Man-made fibers are classified into synthetic and regenerated fibers. The polymers used for the spinning of synthetic fibers are chemical-based. While regenerated fibers are derived from a natural polymer, most commonly cellulose.
The Spinning of Man-Made Fibers
There are three commonest techniques employed within the production of artificial fibers namely wet spinning, melt spinning, and dry spinning. These techniques vary within the method of liquefying the staple (powder or pellet). The term spinning here defines the extrusion process of the liquefied polymer through spinnerets to solidify during a continuous flow. The melt spinning may be a simple transformation of the physical state; however, it is often applied only to polymer having a melting temperature, e. g. PA 6, PA 6.6, PES, PP, etc. In melt spinning, the extruded polymer is transformed directly into a filament due to its fast cooling, and cross-sectional form remains unchanged.
In the case of solution spinning, the polymer is dissolved in variable concentrations consistent with the type of polymer and of solvent to supply a viscous liquid (dope). It’s used for the polymers that degrade thermally at a temperature less than freezing point (cellulosic fibers). The extruded filaments are subject to structural changes thanks to solvent extraction from the polymer mass. the answer spinning is further divided into type, dry spinning, and wet spinning. In dry spinning, the solvent is removed by the flow of warm gas directed to the extruded filaments. The wet spinning method involves the introduction of extruded polymeric viscose into a coagulation bath, where water behaves as a solvent for the polymer-solvent and as a non-solvent for the polymer mass.
The basic element of a cellulose macromolecule is glucose. The formula of cellulose is (C6H10O5 ) n, where n represents the number of glucose molecules constituting the cellulose macromolecule and is named the degree of polymerization (DP). The α-cellulose (insoluble in cold dilute NaOH) features a DP greater than 200. While β-cellulose (hemicelluloses soluble in cold dilute NaOH) has DP but 200. The pulp is employed because of the staple for cellulose and is refined to extend the per-centage of α- cellulose. The share of up to 99 you can also be obtained counting on the cleaning method. The regenerated fibers are produced consistent with the viscose spinning method.
The production of viscose fiber involves the method of solution spinning. The viscose solution for spinning is ready by treating cellulose with NaOH producing alkali cellulose. This alkali cellulose reacts with carbon disulfide to offer cellulose xanthate, which on dissolution in NaOH gives a viscose solution. This solution is extruded from the spinneret into the spinning bath. The composition of the spinning bath, its temperature. The spinning speed is adjusted consistent with the sort of fiber to be spun. The solidification into yarn takes place within the spinning bath. These spun fibers are drawn to realize a daily orientation of the chain molecules.
The spun fibers are further treated to get rid of impurities, increase brightness, and improve adhesive and frictional properties. These treatments may include washing, bleaching, application of some finish, etc. The spinning process parameters allow the manipulation of properties to a wider level, producing certain fibers like high tenacity viscose, highly crimped viscose, hollow fibers, modal, etc. By the addition of suitable chemicals in viscose solution or spinning bath, spin dyed, flame retardant fibers, etc. are often produced.
Acetate Fiber – Man-Made Fibers
The staple for the assembly of acetate fibers is additionally cellulose. But they’re composed of ester. The cellulose is mixed with anhydride and glacial ethanoic acid under the addition of wet splitting chemicals. The spinning is administered consistent with the dry spinning technique. The spinning solution is transported to the spinning pump and extruded through a spinneret. The filaments exiting the spinneret are a skilled stream of warm air within the quench duct which results in evaporation of solvent acetone and alcohol and freezing of filaments. During the passage, the filaments are drawn, combined, oiled, and wound onto bobbins.