Rheological properties crystals

The critical state of stress-induced crystallization at high spinning speeds is governed by the viscoelasticity of the polymer in combination with its crystallization behavior. Any kind of coarse particle obviously disturbs the structure and affects the resistance against deformation. The development of stress is controlled by the rheological properties of the polymer. Shimizu et al. [4] found that increasing the molecular weight drastically promotes the crystallinity under stress conditions. 

Different types of liquid crystals exhibit different rheological properties [16,17]. With an increase in organization of the microstructure of the liquid crystal its consistency increases and the flow behavior becomes more viscous. The coefficient of dynamic viscosity r, although a criterion for the viscosity of ideal viscous flow behavior (Newtonian systems), is high for cubic and hexagonal liquid crystals but fairly low for lamellar ones. However, the flow characteristics are not Newtonian but plastic or pseudoplastic, respectively. 

Liquid-crystalline polymers with stiff backbones have many static and dynamic solution properties markedly distinct from usual flexible polymers. For example, their solutions are transformed from isotropic to liquid crystal state with increasing concentration. While very high in the concentrated isotropic state, their viscosity decreases drastically as the concentration crosses the phase boundary toward the liquid crystal state. The unique rheological properties they exhibit in the liquid crystal state are also remarkable. 

Even when composition is fixed, viscosity and other rheological properties may depend on the size and arrangement of aligned domains within a sample of liquid crystalline material. No studies of this matter seem to have been made, however. Such structural characteristics do influence electrical conduction and diffusion in liquid crystals, as discussed further below. 

This system of equations is solved numerically. The results obtained are physically reasonable up to the axial position where crystallization commences, where the rate of cooling slows down because of the exothermic solidification phenomenon and the rheological properties change sharply. 

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