A SEMIEMPIRIC MODEL FOR ESTABLISHING THE DRAWABILITY OF SOLUTION-SPUN LINEAR POLYAMIDES AND OTHER FLEXIBLE CHAIN POLYMERS

A series of high molecular weight, linear polyamide samples have been subjected to various solution spinning techniques, such as gel, wet, and dry spinning, in an attempt to produce high‐tenacity filaments. The spinning experiments involved polyamide 6, polyamide 12, and copolymers thereof, with a molecular weight Mw in the range of 105−106 kg/kmol. Filaments with a tenacity of 100 cN/tex have been obtained. Their draw ratio never surpassed a value of six, which may also be reached after conventional melt spinning. Apparently, the drawability of polyamides cannot be improved via solution spinning techniques, although a favorable molecular topology for accomplishing high draw ratios has most likely been realized. This behavior is in sharp contrast with the highly increased drawability after solution spinning of less polar polymers, such as polyethylene or polyvinyl alcohol. A semiempirical equation is now proposed that relates the maximum drawability of flexible chain polymers with their polarity, being expressed in terms of cohesive energy. A preassumption underlying this equation is that drawability is not limited by a high entanglement density as is, e.g., the case after melt processing. Copyright © 1990 John Wiley & Sons, Inc.