The feasibility of using the conventional two-step procedure involving the thermal imidization of a high-molecular-weight poly(amic acid) (PAA) for the preparation of self-supporting polyimide (PI) films was studied. Synthesized PAA and PI were analyzed with respect to their molecular weights, chemical structures, and mechanical and thermal properties. The results showed that a high-molecular-weight PAA was successfully synthesized from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane with 3,3 0 ,4,4 0 -benzophenone tetracarboxylic dianhydride. The high intrinsic viscosity of PAA was 1.5 dL/g. Selfsupporting PI films were successfully prepared by the thermal imidization of PAA and reached maximum tensile strength, tensile modulus, and elongation at break values of 103 MPa, 2.2 GPa, and 10.7%, respectively. The PI films were stable to 426-483 C (the 5% weight loss temperature) and had a glass transition at 271-283 C. All these results indicate that the conventional two-step procedure involving thermal imidization is a promising method for preparing self-supporting PI films with reasonable levels of mechanical and thermal properties.

A serial of addition-curable hybrid resins for resin matrix of advanced composites are prepared by thermal prepolymerization between acetylene-functional benzoxazine(BZ) and polyvinylsilazane(PSN) with various weight ratios. Processing capability of BZ-PSN resin is investigated by measuring viscosity. Cure behavior is investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR) spectra. Thermal property of cured BZ-PSN resin is investigated by Thermogravimetric analysis (TGA) and Dynamic mechanical analysis (DMA). BZ-PSN resin shows a low viscosity of 40-180 mPaÁs between 60 and 90 C, and maintains the low viscosity for 6 h, indicating that the resin is suitable for resin transfer molding (RTM) process to fabricate composites. DSC results show that BZ-PSN resin can be cured completely at about 250 C without adding any other curing additives. FT-IRshows the reaction between BZ and PSN take place. TGA shows that thermal stability of cured BZ-PSN resin is increased with the content of polyvinylsilazane increasing both in nitrogen and in air. DMA shows cured hybrid resins have excellent thermal properties. The excellent processability and thermal properties suggest that BZ-PSN resin is a promising candidate for resin matrix of advanced composites.