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Indian Journal of Fibre & Textile Research Vol. 29, June 2004, pp. 1l7-121
A successful weaving trial with a size-free cotton warp
A P S Sawhney", J B Price & T A Calamari
Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, LA 70 124
Received 21 April 2003; accepled 23 JUli e 2003
A combed cotton rotor-spun yarn of high quality was produced using customary industrial equipment. The yarn was warped, ensu ring a consistent individual yarn tension. The warp set was uninterruptedly washed and c leaned in boi ling water containing a mild detergent and a wetting agent, dri ed on a dummy slasher (i.e. without using any conventional sizing agent) to set the yarn twi st torque, and wound onto a loom beam. A 2/1 twill fabri c of a s lightly open construct ion was successfull y woven on a modified fly- shuttle loom, operating under normal speed and mill-like conditions. Although the yarn hairiness increased visibly as the warp raced forward towards the cloth fell, absolute ly no fiber c linging or yarn snagging occurred and, for the first time ever, about 50 m of fabric was woven without a sing le warp yarn failure, which is very encOUl·aging. This preliminary weaving tri al indicates that weaving a singles cotton yarn without the traditional warp sizing may now indeed be feasible at least fo r certain types o f ya rns , fabrics and weaving machinery. Planned size- free weaving tri als invo lvi ng differe nt types of fibers, yarns and modern weaving machinery are ex pected to determine the prospect and commercial scope of size-free weaving.
Keywords: Cotton, Size-free weaving IPC Code: Int. Cl.7 003025/00; D02G 3/00
1 Introduction Cotton warp yarns (singles) have always been tem
porarily sized or coated with some sort of adhesive, such as starch , CMC and PV A, along with several other chemicals to achieve efficient weaving by mainly improving abras ion resistance of the yarns against the harsh mechanical actions during weaving. Since the chemicals used in a size mixture can adversely affect quality of bleaching, dyeing and/or any special finishing of the fabric in the subsequent processes, they must be completely removed at first opportunity by a process called fabric desizing. Both the warp sizing and the fabric desizing processes use, or waste, tons of expensive chemicals, consume a lot of energy and water, and generate a lot of waste water which must undergo an expensive treatment before it can be safely disposed . Thus, both of these centurieso ld processes are very costly, complex and environmentally sensitive. Today's ailing textile industry wants to eliminate the underlying process of warp
a To whom all the correspondence should be addressed. Phone: 2864568; Fax: 001 -504-28644 19; E-mail: aps i [email protected] b Menti on of trade names of commercial products in thi s publication is solely for the purpose of prov iding spec ifi c information and does not impl y recommendation or endorsement by the U. S. Department of Agricu lture.
sizing to reduce textile process ing costs and improve ecological balance. Because of their bal anced twis t torque and reduced hairiness, the use of plied yarns can permit weaving without size, but most conventional fabrics cannot use pli ed yarns.
Although a good volume of research has been conducted for centuries to improve sizes, sizing formu lations , and slashing machinery and practices to improve weaving efficiencies, no significant work on eliminating warp sizing has been reported in recent years. A few researchers 1-4 in recent years have attempted to either reduce conventional warp sizing or replace it with some sort of permanent sizing which wou ld not interfere with the subsequent chemical processes and would beneficially stay on the fabric during its entire useful life. The so-called "sizeless or size-free weaving" of cotton yarns simply does not exist today . However, in the nineteen seventies, Vincent and Gandhi5
-7 investigated the possibility of us
ing rotor yarns for size-less weaving and concluded that protruding hairs from the rotor yarns, despite being less hairy than the comparable ring yarns , get interlocked as a result of yarn abrasion and prevent clear separation of the warp sheet. Broken hairs were released to fa ll onto the oscillating warp ends , which then formed beads or fuzz balls that seriously interfered with the shedding phenomenon. Earlier, Vincent
118 INDIAN 1. FIBRE TEXT. RES., JUNE 2004
and Robinson8 had also experienced similar difficulties while attempting to weave single worsted yarns without sizing. However, by singeing the rotor yarns, Vincent and Ghandi9 showed the possibility of weaving but a high number of warp stops occurred in the production of only a few meters of fabric. They gave no details about the nature of the equipment used to prepare and weave the warp. It can be assumed that few special measures were taken to cater to the unsized warp yarns and that the conventional equipment was used throughout. The authors also did not provide any details of the machine specifications or the physical properties of the rotor yarn other than its linear density.
