(246c) Effects of Copolymer Composition and Polymer Crystallinity in Thermal Transitions in Carbon Dioxide and Foaming Outcomes of Ethylene Copolymers

The foaming with carbon dioxide of three copolymers with varying compositions has been studied to understand the role of crystallinity in governing the foaming outcomes of poly(ethylene-co-vinyl acetate-co-carbon monoxide) (EVACO). In this talk we will present recent findings on the high-pressure characterization and foaming of EVACO-0010, EVACO-1010, and EVACO-2010 in carbon dioxide. The number designations refer to the vinyl acetate (0, 10, and 20 %) and carbon monoxide content (10 %) with the remainder by ethylene.

High-Pressure Torsional Braid Analysis (HP-TBA) characterizations have been performed at 50, 100, 150, 200, and 250 bar in carbon dioxide. HP-TBA allowed for the determination and mapping of the depression of both the melting and crystallization temperatures of these polymers in the presence of carbon dioxide. Saturation pressure of 200 bar in carbon dioxide was found to lead to the greatest reduction in T_m and T_c for each of these polymers. Assessments of the sorption of carbon dioxide with MSB shows that increasing vinyl acetate content leads to an increase the level of carbon dioxide sorption.

Foams were characterized for their average pore size and pore distribution along with assessments of the bulk foam density and outcomes are linked to the depressed thermal transitions in carbon dioxide.