Self-Purification of Isotactic Polypropylene Films from Unknown Impregnated Impurities

Abstract

Commercial films of stereoregular isotactic polypropylene (PP) are the objects of the study. The aim of the work is to substantiate the mechanism of the previously observed weight loss of the PP films as a result of consequtive sorption of hydrophobic and hydrophilic substances, while considering PP as a combination of hydrophobic and hydrophilic localized and delocalized sorbents. A variable sequence of the processes of sorption of probe molecules with different polarities is used as an investigation method, while only an analytical balance serves as a research instrument. It is shown that the weight loss of PP films during the sorption of a hydrophilic substance (water) after their preliminary swelling in a hydrophobic sorbate (hexane) containing a small amount of native water is caused by complexation of water molecules with hydrophilic impurities. As a result, a reverse flow of these complexes out of the polymer occurs along the transport channels that arise during its swelling in the hydrophobic sorbate (hexane).