(161ag) Sustainable and Degradable Epoxy Resins Containing Multifunctional Biobased Components

Lignin was investigated as a sustainable source to produce epoxy resins with desirable physical behavior. Epoxy resins are thermoset polymers widely used in composites, coatings and adhesives, with applications spanning automotive and aerospace industries, structural components, and wind turbine blades, among others. Vanillic acid, a product of lignin depolymerization, was investigated as a replacement for the diglycidyl ether of bisphenol A (DGEBA) in anhydride-cured epoxy resins. Vanillic acid was functionalized with epoxide groups and subsequently cured with an anhydride curing agent. The resulting vanillic acid-based epoxy resins exhibited high glass transition temperatures and similar elongation at break and tensile toughness as compared to conventional DGEBA-based epoxy resins. The presence of ester groups in the cured network was also exploited as a route to enhance the end-of-life options for the epoxy resins. The accelerated hydrolytic degradation behavior of the ester-containing epoxy resins was explored, through monitoring of the polymer mass loss after exposure to a basic solution at moderate temperatures. The vanillic acid-based epoxy resins exhibited rapid degradation in a basic solution, in contrast to the slow degradation rate of the traditional DGEBA-based epoxy resin. The mass loss behavior showed good agreement with predictions from a solid-state kinetic model and mass spectrometry confirmed the mechanism was surface erosion through ester hydrolysis. For comparison purposes, accelerated hydrolytic degradation behavior under mild acidic conditions was also explored. Another degradation model was proposed to describe the degradation behavior of vanillic acid-based epoxy resin in acidic media and mass spectrometry and Fourier-transform infrared spectroscopy confirmed the mechanism was bulk erosion through ester hydrolysis.