Microstructures and properties of bismaleimide matrix composites modified by Al₂O₃ and two kinds of thermal plastic resin

The Al₂O₃-PES-SPEEK/MBAE composites were prepared by using 3,3'-diallyl bisphenol A(BBA) and bisphenol A diallyl ether(BBE) as the reactive diluent, which reacted with 4,4'- diamino diphenyl methane bismaleimide (MBMI) to synthesize MBAE matrix resin, two thermal plastic resins (polyether sulfone(PES) and sulfonated poly(ether ether ketone) (SPEEK)) as the reinforcements, and nano Al₂O₃ prepared by Sol-Gel method as the modifier. The microstructure, mechanical properties and heat resistance of the composites were investigated by FTIR, SEM, impact strength, flexural strength, flexural modulus and thermogravimetric testing. The results reveal that there are sulfonic acid groups in SPEEK, the microstructure is more loose, and the degree of sulfonation is about 41.3%. Al₂O₃ is a nano-sized short-fibrous crystal with hydroxyl groups on its surface. The micromorphology of Al₂O₃-PES-SPEEK/MBAE composites shows that the proper amount of PES, SPEEK and Al₂O₃ are uniformly dispersed in the matrix resin, which improves the fracture surface morphology of the composite, the shape of the section is fish scale, the fracture cracks are irregular and divergent, and the composites are ductile fracture. The mechanical properties indicate that the flexural strength, flexural modulus and impact strength of the Al₂O₃-PES-SPEEK/MBAE composite are the best 172.9 MPa, 4.7 GPa and 21.4 kJ/m², which is 73.1%, 74.1% and 125.3% higher than the matrix resin, respectively. When the mass fractions of PES, SPEEK and Al₂O₃ are 3 wt%, 2 wt% and 3 wt%, the thermal decomposition temperature of the Al₂O₃-PES-SPEEK/MBAE composite is 453.5℃, which is 15.4℃ higher than that of the matrix resin, and the mechanical properties and heat-resistance properties of the Al₂O₃-PES-SPEEK/MBAE composite are significantly improved.