Dynamics of hot-tube spinning from crystallizing polymer melts

Abstract

Computer modeling is applied to discuss hot-tube effects in melt spinning from crystallizing polymers. The set of spinning equations used in the model accounts for stress-induced crystallization, crystallinity-dependent melt viscosity and heat of crystallization. Example computations are performed for polyethylene terephthalate assuming temperature-dependent Newtonian viscosity, strongly modified by crystallization. The consequence of coupling of stress-induced crystallization and crystallinity-controlled solidification is limited range of spinning speeds, and multiple solutions of the dynamic equations of spinning. The range of admissible spinning speeds and multiple (amorphous and crystalline) solutions is strongly affected by the hot-tube temperature.

It is predicted that zone heating, with temperatures above glass transition (hot tube), results in considerable increase of amorphous orientation factor for moderate take-up speeds. In the high speed spinning range, the orientation effects saturate and does not exceed the values predicted for high-speed room-temperature spinning. Application of the hot tube is also predicted to reduce considerably take-up stress.

Available experimental data on amorphous orientation in PET fibers spun by hot-tube technique are in qualitative agreement with the model predictions.