A Rheological Study of Stress Relaxation in Elastomers for in situ X-Ray Diffraction Measurements

Obtaining a deeper understanding of the processes that occur in elastomers during stress relaxation has been identified as a problem of great scientific importance. To this end, stress-strain measurements have been performed in situ with X-ray and neutron diffraction measurements. Here, we develop a mechanism for carrying out these measurements in a compressional strain configuration and compare these results with those in an extensional strain configuration. Measurements of the tensile relaxation moduli of polychloroprene (neoprene) and nitrile butadiene rubber (buna-N) elastomers are performed and analysed. Three techniques of data analysis are employed and contrasted: the standard linear solid model (SLSM), an extended Maxwell model, and the CONTIN algorithm for performing the regularized Laplace transform. Through these techniques, details regarding the magnitude and time-scale of various processes are extracted.