Fibres spinning

PEA is an example of a biodegradable polymer that may not be particularly suitable for injection moulding without nucleating agents, because its crystallisation rate is too slow to allow cycle times typical of common thermoplastics such as PS [42]. Stress induced PEA crystallisation is actually better exploited by processes such as fibre spinning or the biaxial orientation of film. 

PLA can be spun both in a high-speed spinning process with a take-up velocity of up to 5,000 m/min and in a spin drawing process up to a draw ratio of 6 [105]. 

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Polymers owe much of their attractiveness to their ease of processing. In many important teclmiques, such as injection moulding, fibre spinning and film fonnation, polymers are processed in the melt, so that their flow behaviour is of paramount importance. Because of the viscoelastic properties of polymers, their flow behaviour is much more complex than that of Newtonian liquids for which the viscosity is the only essential parameter. In polymer melts, the recoverable shear compliance, which relates to the elastic forces, is used in addition to the viscosity in the description of flow [48]. 

Solution processes are used mainly for coating, film casting and fibre spinning, i.e. in processes where the distance the solvent has to diffuse out of the solution once coated, cast or spun is short. Regulation of this diffusion process is important if products of even quality are to be obtained. 

Flow is generally classified as shear flow and extensional flow [2]. Simple shear flow is further divided into two categories Steady and unsteady shear flow. Extensional flow also could be steady and unsteady however, it is very difficult to measure steady extensional flow. Unsteady flow conditions are quite often measured. Extensional flow differs from both steady and unsteady simple shear flows in that it is a shear free flow. In extensional flow, the volume of a fluid element must remain constant. Extensional flow can be visualized as occurring when a material is longitudinally stretched as, for example, in fibre spinning. When extension occurs in a single direction, the related flow is termed uniaxial extensional flow. Extension of polymers or fibers can occur in two directions simultaneously, and hence the flow is referred as biaxial extensional or planar extensional flow. 

Sponner, A., Unger, E., Grosse, F., and Weisshart, K. (2005b). Differential polymerization of the two main protein components of dragline silk during fibre spinning. Nat. Mater. 4, 772-775. 

Dispersion metal coatings, coating, pulverization, impregnation, cast (for thin films), fibre spinning. 

Melt filtration systems are commonly employed in pigment master-batch production and in situations where the presence of defects in the compound may have a critical effect on its subsequent processing or properties. This is vitally important, for example, in fibre-spinning operations involving extrusion of polyester or polyamide through fine spinneret plates [162], and in minimizing breakdown of polymer cable insulation subjected to electrical stress [163]. 

Finally, one of the first continuous ion-exchange plants installed used a weak-acid resin to recover copper from rayon-fibre spinning solutions. In the Bemberg or copper(II) ammonium process,357 the spinning takes place in an addic copper sulfate solution, and the fibre is then washed in ammonia solution. The wash water contains as much as 30% of the copper required for the spinning operation and its recovery is important in economic and environmental terms. The copper is extracted as the cationic amine complex by the weak-acid resin, and is then stripped from the resin with the acidic spinning solution. Zinc is recovered in a similar manner from vicrose rayon-spinning operations. 

The techniques used in the Ml project were those of fibre spinning, open siphon, filament stretching, contraction flows, converging channel, opposing jets, climbing constants and falling drop methods. The results led to two major findings ... 

Zachariades AE and Porter RS (Eds.), "The Strength and Stiffness of Polymers", Marcel Dekker, New York, 1983. Ziabicki AE and Kawai H (Eds), "High-speed Fibre Spinning", Wiley, New York, 1985. 

Another class consists of extrusion immediately followed by an additional stage. This includes blow moulding, film blowing, quenched film forming, fibre spinning, and extrusion coating. 

Fibre spinning techniques were primarily developed for the production of meat analogues. Unfortunately, their technical success did not result in cost competitive products and most of this type of extrusion processing has been shelved. 

Fibre spinning, ductless siphon Low 1] Process simulator Sample preparation easy Entrance condition Corrections g, Photo... 

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