Polymer Properties
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Numerous theoretical equations of state for polymer liquids have been developed. These, at the minimum, have to provide accurate fitting functions to experimental data. However, for the purpose of this table, the empirical Tait equation along with a polynomial expression for the zero pressure isobar is used. This equation is able to represent the experimental data for the melt state within the limits of experimental errors, i.e., the maximum deviations between measured and calculated specific volumes are about 0.001-0.002 cm3/g. The general form of the Tait equation is: V(P,T) = V(0,T){1 - C ln[1 + P/B(T)]} (1) The Tait equation is particularly useful to calculate derivative quantities, such as the isothermal compressibility and the thermal expansivity coefficients. The isothermal compressibility (P,T) is derived from equation (1) as: (P,T) = -(1/V)(dV/dP) = 1/{[P + B(T)][1/C - ln(1 + P/B(T))]} (8) and the thermal expansivity (P,T) as: (P,T) = (1/V)(dV/dT) = (0,T) - PB1(P,T) (9)