Determination of the Heat Capacities of Gun Propellants by Differential Scanning Calorimetry

Abstract

The specific heat of gun propellants is an important physical parameter, since the burning rate of such materials depends, in part, on the thermal diffusivity of the unaltered solid. In order to support combustion modeling work, the specific heat vs temperature of a typical double-base propellant and four grades of cellulose nitrate were measured with a commercial differential scanning calorimeter, since measured specific heats were unavailable for these materials. The specific heat of the four military grade cellulose nitrates was measured from 298 to 390K. Over this temperature range, the specific heat of each grade may be represented as follows: Grade B, C¯p= (0.0184 + 0.764⊝) cal/g-K; Grade C (Type I), C¯p= (0.0201 + 0.786⊝) cal/g-K; Grade C (Type II), C¯p= (0.0241 + 0.791⊝) cal/g-K; and Grade D (Pyroxylin), C¯p= (0.0256 + 0.817⊝) cal/g-K, where ⊝ = T/1000K. The specific heat of X14 propellant was measured over the temperature interval of 283 to 343K. The specific heat of X14 can also be represented by the same two-term equation as the cellulose nitrates. For X14 the specific heat is C¯p= (0.118 + 0.066⊝), cal/g-K with ⊝ = 1000/T.