Thesis (M.Eng.)--Chulalongkorn University, 2011

This research aims to develop a high performance composite of carbon fiber (CF)-reinforced polybenzoxazine (PBA-a) modified with pyromellitic dianhydride (PMDA). The effect of the carbon fiber and PMDA contents on flammability, mechanical, and thermal properties of the composites were investigated. The 65wt% CF-reinforced PBA-a:PMDA matrix provided a maximum packing, resulting in a remarkable increase in mechanical and thermal properties. The flammability of the composites made from 65wt% of carbon fiber and PBA-a modified with PMDA at various of PMDA contents was examined by limiting oxygen index (LOI) and UL-94 vertical tests. The results showed that the LOI values increased from 26.0 for 65wt% CF/PBA-a to 49.5 for 65wt% CF/PBA-a:PMDA and an improvement in fire resistance of all 65wt% CF/PBA-a:PMDA composites as thin as 1.0 mm was also achieved the maximum V-0 fire resistant classification. In addition, the incorporation of the PMDA into PBA-a matrix significantly enhanced the glass transition temperature (T[subscript g]) and the storage modulus (E') values of 65wt% CF/PBA-a:PMDA composites rather than those of the 65wt% CF/PBA-a. The T[subscript g] values and storage moduli at 35℃ of the obtained 65wt% CF/PBA-a:PMDA composites were found to have relatively high value up to 237℃ and 46 GPa, respectively, while those values of the 65wt% CF/PBA-a is approximately 183℃ and 41 GPa, respectively. From TGA results, all 65wt% CF/PBA-a:PMDA composites exhibited relatively high degradation temperature up to 498℃ and substantial enhancement in char yield with a value of up to 82%, which are somewhat higher compared to those of the 65wt% CF/PBA-a composite, i.e. 405℃ and 75.7%, respectively. From the improvement of flame retardant, mechanical and thermal properties, it was found that the obtained CF/PBA-a:PMDA composites exhibited high potential applications in advanced composite materials that required mechanical integrity and self-extinguishing property.