Examining the Cold Temperature Properties of Elastomeric Systems in the Linear and Non-Linear Viscoelastic Ranges

Knowledge of cold temperature properties of elastomeric materials is critical to material design and engineering decisions. It is often convenient to use the glass transition temperature (Tg) to indicate the temperatures at which the material changes from a rubbery to a brittle state. The current work focuses on filled rubbers and references data obtained from conventional and modulated DSC analyses with measurements done using a dynamic mechanical analyzer (DMA). The DMA tests were done in the planar shear mode at conditions that represented an application relevant DOE for frequencies and dynamic strains. Plots of storage modulus (G’) vs. temperature and Tan delta vs. temperature showed that a ten to hundred fold increase in frequency resulted in 3°C to 7°C increases in the glass transition temperature. These studies were done in the linear viscoelastic range (e.g. 0.005 dynamic strain) and at larger amplitudes (0.02 to 0.1 dynamic strain). The maximum frequency or dynamic strain studied varied according to the failure mode of the respective rubber material. The increased strain caused the characteristic softening (G’ vs. dynamic strain plots) but had a smaller effect on the glass transition temperature.