Effects of wood content on the color, mechanical properties, surface chemistry and morphology of wood-plastic composite

Abstract

Effects of wood content on the color, mechanical properties, surface chemistry and morphological of wood-plastic composite (WPC) based on different mixture ratios of recycled high density polyethylene (rHDPE) and wood flour were investigated. Color measurement, FTIR analysis, mechanical testing and scanning electron microscopy study had employed in this research. The addition of wood flour indicated an increased of total color change and a decreased of lightness. The resulting WPC became darken and the colors were toward to red and yellow if compared with initial value. Functional groups of wood flour in rHDPE matrix can be seen clearer with increasing wood flour content as the shape of the wavenumber determined by FTIR spectroscopy became so obvious to be observed. As an overall, modulus of elasticity was improved by the addition of wood flour, whereas stress at break, strain at break and elongation at break were lowered by the addition of wood flour. Resulting WPC experienced a negative effect on the mechanical properties due to poor interfacial bonding between the polymer matrix and wood flour filler. Unidentified particles with vertex were found in rHDPE due to the impurity of rHDPE as a recycled material. Holes were made by fibres being pulled out from the polymer matrix. Fibre breaking and region of cup-and-cone fracture were examined in the fractured polymer matrix. Gaps between the matrix and fibre were getting visible with increasing wood flour content. This shows that the interaction between matrix and filler was weak, resulting in less and poor interfacial adhesion with an addition of wood flour.