(698c) Squeeze Flow for Enhanced Strain Induced Orientation in Thermotropic Liquid Crystalline Polymers

Authors: 
Mansfield, C. D., Virginia Tech
Qian, C., Virginia Tech
Baird, D. G., Virginia Tech

The low coefficient of thermal expansion, low gas permeability, and high modulus anisotropy of TLCPs may allow for the efficient storage of hydrogen at high pressures and low temperatures.  Blow molding of TLCPs may provide an efficient, cost effective means for mass production of storage capacity for an emerging hydrogen economy.  Extrusion blow molding of a simple bottle geometry involves shearing and stretching of a polymer in the axial direction during extrusion from an annular die and stretching in the hoop direction while expanding into a mold.  It has been observed that the tensile modulus of TLCPs is positively correlated with an increased draw ratio during extrusion blow molding, which suggests an enhancement due to strain induced orientation.  Squeeze flow of injection molded end gated plaques is performed to impart both uniaxial and biaxial orientation in TLCPs.  The effects of annealing time and strain are investigated by varying the warming time of a sample in a hot mold and the degree of strain imparted due to extension of a sample under compression.  The tensile modulus is tested in both the principle flow and transverse directions to determine tensile modulus anisotropy.  It may be that the uniaxial and biaxial orientation induced during squeeze flow may be respectively correlated to the axial stretch ratio and blow up ratio of extrusion blow molded bottles.
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