RESIDUAL NORMAL FORCE AFTER CESSATION OF SQUEEZING FLOW OF LIQUID-CRYSTALLINE POLYMERS

Classical Liquid crystal theories are used to develop a model to compu te the normal forces and shear torques for liquid crystalline polymers . The model is applied to the parallel disk geometry and the normal fo rces from three representative average molecular orientations are comp uted. It is found that a positive normal force lending to separate the parallel disks will always be present whenever the orientation is sub jected to a twisting deformation. For typical parameter values and geo metries, the model predicts that normal forces are six orders of magni tude larger than shear torques. The model predictions are validated wi th the experimental data presented by Langelaan and Gotsis (1996). (C) 1996 Society of Rheology.