Phase diagram of the low-density polyethylene - dimethyl terephthalate system: A new topology

A new type of phase diagram semicrystalline polymer - low molecular mass substance is found for the low-density polyethylene - dimethyl terephthalate mixture. Exploiting an original optical method and differential scanning calorimetry, we demonstrate that the studied system combines the features of polymer - poor solvent and polymer - high-melting substance mixtures. Its diagram also contains a curve describing the solubility of the low molecular mass component in the polymer, which is often missing in the literature. An experimental phase diagram enables us to perform a detailed analysis of the differential scanning calorimetry, optical and scanning electron microscopy data on the cooling of homogenized mixtures of different compositions, which leads to the formation of capillary-porous polyethylene bodies via thermally induced phase separation and following removal of dimethyl terephthalate crystals.