A study of the thermal cure of new trifunctional phenylethynyl terminated imide oligomers with reduced cure temperatures

A series of novel trifunctional phenylethynyl terminated imide oligomers was synthesized from two new triamines, 1,3,5-tris(3-aminophenoxy-4′-benzoyl)benzene (m-TABB) and 1,3,5-tris(4-aminophenoxy-4′-benzoyl)benzene (p-TABB), and systematically compared with the corresponding bifunctional phenylethynyl terminated imide oligomer, BPEPA. DSC isothermal cure kinetics studies were performed at the cure temperature of 320 °C, 350 °C, and 370 °C by applying two different kinetic equations, and in these cases the reaction kinetics followed first order reactions below 90% conversion. The rate of the curing reaction was observed to increase with the number of functional groups, and the TABB-based oligomers showed 20 °C lower curing temperature than the BABB-based oligomer. Tgs and thermal oxidative stabilities of imide films increased with increasing the number of the functional groups in a molecule, which may partly due to the higher crosslink densities. Moreover, trimerization or tetramerization, possible main curing reaction of trifunctional phenylethynyl terminated oligomers, based on the kinetic analysis by isothermal and ramp temperature DSC and calculation of crosslink densities, formed more thermooxidatively stable aromatic ring structures than the main polyene structures appeared in monofunctional or bifuntional phenylethynyl terminated model compounds. m-TABB-based resin exhibited the best combination of melt processibilities, curing temperatures, and thermal properties.