chapter in book

Abstract

The stress growth during start-up of shear flow was studied for the liquid crystalline melts of the copolyesters of PET and pHBA. The shear stress growth reflects the orientation of the LC domains. Orientation seems to occur within less than 2 strain units in this flow. This results in the fact that the primary normal stress difference can exhibit different behaviour than the shear stress response. In particular, for the 60% system, values of N1 are positive and rise gradually to the equilibrium, whereas the 80% system can exhibit negative values of N1. Ericksen's transversely isotropic fluid theory can qualitatively handle some of the observed phenomena. Further studies are needed to be carried out to elucidate the development of this orientation and its relation to the stress growth.

Polymeric Liquid Crystals, pp.183-195, Blumstein ed. Plenum Press, 1985

Transient shear flow behaviour of thermotropic LC copolyesters