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

Abstract

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 °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. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Epoxy Matrices Modified by Green Additives for Recyclable Materials

“…Promising resultsa re obtained on modified epoxy matrices, which are designed for decomposition by an externalc hemical trigger mechanism. Cured epoxies containing acetals in tetrahydrofuran and hydrochloric acid, [5] esters in aqueous sodium hydroxide, [6] and aminals in concentrated sulfonic acid [7] all show degradablep otential. Likewise, concentrated hydrochlorica cid and either ethylene glycol, heptane, or octanehave been demonstrated to fractionate an epoxy matrix containing av ariety of substituted ketal and/or acetal functionalities.…”

Multiply fully recyclable carbon fibre reinforced heat-resistant covalent thermosetting advanced composites

“…So far, three CFRC systems towards this goal have been built by creatively using relatively weak and unstable dynamic covalent structures (Table 1)101112131415161718192021. The first one is the dynamic acetal [-O-CH(CH 3 )-O-] epoxy system established by Hashimoto et al 15,. which can degrade easily via the acid hydrolysis of acetal linkages at room temperature and then generates undamaged but partially disordered CFs1516.…”

“…The first one is the dynamic acetal [-O-CH(CH 3 )-O-] epoxy system established by Hashimoto et al 15,. which can degrade easily via the acid hydrolysis of acetal linkages at room temperature and then generates undamaged but partially disordered CFs1516. The second one is the dynamic polyimine [-C=N-] system brought up by Taynton et al 1718,.…”

Hydrolytic degradation of ROMP thermosetting materials catalysed by bio-derived acids and enzymes: from networks to linear materials

“…The thermosetting materials (6)(7)(8)(9)(10)(11)(12)(13) were prepared by copolymerisation reaction of either 1 or 2, and different amounts of cross-linking agent 3, Scheme 2.…”

“…3,4 Furthermore, epoxy resins containing acetal linkages in the polymer backbone have been shown to degrade into small soluble fragments when subjected to acid catalysed hydrolysis using phosphoric acid 5 and hydrochloric acid. 6 Linear poly(amidoamine)s containing acetal or ketal groups in the polymer backbone have also been reported to degrade in buffer solution at pH 5 affording low molecular weight and soluble fragments. 7 Furthermore, linear poly(1,4-phenylene dimethylene ketal) which contains ketal linkages in its backbone has been subjected to acid catalysed hydrolysis at pH 1.0 to 7.4 using buffer solutions, yielding low molecular weight fragments.…”