Production of mahogany sawdust reinforced LDPE wood–plastic composites using statistical response surface methodology

We produced wood–plastic composite board by using sawmill wastage of mahogany（Swietenia macrophylla） wood and low density polyethylene.We used multi-response optimization to optimize the process parameters of composite board production including mixing ratio,fire retardant（%） and pressing time（min）.We investigated the effects of these three process parameters in the mechanical and physical properties of the composite board.Afterwards,Box–Behnken design was performed as response surface methodology with desirability functions to attain the optimal level of mixing ratio,fire retardant and pressing time（min）.The maximum modulus of elasticity（MOE） and modulus of rupture（MOR） were achieved at the optimal conditions of wood plastic mixing ratio of60：40,pressing time of 9 min and zero fire retardant percentage.The optimized MOR and MOE were 13.12 and1,781.0 N mm-2,respectively.

Novel wood-plastic composite fabricated via modified steel slag:Preparation,mechanical and flammability properties

A novel method was developed to enhance the utilization rate of steel slag(SS).Through treatment of SS with phosphoric acid and aminopropyl triethoxysilane(KH550),we obtained modified SS(MSS),which was used to prepare MSS/wood-plastic composites(MSS/WPCs)by replacing talcum powder(TP).The composites were fabricated through melting blending and hot pressing.Their mechanical and combustion properties,which comprise heat release,smoke release,and thermal stability,were systematically investigated.MSS can improve the mechanical strength of the composites through grafting reactions between wood powder and thermoplastics.Notably,MSS/WPC#50(16wt%MSS)with an MSS-to-TP mass ratio of 1:1 exhibited optimal comprehensive performance.Compared with those of WPC#0 without MSS,the tensile,flexural,and impact strengths of MSS/WPC#50 were increased by 18.5%,12.8%,and 18.0%,respectively.Moreover,the MSS/WPC#50 sample achieved the highest limited oxygen index of 22.5%,the highest vertical burning rating at the V-1 level,and the lowest horizontal burning rate at 44.2 mm/min.The formation of a dense and stable char layer led to improved thermal stability and a considerable reduction in heat and smoke releases of MSS/WPC#50.However,the partial replacement of TP with MSS slightly compromised the mechanical and flame-retardant properties,possibly due to the weak grafting caused by SS powder agglomeration.These findings suggest the suitability of MSS/WPCs for high-value-added applications as decorative panels indoors or outdoors.

Overview of the Synthesis, Characterization, and Application of Tannin-Glyoxal Adhesive for Wood-Based Composites

More than a century after its initial synthesis,urea-formaldehyde(UF)resins still have dominant applications as adhesives,paints,and coatings.However,formaldehyde in this industry produces formaldehyde emissions that are dangerous to health.Scientists have spent the last decade replacing formaldehyde and phenol with environmentally friendly substances such as glyoxal and tannin to create bio-based adhesives.This review covers recent advances in synthesizing glyoxal tannin-based resins,especially those made from sustainable raw material substitutes and changes made to synthetic processes to improve mechanical properties.The efficacy of using tannin-glyoxal adhesives in producing wood-based composites has been proven.The glyoxylate reaction forms cross-linked bridges between the aromatic sites of the tannin and glyoxal molecular structures.Glyoxal tannin adhesive with a greater percentage of glyoxal than tannin will produce an adhesive with better characteristics.The gel time reduces as the hardener concentration rises from 7.5%to 15%when glyoxal is used in adhesives.However,excessive amounts of glyoxal will result in a decrease in viscosity values.Glyoxal exhibits faster delivery degradation when it reaches a maximum temperature of approximately 130°C,although it initiates the curing process slightly slower at 110°C.Adding glyoxal to tannin-based adhesives can improve the mechanical properties of composite boards.The wet shear strength of the resulting plywood is increased by 105.4%with the addition of 5-weight percent tannin-based resin with glyoxal as a cross-linker in Soy Protein Adhesive.With glyoxal as a hardener,the panels produced showed good internal bond strengths(>0.35 MPa)and met the international standard specifications for interior-grade panels.

