Thermal properties of rubber compound : thermal diffusivity

Thermal diffusivity can be conveniently determined by observing temperature change as a function of time for sample geometrical shapes under heating condition. Alternatively of course if k r and Cp are known or separately determine. Thermal diffusivity can be calculated from its definition as thermal diffusivity = k/r*Cp. As specific heat is an additive property, it is generally convenient to calculate specific heats of rubber compound than to measure them. Specific heat of a rubber compound is given by

Cp = w1*C1 + w2*C2 + w3*C3 + …..

where w1, w2 and w3 are weight fractions of the ingredients and C1, C2 and C3 are their specific heat. In general for rubber compound above the grass transition thermal diffusivity tends to decrease slightly with increasing temperature. This is attributed to an increase of specific heat as temperature increase. However some author stated that there is no significant change in thermal diffusivity over the temperature range from room temperature up to 140 *C.