HEAT EXCHANGE AND NONISOTHERMAL CRYSTALLIZATION IN FORMATION OF A PLANE VISCOELASTIC FILM

The processes of heat exchange and of nonisothermal crystallization in the formation of a plane viscoelastic polymer fi lm are investigated. The polymer melt is forced through a plane-slitted extrusion head, subjected to uniaxial stretching and simultaneously to cooling in air, and subsequently gaining access onto a batch-off cooling roll. It is assumed that the fi lm is wide enough, and the distance between the extruder head and the batch-off roll is minimum to such a degree that it is possible to neglect the change in the sheet width in the process of longitudinal stretching. A steady nonisothermal process is considered. It is also considered that the gravity and inertial forces and surface stretching can be neglected. From the rheological point of view, the polymer melt represents a viscoelastic fl uid. The upper-convected Maxwell model is used with viscosity depending on temperature and crystallinity degree. The mathematical model is complemented by the equation of kinetics of nonisothermal crystallization. The problem has been solved numerically by the method of fi nite differences
   
Author:  A. V. Baranov
Keywords:  viscoelastic fl uid, heat exchange, formation of plane fi lms, crystallization
Page:  329