The Effect of die Land Length on the Surface Appearance of Low Melt Index Polythene Extrudates

摘要

It was demonstrated that a decided improvement in the surface finish of cable jacket extrudates can be obtained by the use of dies and mandrels having long lands. This improvement in surface finish is frequently necessary for those low density polythene compounds which exhibit the best physical properties. In the case of 1 inch diameter cable, a land length of 2 inches was found to combine a marked improvement in surface finish with increases of approximately 50% in melt pressure at the breaker plate and 7% in extruder power requirements in comparison to a die and mandrel having no land. These increases are usually commercially tolerable considering the improved quality of the product. Increasing land length above 2 inches gave only minor additional improvement in finish at the expense of further increases in melt pressure at the breaker plate and extruder power requirements. The use of equipment, extrusion temperatures and jacket dimensions other than those used in this trial may produce numerically different results, but the same trends should be observed. (Author)