Warp knitting

Warp knits consists of meshes that are formed, in contrast to knits, in the production direction. Further, the needles do not move individually but in groups connected in needle bars. 

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Commercially, elastomeric fibers are almost always used in combination with hard fibers such as nylon, polyester, or cotton. Use levels vary from a low of about 3% in some filling stretch cotton fabrics to a high of about 40% in some warp-knit tricot fabrics. Raschel fabrics used in foundation garments normally contain 10—20% spandex fiber. 

Microdenier nylon and polyester were a significant spinning breakthrough when demonstrated in 1985. The finer-than-silk fibers added a new dimension to fabric aesthetics, comfort, and performance. Microdenier nylons are used in weaving, warp knits, and weft knits for sports-, leisure-, and... 

Knitted fabric constmction characterization is discussed in ASTM D3887. Characterization of knitted fabrics includes yield (area per weight), width, length, and yam count (number of courses and wales per unit length). The type of knit is also specified, eg, warp knit or weft knit. Yarn analysis may be difficult on account of problems in raveling individual yams from the knitted stmcture, particularly warp knits. 

There are two types of knitting used in mbber product construction, i.e., warp knitting and weft knitting. 

The basic stitch produced in warp knitting is the chain stitch. The yam is looped around the needle stem and another loop of the yam is formed in the hook of the needle and is then pulled through the first loop, itself then becoming the loop held on the needle shaft, whilst another loop is formed in the hook. In this way a chain of interlaced loops is formed. By displacing every other loop onto the next needle, the chains of interlaced loops are linked together to form the simple knotted tricot structure. If one of the yam loops become broken in this type of fabric then the whole fabric, in the line of the yam, will unzip . This problem can be overcome by displacing the throw of the stitches. 

Ko, F.K., Oastorc, C.M., Yang, J.M. and Chou, T.W. (1986). Structure and properties of multi-layer, multidirectional warp knit fabric reinforced composites. In Composites 86 Recent Advances in Japan and the United Slates, Japan Society for Composite Materials, Tokyo. 

In the middle of the pack, the gauzes consist of warp knitted gauzes with lower voidage and possibly smaller diameter wire. 

SOFTENER 900C is a fine particle size colloidal cationic emulsion that produces a silky smooth handle to knitting yarn and circular or warp knit fabrics of natural or synthetic fibers and their blends. 

Softener for tricot and other warp knit synthetics. Minimum effect on crockfastness. 

The goods may be solvent scoured in rotary drum machine, restricting the load to 50% of the machine maximum capacity and the centrifuging time to 1 min to avoid the formation of pressure creases. Warp knitted fabrics are, in general, more stable to tension than weft knitted fabrics. 

Based on the tubular fabric mercerizing machine, Domier, GmbH, has developed a combinable mercerizing and bleaching concept for tubular warp knitted fabrics. The combined mercerizing/bleaching machine (Fig. 9-23) comprises im-... 

Figure 9-23. Combined mercerizing/bleaching machine for tubular warp knitted fabrics (Courtesy of Domier, GmbH).

Warp Knit Fabric Manufacturers Group, National Federation of Textiles, Inc., 389 Fifth Ave., New York 16, N.. Y. G. V. P. Marks, chairman. 

Actually, elastomeric knitted fabrics account for the highest proportion of commercial sportswear. The knitting technology involves warp knitting and circular knitting. The former relates to tricot, raschel, and double-needle-bar raschel the latter involves single knit, interlock, double knit, and rib knits. 

Raschel Warp knit raschel fabrics are produced in a similar way as tricot fabrics except for their stitch motions. The motion results in elastic yams being put into raschel construction as lay-in-yams versus knit-in yams on tricot constractions as shown in Figure 3.7. This lay-in stmcture leads to the raschel fabrics with elastic stretch in the length direction. Other elastic bar movements are possible to increase stretch and modulus in width. Raschel machines can have up to 64 yam guide bars to produce fabric patterns as extensive as jacquard lace. Elastomeric fabrics made by raschel showed good elastic stretch, recovery, and modulus in both length and width directions as elastic yam lap increases. 

Special requirements for warp knitting include the following (1) a device is required for proper density and even tension of elastomeric yams in producing elastomeric fabrics with repeatable results in stretch, recovery, modulus, shrinkage, and elastic fiber content (2) yam let-off must be electronic or electromechanical for best fabric control and reproducibility (3) special selvage holders (pullers), fabric hot-wire slitters. 

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