Effect of processing parameters on phase morphology and mechanical properties of thermoplastic polyurethane and polydimethylsiloxane rubber blends

Abstract

Properties of polymer blends are generally controlled by the characteristics of the individual components, the processing conditions, morphology developed during processing and the interaction between the different blend constituents. The effect of processing parameters on the morphology of thermoplastic polyurethane (TPU)-polydimethylsiloxane rubber (PDMS) blends has been investigated in a Brabender Plastograph, an internal mixer. Phase morphology of the blends has been analyzed using image processing technique to assess the dispersed domain size, domain size distribution and area of each dispersed domain. Taguchi methodology has been adopted to quantify the effect of processing conditions on the mechanical properties of the TPU-PDMS blends. The average shear rate experienced inside the mixing chamber of Brabender Plastograph has been determined and this data has been correlated with the rheological properties to evaluate the viscosity ratio of the blends. The effect of viscosity ratio on the phase morphology of TPU-PDMS blends has been studied and the results are found to be in agreement with those of the effect of processing conditions on the mechanical properties of the blends. The lowest viscosity ratio leads to favorable droplet/matrix morphology resulting in higher mechanical strength properties. Palierne model has been used to estimate the interfacial adhesion between the polymer components in the blends of droplet/matrix morphology which is found to be as low as 3mN/m. This may considered to be the reason for a wide deviation from the log additive rule for the complex modulus of the blends.