Formation of interfacial network structure via photo- crosslinking in carbon fiber/epoxy composites

A series of diblock copolymers (poly(n-butylacrylate)-co-poly(2-hydroxyethyl acrylate))-b-poly(glycidyl methacrylate) ((PnBA-co-PHEA)-b-PGMA), containing a random copolymer block PnBA-co-PHEA, were successfully synthesized by atom transfer radical polymerization (ATRP). After being chemically grafted onto carbon fibers, the photo- sensitive methacrylic groups were introduced into the random copolymer, giving a series of copolymers (poly(n-butylacry- late)-co-poly(2-methacryloyloxyethyl acrylate))-b-poly(glycidyl methacrylate)((PnBA-co-PMEA)-b-PGMA). Dynamic mechanical analysis indicated that the random copolymer block after ultraviolet (UV) irradiation was a lightly crosslinked polymer and acted as an elastomer, forming a photo-crosslinked network structure at the interface of carbon fiber/epoxy composites. Microbond test showed that such an interfacial network structure greatly improved the cohesive strength and effectively controlled the deformation ability of the flexible interlayer. Furthermore, three kinds of interfacial network structures, i) physical crosslinking by H-bonds, ii) chemical crosslinking by photopolymerization, and iii) interpenetrat- ing crosslinked network by photopolymerization and epoxy curing reaction were received in carbon fiber/epoxy composite, depending on the various preparation processes.