Rheology of Injection Molded Oil Palm Empty Fruit Bunch Fiber-Polypropylene Composites: Effects of Electron Beam Processing

摘要

In this study, polypropylene (PP) and oil palm empty fruit bunch fibers (EFB) were irradiated at 10 kGy using an electron accelerator prior to melt mixing to produce composite pellets. Two types of reactive additives that have functional groups of diacrylate and triacrylate were used for preparing the composite pellets. The composites pellets were then subjected to injection molding for preparation of test pieces for physical, mechanical, and rheology properties study. Haake Rheometer RS 150 was used to study the changes in viscosities of the composites at different shear rates. Viscosity change is one of the important parameters in plastic processing particularly in relation to the shear rates for injection molding and extrusion processes. The PP melts showed pseudoplastic behavior. Viscosity was constant at a low shear rate and began to decrease at 5 s~(-1) shear rate. Upon irradiation, the viscosity of the PP decreased due to chain scission and the sudden drop of viscosity at a high shear rate was not significant. The presence of EFB fiber in the PP matrix obviously interrupted the flowability of PP that caused viscosity to increase. Upon irradiation of EFB/PP, the viscosity of the composites decreases. This indicated that no crosslinking occured between the EFB and the PP during melt mixing although PP and EFB active radicals were present in the composites. By adding di- and tri-functional acrylates, however, the viscosity of the irradiated EFB/PP increased significantly. This study showed that di- and tri-functional acrylates play important roles in providing the bridge for a three-dimensional network to be formed between EFB and PP. In this paper, rheology behavior of electron beam irradiated EFB/PP composites were also compared with maleated PP/EFB composites.