Physicomechanical Properties of Sustainable Wood Plastic Composites of Tropical Sawdust and Thermoplastic Waste for Possible Utilization in the Wood Industry

This work investigated and quantified the physicomechanical properties of flat-pressed wood plastic composites produced with recycled polyethylene terephthalate, recycled polyethylene and sawdust derived from selected tropical timbers, namely, Nauclea diderrichii, Brachystegia eurycoma, Erythrophleum suaveolens and Prosopis africana, for possible utilization in the wood industry. The compounding of the polymer blends of the precursor plastics, namely recycled PET (rPET) and recycled PE (rPE) with the sawdust (SD) from the selected timbers to produce the desired wood rPET/rPE composites was carried out via the flat press method. The characterization of the physicomechanical properties of the wood plastic composites (WPCs) produced, such as the density, hardness, flexural strength, ultimate tensile strength, elongation %, thickness swelling and water absorption capacity was carried out using methods based mainly on the European Committee for Standardization (CEN) and the American Society for Testing Materials (ASTM) standards. The results of the investigation on the resultant composites indicated that changes in the SD content affected the density of flat-pressed WPCs in line with literature. Generally, it was observed that as wood dust increased and PET content decreased, the density of composites decreased with some deviations as expected probably due to the anisotropic nature of the wood fillers. The analysis of variance (ANOVA) revealed that there was a statistically significant variation in the wood composites of Nuclea diderichii based on the physicomechanical values as the p-value (0.020) obtained was less than the critical level of α = 0.05. It was also observed that the composite, Wood 1 Sample 5 (W1S5) which was composed of 40% rPE, 40% rPET and 20% SD (derived from Nuclea diderichii), had the highest percentage elongation (26.84%);the highest flexural strength (14.995 N/mm2) and possibly the least carbon footprint in the environment. These properties of W1S5 suggest that it could therefore be the best option for the production of building materials like ceiling boards or floor skirting in the wood plastic composite industry. The results of these investigations have therefore indicated that the fabrication of WPCs from sawdust and rPET/rPE was technically feasible and had prospects for large scale production in the wood industry.

Effects of two modification methods on the mechanical properties of wood flour/recycled plastic blends composites: addition of thermoplastic elastomer SEBS-g-MAH and in-situ grafting MAH

The effect of maleic anhydride grafted styrene-ethylene- buty-lene-styrene block copolymer （SEBS-g-MAH） and in-situ grafting MAH on mechanical, dynamic mechanical properties of wood flour/recycled plastic blends composites was investigated. Recycled plastic polypro-pylene （PP）, high-density polyethylene （HDPE） and polystyrene （PS）, were mixed with wood flour in a high speed blender and then extruded by a twin/single screw tandem extruder system to form wood flour/recycled plastic blends composites. Results show that the impact properties of the composites were improved more significantly by using SEBS-g-MAH compatibilizer than by using the mixtures of MAH and DCP via reactive blending in situ. However, contrary results were ob-served on the tensile and flexural properties of the corresponding com-posites. In General, the mechanical properties of composites made from recycled plastic blends were inferior to those made from virgin plastic blends, especially in elongation break. The morphological study verified that the interfacial adhesion or the compatibility of plastic blends with wood flour was improved by adding SEBS-g-MAH or in-situ grafting MAH. A better interfacial bonding between PP, HDPE, PS and wood flour was obtained by in-situ grafting MAH than the addition of SEBS-g-MAH. In-situ grafting MAH can be considered as a potential way of increasing the interfacial compatibility between plastic blends and wood flour. The storage modulus and damping factor of composites were also characterized through dynamic mechanical analysis （DMA）.

Valorization of Tree Bark-Derived Suberin in Applications for the Bio-Based Composites Industry–A Recent Review

Bark extracts are sustainable sources of biopolymers and hold great promise for replacing fossil fuel-based polymers,for example,in wood-based composites.In addition to primary and secondary metabolites,tree bark also contains suberin,which plays a major role in protecting the tree from environmental conditions.Suberin is a natural aliphatic-aromatic cross-linked polyester present in the cell walls of both normal and damaged external tissues,the main component of which are long-chain aliphatic acids.Its main role as a plant ingredient is to protect against microbiological factors and water loss.One of the most important suberin monomers are suberin fatty acids,known for their hydrophobic and barrier properties.Therefore,due to the diverse chemical composition of suberin,it is an attractive alternative to hydrocarbon-based materials.Although its potential is recognized,it is not widely used in biocomposites technology,including wood-based composites and the polymer industry.The article will discuss the current knowledge about the potential of suberin and its components in biocomposites technology,which will include surface finishes,composite adhesives and polymer blends.

