Biobased epoxy resins, derived from lignin, phenolic acids, and vegetable oils, exhibited rapid degradation through hydrolysis in basic solution.

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.

The production of thermoset polymers is increasing globally owing to their advantageous properties, particularly when applied as composite materials. Though these materials are traditionally used in more durable, longer-lasting applications, ultimately, they become waste at the end of their usable lifetimes. Current recycling practices are not applicable to traditional thermoset waste, owing to their network structures and lack of processability. Recently, researchers have been developing thermoset polymers with the right functionalities to be chemically degraded under relatively benign conditions postuse, providing a route to future management of thermoset waste. This review presents thermosets containing hydrolytically or solvolytically cleavable bonds, such as esters and acetals. Hydrolysis and solvolysis mechanisms are discussed, and various factors that influence the degradation rates are examined. Degradable thermosets with impressive mechanical, thermal, and adhesion behavior are discussed, illustrating that the design of material end-of-life need not limit material performance.

Spiro polycycloacetals were synthesized from vanillin and syringaldehyde, along with high-performance co-monomers, exhibiting high glass transition temperatures and thermal stabilities, and rapid rates of hydrolysis in acidic solutions.