Thermosetting Foam with a High Bio-based Content from Acrylated Epoxidized Soybean Oil and Carbon Dioxide

摘要

A resilient, thermosetting foam system with a bio-based content of 96% was successfully developed. We implemented a pressurized carbon dioxide foaming process that produces polymeric foams from acrylated epoxidized soybean oil (AESO). A study of the cell dynamics of uncured CO-2/ AESO foams proved useful to optimize cure conditions. During collapse, the foam's bulk density increased linearly with time, and the cell size and cell density exhibited power-law degradation rates. Also, low temperature foaming and cure (i.e. high viscosity) are desirable to minimize structural degradation. The AESO was cured with a free-radical initiator (tert-butyl peroxy-2-ethyl hexanoate, T_ⅰ~60°C). Cobalt naphtenate was used as an accelerator to promote quick foam cure at lower temperature (40-50°C). The foam's density was controlled by the carbon dioxide pressure inside the reactor and by the vacuum applied during cure. The viscosity increased linearly during polymerization. The viscosity was proportional to the extent of reaction before gelation, and the cured foam's structure showed a dependence on the time of vacuum application. The average cell size increased and the cell density decreased with foam expansion at a low extent of cure; however, the foam expansion became limited and unhomogeneous with advanced reaction. When vacuum was applied at an intermediate viscosity, samples with densities ~0.25 g/cm3 were obtained with small (