Research and application of composite stochastic resonance in enhancement detection

Aiming at the problem that the intermediate potential part of the traditional bistable stochastic resonance model cannot be adjusted independently, a new composite stochastic resonance(NCSR) model is proposed by combining the Woods–Saxon(WS) model and the improved piecewise bistable model. The model retains the characteristics of the independent parameters of WS model and the improved piecewise model has no output saturation, all the parameters in the new model have no coupling characteristics. Under α stable noise environment, the new model is used to detect periodic signal and aperiodic signal, the detection results indicate that the new model has higher noise utilization and better detection effect.Finally, the new model is applied to image denoising, the results showed that under the same conditions, the output peak signal-to-noise ratio(PSNR) and the correlation number of NCSR method is higher than that of other commonly used linear denoising methods and improved piecewise SR methods, the effectiveness of the new model is verified.

Effects of cement-enhanced soil on the ultimate lateral resistance of composite pile in clayey soil

The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral resistance has not been fully investigated.In this paper,the ultimate lateral resistance of the composite pile was studied by finite element limit analysis(FELA)and theoretical upper-bound analysis.The results of FELA and theoretical analysis revealed three failure modes of laterally loaded composite piles.The effects of the enhanced soil thickness,strength,and pile-enhanced soil interface characteristics on the ultimate lateral resistance were studied.The results show that increasing the enhanced soil thickness leads to a significant improvement on ultimate lateral resistance factor(N P),and there is a critical thickness beyond which the thickness no longer affects the N P.Increasing the enhanced soil strength induced 6.2%-232.6%increase of N P.However,no noticeable impact was detected when the enhanced soil strength was eight times higher than that of the natural soil.The maximum increment of N P is only 30.5%caused by the increase of interface adhesion factor(a).An empirical model was developed to calculate the N P of the composite pile,and the results show excellent agreement with the analytical results.

Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Development and Characterization of Eco-Friendly Non-Isocyanate Urethane Monomer from Jatropha curcas Oil for Wood Composite Applications

The aim of this research work was to evaluate the potential of using renewable natural feedstock,i.e.,Jatropha curcas oil(JCO)for the synthesis of non-isocyanate polyurethane(NIPU)resin for wood composite applications.Commercial polyurethane(PU)is synthesized through a polycondensation reaction between isocyanate and poly-ol.However,utilizing toxic and unsustainable isocyanates for obtaining PU could contribute to negative impacts on the environment and human health.Therefore,the development of PU from eco-friendly and sustainable resources without the isocyanate route is required.In this work,tetra-n-butyl ammonium bromide was used as the activator to open the epoxy ring with 3-Aminopropyltriethoxisylane as a catalyst to yield urethane of JCO(UJCO).The UJCO were characterized by Fourier Transform Infra-Red spectroscopy(FTIR)and their oxirane,and hydroxyl values were measured.The result showed that a decrease in oxirane value was found while the hydroxyl value was increased during the time,confirming that the urethane group was formed.The presence of functional groups in FTIR spectra at wave numbers 1732.08,1562.34,and 3348.42 cm^(−1) indicates the functional groups of C=O(urethane carbonyl),–NH,and–OH,respectively confirmed this finding.The potential applications of NIPU in the wood composite were also outlined.

Environmentally Friendly Chitosan-Based Wood/Wood Composite Adhesive: Review

Due to the world’s energy issues and dependency on petroleum resources, focus has switched to finding new, sustainable raw material sources for wood adhesives. Renewable biopolymers would gradually replace petroleum and natural gas as the primary raw materials used in wood adhesives. Chitosan is a biomass substance having a lot of reserves. Chitosan is one of the most fascinating biopolymers in the adhesive sector because of its potential qualities for adhesive applications, such as biodegradability, biocompatibility, and non-toxicity. Chitosan and its derivatives have so garnered considerable interest in a wide range of adhesive applications. However, its adhesive strength is insufficient to glue wood under normal, humid conditions. There has been a lot of study done on how to make chitosan-based adhesives more cohesive and water resistant. In order to effectively use chitosan-based wood glue in wood/wood composite adhesive that gives comparable performance to synthetic adhesives, numerous new ways have been developed. It has been modified by the addition of various cross-linkers, including aldehydes like glyoxal glutaraldehyde etc., epoxy compounds, blended with other polymers, different acids and chitosan grafted onto vinyl acetate. In the production of wood composites, chitosan can also scavenge formaldehyde. This review of chitosan-based adhesives focuses on various cross-linkers for chitosan modification in order to improve the properties of chitosan-based wood adhesives.

