Effect of expanded polystyrene content and press temperature on the properties of low-density wood particleboard

In this study, three-layer low-density (about 400 kg/m3) particleboards consisting of a mixture of wood particles and expanded polystyrene (EPS) were manufactured. EPS bead was incorporated in the core layer as a light filler. The influence of EPS content (0 %, 2,5 %, 5 %, 7,5 %, 10 % and 12,5 %) and press temperature (110 °C and 140 °C) on the microstructure, density profile, bending properties, internal bond and thickness swelling of the panels was investigated. Results showed that incorporation of EPS beads filled in the voids between wood particles, improved the core layer integrity, and generated a more pronounced density profile. Consequently, the bending properties and internal bond of panels adding EPS were remarkably improved, and the thickness swelling was decreased. However, the variation of the amount of EPS from 2,5 % to 12,5 % had no significant effect on the bending properties and thickness swelling. Comparing the two press temperatures, although higher temperature (140 °C) was more favourable in control panels without EPS as filler, it had a negative effect on the properties of panels with addition of EPS filler, especially for high EPS contents (10 % and 12,5 %), attributing to the shrinkage of EPS bead under press temperature that is much higher than its glass transition temperature (104 °C)

Effect of expanded polystyrene content and press temperature on the properties of low-density wood particleboard

In this study, three-layer low-density (about 400 kg/m3) particleboards consisting of a mixture of wood particles and expanded polystyrene (EPS) were manufactured. EPS bead was incorporated in the core layer as a light filler. The influence of EPS content (0 %, 2,5 %, 5 %, 7,5 %, 10 %, and 12,5 %) and press temperature (110 °C and 140 °C) on the microstructure, density profile, bending properties, internal bond and thickness swelling of the panels were investigated. Results showed that incorporation of EPS beads filled in the voids between wood particles improved the core layer integrity, and generated a more pronounced density profile. Consequently, the bending properties and internal bond of panels adding EPS were remarkably improved, and the thickness swelling was decreased. However, the variation of the number of EPS from 2,5 % to 12,5 % had no significant effect on the bending properties and thickness swelling. Comparing the two press temperatures, higher temperature (140 °C) was more favourable in control panels without EPS as filler. For panels adding EPS filler, 140 °C had a negative effect on the properties of panels, especially at high EPS contents (10% and 12,5%), attributing to the shrinkage of EPS bead under press temperature that is much higher than its glass transition temperature (104 °C

Optimization of Performance of Bamboo Mat Corrugated Sheets Using Response Surface Methodology

In this study, a bamboo composite with a corrugated structure, bamboo mat corrugated sheets (BMCS), was manufactured. As subset of the response surface methodology, Box–Behnken design was used for designing experiments, statistically modeling the processing conditions–properties relationships, and for identification of the potentially optimum conditions for BMCS. Three variables (MC, pressing temperature, and pressing time) at three levels were studied. Results showed that all the tested properties (deformation ratio, failing load, bending strength, and impact strength) were best described by quadratic regression models. Keeping MC at higher level significantly decreased the deformation ratio. All the three factors and interactions between any two of them were significant model terms for failing load. Pressing temperature, pressing time, and their interactions were significant model terms for bending strength. The interaction effect of MC and the other two factors was significant for impact strength. The best optimized conditions were determined using a desirability function approach to be MC 12.3%, pressing temperature 146.2°C, and pressing time 12.8 min that optimized 1.8% for deformation ratio, 542 N for failing load, 185.7 MPa for bending strength, and 36.5 kJ/m2 for impact strength of BMCS.

