The formation and characterization of biaxially and uniaxially oriented poly (p-Phenylene Terephthalamide) films from liquid crystalline solutions

An annular die and oil coated mandrel in conjunction with a wet extrusion operation is used to produce biaxially oriented poly (para-phenelylene terephthalamide) PPD-T film. Extruded and uniaxially drawn films are also produced without the mandrel. The PPD-T is dissolved in 100% sulfuric acid at a concentration of 17% by weight. Water, methanol, ethanol, and combinations of water and alcohol are used as coagulants for the above process. At 17% by weight, PPD-T/H₂SO₄ solutions are liquid crystalline.

It is shown through mechanical testing and wide angle x-ray diffraction techniques using orientation functions and pole figures that a relatively high level of biaxial orientation is achieved using the mandrel process. The above techniques were also used to characterize extruded and uniaxially drawn films. Indications of fairly high tensile strengths were found, as high as 16,000 psi for mandrel processed films and 37,000 psi for uniaxially drawn films. It is believed that the liquid crystalline nature of the PPD-T/H₂SO₄ solutions contribute greatly to the high levels of orientation and good strength characteristics achieved in PPD-T films.