Polymer Liquid Crystals (PLCs) Alloys and Blends
Laboratory of Polymers and Composites
Department of Materials Science
University of North Texas
Denton, TX 76203-5308
Polymer Liquid Crystals (PLCs) show superior properties over conventional thermoplastic
polymers with regard to chemical resistance, low flammability and high modulus.1 In
addition, their low isobaric expansivity combined with their low viscosities at processing
temperatures combine to assist in the development of high tolerance parts. PLCs achieve these
properties due to their unusual phase behavior during temperature variations. In conventional
semi-crystalline thermoplastics, three kinds of relaxational phenomena are seen:
(i) Low temperature solid state transitions (often related to side group chain
Since PLCs have additional phase behavior due to their mesophases, understanding their phase
behavior is vital to their use. In the past we reported on the mechanical behavior and phase
diagram of the transition temperatures versus the mole fraxtion x of a series of PET/xPHB PLCs,
where PET = poly(ethylene terephthalate) and PHB = p-hydroxybenzoic acid.2
To study the effects of blending PLCs with cheaper thermoplastics in order to obtain higher
strength plastics at a lower cost, we continue to study systems of the engineering plastics
(EP) + PLC type.3-5 Rheological experiments show that EP viscosity decreases upon
addition of a PLC, making processing easier while reinforcing the EP at the same
(ii) An alpha transition region in which the segmental mobility of the polymer chains
results in the polymer changing from glassy to rubbery.
(iii) A high temperature melting transition to ensure flow.
1. W. Brostow, Polymer, 1990, 31, 979.
2. W. Brostow, M. Hess, B.L. López, Macromolecules, 1994, 27, 2262.
3. W. Brostow, M. Hess, B.L. López and T. Sterzynski, Polymer, 1996, 37, 1551.
4. W. Brostow, B.L. López and T. Sterzynski, in preparation.
5. W. Brostow, T. Sterzynski and S. Triouleyre, Polymer, 1996, 37, 1561.
Dr. Antje Stein de Vilchez.