Rheological properties of olefinic thermoplastic elastomer blends

Abstract

Thermoplastic Elastomers (TPE) are a class of materials that have rubber-like properties and can be processed like thermoplastic polymers. In this thesis, the rheological properties of two TPE blends are correlated to their morphology. The thermoplastic vulcanisates (TPV) consist of micron-sized, cured elastomer particles while the blends of PP and the triblock copolymer SEBS show co-continuous structures. Both blends also contain considerable amount of paraffinic oil. The difference between the dispersed and the co-continuous morphology manifests itself in the frequency dependent dynamic moduli and in the behaviour of the deformation in creep flow and the recovery strain after cessation of creep flow. These findings are correlated to the processing behaviour of the two materials in capillary flow as used in e.g. extrusion. A new method was developed to determine the distribution of paraffinic oil in the two blends. Using dielectric spectroscopy in combination with the addition of a dielectrically active probe molecule, the oil concentration could be estimated from the reduction of the glass transition temperature.