Nanostructure in hybrid thermosets with interpenetrating networks and its effect on properties

Hybrid resins composed of vinylester (VE) and aliphatic amine (Al-Am)-cured cycloaliphatic epoxy (Cal-EP) were produced and their morphology and properties (toughness, water uptake) determined. According to atomic force microscopy (AFM) results achieved on physically etched (ion eroded) specimens the hybrid resins possessed a nanoscaled interpenetrating network (IPN) structure, the characteristics of which depended on the VE/EP ratio. Characteristics of the IPN morphology, viz strand width and mean roughness data increase with increasing amount of the EP component. The fracture mechanical data (K(Q) and G(Q)) pass a maximum as a function of the VE/EP ratio, similar to that of the phase segregation term (alpha). The latter was deduced from dynamic-mechanical thermal analysis (DMTA) traces. The water sorption and diffusion behavior of the interpenetrated VE/EP hybrids were controlled by the relative amount of the EP (Cal-EP+Al-Am) used.