Effect of Combination of Drawing and Heat-Treatment on the Tensile Properties of Poly(oxy-1, 4-phenyleneoxy1, 4-phenyleneiminoterephthaloylimino1, 4-phenylene) Film

Abstract

Poly(oxy-1, 4-phenyleneoxy-1, 4-phenyleneiminoterephthaloylimino-1, 4-phenylene) (PBTA)was prepared by low-temperature solution polycondensation of 1, 4-Bis(p-aminoxy)benzene with terephthaloyl dichloride in the presence of lithium carbonate as the acid acceptor in N-methyl-2-pyrrolidone. The value of inherent viscosity of PB-TA was 1.41 dllg in sulfuric acid (0.5% conc., 25 °C). In order to enhance tensile properties of PB-TA films cast from hexarnethylphosphoric triamide solutions, the films were drawn and heat-treated under various conditions. The tensile properties of PB-TA films were compared with those of poly(oxy-1, 4-phenyleneiminoterephthaloylimino1, 4-phenylene) (P-1), poly(oxy-1, 4-phenylenecarbonylimino-1, 4phenyleneiminocarbonyl-1, 4-phenylene) (P-2), poly[oxy-1, 4-phenylenecarbonylimino(chloro1, 4-phenylene)iminocarbony1-1, 4-phenylene] (P-3), and poly(oxy-1, 4-phenyleneiminocarbony1, 4-phenylenoxy-1, 4-phenylenecarbonylimino-1, 4-phenylene) (P-4) films which have similar structures to PB-TA. It was difficult to en hance the tensile properties of PB-TA films by cold and heat drawing at a constant temperature. Therefore, the films were drawn in an N, N-dimethylacetamide containing 2 wt% lithium chloride/water mixture (80: 20, v/v, 70 °C) and then were heattreated (temperature was raised from room temp. to 250 °C at the heating rate of 12 °C/min). The values of birefringence, strength at break, tensile modulus, elongation, and breaking energy of the drawn and heat-treated PB-TA films (sample 5 in Table 1) were 476 x 10-8, 540 MPa, 5.9%, 21 MPa, 34 M Jrn-8, respectively. The values of strength at break, t ensile modulus, and breaking energy of the sample 5were changed into 420 MPa, 13 GPa, and 29 M Jm-8 after 2 h of heat aging at 300 °C in air. These results showed the high-temperature durability of the drawn and heat-treated materials.