A MODEL TO PREDICT RESIN PRESSURE BACK FLOW IN THE TAPERED INLET OF APULTRUSION DIE

Pressure analysis for a pultrusion die is very important for improving the finished product quality. The die inlet, which is usually tapered over a very short distance, is responsible for a pressure rise due to the back flow of resin. A mathematical model was developed for back f low/pressure analysis in the tapered die inlet. The model was based on the hydrodynamic theory of lubrication applied to the thin outer visc ous annulus layer. The effects of various parameters such as the resin viscosity, preform size, pull speed, and profile of the inlet taper w ere examined. The present model may be utilized to obtain the best die inlet shape and the process conditions to achieve maximum possible pr essure rise in the die inlet.