EFFECT OF NETWORK STRUCTURE ON THERMAL AND MECHANICAL-PROPERTIES OF BIPHENOL-TYPE EPOXY-RESINS CURED WITH PHENOLS

In the biphenol-type epoxy resin cured with catechol novolac (CN), a v ery weak glass transition and, thus, a very high rubbery modulus were observed. On the other hand, the glass transition was clearly observed in the system cured with phenol novolac (PN). This means that the mic ro-Brownian motion of network chains is highly suppressed in the syste m cured with CN. The reason for this suppression of the chain motion i n the CN-cured system has been pursued from the viewpoint of the confo rmation of network chains. The disappearance of the glass transition i n the biphenol-type resin depends on the formation of the active hydro gens in the curing agents. Thus, it was suggested that the suppression of the micro-Brownian motion is due to the orientation of the bipheny l groups in the network. Moreover, it has been shown that the mechanic al and bonding strength at high temperature is considerably improved b y the suppression of the network chain motion in the CN-cured biphenol resin system. (C) 1995 John Wiley and Sons, Inc.