Studies on melt spinning of nylon 6. I. Cooling and deformation behavior and orientation of nylon 6 threadline

Abstract

Abstract The melt spinning of nylon 6 filament yarns was studied by measuring the filament tensions at the takeup roll, the filament temperatures θ( x ), filament diameters d(x ), and birefringence Δ n(x ) as functions of distance x from the spinneret, and by observing how the molecular orientation was affected by these differences in cooling and thinning. Results were as follows: The thinning of the filament line, d(x ), is affected little by the spinning temperature or by the degree of polymerization of the yarns taken up; it however depends heavily on the takeup speed V Tu and the rate Q of production. Trouton viscosity β( T ) as a temperature function derived from these experiments on nylon 6 is expressed consistently by the equation β ≑ 0.34 exp (3250/ T ), where T is absolute temperature. Nylon 6 filaments exhibit higher Trouton viscosity values than polyester or polypropylene filaments under the same spinning temperature. Filament temperature θ( x ) versus distance x agreed well with theoretical values. The speed of molecular orientation was highest in the temperature range from 120°C to 40°C (the latter being the glass transition temperature of nylon 6). Furthermore, the larger the time rate of polymer deformation and the longer the residence time of polymer in the above temperature range, the higher was the orientation of the filament yarns taken up.