The nature of the boundary layer between polyvinylchloride and a filler surface

The gel-fractions of PVC compositions filled with Aerosil, kaolin, chalk, silica flour and modified Aerosils have been studied. It has been shown that the amount of the gel-fraction increases rapidly beginning at a filler concentration where a three-dimensional structure is formed by the particles. Thermogravimetric analysis and IR spectroscopy of the gel-fractions, as well as a study of the volume reversibility during extension, have been used to observe the presence of a crosslinked PVC layer close to the filler surface, the “ordinary” boundary layer being connected to this crosslinked layer.