耐350℃聚酰亚胺复合材料热模压成型工艺研究

Investigation of Hot Compression Molding Process for Polyimide Composites with 350˚C Resistance

摘要: 通过对降冰片烯基封端(PMR)聚酰亚胺树脂进行TG与DSC测试与分析，并研究了加压点温度、压力和保压时间对T800/PMR-350复合材料力学性能的影响，确定了最优热模压成型工艺。结果表明：PMR-350树脂分为去溶剂、亚胺化、压力成型以及后固化四个工艺阶段，且在320~340℃时粘度最低，达145.8 Pa∙s，表现出良好的热模压成型工艺性。通过对比分析加压点温度、压力和保温时间对复合材料孔隙率和力学性能的影响，选择330℃、90 min和6 MPa的热模压成型工艺较为合理，复合材料的孔隙率仅为0.96%，室温拉伸强度为868.2 MPa，压缩强度为465.7 MPa，层间剪切强度为88.6 MPa，面内剪切强度为111.5 MPa，350℃下高温拉伸强度保持率大于100%，压缩、层剪和面内剪切强度保持率均大于50%，表现出良好的常/高温力学性能。350℃热氧老化300 h后，复合材料的热失重率仅为4.4%，室温拉伸强度保持率为76.8%、压缩强度保持率为51.5%、层间剪切强度保持率为66.9%、面内剪切强度保持率为71%，且复合材料及界面结合良好，表现出优异的抗350℃高温热氧老化性能。

Abstract: Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests were conducted on the norbornene-terminated (PMR) polyimide resin. The effects of pressing temperature, pressure, and holding time on the mechanical properties of T800/PMR-350 composites were investigated, and the optimal hot-molding process parameters were determined. The results show that the PMR-350 resin processing involves four distinct stages: solvent removal, imidization, pressure molding, and post-curing. The resin exhibits its lowest viscosity in the range of 320~340˚C, reaching 145.8 Pa∙s, demonstrating excellent processability for hot compression molding. Through a comparative analysis of the effects of pressure application temperature, pressure, and holding time on the void content and mechanical properties of the composites, a hot compression molding process at 330˚C, 90 min, and 6 MPa was selected as optimal. The resulting composites exhibited a void content of only 0.96%, a room-temperature tensile strength of 868.2 MPa, a compressive strength of 465.7 MPa, an interlaminar shear strength (ILSS) of 88.6 MPa, and an in-plane shear strength of 111.5 MPa. At 350˚C, the retention rate of tensile strength exceeded 100%, while the retention rates of compressive strength, ILSS, and in-plane shear strength were all above 50%, indicating good mechanical properties at both ambient and elevated temperatures. After thermo-oxidative aging at 350˚C for 300 h, the composites showed a weight loss of only 4.4%, with retention rates of 76.8% for room-temperature tensile strength, 51.5% for compressive strength, 66.9% for ILSS, and 71% for in-plane shear strength. Furthermore, the composites still maintained good interfacial adhesion, demonstrating excellent resistance to thermo-oxidative aging at 350˚C.