Variation of thermal stress and dimension of rubber solids upon heating

Gaining an understanding of the dimensional changes and thermal stresses of rubber materials upon heating is very important for the product safety, improved performance and optimum design of the products designed for use under elevated temperatures. The dimensional changes and thermal stresses of pre-deformed natural rubber (NR) and styrene-butadiene rubber (SBR) specimens were investigated and the developed thermal stress was measured at the same conditions as the dimensional change measurement. The dimensions of the stretched rubber specimen initially shrunk at an elevated temperature due to entropic movements, but later increased due to thermal expansion or viscoelastic response. The developed thermal stress increased with increasing pre-strain and temperature because of the entropic nature. The NR specimen showed higher thermal stresses than the SBR specimen.