Comparison of mechanical behaviors of microwave and thermal cured on SiC whisker-filled polybenzoxazine

Abstract

To investigate the effect of microwave cure and thermal cure in silicon carbide whisker (SiCw) filled in polybenzoxazine (PBZ) composite on its corresponding thermal and mechanical behaviors. SiC whisker is thus, used as a filler of the polybenzoxazine to enhance the microwave absorption capability of the molding compound and to reinforce the material. The experimental results reveal that the benzoxazine resin (BA-a) was hardly cured at a high power of 1 kW for 15 min. However, with a relatively low content at 4% by weight SiCw, the benzoxazine resin was found to be cured relatively well. Therefore the strong microwave interaction of the benzoxazine molding compound, due to the presence of SiCw, significantly helps reduce the processing time of the molding compound from few hours at 200 ํC to be less than thirty minutes at 4% by weight of SiCw using the irradiation power of merely around 300 watts. To achieve the maximum cure, polybenzoxazine/SiCw composits cured by microwave oven consumed less energy than that required by the traditional thermal cure by approximately 20 to 30 times. At 4 wt% of SiCw content, the mechanical and thermal properties of the polybenzoxazine composites cured by thermal and microwave heating showed no significant change. The flexural modulus and strength of the thermal cured composites at 4 wt% SiCw were determined to be 5.3 +- 0.48 GPa and 119 +- 28 MPa while those of the microwave cured specimens were about 5.7 +- 0.2 GPa and 118 +- 7 MPa respectively at the same filler content. The neat polybenzoxazine and the SiCw-filled polybenzoxazine composites possess a glass transition temperature, determined by DSC ranging from 155 to 160 ํC for both thermal and microwave cured. Moreover, the thermal and mechanical properties were increased with increasing the SiCw content. Their fracture surface morphology could be observed by SEM studies which revealed substantial bonding between the two phases. The fracture surface of the composites was significantly rougher than that of the pure matrix. The microwave cure for SiCw-filled polybenzoxazine composite could drastically reduce the curing time and energy-consumption while the microwave-cured specimens still maintained the good thermal and mechanical properties.