Biobased Epoxy Resin by Electrochemical Modification of Tall Oil Fatty Acids

A biobased epoxy resin was prepared from tall oil fatty acids (TOFAs), a byproduct of the pulping industry. As free carboxylic acids compromise resin stability, TOFA was subjected to non-Kolbe decarboxylation to give alkenes upon loss of CO₂. Thereby, the degree of unsaturation is significantly increased. This electrosynthetic protocol using an undivided cell setup and inexpensive graphite electrodes in a galvanostatic operation mode was scaled to a 1.5 L reactor, making use of electric current as a green and waste-free reagent. Simple, cost-efficient epoxidation using oxone subsequently gives an epoxy resin of low viscosity. Curing with anhydrides yields thermoset materials. Dynamic mechanical analyses and tensile and flexural tests were conducted to determine the effect of different curing agents on the thermomechanical properties. For methyl tetrahydrophthalic anhydride (MTHPA) and methyl-5-norbornene-2,3-dicarboxylic anhydride (MNA), good mechanical properties were observed, whereas dodecenyl succinic anhydride (DDSA) resulted in a brittle material with low T_g.