酚醛树脂/碳化硼/聚硼氮烷复合物的固化行为及其热解性能

酚醛树脂作为一种热固性树脂基体具有广泛的应用。为了满足其作为高性能树脂基体在苛刻条件（耐高温和抗氧化）下的使用，进一步提高酚醛树脂的耐热性能并兼顾其工艺性能显得尤为重要。采用含有无机元素的耐热性聚合物（聚硼氮烷）和碳化硼纳米粒子协同改性酚醛树脂的方法，能够克服单独加入碳化硼导致的酚醛树脂固化温度升高的问题。固化动力学分析表明，加入聚硼氮烷的酚醛树脂改性体系，其固化转化率显著高于同温度下酚醛树脂或碳化硼改性酚醛树脂的转化率。同时，聚硼氮烷和碳化硼协同改性酚醛树脂固化物在高温阶段（800～1000℃）的热解稳定性较改性前有大幅度的提高。通过红外光谱分析了不同热解程度下酚醛树脂及其改性物的结构，进一步阐述了聚硼氮烷和碳化硼协同作用对酚醛树脂改性体系固化行为和热解过程的影响机制。上述采用耐热性活性聚合物和碳化硼陶瓷粒子协同改性热固性树脂的方法，有望在高性能复合材料树脂基体中得到运用。

Curing and pyrolysis behavior of PF/B4C/PBZ composite

Phenol-formaldehyde resin (PF) has been widely used as an excellent thermosetting resin owing to its toughness, heat tolerance, chemical inertness and good electronic property. For high performance application, especially for expanding its usage in harsh environment demanding superior thermal and oxidation stability, further enhancement of the comprehensive properties is vital. Here, a thermally stable polyborazine (PBZ) and boron carbide ceramic microparticles (B₄C) were incorporated simultaneously into the phenolic resin matrix. The curing kinetics and structure evolution of the PF/B₄C/PBZ composite were investigated with differential scanning calorimetry (DSC), Fourier transform IR (FTIR) and thermal gravimetric analysis (TGA). Both the curing initiation and peak temperatures of the composite were lowered as a result of the presence of active hydrogen atom of PBZ and the hydrogen bonding among PBZ and PF. In addition, the thermal stability of PF was improved in the temperature range of 800-1000℃, with mass loss decreased from 18.2% to 5.6%, during pyrolysis with the synergistic modification of PBZ and B₄C. Furthermore, after carbonization at 1550℃ for 2 h, graphitization of PF was enhanced and interlayer distance decreased from 0.3638 nm to 0.3494 nm due to the presence of PBZ and B₄C. The strategy to high performance of PF via the combination of PBZ and B₄C is feasible, and it allows a better way to modify the curing behavior without compromise to thermal stability.