MODERN MODELS OF FORMATION OF WELDED JOINTS OF POLYMER MATERIALS (REVIEW).

The process of welding plastics is determined as a gradual disappearance of the interface between parts to be joined and the formation of a transition layer between them, whose structure is significantly different from the structure of the base polymeric material. The models of formation of welded joints of polymers existing today are based on different physical phenomena: mutual adhesion of substrates, diffusion of macromolecules and melt rheology. The most common is the diffusion model of macromolecules reptation in the welding zone, which many researchers refer to in order to explain experimental data. Without denying the possibility of progressive diffusion of elements of the molecular chain through the fusion surface, the postulate that this diffusion provides the main mass transfer during the formation of welded joints of polymers is considered to be controversial. The theory of the formation of welded joints of polymers due to conformational transformations of macromolecule fragments, being developed by the Scientific School of the PWI, is more realistic. In the development of this conformational theory, the model of homogenization of the transition layer on the interface during welding of polymers is proposed based on a vacancy-conformational principle. [ABSTRACT FROM AUTHOR]