TESTING THE RHEOLOGICAL CHARACTERISTICS OF THERMOPLASTIC ELASTOMERS TO PROVIDE GUIDELINES FOR THEIR APPLICATION AND THEIR PROCESSIBILITY

Rheology is no doubt one of the means to characterize polymers with respect to their molecular structure and their processibility. Melt viscosity values may be measured by a number of instruments such as rotational viscometers, capillary viscometers or torque rheometers with mixer measuring heads. Data describing the melt viscosity of several types of thermoplastic elastomers (TPEs) determined by the above mentioned methods are thus presented. These methods cannot however be used to classify solidified specimens of TPE at and around room temperature with viscosities decades above their melt viscosities and an elastic response to deformation greatly exceeding their viscosity. Rheological data on TPEs especially in the low temperature range of their normal application is required to assist the product engineer in selecting the optimized polymer blend for parts to be made from TPEs. This data is provided by a new computerized two-plate-plastometer able to measure and visualize the elastic and viscous response of TPEs with respect to the test parameters such as variable compression loads, single or multiple cycles of deformation and relaxation and variable temperatures. TPE-samples, being almost alike with respect to their melt viscosities show very great differences in their theological response at their application temperature. This could be important for the selection of a suitable batch quality control method. To allow some comparison with other polymers, similar data is presented for cured rubber and uncured rubber compounds.