High-Barrier Plastics from Liquid Crystal Polymers

A form of synthetic compounds are demonstrating outstanding stiffness, strength, conductivity and even gas and water vapor resistance. A lower-cost potential replacement for polyimide, fluoropolymer, nylon and other films, these liquid crystal polymers are being heavily researched for applications as diverse as beer bottling, electronic circuit boards and medical tubing.

At first, LCPs were difficult to process, owing to their highly-oriented, rod-like microstructure. The problem was overcome by Superex Polymer, Waltham, MA, when their engineers developed a process using counter-rotating dies to control the direction of the LCP molecules. The result was a controlled cross-hatch pattern of orientation that brought the transverse mechanical properties closer to those in the flow direction. Not only was the extruded material stronger, but its barrier properties were much improved -- more than 100 times better than polyester film. Superex has since formed licensing and strategic business agreements with US and international organizations to use its technologies for films, tubing and molded
articles.

In the bottling industry, a film of LCP material inside the bottle would prevent oxygen infiltration that would adversely affect the flavor of the beverage, a particularly critical factor in the beer industry. Conversely, a layer of the film overlaid on a printed circuit board would produce increased stability in normal and humid environments, owing to the film's high moisture resistance. As the circuit board substrate, a sheet of LCP material at a thickness of 0.002 in. has a volume resistivity of 10¹⁶ (omega)-cm, a dielectric constant of 2.6 at 1 GHz, and a maximum operating temperature of 230°C. LCPs are also being studied for plastic fuel tanks in vehicles, since the material would provide a higher barrier to the fuel vapors than other plastic materials of the same thickness, weight or cost. Rigid tubing made from LCPs can be used in minimally-invasive surgical devices such as laparascopic instruments, cannulae and aspiration-irrigation tubes. The tubing has a dielectric strength of 1000V/mil, and can be sterilized in an autoclave.

--RM

For more information:

Circle 555 - Superex Polymer, Inc.