Effects of temperature, strain rate, and cyclic loading on mechanical behavior of silane-modified polyurethane sealant

To evaluate the mechanical properties of modified polyurethane sealants in engineering applications, the influences of temperature, strain rate, and cyclic loading on the mechanical properties of silane-modified polyurethane sealant were experimentally investigated. The monotonic tensile experiments with various strain rates and temperatures were conducted, and strain rate and temperature dependent nonlinear stress-strain curves were obtained. The results showed that the silane-modified polyurethane sealant exhibited temperature dependence at constant strain rate and rate dependence at room temperature. However, it is shown no obvious rate dependence at temperature of 150 degrees C. In addition, the multi-step cyclic loading experiments with mean strain decrease and increase at each step were carried out to analyze the influence of cyclic loading and cyclic loading history at different temperatures. The results demonstrated that the viscous behavior of the materials was evidently observed in the first step and disappeared in other steps for the four-step cyclic loading with mean strain decrease case. Moreover, the cyclic stress relaxation of the materials was not obvious due to the prior cyclic loading with higher mean strain history, while the cyclic stress relaxation of the material continued to occur for the prior cyclic loading with lower mean strain history, and the cyclic strength of the materials decreased with the increase of temperature.