Study of viscous flow during thin film polymer coating and drawing of continuum

This study involves both theoretical and experimental thin polymer coating on wire as well as drawing of wire by hydrodynamic pressure technique. Hydrodynamic pressure technique is a relatively new and innovative technique for wire drawing and thin polymer coating. The wire submerged in polymer melt inside the pressure unit of different geometry, when pulled developed hydrodynamic pressure in the melt. This pressure is largely responsible for wire drawing or coating. Most of the theoretical works earned out to date on this new process have considered that the viscosity of the polymer remains unchanged dunng the process Change in shear stress was also not accounted for in those studies Also the pressure in the fluid film was considered to be constant across the film thickness. It is felt that any analysis of the process addressing the above shortcoming would give a more thorough understanding of the process. With this aim in view, several numerical and analytical models were developed for the process. These models help to predict the pressure, temperature and deformation profiles for different die geometries. Finite difference and finite element technique were used to obtain the solution.s Theoretical results from these models were compared with previous expenmental and theoretical results. All models predict closer or marginally closer results to the experimental results than the previous. As the wire is first pulled through the polymer melt chamber before the hydrodynamic pressure unit, the first interaction between the wire and the polymer melt plays an important role for subsequent process in the pressure unit. Theoretical study of the effect of the melt chamber condition on the whole process was so far been overlooked. In this project some theoretical models were developed to study the temperature and velocity gradient boundary layer thickness as well as the melting profile of the solid polymer layer within the polymer melt chamber. Finally, most experimental works on the process concentrated on wire or other continuum drawing Works on good thin polymer coating by the process had mixed success. The maximum wire speed attained m these works was 0 6 m/s which is considered to be rather low for industnal scale production. The experimental work in this project was mainly focused to attain at 15 to 20 times higher than the best previous achievement. To this end, the work bench, wire feed mechanism, polymer feed system and hydrodynamic pressure units were either modified or designed and manufactured a new. With this new set up it was possible to produce quality coating at as high as 12 m/s speed of the wire at different temperatures and back pressures of the polymer melt