Water Absorption, Dimensional Stability, and Mold Susceptibility of Organically-modified-Montmorillonite Modified Wood Flour/Polypropylene Composites

Wood flour (WF) was modified by sodium-montmorillonite (Na-MMT) and didecyl dimethyl ammonium chloride (DDAC) in a two-step process to form organically-modified-montmorillonite (OMMT) inside the WF with varied MMT concentration (0.25, 0.5, 0.75, and 1%, respectively). Then, the modified WF was mixed with polypropylene (PP) to produce WF/PP composites. The WF and WF/PP composites were characterized, and the water absorption, dimensional stabilities, and the mold susceptibility of the composites against Aspergillus niger, Penicillam citrinum, and Trichoderma viride were investigated. The results showed that Na-MMT was successfully transformed to OMMT inside WF. Owing to the hydrophobic nature and barrier effect of OMMT on water permeability, the composites showed some improvements in water resistance, dimensional stabilities and antibiotic performance. MMT concentration was also an important factor. The water repellency and dimensional stability were improved with increasing MMT concentration at first and then dropped after the MMT concentration exceeded 0.5%. However, the mold resistance of the composites increased along with increasing MMT concentration. With 1% MMT treated, the mold growth rating decreased to 1 (mold covering of 0-25%). These results suggested that OMMT modified WF had a positive effect on restricting water absorption, swelling, and mold susceptibility for the WF/PP composites

Enhancing Crystallization and Toughness of Wood Flour/Polypropylene Composites via Matrix Crystalline Modification: A Comparative Study of Two β-Nucleating Agents

Incorporation of short wood fillers such as wood flour (WF) into polypropylene (PP) often results in a marked reduction of toughness, which is one of the main shortcomings for WF/PP composites. This research reports a facile approach to achieve toughening of WF/PP composites via introducing self-assembling β-nucleating agents into PP matrix. The effect of two kinds of nucleating agents, an aryl amide derivative (TMB5) and a rare earth complex (WBG II), at varying concentrations on the crystallization and mechanical properties of WF/PP composites was comparatively investigated. The results showed that both nucleating agents were highly effective in inducing β-crystal for WF/PP, with β-crystal content (kβ) value reaching 0.8 at 0.05 wt% nucleating agent concentration. The incorporation of TMB or WBG significantly decreased the spherulite size, increased the crystallization temperature and accelerated the crystallization process of WF/PP. As a result of PP crystalline modification, the toughness of composites was significantly improved. Through introducing 0.3 wt% TMB or WBG, the notched impact strength and strain at break of WF/PP increased by approximately 28% and 40%, respectively. Comparatively, although WF/PP-WBG had slightly higher Kβ value than WF/PP-TMB at the same concentration, WF/PP/TMB exhibited more uniform crystalline morphology with smaller spherulites. Furthermore, the tensile strength and modulus of WF/PP-TMB were higher than WF/PP-WBG. This matrix crystalline modification strategy provides a promising route to prepare wood filler/thermoplastic composites with improved toughness and accelerated crystallization

Interfacial Improvements in a Green Biopolymer Alloy of Poly(3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate) and Lignin via in Situ Reactive Extrusion

Green biopolymer alloys based on the bacterial polyester poly­(3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate) (PHBV) and softwood Kraft lignin were successfully prepared via dicumyl peroxide (DCP) initiated free radical grafting during melt extrusion to improve interfacial adhesion. It is postulated that lignin was grafted onto PHBV to form a cross-linked copolymer gel. The gel fraction of the biopolymer alloy grafted at four different loading levels of DCP was determined. At an optimal total concentration of 2 wt % DCP, tensile strength, Young’s modulus, and storage modulus, by dynamic mechanical analysis (DMA), of the biopolymer alloy showed a maximum, coinciding with the highest gel yield. The presence of both lignin and PHBV characteristic bands by Fourier transform infrared spectroscopy (FTIR) in the extracted biopolymer alloy gel confirmed lignin was successfully grafted onto PHBV. Adhesion factor calculated from DMA data also indicated improved interfacial interaction. The crystallinity degree in the grafted alloy was reduced while crystallization temperature was increased as determined by FTIR, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses. Hot stage polarized optical microscopy observation confirmed that DCP induced grafting significantly reduced the spherulite size and increased nucleation density of PHBV. Glass transition temperature, thermal stability, and melt strength of the biopolymer alloy were all enhanced as a result of better molecular interaction by grafting. This study opens up a pathway to utilize effectively the low-cost and renewable lignin as a component in a biopolymer alloy based on sustainable materials