Measurements of specific heat were made on a sample of Hycar O.R. synthetic
rubber from 15° to 340° K by means of an adiabatic vacuum-type calorimeter.
The experimental values of the specific heat between 15° and 22° K were well represented
by the Debye specific-heat equation, using a {3v value of 80, and
accordingly the values below 15° K were calculated with this equation. At about
250° K the material has a transition of the second order, the specific heat increasing
by about 40 percent to a value of 1.84 Int. joules·gram-·I.degree-I just
above the transition. From 250° to 340° K the specific heat-temperature curve is nearly linear, and the values can be calculated to within 0.2 percent from the
formula Cp =0.00283T+ 1.126, in Int. joules· gram-I. degree-I. At 298.16° K
(25°0) the specific heat is 1. 971 Int. joules· gram-I. degree- I (0.4712 calories· gram-Idegree- I). The increase in entropy resultin&. from heating from 0° to
298.16° K was calculated to be 1.743 ± 0.002 Int. joules· gram-I. degree- I