| Abstract: | A novel process for the formation of biaxially balanced films of poly(p-phenylene terephthalamide) was developed. The liquid crystalline sulphuric acid solution is extruded through a slit die on a flat plate. The optically anisotropic to isotropic transition is generated by controlling the temperature and/or the water content in sulphuric acid before coagulation. The wet gel films are dried while holding their width and length constant. The films thus produced are transparent and biaxially oriented. Young's modulus of 12 GPa, tensile strength of 450 MPa, and elongation at break of 25% were obtained in the plane of the film. Such films which possess high dimensional and thermal stabilities are expected to be useful for new practical uses under severe conditions. |
