Effect of long-term thermo-oxidative aging on weight and fracture toughness of polycyanate neat resin

This study focuses on the effect of long-term thermo-oxidative aging on weight and fracture toughness (K_IC) of polycyanate ester (PCy) neat resin (FSD-M-08178). Thermo-oxidative aging was conducted at 180 °C up to 8000 h under atmospheric pressure in order to investigate susceptibility to thermo-oxidative environment in the PCy. Weight and K_IC changes were investigated with chemical structure changes due to thermo-oxidative degradation. The chemical structure changes were analyzed by means of Fourier transformed infrared spectroscopy with attenuated total reflection system. To investigate degree of degradation, carbonyl index (CI) was analyzed with triazine ring peak which is characteristic peak of the cured polycyanate resin. Single-edge-notch bending test was conducted for each aged (non-aged, 100, 197, 500, 1000, 2000, 4000, and 8000 h) condition to investigate K_IC change and evaluated with CI. The result indicated that the weight increased first 500 h. Then, the weight decreased. The result also indicated that the K_IC sharply dropped first 100 h. After 100 h, the K_IC was almost same up to 8000 h. The result suggested the K_IC depend on the CI which was chemical structure changes of the specimen surface due to thermo-oxidation degradation.