Warp yarns

Luana A fabric characterized by a crosswise rib effect, usually made with a filament yarn warp and a spun yarn filling. 

Table 13.2 Mean roll distance as a measure of the laser-generated surface topography on the filaments of the PET multifilament yarn (warp yarn).

Forming fabrics are manufactured on weaving looms with a width of up to 15 m, where CD yarns (wefts) and MD yarns (warps) are interlaced with each other. The weft insertion is typically made by using shuttles, projectiles or band rapier systems. 

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. 

A recently developed medium known as a double weave incorporates different yarns in warp and fill in order to combine the specific advantages of each type. An example of this is Style 99FS, made by SCAPA Filtratiou (formerly P S Filtratiou), in which multifilameut warp yarns provide good cake release properties and spun staple fill yarns contribute to greater reteutivity. 

It is also common practice to classify filter media by their materials of construction. Examples are cotton, wool, linen, glass fiber, porosmooth surface caused by carrying the warp (or the weft) on the fabric surface over many weft (or warp) yarns. Intersections between warp and weft are kept to a minimum, just sufficient to hold the fabric firmly together and still provide a smooth fabric surface. The percentage of open area in a textile filter indicates the proportion of total fabric area that is open, and can be determined by the following relationship ... 

The choice and combinations of different size components must take account of many factors if optimum results are to be obtained. Much has been published regarding the optimisation of size formulations in relation to desizing processes [177-183]. Cotton warp yarns sized with starch are normally woven at high humidity (80% and above) to keep yarn breakages low, as the starch film is brittle at low humidity. It has been shown [183], however, that improved weavability at moderate relative humidity (e.g. 65%) can be obtained using (a) starch/acrylamide or hydroxyethyl starch at not less than 15% add-on or (b) poly(vinyl alcohol), which gave excellent results even at a low add-on of 5-6%. 

The special requirements of the indigo dyeing of cotton warp yarns for denim are capable of being met by indirect electrolysis systems [241]. Examples of four suitable redox systems are shown in Table 12.37. Uniform build-up of depth was observed with each successive step, the results being at least equal to those from the conventional dithionite-based process. Apparendy these processes are amenable to scaling up to bulk production levels [241]. 

One of the problems encountered in early polyester fibre processing was that the sizes generally used with other classes of fibre to protect yarns, particularly warp yams, against damage during weaving were not sufficiently adherent to the yarn. ICI found a surface treatment that would improve the adhesion of sizes to... 

ISO 4602 1997 Reinforcements - Woven fabrics - Determination of number of yarns per unit length of warp and weft... 

Fabrics. These are characterized by o the weave pattern or crossing scheme of the warp (lengthwise) and weft (perpendicular to the warp) yarns... 

Fig. 8.24. Weft knit with laid-in weft and warp yarns. After Ko (1989).

Before weaving, the warp is covered with a layer of polymer to withstand the mechanical stress (abrasion, tension) during weaving. These polymer coatings are so-called sizes. Normally native starch, modified starch like carboxymethyl-starch (CMS), carboxymethyl-cellulose (CMC), polyvinylalcohols (PVA), polyacrylates, and proteins can be used. The amount of added polymer for staple yarns like Co is between 8 and 20% of the weight of the warp. As a result, in many cases the final amount of polymer to be removed in the desizing step is approximately 5-10% of the weight of the fabric. 

SIZING COMPOUND. 1. A material such as starch, gelatin, casein, gums, oils, waxes, asphalt emulsions, silicones, rosin, and water-soluble polymers applied to yarns, fabrics, paper, leather, and other products to improve or increase their stillness, strength, smoothness, or weight 2. A material used to modify the cooked starch solutions applied to warp ends prior to weaving. 

Woven fabrics have ordered structure in which warp and filling yarns are precisely addressed and controlled. 

Materials. The modern silk fabric tested was Testfabrics style 607 broadcloth, degummed but undyed and unbleached. The fabric yarn was 140/2 cotton count and the warp and filling threads/0.01 m are 40 and 33, respectively. Fabric weight was approximately 56 gm/m. ... 

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