Viscosity characteristics of some para‐nonylphenol formaldehyde novolac epoxy resins

Para-nonylphenol formaldehyde novolac epoxy resins with molecular weights between 640 and 3150 were studied regarding the viscosity behaviour. The estimation of both the intrinsic viscosity and the molecular weight of the epoxidized resins resulted in a straight relationship between these experimental parameters: [η] = k1 + k2Mn, where k1 = 137 dl/g and k2 = 99.2·10−3 dl/g. Study of the flow behaviour of the molten epoxide resins allowed the measurement of the apparent shear viscosity, the shear stress, the shift factor, the melt flow index, the consistency index, and the flow activation energy. The flow data, which were analysed both as a function of temperature and of the shear rate, led to the conclusion that para-nonylphenol formaldehyde novolac epoxy resins show a non-Newtonian rheological behaviour of pseudoplastic type.