Degradation Behavior of Biobased Epoxy Resins in Mild Acidic Media

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.

Recent development on bio‐based thermosetting resins

“…Owing to the epoxy group can also be cured by carboxyl or anhydride, based on which, the ester‐containing and biodegradable networks can be obtained directly 20 . Robertson and coworkers carefully investigated the degradation mechanism of ester‐containing bio‐based epoxy resin under both acid and alkali conditions 82,83 . Varganici and coworkers 84 developed an epoxy coating derived from vegetable oil and rosin acid, which not only exhibited good adhesion to wood, but also showed antifungal effect by blocking the entry of water and fungi.…”

Harnessing autocatalytic reactions in polymerization and depolymerization

“…Similar to polymerization, free radicals play central roles in degradation and depolymerization of polymers [17,18] . In a series of papers by Simha and coworkers [30][31][32] , free-radical depolymerization was described by assuming that it follows similar four steps as in polymerization: initiation/generation of radicals, propagation along a chain, chain transfer (inter-and intrachain), and termination.…”

“…These databases and neural networks, trained on models capable of describing autocatalysis (e.g., by Lotka-Volterra equations [12,13] ), can be used to understand various aspects of autocatalysis in polymerizations. [14][15][16] Furthermore, many decomposition [17,18] reactions such as those involved in photooxidation are autocatalytic in nature and in certain cases, [19] external forces such as fluid flow can be used to further accelerate various reactions. A detailed understanding of autoacceleration in these reactions will be useful for designing the next generation of energy-efficient chemical upcycling protocols, [18] photo-initiated polymerizations [20] relevant to 3D printing processes, and design of supramolecular polymeric materials such as self-generating micelles.…”

“…[14][15][16] Furthermore, many decomposition [17,18] reactions such as those involved in photooxidation are autocatalytic in nature and in certain cases, [19] external forces such as fluid flow can be used to further accelerate various reactions. A detailed understanding of autoacceleration in these reactions will be useful for designing the next generation of energy-efficient chemical upcycling protocols, [18] photo-initiated polymerizations [20] relevant to 3D printing processes, and design of supramolecular polymeric materials such as self-generating micelles. [6] In this prospective article, we discuss the most interesting directions of research relevant to polymers based on the concepts of physical and chemical autocatalysis.…”

Estrogenic activity of lignin-derivable alternatives to bisphenol A assessed via molecular docking simulations

“…Lignin is the most abundant feedstock for potential biobased aromatic chemicals and serves as a platform for the development of a wide range of renewable polymers. 1,2,4,[24][25][26][27][28][29][30][31][32][33][34][35][36] Bulk lignin mainly consists of three subunits: p-hydroxyphenyl (H) (no methoxy groups on the aromatic ring), guaiacyl (G) (one methoxy group on the aromatic ring [monomethoxy]), and syringyl (S) (two methoxy groups on the aromatic ring [dimethoxy]) groups. 1,2,4,33,37 The compositions of these units can vary as a function of biomass source: sowoods contain a majority of G units, hardwood include a mixture of G and S units, and grasses contain a mixture of H, G, and S units.…”