Mechanical Properties Of Wood Polymer Composites Research Articles

Modeling of mechanical properties of wood-polymer composites with Artificial Neural Networks

Mechanical properties (tensile strength (TS), modulus of elasticity in tensile (MET), flexural strength (FS), modulus of elasticity (MOE)) of the material to be obtained depending on the production parameters in the production of high-density polyethylene (HDPE) wood-polymer composites with Scots pine wood flour additive were predicted using Artificial Neural Networks (ANN) model and without destructive testing. In the first stage of the study, an ANN model was developed using data from 56 different studies in the literature on the mechanical properties of wood polymer composites. In the second stage, in order to determine the reliability of the model, output values were estimated using input parameters that had not been used in training and testing of the model. Based on the same input parameters, test specimens were produced and mechanical tests were performed. The results obtained from the experiments and ANN model were compared by considering the mean absolute percentage error (MAPE) value. The coefficient of determination (R2) values obtained in the training and testing phase of the ANN models were all higher than 0.90. In this way, the mechanical properties of the wood polymer composite were successfully predicted by the ANN model. Because most of the MAPE values obtained from the mechanical tests were below 10%, the model was considered a reliable model.

A comparative study on graft copolymerization of MMA onto wood fiber under microwave and conventional heating

Wood polymer composites (WPC) are gaining popularity and widespread usage due to an increased awareness of human population towards the importance of environmental effects and green eco-friendly materials. Mechanical properties of WPC could be improved through graft copolymerization of monomer onto wood fiber to improve interfacial bonding. In this study, a comparison of free radical graft copolymerization using microwave-assisted and conventional heating method was performed. Methyl methacrylate (MMA) monomer is used in graft copolymerization of Meranti wood using a free radical initiator system consisting of ferrous sulfate and hydrogen peroxide. Grafting reaction time was varied while other graft parameters were kept constant including monomer concentration, initiator molar ratio, reaction temperature and solvent volume. Maximum graft yield of 11.75% and 10.17% were obtained for water bath heated and microwave-assisted method respectively. The presence of grafted monomer was proven by FTIR spectra analysis. Thermogravimetric analysis performed on grafted wood fibers showed improved thermal resistance compared to ungrafted wood fiber.

Mechanical properties of wood polymer composites made of sawdust waste and recycled high density polyethylene

This work investigated the mechanical properties of wood polymer composites (WPCs), which were made using recycled high density polyethylene (HDPE) and sawdust waste. Degraded HDPE was used as a coupling agent. Different blends of virgin (vPE) and recycled (rPE) poly ethylene's with various ratio (100/0, 75/25, 50/50, 25/75 and 0/100) were prepared in order to be used as matrices. PE blends and composites were prepared by melt-mixing technique using mini twin-extruder. Mechanical properties such as ultimate tensile strength (UTS), impact strength and Shore hardness were determined for vPE, rPE, PE blends and PE composites. The mechanical properties of PE blends and composites were mainly depended on the composition of its matrices. Presences of degraded HDPE as a coupling agent played an important role on the mechanical properties of WPCs. Increasing the rPE content in the blend composition displayed decrease in the UTS and impact strength properties. The incorporation of only sawdust into vPE, rPE and PE blends matrices caused reduction in UTS and impact strength properties and an increase in Shore hardness. UTS, impact strength and Shore hardness for all WPCs were improved when 5% degraded PE was added. UTS and Shore hardness for composites with 5% degraded PE were higher than that of its matrices. The properties of PE composites were better than that of PE blends, which suggesting that using rPE to attain blends with vPE and then making composites appears to be more preferable than making only PE blends.

Mechanical Properties of Barley Straw/HDPE Composites Produced with Extrusion Process

This paper is devoted to the study of the technological process for the production of tape from polyethylene and wood-polymer composite by extrusion. At the first stage, the wood-polymer composite granulate was obtained on a co-rotating twin-screw extruder. The tape was made on a Rheomex 19/25 PolyLab OS single-screw extruder with a barrel length L/D = 25. The processing temperature of the wood-polymer composite was in the range of 145 ... 160°C. The tensile strength and elasticity modulus in tension, water absorption per day and density were investigated for the developed wood-polymer composite and polyethylene. It has been found out that for the developed wood-polymer composite, the strength and elastic modulus along the stretch direction increase by 11% and 6%, respectively. Orientation stretching has a significant effect on the physical and mechanical properties of wood-polymer composites.

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.

EFFECT OF THE ACIDIC TREATMENT OF DOMESTIC WOOD RESIDUE ON BIOCOMPOSITE WETTABILITY AND MOISTURE SORPTION PROPERTIES

The aim of the work was to evaluate the effect of the acidic treatment temperature of aspen sawdust as a filler on the moisture sorption, wetting and mechanical properties of wood-polymer composites. Aspen wood sawdust was treated with the dilute hydrochloric acid solution at 60oC and 90oC during 5 h. Both the treated particles and the filled composites were studied in terms of moisture sorption and wettability; their surface free energy was calculated using the Owens-Wendt-Rabel-Kaelble (OWRK) approach. The obtained results have shown that the acidic treatment of aspen wood sawdust at 90oC leads to an increase in its hydrophobicity that decreases the wettability and moisture sorption of the obtained composite and increases its mechanical properties.

