Characterization of elastomer compounds by thermal analysis

Abstract

Thermal analysis provides very useful tools for the characterization and identification of both, elastomer compound and finished product. This investigation focuses on the use of different thermal techniques for compositional analysis, characterization of thermal, oxidative stability and glass-transition temperature ( T g) of different components present in the elastomeric systems. Thermogravimetry (TG) is critical for identification of composition. TG analysis of three compositions ( S 1, S 2 and S 3) shows S 1 and S 2 are soft-oil extended compounds and S 3 is a hard compound, all comprising ethylene propylene diene rubber (EPDM). Energy dispersive X-ray analysis (EDAX) of the residues from TGA reveals the presence of mineral filler clay in sample ( S 3) besides carbon black. The use of high-resolution TG has been found to give better resolution between overlapping weight loss steps leading to better quantification of various components compared to conventional TG. The coefficient of expansion of the rubber compound (from thermo-mechanical analysis – TMA) above T g is correlated to the hardness of the samples. The use of differential scanning calorimetry (DSC) to determine oxidative stability identifies also the presence of similar antioxidants. Dynamic mechanical analysis (DMA) is found to be very sensitive for characterization of glass-transition temperature, visco-elastic properties and, in particular, the adhesion between the elastomer compound and coating.