Structure and Water Absorption of Starch and Polyethylene-Octene Elastomer Composites

Abstract

Four modified starches, including gelatinized starch (GS), crosslinked starch (CS), oxidized starch (OS) and esterified starch (ES), were blended with polyethylene-octene elastomer (POE) at 20 wt% starch content. The graft copolymer POE-g-MAH acted as a compatibilizer where 5 wt% was added to POE and various starch blends. The crosslinked starch was blended with POE in different proportions and conditioned at various relative humidities (RH), 11%, 32%, 43%, 75% and 100%, respectively until equilibrium to study the water absorption of POE/starch blends. Although different types of starch were used, the mechanical properties of each POE/starch blend were not significantly different. The compatibilizer had an obvious influence on the morphology and mechanical properties of each POE/starch blend. The starch dispersed in POE matrix better and the interfacial adhesion between starch and POE phase improved after adding the POE-g-MAH, also the tensile strength of POE/starch blends increased. With increasing starch content, both the tensile strength and elongation at break of POE/CS blends decreased. The water uptake of POE/CS blends increased with increasing time and starch content. The POE/CS blends without compatibilizer had higher water uptakes than those samples with compatibilizer. After equilibrium at different RH, the tensile strength of POE/CS blends decreased as RH increased, but the elongation at break increased with increasing RH.