Abstract
Toughening of cycloaliphatic epoxy resin with polyvinyl formal resins (PVF) that have good compatibility with the epoxy resin was investigated. The fracture energy in tensile tests and KIC in fracture toughness tests of the cured resin modified with 10wt% of PVF are three times and 1.3 times higher than those of the unmodified cured resins, respectively. In addition, the modified epoxy resins maintain high glass transition temperature (Tg>200℃) and high transparency even after the addition of PVF. The fractured surfaces of the unmodified and PVF-modified resins were observed with Atomic Force Microscope (AFM). It was clearly shown that the diameter of microgel increased considerably and its boundary became to be indistinct with the addition of PVF. These mean that the coexistence of PVF molecules in the gelation process of the epoxy resin suppressed the formation of the microgel. Such a suppression of the formation of microgel results in the increase in the toughness of the cured resins. SynopsisToughening of cycloaliphatic epoxy resin with polyvinyl formal resins (PVF) that have good compatibility with the epoxy resin was investigated. The fracture energy in tensile tests and KIC in fracture toughness tests of the cured resin modified with 10wt% of PVF are three times and 1.3 times higher than those of the unmodified cured resins, respectively. In addition, the modified epoxy resins maintain high glass transition temperature (Tg>200℃) and high transparency even after the addition of PVF. The fractured surfaces of the unmodified and PVF-modified resins were observed with Atomic Force Microscope (AFM). It was clearly shown that the diameter of microgel increased considerably and its boundary became to be indistinct with the addition of PVF. These mean that the coexistence of PVF molecules in the gelation process of the epoxy resin suppressed the formation of the microgel. Such a suppression of the formation of microgel results in the increase in the toughness of the cured resins.
