Effects of filler content and various coupling agents on properties of polypropylene/cocoa pod husk biocomposites

Abstract

Chemical modification plays an important role in enhancing interfacial adhesion in thermoplastic biocomposites. In this study, the cocoa pod husk (CPH) filled polypropylene (PP) biocomposites were prepared using Brabender Plastrograph EC Plus intermixer at temperature of 180oC and rotor speed of 50 rpm. The effect of CPH content and chemical modification using different types of commercial coupling agents (such as, maleated polypropylene (MAPP), methacrylic acid (MAA), sodium dodecyl sulfate (SDS), and 3-mercapropyltrimethoxysilane (MPS)), and new green coupling agents (GCA) developed from virgin coconut oil (GCA-C) and palm oil (GCA-P) on processing torque, tensile properties, water absorption behavior, morphological, thermal and rheological properties of PP/CPH biocomposites were investigated. The results found that the increases of CPH content increased the processing torque, Young’s modulus, water absorption, crystallinity, but reduced the elongation at break and tensile strength of PP/CPH biocomposites. The incorporation of CPH cause the early thermal degradation of PP/CPH biocomposites, but at higher temperature the thermal stability increased with increases of CPH content. Scanning electron microscopy (SEM) evidenced the poor interfacial adhesion between CPH and PP matrix. The increases of CPH content increased the pseudoplastic characteristic, viscosity and activation energy (Ea) of PP/CPH biocomposites.