Recyclable carbon fiber‐reinforced plastics (CFRP) containing degradable acetal linkages: Synthesis, properties, and chemical recycling

Abstract

Two epoxy resins containing degradable acetal linkages were synthesized by the reaction of cresol novolak-type phenolic resin (CN) with vinyl ethers containing a glycidyl group [cyclohexane dimethanol vinyl glycidyl ether (CHDMVG) and 4-vinyloxybutyl glycidyl ether (VBGE). Carbon fiberreinforced plastics (CFRPs) were prepared by heating laminated prepreg sheets with CN-CHDMVG resin (derived from CN and CHDMVG) and CN-VBGE resin (derived from CN and VBGE), in which carbon fibers are impregnated with epoxy resins containing curing agents [dicyandiamide (DICY)] and curing accelerator [3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)]. CN-CHDMVG-based CFRPs and CN-VBGE-based CFRPs exhibited almost the same tensile strength as the conventional bisphenol-A-based CFRPs. CN-CHDMVG-based CFRPs andCN-VBGE-based CFRPs underwent smooth breakdown with the treatment of hydrochloric acid in tetrahydrofuran at room temperature for 24 h to regenerate strands of carbon fibers. The surface conditions of the recovered carbon fibers had little changes during degradation and recovery processes on the basis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The recovered carbon fibers exhibited almost the same tensile strength as virgin carbon fibers and hence would be reused for the production of CFRPs.

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

“…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,.…”

Synthesis of crosslinked PEG/IL blend membrane via one‐pot thiol–ene/epoxy chemistry

“…Epoxy resins, or called polyepoxides, are a class of polymers formed by monomers or oligomers containing epoxy groups, usually with the presence of crosslinkers, such as amines. The excellent chemical and thermal resistance, good mechanical properties, and notable adhesion of epoxy resins allow them to play important roles in various industrial applications, such as coating, reinforcement, and adhesives . Recently, several groups have expanded these materials to gas separation, especially as CO 2 separation membranes, thanks to the facile and rapid crosslinking, tunable chemical structure and the presence of secondary amines .…”

Simultaneous Recovery of Matrix and Fiber in Carbon Reinforced Composites through a Diels–Alder Solvolysis Process

“…The system was used to recover carbon and flax fibers from epoxy composites [10,11]. Analogous approaches require the introduction of tertiary amine [12] or acetal functionalities [13] into an epoxy cleavable network that could undergo de-crosslinking and allow fiber recovery from acidic media. A step forward in the valorization of the recovered matrix was made possible with the introduction of the concept of covalent adaptable networks (CANs) [14], which enables re-crosslinking the matrix after fiber recovery.…”