THERMAL-CONDUCTIVITY AND THERMAL-DIFFUSIVITY OF SILICONE - POLY(STYRENE BUTADIENE) RUBBER BLENDS FROM 60 TO 300-K

The variation of thermal conductivity and thermal diffusivity with temperature for silicone rubber - styrene butadiene rubber (SBR) blends having compositions of 0 to 100% of SBR is reported. It is observed from the experimental data that polymers with high chain branching and heavy side groups play a predominant role in their variation with temperature. These properties increase with temperature and attain a peak value near the T(g) of SBR and then decrease rapidly asymptotically to a value near room temperature. The experimental values of thermal conductivity for the entire blend composition are empirically correlated by a single polynomial equation for the above temperature zone in the form of C(T) = A1T + A2T2 - A3T3 where the constants A1, A2 and A3 are functions of composition, F. This empirical equation fits the experimental values throughout the range except in the glass transition region of SBR. An approximate theoretical model of thermal conductivity on the basis of Klemen's theory with Ree's modification in the cryogenic temperature region is developed and compared with the experimental results. It shows that except in the transition region it matches qualitatively with the experimental values. The change of thermal diffusivity is also calculated. It is found that these values also match the existing theoretical propositions.