Solubility parameters of two chlorinated polyethylene polymers

An equation that appears adequate for the calculation of the solubility parameter of random copolymers was tested with two nonrandom copolymers, chlorinated polyethylene (CPE) AK 227 and AK 243, containing 27.8% and 42.1% chlorine, respectively. Flory's equation relating the energy of interaction between polymer and diluent to the depression of the melting point of the pure polymer was used to estimate the solubility parameter of the polymers from solution temperature studies in chlorobenzene, toluene, o-xylene, and p-xylene. Using data obtained on PE as a criterion, agreement within 3% was obtained between the reported δ-value and that estimated from solution temperature studies when toluene, o-xylene, and p-xylene were used as diluents. In the case of the two CPE polymers, values for the gas constant and for the heat of fusion in units of cal/cm³ polymer °K and cal/cm³ polymer, respectively, were obtained by solving simultaneous equations. From the derived gas constant values, the weight of an average repeating unit of CPE polymer was obtained, 39.38 for AK 227 and 46.95 for AK 243, which compares favorably with values obtained using the expression n₁M₁ + n₂M₂ = M_x. For ΔH, the results showed that in going from PE to CPE, a reversal in the sign of ΔH occurs indicating that, in the diluents studied, the value of χ is positive in the case of PE and negative for the CPE polymers. Taking this into account, agreement between calculated δ-values and those estimated from solution temperature studies is within 2% for AK 227 (toluene, o-xylene, p-xylene) and within 1% for AK 243 when toluene and o-xylene were used as diluents. Anomalous results were obtained in the latter case when p-xylene and chlorobenzene were used as diluents and from solution temperature studies of PE in chlorobenzene. The results do indicate that the equation used to calculate the solubility parameter of random copolymers may also be used for nonrandom copolymers such as CPE.