Dual-curing propargyl/phthalonitrile monomers for composites by vacuum infusion process

Four different bifunctional monomers were synthesized: two monomers containing N- propargylamine and phthalonitrile groups and two monomers containing O-propargyl ester and phthalonitrile groups. It was shown that only the latter one can be used to obtain composite materials by vacuum infusion (viscosity 40 mPa*s at 120 °C. The N-propargylamine containing monomers demonstrated high viscosity of the melts and degradation with allene evolution while curing. Carbon fiber reinforced plastics (CFRP) were successfully obtained from 4-[3-(prop-2-yn-I-yloxy)phenoxy]benzene-I,2-dicarbonitrile by a vacuum infusion molding process. Mechanical testing of the composites samples was performed. Influence of end-curing temperature on mechanical properties and morphology of composites was investigated. The curing temperature of 375 °C critically affects the properties of the composite due to the high shrinkage. Composites cured at 375 °C lost 18% of mechanical properties at 300 °C but cured at 330 only 10%. LOI for composites with a matrix of propargyl/phthalonitrile dual-curing polymers was equal to 75, which is higher than most materials obtained from thermosets.