Viscoelastic properties and heat generation in urethane elastomers

Static and dynamic properties were studied in a series of polyurethane elastomers as a function of selected compositional variables such as curative system, curative level, catalyst level, and curing temperature. A number of physical properties including swelling ratio, density, glass transition temperature, stress–strain behavior, and thermal conductivity were also measured on these elastomers. The selected variables affect dynamic mechanical properties as well as heat buildup. A good correlation was noted between the loss modulus and the heat generation. The loss modulus and the heat generation decrease with decreasing curative level. The elastomers cured with a mixture of triol and diamine give lower loss modulus and heat buildup than those cured with diamine alone. These responses are believed due to the increase in covalent crosslinks. The observed low heat generation of the elastomer cured with 0.2 phr azelaic acid as a catalyst level was also attributed to the high crosslink density. The curing temperature, in the range investigated, appears to have very little effect on the properties. Thus, the choice of formulation variables, especially the use of diamine–triol blends, provides an effective means of minimizing heat generation in dynamic applications of polyurethane elastomers.