Effect of a Combination of Drawing and Heat Treatment on the Tensile Properties of Poly[1,3,4-oxadiazole-2,5-diyl- 1,4-phenyleneimino(chloroterephthaloyl)imino-1,4-phenylene] Film

Abstract

Abstract Poly[1,3,4-oxadiazole-2,5-diyl-1,4-phenyleneimino(chloroterephthaloyl)imino-1,4-phenylene] (PBO-ClT) was prepared by the low-temperature solution polycondensation of 2,5-bis(p-aminophenyl)-1,3,4-oxadiazole with 2-chloroterephthaloyl dichloride in the presence of lithium carbonate as an acid accepter in 1-methyl-2-pyrrolidinone (NMP). The value of the inherent viscosity of PBO-ClT was 1.79 dl g−1 in sulfuric acid (0.5 g/100 ml, 25 °C). PBO-ClT was easily dissolved in NMP and N,N-dimethylacetamide (DMA). The solubility of PBO-ClT, chloro-substituted polymer, was larger than that of poly(1,3,4-oxadiazole-2,5-diyl-1,4-phenyleneiminoterephthaloylimino-1,4-phenylene) in these organic solvents. In order to enhance the tensile properties of PBO-ClT films cast from NMP solutions, the films were drawn and heat-treated under various conditions. The films were drawn in a DMA/water mixture (80 : 20, v/v, 70 °C) and subsequently heat-treated (the temperature was raised from room temp to 300 °C at a heating rate of 12—15 °C min−1). The values of the tensile strength, tensile modulus, and breaking energy of the drawn and heat-treated films were 1.30 GPa, 22.8 GPa, and 37.3 MJ m−3, respectively. These values were changed into 1.02 GPa, 18.5 GPa, and 26.9 MJ m−3 after 2 h of heat-aging at 350 °C in air. These results showed the high-temperature durability of the drawn and heat-treated materials.