Toughening modification of cyanate ester with amino-terminated polyoxypropylene

Abstract

An amino-terminated polyoxypropylene (DA2000) was used to modify a bisphenol A-type cyanate ester resin (BADCy). A series of BADCy/DA2000 resins with different DA2000 contents were prepared and investigated by mechanical tests, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The results of mechanical tests demonstrated that the addition of DA2000 improved the bending and tensile strength of the modified resins. Compared with those of pure BADCy, the K IC and G IC values of the modified resins increased, indicating an improvement in toughness of the resin system. The DMA curves of modified resins showed that the storage moduli dropped with the increase in temperature and the T g values decreased with the increase in modifier content. Simultaneously, the moduli showed different changing trend at different temperature stages, indicating the existence of phase separation, which was also demonstrated by the fracture morphologies. At 20 wt% of DA2000 content, the fracture surface showed its characteristic strong ductile tear. Based on the above results, it was concluded that the –NH2 groups of DA2000 reacted with the –OCN groups of triazine ring to form flexible segments, which were embedded into the main chains of the curing network; the distance between the triazine rings increased, the cross-link density decreased and the yield deformation of the system was enhanced. Meanwhile, DA2000 reacted with BADCy monomers to form linear macromolecular chains, which interpenetrated into the network matrix, and enhanced the plastic deformation of the system. The formation of flexible segments, low cross-link density and the yield and plastics properties led to toughened cyanate ester (CE) resins.