Influence of the reactive diluent on electron beam curable funtionalized N-(4-hydroxyl phenyl) maleimide derivatives – Studies on thermal degradation kinetics using model free approach

Highlights: • Materials with maleimide and NVP ratio of 80:20 show better thermal stability. • The initial degradation temperatures are high at higher NVP concentration. • The E_a values for ENVP are low compared to other materials investigated. • Polymers derived from DCNX needs highest E_a value. • Cyanate ester functionalized materials offers better thermal stability. - Abstract: Electron beam curing of N-(4-acryloyloxy phenyl) maleimide, N-(4-methacryloyloxy phenyl) maleimide, and N-(4-cyanato phenyl) maleimide with different concentrations (80:20, 60:40, 40:60, and 20:80) of the reactive diluent N-vinylpyrrolidone (NVP) and pure NVP were investigated. The structures of all the polymers prepared were confirmed by FTIR studies and to understand the effect of the diluent concentration on the thermal stabilities of the E-beam cured polymers detailed thermogravimetric analyses were carried out. The thermal degradation kinetics is investigated using Vyazovkin, Flynn–Wall–Ozawa and Friedman methods. Of all the liquid compositions investigated materials with functionalized maleimide to NVP concentration in the ratio of 80:20 need highest activation energies for the thermal degradation and are found to have better thermal stabilities. The composition N-(4-cyanato phenyl) maleimide (80%) and NVP (20%) cured by E-beam radiation (400 kGy) lead to thermoset which showed the highest char value (30%) at 600 °C in nitrogen atmosphere