STUDY OF BINARY INTERACTIONS INVOLVING POLYETHYLENE AND HYDROCARBONS BY THE MELTING-POINT DEPRESSION METHOD

The thermodynamic interaction parameter, chi-phi, for a low-density polyethylene in p-xylene, ethylbenzene, and n-octane has been determined over a range of segment fraction, phi-2, from 0.2 to 0.7 using the melting point depression method. Taking advantage of a unique feature of polyethylene, a new procedure has been proposed for evaluating the equilibrium melting points from data obtained by differential scanning calorimetry. The experimental chi-phi-phi-2 relations conform well to the recent equation-of-state theory of polymer solutions. The exchange parameters of the model X12 and Q12 are accessible by a nonlinear least-squares algorithm. Apparently, the observed small values of chi-phi for the foregoing dispersion force interactions are originated from the negative contribution of the effective interaction energy as concluded by the present findings.