Mesophase flow behavior, effect

Admittedly, the existence of the postulated transient mesophase would still require structural confirmation. Even so, the taking of a sharp drop In viscosity as Indicator of mesophase formation has well established precedents In the liquid crystal field. Such Is e.g. the well documented effect In Kevlar referred to above (12) which In many respects has similarities to the presently discussed PE, except that Kevlar Is "mesogenlc" and can exist as stable liquid crystal under ambient conditions, while the mesophase In the flexible PE Is "virtual". The latter "virtual" phase only becomes "real" transiently, which suffices to dramatically affect the entire flow behavior of the material, the effect through which It Is being detected. 

From practical considerations, two properties are of prime interest The effect of liquid crystalline behavior on viscosity and the ability of the polymer to retain the ordered arrangement in the solid state. Liquid crystalline behavior during the melt results in lower viscosity, because the rigid polymeric mesophases align themselves in the direction of the flow. As a result, the polymer is easier to process. Also, retention of the arrangement upon cooling yields a material with greatly improved mechanical properties. Several thermotropic liquid crystalline copolyesters are now available commercially. 

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