Determination of Thermodynamic Compatibility of Crystallizing Polymers and Plasticizers

Abstract

A method for determination of thermodynamic compatibility (TDC) of the components of a binary system “crystallizing polymer - plasticizer” is developed. The method is based on experimental determination of the melting point of the system using differential thermal analysis (DTA). TDC of the plasticizer and polymer is determined from the absolute value and sign of the energy interaction parameter which is obtained from the Flory equation that describes lowering of the melting point of the polymeric crystal with a solvent present. Computerized calculation of the energy interaction parameter from experimental data is carried out using the least squares technique. The experimental procedure includes preparation of “polymer - plasticizer” compositions: mechanical mixing of the components with the plasticizer content in a binary mixture ranging within 0 - 50% (in 10% increments) and studying of the compositions weighting about 0.2 g in a DTA device. The results of TDC determination of some known plasticizers with a crystallizing polymer (the crystallinity of 50 - 70 %) are presented.