Effect of Ultrasound and Strain Rate on Tensile Behavior of Neat Thermoplastic Polyurethane Thin Films

Thermoplastic Polyurethane (TPU) thin films have many applications in engineering and biomedical fields. Examples include moisture sensors, load cells, optical element and biocompatible stens. The TPU is a block copolymer naturally phase segregates into thermodynamically incompatible hard- and soft-segments. The size of the segments and their spatial distribution can significantly affect the microstructure and mechanical properties of the TPU. In this paper, we propose to investigate the effect of ultrasound energy on mechanical properties of TPU thin films fabricated via a solution route utilizing Tetra Hydro Furan (THF) as a solvent. The times of sonication was fixed at 60 minutes whilst all films were fabricated at average thickness of 20+/-5 um. The primary objective of the study was to understand the influence of ultrasound and strain rates on the material microstructure and the resulting mechanical properties. Mechanical tests have been conducted at two different displacement rates, namely 5 and 10 mm/min. Our preliminary results indicate that ultrasound improves the strength of the neat TPU films. We also see that strain hardening is displacement or strain rate dependent. We attribute these results to changes in the hard (H) and soft (S) domain structure. To further understand these microstructural variations, we propose to conduct Differential Scanning Calorimetry (DSC). The data has been interpreted in conjunction with our mechanical test data.