Study of a thermotropic liquid‐crystalline polyester at elevated pressures

Publisher Website
Google Scholar
Abstract
A thermotropic liquid‐crystalline copolyester of 20% hydroxybenzoic acid, 40% isophthalic acid, and 40% hydroquinone polymer was studied at elevated pressures. The characterization techniques at elevated pressures (0–1000 bar) included high‐pressure differential thermal analysis and dilatometry; at atmospheric pressure, differential scanning calorimetry, thermal optical analysis, and x‐ray analysis were employed. The mechanical properties of the solid specimens prepared at different pressures were studied by compression and dynamic rotation mechanical testing techniques. High‐pressure induced a new crystal habit in the solid state and a new mesophase in the melt. These transitions are summarized in a proposed phase diagram. Mechanical tests on the material produced at elevated pressure indicate the possibility of improved properties, implying that the pressure‐dependent morphological changes in thermotropic copolyesters could be of practical significance. The finding of a pressure‐induced mesophase also confirmed the possibility of extending the range of polymers which might exhibit liquid crystallinity via the application of pressure.