Effect of formulation on properties and morphology of polyurethane elastomers

Abstract

AbstractA model polyurethane elastomers system has been used to study the relationships between chemical formulation, polymer physical structure and mechanical properties. The elastomers were made from formulations comprising a polyether polyol blend (diol plus triol), a chain extender blend (1,4 butane diol plus 1,1,1‐trimethylol propane) and 4,4′‐di‐isocyanate diphenylmethane. The morphologies of the elastomers were investigated in detail, mainly by means of small angle X‐ray scattering techniques. It was confirmed that the polyurethane systems examined comprised domains 50 to 100 Å in size and spaced around 100 to 200 Å apart. A complete decription of the polyurethane morphology has been made in terms of the volume fraction of domains present, the average domain size and the average domain–domain separation. The results suggest that, whilst it is possible to correlate, in general, formulation changes with variations in the elastomer morphology, it seems that direct correlations between physical structure and mechanical properties are not very meaningful in the present model system. However, it is clear that knowledge of the morphology is of considerable importance in interpreting the effects of formulation on observed properties.