Thermal and Mechanical Properties Enhancement Obtained in Highly Filled Alumina-Polybenzoxazine Composites

Highly filled polymer composites based on bisphenol-A/aniline based polybenzoxazine (PBA-a) and alumina particles were investigated. A very low A-stage viscosity of benzoxazine monomer gives it excellent process-ability exhibiting maximum alumina content as high as 83% by weight (60% by volume) which is one of the highest maximum packing values with negligible void contents. The storage modulus (E') at room temperature was increased from 5.93 GPa of the polybenzoxazine to 45.27 GPa of the composites. The significant high microhardness of the composites up to 1124 MPa was obtained and the behavior can be well predicted by the Halpin-Tsai model. Moreover, the modulus dependence of the composites on the alumina contents is well fitted by Lewis-Nielsen equation. Glass transition temperatures, degradation temperature, and solid residue of the composites also significantly increased with increasing the alumina contents. Finally, the scanning electron microscope of the composite fracture surface indicated a good distribution of the alumina particles in the PBA-a matrix. The resulting PBA-a/alumina composites are a highly attractive for an application that requires high modulus and hardness as well as high thermal stability. (C) 2014 Society of Plastics Engineers