Melt spinning, polymer-processing technique

Electrospiiming is a polymer process technique that uses electrostatic forces to uniaxially stretch a viscoelastic jet derived from a polymer solution or melt, to produce crmtinuous nanometric and micrometric fibers, typically assembled into nonwoven mats [1—3]. Advancements in proper material design, in controlling process parameters, and in the use of iimovative spinning devices, have allowed a dramatic expansion of the potentialities of the technology. 

Reservoir or coaxial fibers can be produced from the glycolide/ lactide polymers (53,55). Two different methods have been investigated. Dunn (53) utilized a melt-spinning technique in which the drug was introduced during the spinning process as a suspension or solution in a suitable lumen fluid. Eenink (55) developed a dry-... 

Wet spinning. This technique is characterized by spinning a filtered viscous polymer mass, dissolved in a suitable solvent, into contact with a precipitation or coagulation bath. Polyacrylonitrile, polyvinyl acetate, cellulose acetate, and other materials are processed by this method. Thermal requirements for pigments are less stringent than for melt spinning but pigments are expected to be fast to the solvents and chemicals used. 

Because of its extremely low solubility in low-boiling and inexpensive organic solvents, nylon 66 required a new technique for converting the solid polymer into fibers hence the development of melt spinning, the third basic method for producing manufactured fibers. The following description refers essentially to nylon 66 because it was the first to use the method, but the process applies, in general, to all melt-spun manufactured fibers. 

A similar technique can be employed when dry-spinning PHB from solution. In fact there is somewhat greater latitude in the drawing conditions for this process since the spherulitic morphology of solution-cast PHB is much finer and intrinsically more ductile than that of melt-cast polymer. Moreover, residual solvent in the thread line can act as a temporary plasticizer to aid the drawing process. 

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