Textile substrates are formed from yarns or fibre webs by several techniques including weaving, knitting, tufting, and nonwoven formation. Composites of textile substrates are formed by bonding two fabrics together by use of an adhesive to form a bonded substrate or backed substrate or by application of cut fibres to an adhesive-coated substrate to form a flocked substrate.
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Textile Substrate Formation
Yarns often must undergo additional processing before they are ready for use in forming of a texti 1e substrate. The yarns may need to be rewound onto appropriate packages, reinforced by application of size, lubricated by appl ication of spinning oil, and/or drawn-in and tied into the machine used in fabric forming. The combined process used for size application and lubrication of warp yarns in weaving and warp-knitting is called slashing.
Winding processes involve movement of yarn from one package to another and often conversion of the overall size, shape and tightness of the packages. These processes also serve other important functions. Winding allows clearing of the yarn to eliminate thin spots, thick spots, knots, and other imperfections, and makes it possible to regulate tension within the package, combine or segment yarn packages, and prepare packages for dyeing prior to substrate formation.
The yarn is wound onto the pirn sequentially in such a way to assure steady and even release of yarn from the pirn during the weaving process.
Warping and Slashing
A specialized type of package formation is involved in preparing warp beams for weaving or warp knitting. A high degree of tension is placed on the warp during these processes, therefore the yarns must be lubricated to minimize friction between yarn and machine parts and adhesive must be appl ied to the yarn to strengthen and reduce the hairiness of the yarn.
Staple yarns and some filament yarns must undergo slashing. Slashing involves simultaneous application of sizing and lubricant to the warp from one bath called a size box, followed by drying to remove water or solvent, breaking the slashed warp yarns away from one another using least rods, and rewinding of the warp. Sizes and lubricants used on warps will vary with fiber type. Sizes used include starches and gums, cellulose derivatives such as carboxymethyl cellulose, proteins, polyvinyl alcohol, polyvinyl acetate. and acrylic copolymers, while the lubricants used are similar to spinning oils and include mineral and vegetable oils and waxes as well as derivatives of these materials.
Drawing-In and Tying-In
After warp beams are prepared, the warp yarns must be drawn through certain elements in the loom or warp knitting machine before fabric can be produced.