Phase equilibria and transformations in low-density polyethylene–p-xylene system

Abstract

The state diagram of the low-density polyethylene–p-xylene system that contains the solubility curve of p-xylene in the polymer is first built using the optical method with the involvement of the DSC data. It has been shown that, at 72°C, in a blend with a polymer mass fraction of 0.28, the full amorphization of the polymer proceeds simultaneously with the dissolution of p-xylene in it. Blends with a lower polymer content are also homogenized at the same temperature, although the duration of this process can take several days. In blends with a high polymer content, homogenization occurs at a higher temperature. This process is preceded by the formation of microheterogeneous single-phase gel with network junctions as polymer crystallites and amorphous regions saturated by p-xylene. Cooling of the homogeneous blends to–20°С is not accompanied by the full separation of low- and high-molecular-mass phases; in this case p-xylene not only forms an individual crystalline phase, but also partially crystallizes in amorphous regions of the polymer.