Crystallization‐controlled limitations of melt spinning

Abstract

A numerical simulation of melt spinning reveals bifurcation of dynamic solutions leading to limited spinning conditions. The bifurcation phenomenon is controlled by stress-oriented crystallization and crystallinitydependent polymer viscosity. Under the conditions of bifurcation, the space of the spinning conditions (take-up velocity  filament thickness) splits into three regions corresponding to amorphous fibers, partially crystalline fibers, and inaccessible conditions. Major factors affecting the maximum spinning speed and minimum filament thickness for melt-spun poly(ethylene terephthalate) are analyzed.

Kinetics of oriented crystallization of polymers in the linear stress-orientation range in the series expansion approach

“…The increase in crystallization rate is estimated for several orders of the magnitude in fast melt spinning processes. Rapid oriented crystallization causes hardening of the polymer which prevents further drawing of the filaments on the spinning line and introduces limitation in the attenuation of the fiber and achievable spinning speed [4,5,28]. The influence of crystallization on the rheological behavior has been investigated experimentally, as well as by using modeling concepts [24,[29][30][31][32][33][34][35][36][37][38][39][40].…”

“…The influence of crystallization on the rheological behavior has been investigated experimentally, as well as by using modeling concepts [24,[29][30][31][32][33][34][35][36][37][38][39][40]. Significant effects of oriented crystallization has been indicated by modeling of melt spinning processes that include effects of hardening of the polymer by online crystallization, such as high-speed melt spinning [4,5,24,28], melt blowing [41][42][43], pneumatic melt spinning in the Laval nozzle under supersonic air jet [43,44]. In the modeling of polymer processing under variable molecular orientation and temperature conditions, the crystallization rate has been expressed by a quasi-static formula [5,6] obtained by an extension of the Avrami-Evans formula basing on the nonisothermal Nakamura approach [45,46].…”

“…The formulas have been determined in the range of large undercoolings, and there is no reliable information, experimental or theoretical, from which the coefficient could be determined in the entire temperature range. Modeling of melt spinning processes with the oriented crystallization effects indicates that the oriented crystallization coefficient is responsible for important effects in the process dynamics and structure formation [4,5,28,[41][42][43][44]. None of the actually available models are satisfactory for calculating the kinetics of oriented crystallization under variable temperature in the entire range of undercooling with the use of the oriented crystallization coefficient proposed by Ziabicki [2,47].…”

Heat - Mechanically Induced Structure Development in Undrawn Polyester Fibers

“…The performances of the non-isotropic polymer systems strongly depend on their super molecular structure (Wu et al, 2001;Shabana, 2004;Keum & Song, 2005;Ziabicki & Jarecki, 2007;Sulong et al, 2011). The wide application and consequently higher production of flexible chain fiber forming polymers, in particular poly (ethylene terephthalate) (PET) is due to the possibility of the heat mechanical modification to obtain highly modular and high strength materials from them (Llana & Boyce, 1999;Bai et al, 2000;Dupaix & Boyce, 2005;Guzzato et al, 2009).…”

Birefringence in heat-mechanical modified freshly moulded polyester fibers

“…The final structure of the polymeric filaments depends mainly by the melt spinning conditions and by the subsequent heat-mechanical modifications, too. The desirable super molecular structure and the needed final morphologies and properties of the polymer fibers can be obtained by controlling of the forming process parameters as well as the subsequent treatments [4][5][6]. Several experimental aspects of the deformation behavior and super molecular structure rearrangement in PET fibers caused by heat and mechanical treatments have been investigated in the recent years including participation of the authors of this article.…”