When a thermoplastic shape is extruded and drawn into a quenching medium and the drawing speed increases continuously, the cross‐sectional extrudate area decreases. At a critical take‐up speed, a cyclic gauge pulsation begins, becoming more pronounced with increasing drawing speed until the extrudate eventually breaks at the air‐coolant in terface. This phenomenon, “draw resonance,” originates in the air gap and is independent of any melt fracture phenomena. Correlations show increasing pulsation severity with increases in speed ratio, air gap, viscosity‐average molecular weight, and decreasing melt temperatures. Draw resonance occurs with polypropylene and various types of polyethylene and polystyrene. Ribbon‐type and round‐hole dies give equivalent results. A semi‐quantitative theory is advanced is explain these phenomena in terms of thermodynamic relationships and basic molecular properties.
No takes yet. Share an insight, caveat, or question.
Bergonzoni et al. (1966) studied this question.