour, coupling agent, graphene nanoplatelets (GNPs), and azodicarbonamide as a foaming agent were melt compounded using a twin-screw extruder. Finally, the samples were foamed via a batch process using a compression molding machine. Thereafter, the morphological aspects of the specimens including cell size and cell density were characterized using a scanning electron microscope. Further, the density, flexural strength, tensile strength, water absorption, and thickness swelling of the specimens were evaluated. Results indicated that the cell size of the specimens was found to decrease with the incorporation of GNPs while the cell density increased, owing to the reinforcing effect of the GNPs in the composites. The cell nucleation efficiency of the samples using GNPs was significantly enhanced when compared to that without nanoparticles. The density of composite foams decreased with the addition of GNPs due to more bubble nucleation originating from nanoparticles. Mechanical properties of the specimens improved when using GNPs in comparison to those of foams without GNPs as a result of better interaction with the polymeric matrix. The highest flexural and tensile values were observed for the composite foams containing 1 phr GNPs. Furthermore, the water absorption and thickness swelling of the samples were remarkably reduced with the addition of GNPs. The specimen foams produced with 4 phr GNPs exhibited superior water resistance and dimensional stability.

Mechanical, flammable, and thermal performances of co-extruded wood polymer composites with core–shell structure containing barite-filled shells

Wood polymer composites (WPCs) with core–shell structure reinforced with barite (BA)-filled high-density polyethylene (HDPE) shell layer were successfully fabricated, and their thermal expansion and mechanical properties were thoroughly analyzed. The incorporation of BA improved the flexural properties and reduced the impact strength and linear coefficients of thermal expansion (LCTEs) of the resulting composites, in comparison with unmodified HDPE. The use of relatively rigid pure HDPE with high LCTE values reduced the overall thermal stability and modulus of the WPCs. Both flexural properties and thermal expansion were significantly enhanced for BA-filled HDPE shells compared to the unmodified material. Thus, the novel core–shell layer showed a well-balanced performance. The employment of BA HDPE or unmodified HDPE layers as the shell for the WPC core significantly enhanced the impact strength of the co-extruded WPCs. The tensile modulus for BA-filled composite was predicted by the PPA-based model.

Termite Resistance of a Fast-Growing Pine Wood Treated by In Situ Polymerization of Three Different Precursors

This study aims to compare the resistance against subterranean termites of wood–polymer composites produced by in situ polymerization. The biological tests were carried out by choice and no-choice feeding tests. Poly (furfuryl alcohol), poly(styrene) and poly (methyl methacrylate) were studied here. They were impregnated into a Brazilian fast-growing pine wood using a vacuum:pressure method and then cured under simple heating. These treatments were evaluated using chemical (by infrared spectroscopy) and morphological (by scanning electron microscopy) analyses. The termite attack was evaluated by mass loss determination and photography. In general, all the treatments were effective in protecting the fast-growing pine wood. Results obtained by no-choice tests indicated that the treatment solution with 75% of furfuryl alcohol was less effective than the others, which indicates that both choice and no-choice tests may be important in a comprehensive study on the termites resistance of solid woods.

Effect of gamma-ray and melt flow index of polypropylene on the properties of the lignocellulosic composite

Utilization of ionizing rays such as gamma-ray in polymers to correct their properties has attracted a great deal of attention from researchers. Accordingly, in this study, composites consisting of three different polypropylene melt flow indices as the composite matrix, maleic anhydride as the compatibilizer material, and poplar wood as the filler were exposed different doses of gamma-ray radiation in a variety of 0–75 kGy. The main purpose of this study is to investigatie the probable benefits of gamma-ray radiation for improving some of the physical and mechanical properties of composites and to investigate their morphological and thermal properties. The results indicated that the physical and mechanical properties could be improved significantly by increasing the melt flow index of the polypropylene. Also, radiation of gamma-ray improved the physical and mechanical properties of wood polymer composites while reducing the thermal stability. The uniformity of the micrographs obtained from the scanning electron microscopy (SEM) indicated the interaction between the polymer and wood fibers.

