The effects of filler loading and coupling agents on properties of recycled high density Polyethylene/wood fiber composites

Abstract

The recycled high density polyethylene (rHDPE)/wood fiber (WF) composites had been prepared using Brabender Plasticorder at temperature 160˚C with rotor speed of 50 rpm. The effect of wood fiber loading and coupling agents on tensile properties, water absorption, morphology, spectroscopy infrared (FTIR) analysis, thermogravimetric analysis (TGA) and x-ray diffraction (XRD) of rHDPE/WF composites were investigated. The results show that the addition of wood fiber reduced the tensile strength, elongation at break and interparticle spacing (d), whereas the modulus of elasticity, equilibrium water absorption percentage, thermal stability, and the crystal orientation ratio of composites increased. The coupling agents such as salicylic acid, maleic anhydride, and phthalic anhydride were used, which resulted in positive effect on tensile properties, water absorption, thermal stability and percentages of crystallinity of rHDPE/WF composites. Whereas the presence of coupling agents had increased the tensile strength, modulus of elasticity, thermal stability and crystal orientation ratio but decreased the elongation at break, water absorption and interparticle spacing (d). The results of various coupling agents on properties of rHDPE/WF30 composites have been examined. The study was showed that rHDPE/WFm/MAH composites showed higher tensile strength, modulus of elasticity, thermal stability and crystal orientation ratio followed by rHDPE/WFm/PAH composites > rHDPE/WFm (wood fiber treated salicylic acid) composites > rHDPE/WF composites in orders. Furthermore, lower the elongation at break, lower percentage equilibrium water absorption and lower interparticle spacing (d). The scanning electron microscopy (SEM) micrographs of tensile fracture surfaces for the composites with coupling agents of salicylic acid, maleic anhydride, and phthalic anhydride indicated that the interfacial interaction and adhesion between WF and rHDPE phases were better than rHDPE/WF composites.