Mechanical, Tensile Creep and Viscoelastic Properties of Thermoplastic Polyurethane/Polycarbonate Blends

Abstract

This study investigated the morphological, mechanical and solid-state creep properties of thermoplastic polyurethane/polycarbonate blends. Blend film samples were prepared via the solution-mixing method. The morphological and mechanical properties of the samples were investigated by scanning electron microscope (SEM) and universal test machine. Solid-state creep tests were also performed by dynamic mechanic analyzer (DMA) under a stress value of 3 MPa at different temperatures (30, 40, and 50 °C). Morphological observations indicated that the blend samples had a compatible structure due to the polar nature of PC and TPU. In the mechanical tests, it was found that the tensile modulus value improved significantly by incorporation of PC, whereas the strain at break and toughness values reduced. Accordingly, the blend sample that contained PC at the rate of 10 % (wt.) showed a higher tensile modulus and lower toughness than neat TPU by 2.85 and 0.56 times, respectively. In the creep strain analyses, the viscoelastic structure and long-term creep performance of the samples were analyzed by the Burger model, time-temperature superposition (TTS) approach and Findley model. The experimental values and the model predictions indicated that incorporation of PC into the TPU phase improved the creep resistance of TPU significantly. For example, the creep strain value of neat TPU could be reduced by 68 % and 98 % in the respective cases of the PC concentrations of 10 % (wt.) and 50 % (wt.). Finally, the experimental creep-recovery behavior of the samples was investigated, and the permanent strain values were determined by the Weibull Distribution Function (WDF).