Effect of Silane Crosslinker on the Thermal Properties of Rice Straw/HDPE Biocomposite

Abstract

A formulation was designed to produce silane crosslinkable rice straw/high density polyethylene (RSPE) compound suitable for injection molding process. The formulations consist of high density polyethylene (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, dibutyltin dilaurate (DBTL) as the condensation catalyst. Lignocellulosic material, rice straw was oven dried at 70°C for 24 h, grinded and sieved. A counter rotating twin shaft high speed mixer was utilized to mix the rice straw, HDPE and the processing aids. Blends were then compounded on co-rotating and intermeshing twin screw extruder. Test specimens were prepared via injection molding process followed by oven curing at 90°C. Fourier Transform Infra Red (FTIR) was used to determine the chemical group involved in the crosslinking reaction. Degree of crosslinking in the silane crosslinked compound was measured by determining their gel content. Thermal properties were analyzed on the Differential Scanning Calorimetry (DSC) for the melt temperature, Tm, whereas Thermogravimetric (TGA) analysis for its thermal stability behavior. The degree of crosslinking in RSPE increases 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 behavior of the compound illustrated that the crosslinked RSPE was more stable than the uncrosslinked RSPE and pure HDPE, while the Tm was unchanged.