CO-CONTINUOUS, WOOD-POLYMER COMPOSITES WITH IMPROVED FIRE RESISTANCE
Scott A. Eastman, Alan J. Lesser, and Thomas J. McCarthy
A composite fabrication method has been designed to incorporate polymer precursors into bulk cellulosic substrates and subsequently crosslink the additives in situ. This process utilizes supercritical CO2 as a transport and reaction medium resulting in co-continuous, cellulosic composites that have been uniformly infused with crosslinked silicone. Improvements in flexural properties of cellulosic-silicone composites were determined to depend on the cellular morphology of the cellulosic substrate as well as the composition of the incorporated additive. Flexural properties of the composite after thermal degradation were significantly improved compared to the virgin aspen char. Energy release rate, total energy released, and char yield of the cellulosic-silicone composites were improvement for all cellulosic substrates after the incorporation of silicone. Samples were also exposed to a controlled thermo-oxidative environment under an applied stress to measure lifetimes of each sample at given temperatures and stress levels. The data were subjected to an Arrhenius analysis and show a good linear correlation. The composite systems demonstrate significantly longer lifetimes than virgin substrates and the Arrhenius analysis suggest that no change in the chemical degradation mechanism has occurred.