A.P.S. Sawhney

Improved Method of Producing a Cotton Covered/Polyester Staple-Core Yarn on a Ring Spinning Frame

A new, better method of producing cotton covered/polyester staple-core yarn on a modified ring spinning frame is described. The method uses the concept of twisting a “sandwich” formed by two drafted strands of cotton (rovings) on the outside and a drafted strand of polyester on the inside, thus using a total of three rovings. The earlier method used only one cotton roving and one polyester roving [10]. The new method is simple and easily adaptable to the existing spinning frames; piecing of broken ends is also easy. A 67/33 cotton/high tenacity polyester staple-core yarn produced by the new spinning system is evaluated. The core of the yarn is almost totally covered with a firm sheath of cotton, giving the an appearance of a 100% cotton spun yarn. Compared with conventional yarns of 100% cotton and 67/33 cotton/polyester intimate blends, the core yarn is significantly stronger than the equivalent 100% cotton yarn and the intimate blend yarn of regular tenacity polyester. These yarns may be useful where a co-axial segregation of different fibrous materials is important or critical. The new staple-core spinning technology can be applied to produce yarns from a variety of core and sheath materials, such as Kevlar, PBI, Nomex, cotton, and wool, among others.

Comparison of Filament-Core Spun Yarns Produced by New and Conventional Methods

In recent years, we have been reporting our research on composite yarns of mostly cotton content produced on a modified ring spinning system. Recently, we reported an improved method of producing an all staple-core spun yarn, and we have applied the same method to filament-core spinning, obtaining a yarn of greatly improved quality. The new filament-core yarn has almost total core coverage, does not strip, and is about 10% stronger (probably due to its improved yarn structure) than a conventional filament-core yarn. This paper briefly describes the new and conventional core spinning methods and evaluates nylon filament-core/cotton-wrap yarns produced with them. There is also a comparison of the cover factor, strip resistance, and microscopic cross sections of a few other core yarns (with Kevlar, fiberglass, and polyester cores). A significant improvement in the cover factor of the new yarn suggests that it may be very useful for sewing threads; ropes; twines; cables; special military, industrial, and surgical fabrics; and other textiles in which the high strength, durability, and a 100% cotton surface (for ease of finishing or coating) are important.

Comparison of Cotton/Polyester Core and Staple Blend Yarns and Fabrics:

Cotton wrapped polyester core yams produced on a modified ring spinning frame were compared with yams spun from staple fiber blends. The yams contained ap proximately 70% cotton and 30% polyester. Yarns and fabrics made from both regular and high tenaeity polyesters were evaluated. Fabrics produced from the core yams were stronger and more durable than those of the staple blends, and they maintained their superiority in these properties through wet processing and resin .finishing. Other advantages of the core-yam fabrics included better cover and abrasion resistance.

A Unique Polyester Staple-Core / Cotton-Wrap Yarn Made on a Tandem Spinning System

A unique, all-staple, core/wrap composite yarn of relatively fine size and low core content has been developed using the air-jet spinning and friction spinning technologies in tandem. First, a fine, high tenacity polyester staple yarn of 10-tex is spun on a Murata air-jet spinner, and this yarn is then used as the core material on a Dref-3 friction spinner. The air-jet yarn is covered with a wrap or sheath of 100% cotton fibers, producing a 30-tex, 33/67 polyester/cotton, composite yarn with a nearly 100% cotton surface. We have tested the yarn for its physical and mechanical properties, including core coverage factor and strip resistance, and compared it with the equivalent size polyester staple-core/cotton-wrap yarns produced by the USDA-patented ring spinning system. Because of the relatively fine size and low core percentage of the yarn, we were unable to produce a satisfactory comparable yarn on the Dref-3 spinner alone. The new air-jet/friction spun composite yarn can be knitted and woven without encountering stripping or other problems. This preliminary feasibility study has suc cessfully led to a unique integrated tandem spinning process that continuously and uninteruptedly produces an all-staple composite yam. The process will be reported on shortly.

Comparison of DREF-3 Cotton Yarns Produced by Varying Yarn Core Ratios and Feed Rates

This study evaluated yams produced on the DREF-3 friction spinning machine using varying core inlet sliver linear densities and output yam core proportions. A long staple, medium micronaire, Acala cotton was spun into 74, 54, and 45 tex yams at constant spinning drum and outlet speeds. Inlet sliver of 1.77, 2.47, and 3.18 ktex linear densities was supplied to the yam core at rates required to produce yams con taining between 40 and 70% core. To make yams of the same size and core ratio, lighter core sliver had to be supplied at faster inlet speeds or heavier core sliver at slower speeds. Using lighter core sliver at greater inlet speeds improved yam strength and evenness. Among these, coarser yams and those with higher core ratios showed better uniformity. Yarns supplied by lightweight core sliver showed similar elongation; those supplied by heavyweight core sliver showed more variation over the range of core ratios.

