Degradable and chemically recyclable epoxy resins containing acetal linkages: Synthesis, properties, and application for carbon fiber-reinforced plastics

Four sorts of epoxy resins containing degradable acetal linkages were synthesized by the reaction of bisphenol A (BA) or cresol novolak (CN) resin with vinyl ethers containing a glycidyl group [4-vinlyoxybutyl glycidyl ether (VBGE) and cyclohexane dimethanol vinyl glycidyl ether (CHDMVG)] and cured with known typical amine-curing agents. The thermal and mechanical properties of the cured resins were investigated. Among the four cured epoxy resins, the CN-CHDMVG resin (derived from CN and CHDMVE) exhibited relatively high glass transition temperature (Tg = ca. 110 degrees C). The treatment of these cured epoxy resins with aqueous HCl in tetrahydrofuran (THF) at room temperature for 12 h generated BA and CN as degradation main products in high yield. Carbon fiber-reinforced plastics (CFRPs) were prepared by heating the laminated prepreg sheets with BA-CHDMVG (derived from BA and CHDMVE) and CN-CHDMVG, in which strands of carbon fibers are impregnated with the epoxy resins containing conventional curing agents and curing accelerators. The obtained CFRPs showed good appearance and underwent smooth breakdown with the aqueous acid treatment in THF at room temperature for 24 h to produce strands of carbon fiber without damaging their surface conditions and tensile strength. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012