Structure in Polyurethane Elastomers

The formation of radial spherulites in urethane elastomers is also known. Increased degrees of crosslinking in these elastomers reduces their ability to crystallize. 

Strength retention in any elastomer over an extended range of temperature is usually ascribed to the presence of a dispersed phase which results from the presence of strain-induced crystallites or the presence of a small particle-size particulate filler (with a chemically active surface). It is the domain structures in a urethane elastomer that are considered to provide these functions. 

Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) is widely used to detect and measure the different types of structure present in a urethane elastomer. The observed transitions usually fall into the following three groups  

Endotherms in the region of 60-100°C are usually ascribed to dissociation of the urethane flexible-segment hydrogen bonds. 

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