The Modelling of Orientation in Planar Polymer Welding Flows.

Welding flows occur in many important polymer processing operations. When two streams of molten polymers meet and form a weld interface, the macromolecules near the interface can be highly oriented due to the flow history. Weld interfaces would vanish very quickly in a low molecular weight material. However, macromolecules need a long time to diffuse across the interface induced orientation on the welding process is largely unknown. This work establishes a mathematical model quantifying orientation development in two-dimensional welding flows of polymer liquids and tests the model experimentally. The modelling consists of three phases 1. Determination of the approximate kinematics by using a finite element analysis. 2. Integration of the deformation history by tracking material elements based on continuum mechanics. 3. Calculation of the stress by using a memory integral constitutive equation. The modelling applies to molten homopolymers.