Processing and Characterization of Thermoplastic Polyurethane Nanocomposite Thin Films

In this article, we have set up protocols for fabricating thermoplastic polyurethane thin films of about $30μm$ (neat polyurethane and carbon nanofiber (CNF) containing polyurethane) via ultrasound assisted atomization at 20 kHz. From processing to thin film peel off, we have set up procedures for fabricating our samples. Using optical microscopy, we have examined the manufacturing of these films from a droplet diameter perspective. Our optical microscopy results indicate that the final film microstructure was directly dependent on the physical properties of the neat/CNF reinforced solution. Mechanical testing of these films was then carefully carried out using a dynamic mechanical analyzer (DMA) unit utilizing a specialized thin film test clamp fixture. These test results were compared with control cast films fabricated from the same solutions. For the similar extensions, we observed a drastic increase in the softness of the atomized film. We surmise that the ultrasound assisted droplet generation concurrent with secondary atomization and evaporation could have resulted in reduction of the molecular weight of the polyurethane in our atomized samples relative to the neat ones. Differential scanning calorimetry (DSC) scans have been conducted to confirm the changes in molecular weight. Although results were inconclusive there is evidence of exotherms at 49C in our atomized samples suggested of changes to molecular weight distribution.