Specific heats of guayule and natural rubbers above the glass transition temperature

Heat capacities of guayule and natural rubbers were measured between 228 and 333 K using a DuPont 990 Differential Scanning Calorimeter. Data obtained were fitted to a straight line. We obtained the following equations where C_p is given in cal g^?1 K^?1. For guayule rubber, C_p = 22.6152 × 10^?4T + 0.7731 (correlation factor = 0.99). For natural rubber. C_p = 16.9195 × 10^?4T + 0.9209 (correlation factor = 0.98). Furthermore, some theoretical considerations and instrumental conditions were analyzed so that the determinations of heat capacities could be improved.