Specific heat of the synthetic rubber Hycar O.R from 15 to 340 K

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 D ebye 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-Ijust 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 (0.4167 ± 0.0005 calories• gram-I.degree-I).