Static Bending Creep Properties of Glass Fiber Surface Composite Wood

To study the static bending creep properties of glass fiber reinforced wood,glass fiber reinforced poplar(GFRP)specimens were obtained by pasting glass fiber on the upper and lower surfaces of Poplar(Populus euramevicana,P),the performance of Normal Creep(NC)and Mechanical Sorptive Creep(MSC)of GFRP and their influencing factors were tested and analyzed.The test results and analysis show that:(1)The MOE and MOR of Poplar were increased by 17.06%and 10.00%respectively by the glass fiber surface reinforced composite.(2)The surface reinforced P with glass fiber cloth only exhibits the NC pattern of wood and loses the MSC characteristics of wood,regardless of the constant or alternating changes in relative humidity.(3)The instantaneous elastic deformation,viscoelastic deformation,viscous deformation and total creep deflection of GFRP are positively correlated with the stress level of the external load applied to the specimen.Still,the specimen’s creep recovery rate is negatively correlated with the stress level of the external load applied to the specimen.The static creep deflection and viscous deformation of GFRP increase with the increase of the relative humidity of the environment.(4)The MSC maximum creep deflection of GFRP increased by only 7.41%over the NC maximum creep deflection,but the MSC maximum creep deflection of P increased by 199.25%over the NC maximum creep deflection.(5)The Burgers 4-factor model and the Weibull distribution equation can fit the NC and NC recovery processes of GFRP well.

Influence of Plastic and Coconut Shell (Cocos nucifera L.) on the Physico-Mechanical Properties of the 8/6 Composite Rafter

In this paper, the authors aim to propose the use of waste plastics as a binder in a coconut shell reinforcement for the development of an 8/6 size composite rafter to replace the natural 8/6 size backbone in construction. Following a study into the choice of the best proportions, a total of 30 size 8/6 composite rafters with different proportions of 20%, 25%, 30%, 35%, 40% and 50% plastic content were developed. All the 8/6 composite rafters were subjected to mechanical (3-point bending strength and Monnin hardness) and physical (bulk density and water absorption) characterization analyses. The results show that flexural strength increases from 27.56 MPa to 33.30 MPa for proportions ranging from 20% to 35% plastic content. Above 35% plastic, the strength drops to 19.60 MPa for a 50% plastic content. Similarly, the Monnin hardness drops from 9 mm to 5 mm when the plastic content varies from 20 to 50%. As for the results of the physical characterisation, the values obtained for apparent density vary from 0.89 to 1 for proportions varying from 20% to 35% plastic content and drop to 0.94 for 50% plastic content. As for water absorption, values drop from 6.82% to 2.45% when the plastic content increases from 20% to 50%. These mechanical strengths stabilise at 35% plastic content. The development of an 8/6 chevron composite material based on plastic and coconut shell could therefore be a way of recovering waste and solving the problem of deforestation.

Life Cycle Assessment of Creosote-Treated Wooden Railroad Crossties in the US with Comparisons to Concrete and Plastic Composite Railroad Crossties

Creosote-treated wooden railroad crossties have been used for more than a century to support steel rails and to transfer load from the rails to the underlying ballast while keeping the rails at the correct gauge. As transportation engineers look for improved service life and environmental performance in railway systems, alternatives to the creosote-treated wooden crosstie are being considered. This paper compares the cradle-to-grave environmental life cycle assessment (LCA) results of creosote-treated wooden railroad crossties with the primary alternative products: concrete and plastic composite (P/C) crossties. This LCA includes a life cycle inventory (LCI) to catalogue the input and output data from crosstie manufacture, service life, and disposition, and a life cycle impact assessment (LCIA) to evaluate greenhouse gas (GHG) emissions, fossil fuel and water use, and emissions with the potential to cause acidification, smog, ecotoxicity, and eutrophication. Comparisons of the products are made at a functional unit of 1.61 kilometers (1.0 mile) of rail-road track per year. This LCA finds that the manufacture, use, and disposition of creosote-treated wooden railroad crossties offers lower fossil fuel and water use and lesser environmental impacts than competing products manufactured of concrete and P/C.

Ultrathin Wood Laminae–Thermoplastic Starch Biodegradable Composites

Novel fully biodegradable thermoplastic composite laminates reinforced with ultrathin wood laminae were prepared through a hot-pressing process by using two different thermoplastic starch(TPS)matrices.The microstructure and physical properties of the resulting unidirectional and bidirectional laminates were studied.The investigated materials presented a complex microstructure,in which the porosity of the wood laminae was almost entirely occluded by the polymer matrix.The mechanical behavior of the laminates was strongly affected by the obtained microstructure,and matrix penetration in wood pores led to biodegradable composites with elastic modulus and tensile strength higher than those of their constituents.Finally,thermal welding and thermoformability tests proved how these materials possess features typical of thermoplastic materials.

