Degradation Behavior of Biobased Epoxy Resins in Mild Acidic Media
Minjie Shen, Megan L. Robertson
Abstract
The accelerated hydrolytic degradation of biobased epoxy resins, prepared through anhydride curing of epoxidized vanillic acid (EVA, a product of lignin depolymerization) and epoxidized soybean oil (ESO), was investigated in acidic solutions. The biobased epoxy resins exhibited sigmoidal degradation kinetics in acidic solutions, consistent with bulk erosion mechanisms observed in linear polyesters. By contrast, earlier work reported surface erosion behavior of these biobased epoxy resins in basic solution. A solid-state reaction order model with autocatalysis was utilized to predict the mass fraction remaining as a function of exposure time in acidic solution, and the data and model were in good agreement. Mass spectrometry and Fourier transform infrared spectroscopy analyses confirmed the degradation mechanism as cleavage of ester groups in the cross-linked structures. The influences of solvent composition and temperature on degradation kinetics were also explored. These results demonstrate that ester-containing epoxy resins undergo hydrolysis in acidic solutions, providing a route for end-of-life management of thermoset waste.