Development of novel cardo-containing phenylethynyl-terminated polyimide with high thermal properties

A phenylethynyl-terminated reactive diluent [Card-4-phenylethynylphthalic anhydride (PEPA)], which contained fluorenyl cardo structures, was successfully synthesized and used as a modifier for flexible phenylethynyl-terminated imide oligomer (PEI-PEPA). The chemical structure, crosslink characterization, molecular weights, and thermal properties of the products were characterized. The imide systems with addition of 10, 20, 30, and 40wt% Card-PEPA to PEI-PEPA (PEI-PEPA-Card) and their cured resin systems were prepared. The thermal curing behaviors of imide systems at different heating rates were analyzed by using differential scanning calorimetry. Thermal properties such as glass transition temperature (T-g) and char yield at 800 degrees C of the resultant resin systems were studied by differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The rheological properties were also investigated using a dynamic rheometry. These properties were found to be outstanding compared with pure PEI-PEPA. The uncured imide systems exhibited lower T-g and lower isothermal viscosity with addition of Card-PEPA. Furthermore, the T-g and char yield of the cured resin systems increased with addition of Card-PEPA. The cured resin systems containing 40wt% Card-PEPA exhibited the highest T-g of 359 degrees C and char yield at 800 degrees C of 66.5%. Copyright (c) 2016 John Wiley & Sons, Ltd.