The effect of extrusion conditions for a screw-disk plasticizing system on the mechanical properties of wood-polymer composites (WPC)

The effect of extrusion conditions for a screw-disk plasticizing system on the mechanical properties of wood-polymer composites (WPC)

Photostability Characterization of Wood Polymer Composites of Polyvinyl Chloride and Rice Husk to Ultra-Violet Irradiation Exposure

In this study, the photostability of wood polymer composites (WPC) was assessed by using ultra-violet accelerated weathering test. Meanwhile, the mechanical properties of WPC show strength improvement at prolonged UV irradiation exposure with 43.21 MPa and maximum strain of 4.08 % at 5000 hours and 1000 hours UV irradiation exposure respectively. The colour stability of WPC was improved by addition of Ultraviolet (UV) stabilizer during pre-mixing process which shows positive effect on the colour stability and prevented chalking of the composites for external use. Generally, discolourations of WPC during test exposure were caused by degradation of both wood and plastic. Therefore, incorporation with pigments and other additives gives improvement to the photostability of WPC. This is based on the increment of WPCs mechanical property while the morphological fracture surface of dumbbell test specimens revealed the pull out rice husk fiber which contributed to the distribution of load in the WPC samples.

Accelerated and Natural Weathering of Wood-Polypropylene Composites Containing Pigments

In general, wood-polymer composites are vulnerable to weathering factors such as UV radiation, moisture, freeze-thaw action. Weathering can cause discoloration, chalking, dimensional change, and loss of mechanical properties of wood-polymer composites. This comparative study was focused on weatherability of wood–polypropylene composites made with and without pigments. Two types of inorganic pigments were applied: carbon black master-batch and synthetic iron oxide. Wood-polypropylene composite made without pigment was used as a reference. Also, composites prepared with addition of wollastonite were tested. The composite samples were exposed to outdoor weathering and in a parallel the accelerated UV weathering was conducted in xenon weathering chamber for the 2000 hours. The colour change was estimated by spectrophotometric method, and the change of Charpy impact strength after weathering was determined. The surface morphology was studied with scanning electron microscopy (SEM). The addition of pigments decreased the lightness of non-weathered composites. The change of lightness and total colour change of weathered composites were affected a lot by type of pigment and method of weathering. As, expected wood-polypropylene composite made with carbon black showed the best results in colour stability of composites exposed to weathering. SEM showed that accelerated weathering in the xenon chamber caused more significant changes in the morphology of the polymer surface layer of the composites than outdoor weathering. Charpy impact strength of all studied composites was found to retain after 2000 hours of outdoor weathering, although accelerated weathering caused significant reduction of Charpy impact strength of these composites.

The Chemical Modification of Waste PET and its Application for a Wood-Polymer Composite Binder

The application of hydroxyl terminated polyethylene terephthalate (PET-OH) as a starting pre-polymer to react with polymeric methylene di-isocyanate (p-MDI) for synthesis of polyurethane as a wood-composite binder was studied. The PET-OH was modified from waste polyethylene terephthalate (PET) bottles by glycolysis reaction. The effect of weight ratios of binder and rubber-wood sawdust particles and the mole ratios of hydroxyl (OH) of PET-OH and isocyanate (NCO) of p-MDI on mechanical properties were investigated. The properties of wood-polymer composites from PET-OH were also compared with the polyurethane composites from polyethylene glycol (PEG) as a commercial polyol. It was found that mechanical properties of wood-polymer composites increased with the increase of binders and polyol contents and then decreased and PET-OH showed the greater properties than PEG. The ratio of wood particle and the binder of 60:40 by weight and the ratio of OH and NCO of 0.01:1 by mole gave the best mechanical properties.

Physical and Mechanical Properties of Wood-Polypropylene Composites Made with Virgin and/or Recycled Polypropylene

The physical and mechanical properties of wood-polymer composites made with virgin or recycled polypropylene, or a mixture of these were studied. The composites made with recycled polypropylene had higher density, lower porosity, and higher dimensional stability compared to the composites made with virgin polypropylene. Although the composites made with recycled polypropylene exhibited lower tensile strength than those made with virgin polypropylene, they had higher Charpy impact strength. Scanning electron microscopy analysis of the fractured surfaces of the composites showed no significant differences in the fracture mechanisms of the studied composites. The degree of crystallinity was estimated to be higher for the virgin polypropylene than for the recycled one.

Effect of Laboratory Aging on the Physical and Mechanical Properties of Wood-Polymer Composites

The long-term performance of wood-polymer composites (WPC) under severe weather conditions is not well known. This study evaluates the changes in physical and mechanical properties of three commercially available WPC and treated southern yellow pine (SYP) under a modified 6-cycle accelerated aging process. The accelerated aging causes warping, splitting, discoloration, and significant changes in physical and mechanical properties of SYP. The compressive and flexural strength of the WPCs show negligible changes whereas stiffness, hardness, and screw withdrawal force show considerable deterioration and some recovery during accelerated aging. The composition and manufacturing process influence the performance of WPC under accelerated aging.