A viscosity function for thermoplastics blended with a thermotropic liquid crystalline polymer

The capillary flow behavior of thermoplastic blends containing thermotropic liquid crystalline polymers (TLCP) was studied both theoretically and experimentally. Significant viscosity reductions were observed for a polyethersulfone (PES) blended with a TLCP at 10 and 30 wt %, respectively. A viscosity function was developed and tested to evaluate the relationship between the blend viscosity reduction and weight fraction including some property-related parameters: η = η₀[1 - φ + φ/δ + K(1 - φ)(1 - λ)φε]^-1, where η and η₀ stand for blend and matrix viscosity, respectively. φ is the weight fraction; δ, the viscosity ratio of the two parent components; λ, the critical stress ratio; and ε, an exponent. Interfacial slippage in the blend has been suggested as the flow mechanism by which a substantial reduction in the melt viscosity takes place upon the addition of a small amount of TLCP. The fact that experimental data could be fitted to the viscosity function with satisfactory accuracy should make the function an acceptable way of modeling, analyzing, and parameterizing the experimental rheological data of these blends.