Tensile properties, thermal and morphological analysis of thermoplastic polyurethane films reinforced with multiwalled carbon nanotubes

The paper reports on thermal, tensile and morphological properties of thermoplastic polyurethane (TPU) based films obtained by melt-compounding and chill-roll extrusion. Composite films containing up to 1 wt% of multiwalled carbon nanotubes (MWNTs) are characterized in terms of thermal properties, tensile behavior and morphological issues taking the neat TPU film as the reference material. The filler content does not alter the melting temperatures of the hard and soft phases of the matrix but it influences, as the tensile strain, their degree of crystallinity. Mechanical results have highlighted that the tensile behavior of composite films is strongly related to structural changes induced by the process and testing on the complex morphology of the hosting matrix. In this context, all results, collected on as produced and tensile strained films, are interpreted by assumptions based on the mutual organization of hard and soft phases of the matrix induced by the filming process and strain-crystallization phenomena coming from the included filler and deformations as confirmed by tapping mode atomic force microscopy (AFM) observations.