Preparation of alkynyl terminated telechelic polyimides (API) and properties of T300 carbon fiber cloth/API composites

Six types of telechelic polyimides with terminal alkynyl groups (API) were prepared from 3,4'-oxydiphthalic anhydride, 1,3-bis(aminopropyl)tetramethyldisiloxane and m-amino phenylacetylene or p-aminophenyl propargyl ether. The T300 carbon fiber cloth (T300 cloth) reinforced API (T300 cloth/API) composites were also prepared by hot press molding. The structure and properties of the API resins and the T300 cloth/API composites were studied by FTIR, ¹H NMR, DSC, TGA, DMA and other methods. The results show that the six API resins have good solubility and good processability. The processing window of six API resins becomes wider as the molecular weight of the API resins increases. The processability of the API resins with terminal propargyloxy groups (API-e) is better than that of the API resins with terminal ethynyl groups (API-a). The thermal stability of the cured API resins decreases with the increasing of molecular weight. The temperature at 5% mass loss (T_d5) and residual yield at 800℃ of the cured API-a resins are higher than that of the cured API-e resins, which are 473.7℃ and 48.8%, respectively. The glass transition temperature (T_g) of the T300 cloth/API composites can reach up to 220℃. The mechanical properties of T300 cloth/API composites increase with the increase of the molecular weight of API matrices. And the T300 cloth/API-e composites have better mechanical properties than the T300 cloth/API-a composites at room temperature and 200℃. The flexural strength, tensile strength and interlayer shear strength (ILSS) of the T300 cloth/API-e composites are 636.5 MPa, 406.1 MPa and 48.4 MPa at room temperature, respectively. The flexural strength and ILSS of T300 cloth/API-e composites at 200℃ are 381.9 MPa and 33.9 MPa, respectively.