Abstract
Several kinds of epoxy resins having biphenyl structure were synthesized, and the relation between the strucrure and properties of their cured products with phenol novolac was studied.
The measurements of fracture toughness of the cured products showed that the epoxy resin prepared from 4, 4′-dihydroxybiphenyl exhibited higher fracture resistance than 2, 2'-isomer. 4, 4′-isomer gave small storage modulus below Tg in dynamic mechanical analysis and gave small specific gravity, depending on its increased free volume fraction caused by the prevention of packing of molecular chains in cured product of epoxy resin having a stiff backbone like 4, 4′-biphenyl structure. The increased toughness of 4, 4′-isomer seems due to the increase of plastic deformation at crack-tip because of its large free volume fraction.
