Effect of CTBN Concentration on Thermal and Morphological Properties of Binary Copolymers of o-Cresol Novolac Epoxy Resin and Bismaleimide

Reactive rubber is the most used material to improve toughness of epoxy resins. Allylated o-cresol novolac resin with certain allylation degree was prepared and characterized, then was used to cure o-cresol novolac epoxy resin and 4,4'-Bismaleimide to prepare a heat-resistant epoxy resin. So, CTBN was introduced to improve its toughness. The effect of CTBN on thermal stability and morphology were studied. With the increase of CTBN, the storage modulus of BACC resins was increased basically indicating that CTBN was homogeneously dispersed in the matrix, and there were two glass transition temperatures of BACC resins indicating that the poor compatible between BACC and CTBN than between epoxy resin and CTBN. From the morphology of BACC resins, the effect of CTBN was similar to the other terminally reactive rubber. When the content was small, there was homogenous distribution of smaller CTBN particles in cured BACC matrix, and then the phase inversion occurred with the increase of CTBN. So, in order to improve toughness of cured BACC resin, a homogenous distribution of smaller CTBN particles is necessary. These conclusions revealed that the properties of BACC resins can be tailored and it must be useful to direct design of materials.