Injection molded silane crosslinkable rice straw/high density polyethlene biocomposite

Abstract

A formulation was designed to produce silane crosslinked rice straw/High Density Polyethylene (RSPE) compound suitable for injection molding process. The formulation consist of HDPE as the base polymer, rice straw as the filler, processing aids and a mixture of crosslink chemicals. Crosslink chemicals consist of vinyltrimethoxysilane (VTMO) as crosslinking agent, dicumyl peroxide (DCP) as the initiator and dibutyltin dilaurate (DBTL) as the condensation catalyst. The rice straw was oven dried at 70ºC for 24 hours, grinded and followed by sieved. A counter rotating twin shaft high speed mixer was utilized to mix the rice straw, HDPE and the processing aids. The blends were then compounded on twin screw extruder. Test specimens were prepared via injection molding process followed by oven cured at 90ºC. Fourier Transform Infra Red (FTIR) was used to determine the chemical functional group involved in the crosslinking reaction. Degree of crosslinking in the silane crosslinked compounds was measured by determining the gel content. Thermal properties were analyzed on the Differential Scanning Calorimetry (DSC) for the melt temperature whereas Thermogravimetry Analysis (TGA) for its thermal stability behavior. The degree of crosslinking in RSPE increased with an increased in VTMO and DCP concentration. The results from FTIR showed the presence of Si-O-Si bond and Si-O-C indicative of crosslinks formation. Thermal stability of the compound illustrated that the crosslinked RSPE was more stable than the uncrosslinked RSPE while the melting point was unchanged. Tensile strength and flexural strength improved after crosslinking and increased with the amount of VTMO and DCP, whilst impact strength showed an optimum value with respect to crosslink chemicals composition. The concentration of 3 phr VTMO, 0.5 PHR dcp AND 0.015 phr DBTL was the optimum crosslinked chemical composition to produce the crosslinked RSPE, significant properties enhancement.