RHEOLOGY AND PROCESSING OF THERMOTROPIC LIQUID CRYSTALLINE POLYMERS FOR PRESSURE VESSELS

摘要

Aromatic polyesters and polyester-amides are rigid chain polymers which form melts with liquid crystalline order, referred to as thermotropic liquid crystalline polymers (TCLP's). TLCP's lead to materials which exhibit high modulus and strength, possess negligible thermal expansion, and have exceptional barrier properties (i.e. resist permeation of gases such as O_2, H_2, etc.). Taking advantage of their unique rheology, one can potentially process these materials into a wide range of high performance structures such as tanks for storage of oxygen and possibly hydrogen. In this presentation conditions are identified that lead to the successful rotational molding of a TLCP, Vectra B 950. A technique was developed to produce particles suitable for rotational molding because TLCP's cannot be ground into a free flowing powder. Because the viscosity at low shear rates can be detrimental to the sintering process, coalescence experiments with isolated particles were carried out to determine the thermal and environmental conditions where sintering should occur. These conditions were then applied to static sintering experiments to determine whether coalescence and densification of the bulk powder would occur. Finally, the powders were successfully rotationally molded into tubular structures in a single axis, lab-scale device. The density of the molded structure was essentially equivalent to the material density and the tensile strength and modulus were approximately 18 MPa and 2 GPa, respectively, which are about 50% of those based on compression molding of the same material.