Development and characterization of WPCs produced with high amount of wood residue

In this work, high levels of wood residue were incorporated into high density polyethylene (HDPE). The composite processing was carried out in a twin screw extruder. Due to the large amount of solid charge, adaptation of the equipment was necessary. Wood polymer composites (WPCs) with 60, 65 and 70% wood residue were obtained. In order to use composites in applications such as profiles for application on floors, an analysis of the fatigue strength of the composites was performed, as well as the water absorption capacity. The effect of ultra violet (UV) radiation on the surface of the composites was also evaluated using simulation in a degradation chamber. There was a significant increase in the stiffness of the composites and a reduction in flexural strength. Due to the large amount of load, formation of agglomerates was observed, which reduced the impact resistance. In spite of the use of compatibilizers, it was observed a weak adhesion between the phases, which impaired in the number of cycles under fatigue. When subjected to UV-degradation, the materials exhibited a small reduction in tensile strength. In general, the results indicate that the developed WPCs, considering applications in floors, presented some suitable properties such as rigidity and flexural strength, however, the processing conditions must be adequate for greater interaction between the phases.

Influence of organically modified nanoclay and TiO2 nanopowder on the properties of Azadirachta indica wood flour-reinforced high-density polyethylene, low-density polyethylene, polypropylene, and polyvinyl chloride nanocomposite

The nanocomposites of high-density polyethylene, low-density polyethylene, polypropylene, and poly(vinyl chloride) reinforced with Azadirachta indica wood flour (WF) and different amounts of the organomodified nanoclay and titanium dioxide (TiO2) nanopowder were produced by melt-blending process followed by compression molding. Polyethylene- co-glycidyl methacrylate (PE- co-GMA) was used as a compatibilizer. TiO2 nanopowder was synthesized by sol–gel method and characterized using transmission electron microscopy (TEM). The average size of the synthesized nano-TiO2 was 17.5 nm, which was confirmed both by TEM and X-ray diffraction (XRD) study. The distribution of nanoparticles in the nanocomposites was also examined by the XRD study. The surface modification of the TiO2 nanoparticles by organic surfactant cetyl trimethyl ammonium bromide and their interaction with the wood and the polymer were studied by Fourier transform infrared spectroscopy. Incorporation of compatibilizer PE- co-GMA, nanoclay, and nano-TiO2 significantly influenced the mechanical and thermal properties of the WF-reinforced composites. Wood polymer composites (WPC) reinforced with nanoclay and nano-TiO2 showed improved tensile strength, tensile modulus, flexural strength, flexural modulus, and hardness. Maximum improvement in mechanical properties was shown by WPC loaded with 40 phr WF, 2 phr nanoclay, and 2 phr of nano-TiO2. On inclusion of organically modified nanoclay and nano-TiO2, the WPC samples showed lower water uptake and higher chemical resistance. The nanocomposites were further examined by TEM study and thermogravimetric analyzer.

Resistance of different wood-based materials against mould fungi: a comparison of methods

Wood-based materials are generally prone to colonization by mould fungi and other discoloring microorganisms, but their resistance to fungal discoloration varies. Different standardized test methods for determining the susceptibility to mould fungi have been used to evaluate various wood-based materials, but the obtained results suggest that mould resistance depends on the method applied. Therefore, this study aimed at a comparative evaluation of two commonly used methods for determining the mould resistance of wood-based materials, i.e. the chamber method according to BS 3900—Part G6 and the malt agar plate method according to ISO 16869. Solid wood, wood fiber insulation boards and wood polymer composites were inoculated, incubated for different time intervals, and assessed with regard to superficial mould growth. Mould growth ratings obtained with the two methods did not correlate well, neither within one type of material nor across different materials, which can be attributed to higher moisture contents and additional nutrients available for the specimens in the agar plate test compared to those in the chamber test. It was concluded, that the experimental set up could have an overriding effect on the results of mould resistance tests.

The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties.

