ADVANCES IN LIQUID CRYSTALLINE POLYESTERS

Advances have been made in understanding the interactions of composition, molecular weight, liquid crystallinity,orientation, and three-dimensional crystallinity on the properties of injection-molded and melt-spun liquid crystalline polyesters (LCP's). Two classes of potentially low-cost LCP's were compared:(1) semiflexible LCP's prepared from 1,6-hexanediol and the dimethyl ester of either trans-4, 4'stilbenedicarboxylic acid or 4.4 ' biphenyldicarboxylic acid and (2) all-aromatic LCP's prepared from terephthalic acid, 2, 6-naphthalenedicarboxylic acid, the diacetate of hydroquinone, and the acetate of p-hydroxybenzoic acid. The effects of composition on the plastic properties of the 4-component all-aromatic LCP's were determined with the aid of a 3 x 3 factorial statistically designed experiment, the generation of equations with a computer program, and the plotting of three-dimensional figures and contour diagrams. The effects of absolute molecular weight (M_w) on the tensile strengths of the semiflexible LCP's and one of the all-aromatic LCP's having an excellent balance of plastic properties were also compared, and it was observed that the semiflexible LCP's required M_w's about 4 times higher than the all-aromatic LCP to attain a given strength. Persistence lengths and molecular modeling were used to explain these differences.

ADVANCES IN LIQUID CRYSTALLINE POLYESTERS

Advances have been made in understanding the interactions of composition, molecular weight, liquid crystallinity,orientation, and three-dimensional crystallinity on the properties of injection-molded and melt-spun liquid crystalline polyesters (LCP's). Two classes of potentially low-cost LCP's were compared:(1) semiflexible LCP's prepared from 1,6-hexanediol and the dimethyl ester of either trans-4, 4'stilbenedicarboxylic acid or 4.4 ' biphenyldicarboxylic acid and (2) all-aromatic LCP's prepared from terephthalic acid, 2, 6-naphthalenedicarboxylic acid, the diacetate of hydroquinone, and the acetate of p-hydroxybenzoic acid. The effects of composition on the plastic properties of the 4-component all-aromatic LCP's were determined with the aid of a 3 x 3 factorial statistically designed experiment, the generation of equations with a computer program, and the plotting of three-dimensional figures and contour diagrams. The effects of absolute molecular weight (M_w) on the tensile strengths of the semiflexible LCP's and one of the all-aromatic LCP's having an excellent balance of plastic properties were also compared, and it was observed that the semiflexible LCP's required M_w's about 4 times higher than the all-aromatic LCP to attain a given strength. Persistence lengths and molecular modeling were used to explain these differences.