Strategy of fabrication of controlled thermosetting gel based on soybean oil towards supercritical carbon dioxide foamingElectronic supplementary information (ESI) available: Orthographic factorial design for preparation of AESO/St gel, time dependence of gel content and extent of polymerization, dependence of storage modulus on extent of polymerization. See DOI: 10.1039/c3gc41506f

To produce soybean oil based foam plastics in terms of the supercritical carbon dioxide foaming technique, the B-stage gel formed by the radical copolymerization of acrylated epoxidized soybean oil (AESO) and styrene (St) was prepared and studied. Accordingly, a dual initiator system consisting of cyclohexanone peroxide (CP) and di- tert -butyl peroxide (DTBP) catalyzed by cobalt octoate (CoOct) was introduced, which provided the gel with (i) good permeability and sufficient thermal stability for saturation in the supercritical carbon dioxide and (ii) polymerizability for freezing the depressurization induced cells during post cure at higher temperatures. The relationships among the reaction processes, structural evolvement and properties variation were characterized and analyzed. Additionally, the experimental results were verified by a numerical simulation. It is hoped that the outcome of this work would not only deepen the understanding of the intermediate status of thermosets, but also help to determine the optimal conditions for fabricating thermosetting foams by supercritical carbon dioxide foaming. A dual initiator system is proposed to fabricate controlled thermosetting gel from soybean oil suitable for supercritical carbon dioxide foaming.