Synthesis and Thermal Properties of Ethynyl Phenyl Azo Phenol-biphenylene Resin

A novel addition curing ethynyl phenyl azo phenol-biphenylene resin (EPABN) was synthesized by introducing ethynylphenyl group into biphenyl novolac resin (BN) through diazo coupling reaction. Its synthesis reaction and curing mechanism were also proposed. Fourier transform infrared spectroscopy and ¹H NMR spectroscopic analysis showed that the ethynylphenyl group was successfully linked to the BN molecular chain. By differential scanning calorimetry analysis, the curing process of EPABN resin was determined to be 150 °C/2 h + 172 °C/2 h + 203 °C/4 h + 255 °C/4 h + 300 °C/4 h. Gel permeation chromatography and elemental analysis showed that the introduction of ethynylphenyl group increased the number-average molecular weight and weight-average molecular weight of EPABN. Thermogravimetric analysis showed that the EPABN resin synthesized under the obtained optimum conditions has excellent heat resistance, ablation resistance, and mechanical properties. T _d ⁵ and T _d ¹⁰ of heat resistance of the cured EPABN resin are 463 and 531 °C, respectively, and its residual char yield at 700 and 1000 °C is 78.2% and 72.1%, respectively.