Influence of the composition on the crystallinity and adhesion properties of thermoplastic polyurethane elastomers

Crystallinity and adhesion properties of nine thermoplastic polyurethanes (TPUs) prepared by varying the hard-to-soft segments ratio, the molecular weight of the macroglycol (related to the size of the soft segments) and the chain extender size and nature (i.e. hard segments length and morphology) were studied. TPUs structure was characterised using 1H Nuclear Magnetic Resonance (1H NMR), and their properties were studied using Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Diffraction (WAXD). TPUs were used as raw materials of solvent-based adhesives. The adhesion properties were measured from T-peel tests of solvent-wiped polyvinyl chloride (PVC)/polyurethane adhesive joints. It was found that the composition of the TPUs influenced their structure and properties. An increase in the hard segments content in the TPUs reduced the degree of phase separation and the organisation of their structure, resulting in less crystalline polymers with worse adhesion properties.