Construction and demolition waste (CDW), including valuable materials such as plastics, have a remarkable influence on the waste sector. In order for plastic materials to be re-utilized, they must be identified and separated according to their polymer composition. In this study, the identification of these materials was performed using near-infrared spectroscopy (NIR), which identified material based on their physical-chemical properties. Advantages of the NIR method are a low environmental impact and rapid measurement (within a few seconds) in the spectral range of 1600-2400 nm without special sample preparation. Limitations include its inability to analyze dark materials. The identified polymers were utilized as a component for wood-polymer composite (WPC) that consists of a polymer matrix, low cost fillers, and additives. The components were first compounded with an agglomeration apparatus, followed by production by extrusion. In the agglomeration process, the aim was to compound all materials to produce uniformly distributed and granulated materials as pellets. During the agglomeration process, the polymer (matrix) was melted and fillers and other additives were then mixed into the melted polymer, being ready for the extrusion process. In the extrusion method, heat and shear forces were applied to a material within the barrel of a conical counter-rotating twin-screw type extruder, which reduces the risk of burning the materials and lower shear mixing. The heated and sheared mixture was then conveyed through a die to give the product the desired shape. The above-described protocol proved the potential for re-utilization of CDW materials. Functional properties must be verified according to the standardized tests, such as flexural, tensile, and impact strength tests for the material.

Evaluation of particle swarm optimization for strength determination of tropical wood polymer composite

A wood-polymer composite (WPCs) refers to wood-based components that are coupled with polymers to produce a composite material. Obtaining the best strength for the tropical WPCs is still a lack of research mainly for the tropical timber species and require a large consumption of time and cost. This paper highlighted the evaluation of particle swarm optimization (PSO) to assist in finding the optimal value of the composition of tropical WPCs to obtain the best strength that would offer a betterment in a quality product of WPCs. The findings demonstrate that PSO has been shown as a viable and efficient method for WPCs strength. The composition of Sentang, wood sawdust of 50%, HDPE of 49% and 1% coupling agent is demonstrated the best strength for the WPC. The employment of PSO as an assisted tool would give significant benefit to the manufacturer and researcher to determine the composition of material with less cost and time.

Prediction of the modulus of elasticity of building materials based on wood-polymer composites

The modulus of elasticity of mixtures of two polymers in glassy or crystalline states is predicted. In addition, the elastic modulus of composites containing a mixture of organic polymers and a mineral filler is predicted. The preparation of wood-polymer composites increases the elastic modulus from 2400 to 4660 MPa under tensile conditions. The introduction of a mineral filler in the form of CaCO3 leads to an increase in the E modulus to 3230 MPa with a CaCO3 content relative to the wood filler of 42%. The prediction of the elastic modulus for composites containing moso bamboo as a wood filler shows that with this content of wood filler, the modulus of elasticity can increase to 4400 MPa.

Correlation between Mechanical Properties and Processing Conditions in Rubber-Toughened Wood Polymer Composites.

The use of wood fibers is a deeply investigated topic in current scientific research and one of their most common applications is as filler for thermoplastic polymers. The resulting material is a biocomposite, known as a Wood Polymer Composite (WPC). For increasing the sustainability and reducing the cost, it is convenient to increase the wood fiber content as much as possible, so that the polymeric fraction within the composite is thereby reduced. On the other hand, this is often thwarted by a sharp decrease in toughness and processability—a disadvantage that could be overcome by compounding the material with a toughening agent. This work deals with the mechanical properties in tension and impact of polypropylene filled with 50 wt.% wood flour, toughened with different amounts (0%, 10%, and 20%) of a polypropylene-based thermoplastic vulcanizate (TPV). Such properties are also investigated as a function of extrusion processing variables, such as the feeding mode (i.e., starve vs. flood feeding) and screw speed. It is found that the mechanical properties do depend on the processing conditions: the best properties are obtained either in starve feeding conditions, or in flood feeding conditions, but at a low screw speed. The toughening effect of TPV is significant when its content reaches 20 wt.%. For this percentage, the processing conditions are less relevant in governing the final properties of the composites in terms of the stiffness and strength.