Dynamic mechanical analysis of tropical wood-polymer composites

Abstract

Wood-polymer composites (WPC) of Geronggang (GE; Cratoxylon arborescens), a light tropical hardwood, impregnated with methyl methacrylate (MMA) and styrene-co-acrylonitrile (3:2; STAN), were prepared by in situ polymerization using γ radiation or catalyst-heat treatment. The dynamic flexural storage modulus, E′, for oven-dried GE, moist GE, and GE-MMA and GE-STAN composites decreased with increasing temperature. The percentage decreases for GE with 10 and 16.5% moisture contents were 74.5 and 98.2%, respectively, which were higher than those for GE and GE composites, which ranged between 40 and 50%. The impregnated polymers were not as effective as water in acting as plasticizers, due to their nonpolar nature and much higher molecular weights. The α-transition peaks for moist GE and GE composites were more distinct and were shifted to lower temperatures than those for oven-dried GE. The values ranged between 75 and 150°C for moist GE and between 102 and 170°C for the GE composites. The α-transitions of the catalyst-heat-treated GE composites were lower than that of the radiation-induced counterparts. GE-STAN composites were also observed to have lower α-transition temperatures than those for GE-MMA for the respective treatment process, which seems to suggest that STAN interacted to a greater extent with cell wall components than did MMA.