Comparison of Fabrics Made with Cotton Covered Polyester Staple-Core Yarn and 100% Cotton Yarn

Cotton covered/polyester staple-core yams [6, 8], recently developed at the Southern Regional Research Center, and conventional 100% cotton yarns of equivalent size were woven and knitted into various fabrics for evaluation. The woven fabrics were tested for abrasion resistance and tear and tensile strengths. The knitted fabrics were tested for bursting strength, air permeability, pilling resistance, dimensional stability, and DP rating (after a light application of DP finish on the heat set fabric). The staple- core yams, which were only modestly stronger than equivalent 100% cotton yams, produced fabrics remarkably improved in all the important properties when compared to the fabrics made with conventional 100% cotton yams. Fabrics from staple-core yams should therefore be useful where strength, weight, durability, abrasion resistance, dimensional stability, easy care, and comfort are desirable or critical.

New Technique to Produce a Cotton/Polyester Blend Yarn with Improved Strength

This paper describes a newly developed, relatively simple but effective technique of producing a novel pseudo-composite cotton-rich staple blend yarn with improved tensile properties. The spacing between cotton and polyester rovings drafted simultaneously on a ring-spinning frame affects yarn structure, resulting in significantly stronger yarns than those produced by drafting the same two rovings together. The new composite or combination yarns may be useful in developing relatively stronger cotton-rich materials suitable for a variety of finishes and end uses.

Cotton Covered Nylon-Core Yarns and Greige Fabrics

Physical and mechanical properties of some specific cotton-rich, high tenacity, nylon- core yams and greige fabrics developed for military protective clothing are described. The core yams were produced on a modified ring spinning frame, and the fabrics were woven on a conventional dobby loom. The core yams and the fabrics developed from them contained approximately 70% cotton as cover and 30% high tenacity nylon filament as core. The core yams were about 25% stronger than comparable 70/30 cotton/nylon staple intimate blend or all-cotton yams, and the developmental greige fabrics were over 30% stronger. The developmental fabrics, after special finishing, may provide adequate flame retardancy as well as high strength retention. Properties of the finished fabrics will be reported separately.

Cotton Fabrics Produced with Twistless Wrap Spun Yarns

Properties of fabrics woven with wrap spun yarns and equivalent ring spun yarns of Upland cotton have been investigated. Experimental wrap spun yarns were made on a modern, special machine, which produces so-called twistless yarns from staple fibers that are held together by a fine multifilament wrap yarn. The filament wrap used for the experimental yarns was water soluble polyvinyl alcohol. Ring spun yarns were produced conventionally. Each kind of yarn was woven separately as both warp and filling into plain, twill, and sateen fabrics. The water soluble wrap of the wrap spun fabrics was removed during normal wet processing, yielding completely twistless cotton fabrics. The various fabrics were evaluated for their important mechanical properties. Results show that, compared to the ring spun equivalents, the tighter, plain-woven, twistless fabric (of typical average density) fared reasonably well in tensile breaking strength but was slightly weaker in tearing strength; the relatively looser twill and sateen twistless fabrics were significantly weaker in both tensile and tear strengths. Respective fabrics of the two yarn types, however, showed no significant difference in abrasion resistance, although the twill and sateen fabrics made with both yarns generally had lower flex abrasion resistance than the corresponding plain fabrics. Twistless fabrics, like their ring spun counterparts, maintained their tensile and tear properties after repeated laundering.

Finishing and Properties of Fabrics Produced with Polyester Staple-Core/Cotton-Wrap Yams

Plain and twill weave fabrics produced with unique 67/33 cotton covered, high tenacity polyester staple-core yams in the warp and filling directions were appropriately finished without difficulty. The greige fabrics were desized, heat set, bleached, union dyed, and treated with different levels of dimethyloldihydroxyethyleneurea (DMDHEU) resin finish to assess the effect on important properties, including durable press rating, wrinkle recovery angle, dimensional stability, Stoll flex abrasion resistance, pilling resistance, breaking strength, and tearing strength. The test results show that the staple-core-yam fabrics attain satisfactory durable press and dimensional stability after an ordinary process of heat setting at 190°C for 65 seconds. DMDHEU resin slightly improves the durable press rating and wrinkle recovery angles, but more resin does not necessarily improve the properties proportionally; resin as low as 1% in solution gives acceptable DP results and improves pilling resistance. The DMDHEU resin finish diminishes flex abrasion resistance, breaking strength, and tearing strength, but the deterioration is much less than with similar 100% cotton fabrics. The breaking and tearing strengths remain especially high.