Adjunct Professor University of Minnesota Saint Paul, Minnesota, United States
Abstract: PVC is the third largest commodity plastic useful for versatile applications when compounded with plasticizers that impart flexibility. The most prevalent class of plasticizers are petroleum derived phthalate esters that have EHS concerns. In this study a series of bioplasticizers, epoxy fatty acid ester estolides were synthesized and evaluated as alternative plasticizers to phthalates. Soy fatty acid alkyl esters were prepared by transesterification with various aliphatic alcohols (methyl, n-butyl, n-pentyl, mixed pentyl, 2-ethylhexyl, and isononyl). The double bonds of the fatty acid esters were epoxidized using in situ generated peracetic acid in the presence of solid acid catalyst, Amberlite IR120. The epoxy fatty acid esters were partially ring opened with acetic anhydride to yield the final products, epoxy fatty acid ester estolides. The epoxy fatty acid ester estolides thus prepared were characterized by NMR and their properties determined. The experimental plasticizers were compounded with PVC by a plastisol method and their plasticizer properties, such as volatility, gelation, hardness, efficiency, water storage, and compatibility were evaluated and compared to commercial plasticizers, diisononyl phthalate (DINP) and cyclohexane-1,2-dicarboxylic acid, diisononyl ester (DINCH, Elatur® CH). The lower molecular weight experimental plasticizer methyl ester showed excellent gelation properties that can be useful as fast fuser in plasticizer formulations but had high volatility compared to commercial plasticizers. The higher molecular weight of experimental plasticizers 2-ethylhexyl and isononyl esters showed inferior properties compared to commercial plasticizers. The medium molecular weight butyl and pentyl esters showed comparable or better plasticizer properties and are good candidates to replace the phthalates in many PVC applications.
