Instabilities in Fiber Spinning

FIGURE 9.11 Breakup of a molten thread due to capillary wave 

FIGURE 9.12 Space of aU possible melt-spinning conditions, including regions of hydrodynamic stability H, cohesive fracture F, capillary breakup C, spinnability S, and hydrodynamic instability x-H. (Reprinted by permission of the publisher from Ziabicki, 1976.) 

The various melt-spun materials can be divided into three groups (Ziabicki, 1976) (1) metals and glasses, (2) linear polycondensates (polyesters and polyamides) with relatively low molecular weights (from 10,000 to 30,000), and (3) linear polyolefins and vinyl polymers (PE, PP, PVC, etc.), with relatively high molecular weights (from 50,000 to 1,000,000). The basic differences between these groups are the following  

Metals and glasses are primarily Newtonian fluids with high surface tension (from 100 to 500 mN/m) and thus a high probability of capillary breakup. 

FIGURE 9.13 Diameter ratio of a drawn silicone oil filament as a function of draw ratio. Polymer volumetric flow rate in mm /s and spinning length in mm are A—64.1, 20 Q—44.4, 20 —30.8, 40. (Reprinted by permission of the publisher from Donnelly and 

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The experimental and theoretical literature on instabilities in fiber spinning has been reviewed in detail by Jung and Hyun (28). The theoretical analysis began with the work of Pearson et al. (29-32), who examined the behavior of inelastic fluids under a variety of conditions using linear stability analysis for the governing equations. For Newtonian fluids, they found a critical draw ratio of 20.2. Shear thinning and shear thickening fluids... 

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