Filling Behavior of Wood Plastic Composites

WPC （wood plastic composites） are a young generation of composites with rapidly growing usage within the plastics industry. The advantages are the availability and low price of the wood particles, the possibility of partially substituting the polymer in the mixture and sustainable use of the earth＇s resources. The current WPC products on the market are to a large extent limited to extruded products. Nowadays, there is a great interest in the market for consumer products in more use of WPC as an alternative to pure thermoplastics in injection molding processes. This work presents the results of numerical simulation and experimental visualization of the mold filling process in injection molding of WPC. The 3D injection molding simulations were done with the commercial software package Autodesk~ Moldflow Insight 2016 （AMI）. The mold filling experiments were conducted with a box-shaped test part. In contrast to unfilled polymers, the WPC has reduced melt elasticity so that the fountain flow often does not develop. This results in irregular flow front shapes in the molded part, especially at high filler content.

Preliminary study of the effects of EVA coupling agents on properties of wood-plastic composites

As a hot-melt adhesive, ethylene-vinyl-acetate （EVA） has been used in many industrial applications. But studies of the application of EVA in wood-plastic composites （WPC） are relatively few, so we have investigated the proposition of whether EVA is a suitable coupling agent for WPC or not. The results show that EVA with 8% VA is not a suitable coupling agent, because it reduces the mechanical properties of WPC without any significant effect on its physical properties. With an increase in the amount of wood powder, the mechanical properties of WPC decrease and the ability of water absorption of WPC increases.

Mechanical properties of wood flour/recycled-thermoplastic-blends composites

The mechanical properties of composites prepared from wood flour and thermoplastic blends were investigated. Thermoplastic mixtures of polypropylene (PP) and high-density polyethylene (HDPE) and polystyrene (PS), virgin or recycled, were mixed with wood flour in a high speed blender and then extruded by a specially designed twin/single screw extruder system to form wood-flour/thermoplastic-blends composites (WTBCs). Comparative studies were made to evaluate the effectiveness of the two modification methods of the thermoplastic blends, the one of the addition of maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MAH) as compatibilizer and the other of blend grafting of maleic anhydride (MAH) using dicumyl peroxide (DCP) as initiator by reactive extrusion. The results showed that the impact properties of WTBCs using SEBS-g-MAH as compatilizer were better improved than that of the blend grafting. However, adverse results were observed on the tensile and flexural properties of the corresponding WTBCs. The mechanical properties of WTBCs prepared from recycled plastic blends were poorer to some extent than that from virgin plastic blends in general, especially in elongation break. The morphology of WTBCs breaking section was analyzed by scanning electron microscopy (SEM) and the results showed that a good interfacial adhesion between wood flour and polymer matrix was observed with both of the two modification methods. However, by blend grafting of adding DCP as initiator and MAH as monomer, a better interfacial bonding between wood and plastic matrix was obtained than that of the addition of SEBS-g-MAH. Blend grafting can be considered as a potential way of increasing the interfacial compatibility of different plastics and between plastic blends and wood.

Application of Plastic Wood Composite in Outdoor Furniture

Concept of plastic wood and plastic wood furniture was summarized, categories of outdoor furniture in a narrow and broad sense introduced respectively. Furniture of plastic wood composite is characterized by "leisure, natural and concise", dynamic loading is the major connection mode, and traditional mechanical connection is applied. Common damages of plastic wood composite and countermeasures were concluded, and corresponding resolutions proposed in view of existing problems of outdoor plastic wood composite furniture.

A Simulation Software for the Prediction of Thermal and Mechanical Properties of Wood Plastic Composites

Modelling and simulation has become an important tool in research and development. Simulation models are used to develop better understanding of the internal properties and impact of various parameters on the final quality of the product or process. Simulation model reduces the number of experiments and saves the wastage of material, time and money and are widely used in automobile industry, aircrafts manufacturing, process engineering, training for military, health care sector and many more. Wood Plastic Composite （WPC） is a bio-composite made by mixing wood fibers and plastic granules together at high temperature by compression molding or injection molding. A large quantity of WPC is rejected due to poor quality and low mechanical strength. There is a need to improve the understanding of the wood plastic composites, with both theoretical and experimental analysis. The impact of various parameters and processing conditions on the final product is not known to the industry people, due to less simulation models in this field. A new simulation software WPC Soft is developed to predict the mechanical and thermal properties of WPC. The software can predict the mechanical and thermal properties of WPC. The simulation results were validated with the experimental results and it was observed that the predicted values are quite close to the experimental values and with the further refining of the model, prediction can be further improved. The present simulation software can be easily used by the industry people and it requires very little knowledge of computers or modeling for its operation.