Synthesis of networks and interpenetrating networks from functionalized castor and soybean oils

Abstract

In this study, castor oil is maleated to give maleated castor oil (COMA). This macromonomer is capable of reacting as epoxy curing agent through its carboxylic end as well as undergoing free radical polymerization with polymerizable vinyl monomers through its double bond. The maleation of castor oil is carried out using the methodology known in literature with some small modifications increasing the maleation extent. COMA is then reacted with epoxidized soybean oil (ESO) to give a thermoset polymer ESOCOMA, as the initial network. The double bonds on maleate groups of COMA which are still intact and available to react, are then polymerized in presence of a free radical initiator to give a second interpenetrating network. This network is entirely composed of two functionalized triglycerides. Reaction of COMA and ESO with a vinyl group bearing monomer, styrene, in presence of free radical initiators resulted in a simultaneous interpenetrating network abbreviated here as Styrene-X. Another interpenetrating network is formed by using an oil based macromonomer instead of styrene, acrylated epoxidized soybean oil (AESO) to give AESO-X. All of the networks produced have considerably high oil content, especially AESO-X is unique in the sense that only the maleate and the acrylate modifications are the non-oil based portions resulting in a very high oil content of 80%. The products obtained from these reactions are all insoluble in common organic solvents so the characterization is done by FTIR. The thermal and mechanical tests such as DSC (Differential Scanning Calorimetry), DMA (Dynamic Mechanical Analysis) are carried out to further analyze the properties of the thermosets. The optimum stoichiometry for ESO/COMA is determined by surface hardness values measured by durometer whereas the effects of compositions of styrene and AESO monomers were analyzed by DMA experiments. COMA is also reacted with commercially available epoxy resins to give clear, tough, high tensile strengths thermosets. The optimization and characterization studies of COMA as an epoxy curing agent are currently in progress.