Since the seventies, there have been many significant changes in rotor spinning which have influenced yarn quality as well as productivity. Modifications in rotor design, navel topography, opening roller design and spinbox characteristics have reduced the difference between ring and rotor yarn strength from 15 -20% to 10 - 15%, in addition to the improvement in other quality parameters. This particularly included the significant reductions in imperfection frequencies which have occurred steadily even over the last few years , and the ability to produce smoother, leaner, more uniform, and less hairy yarns. Also, the study on the use of combed cotton for rotor spinning has shown that a significant improvement in yarn quality can be made by the removal of a small quantity of noils (short fi bers) . The higher proportion of longer fibers in combed sliver provides stronger and more uniform yarns with fewer protruding hairs. Thus, in view of the significant improvements in fiber and yarn qualiti es and many developments in textile processing machinery and procedures in the last couple of decades, it is believed that size-free weaving of cotton warps is indeed feasibl e. Accordingly, in the present work, a mUlti-pronged research approach was tried to attain size-free weaving wherein the most desirable yarn, preparation, and weaving attributes (that were theoretically deemed vital for efficient weaving) were simultaneously incorporated for the purpose of a rapid, overall assessment of s ize-free weaving. The research approach bas ically involved the fo llowing major technological factors:
Improved and Consistent Yam Quality: A rotor-spun combed cotton yarn inherently has the
desired characteristics for size-free weaving. Relati ve ly low yarn hairi ness to minimize fiber-ta-fiber
clinging or yarn-to-yarn snagging, high yarn abrasion resistance, high tensile strength and uniformity , and good consistency of individual yarn tension in the entire warp on the loom were considered critical attributes for efficient weaving.
Improved Warp Preparation/or Weaving: Setting of yarn twist liveliness is also critical for
weaving. It was planned to balance the yarn twist torque by an ordinary washing and drying treatment of the warp, which probably would also partly clean and lubricate the warp. Greige cotton's natural sugars, waxes and other contaminants could create serious problems of "fiber-to-fiber clinging" and/or "yarn-toyarn snagging" during weaving. Any obstruction in the free movements of the warp and filling yarns is detrimental to weaving and can cause an unnecessary yarn failure, machinery stoppage and fabric defect.
Modification 0/ Weaving Machinery and Conditiolls: To minimize yarn abrasion and the resulting hairi
ness during weaving, which is extremely critical in weaving, modification of weaving machinery and conditions was done. Special finishing or coating of critical loom components, viz. reed, heddles and dropwires, with a suitable polymer along with high ly pol ished drag rolls were considered the means to minimize yarn abrasion.
2 Materials and Methods
2.1 Production and Preparation of a Size-less Warp A good quality Upland cotton fiber (Acala maxxa)
was purposely selected to produce a strong, uniform and smooth warp yarn as free from protruding hairs as possible. Table 1 shows the compari son of typical properties of Acala cotton used and normal Delta cotton. The cotton was opened and cleaned by passing from Whitin hopper-feeder to Superior inclined cleaner and Fiber Controls Corporation Vertical Fine Opener to one side of a Crosrol Twin Feed Unit. The opened and cleaned cotton was then supplied to the chute of a Crosrol Mark 4 single card and carded at about 30kg (65Ib) per hour. The card sliver was drawn once with autolevelling on a Hollingsworth 990SL drawframe, formed into laps with a modifi ed Whitin Super Lapper, and combed using a Hollingsworth comber running at 200 nips/min . The quantity of noils removed was 12%, which enriched the proportion of longer fibers. The combed sliver was drawn once with autoievelling in preparation for
SA WHNEY et al.: SUCCESSFUL WEAVING TRIAL WITH SIZE-FREE COTTON WARP 119
Table I- Fiber properties Instrument Property Acala A typical Delta
cotton cotton (regular) Strength , gf/tex 32.14 23-28
HVI Elongati on, % 11.7 8-9 Upper half mean length, 1. 193 0 .91-1.1 inch Uniformity ratio, % 84.3 80-85 Short fiber content (In- 6.78 8-10 dex) Micronaire 4.09 4.0-4.9.0 Reflectance, Rd 80. 1 78 Hunter' s yellowness (+b) 8.9 Leaf 1.4 Up to 2.4 Area 0.44 0 .55 Count 9 Grade 11 - 12
Deri ved Maturity ratio 0.906 0.78-0.88
from AFIS Fineness, m/tex 163 .7 140- 150 data
rotor spinning using the same drawframe. A 30 tex (20 Ne) yarn was spun at a rotor speed of 110,000 rpm and twist multiplier (atex ) of 145 (ae 4.8) using a Schlafhorstb Autocoro machine, with Corolab yarn monitoring set, to remove major imperfections. The purpose of deploying rotor spinning was to achieve desired consistency of linear density and other yarn properties . Another advantage of the rotor spun yarn ' s use over the ring yarn's was the likelihood of increased abrasion resistance.
Warp section beams were produced directly from the spun packages ensuring a consistent running tension of 10 ± 2 cN at each end in the creel. It was thought that some warp yarn failures during weaving probably occur due to the progressive increase in tension in certain initially taut yarn strands on the loom beam as the weaving progresses and the yarns travel from the loom beam to the cloth fell. Due to inherent tension variations of individual yarn strands among the several thousand yarn strands that usually comprise a loom beam, certain "relatively tighter or tightly-wound strands" on the loom beam could progressively get even tighter and ultimately cause their failures beyond their endurance thresholds. The increase in tension occurs in certain yarn strands because the "cloth take-up" on a loom generally takes place with a relatively much greater precision than the "yarn let-off," which essentially is dependent on and hence directed by the overall tension of the entire warp sheet (and not of the individual yarn strands) . A loom's "cloth take-up" and "yarn let-off' mechanisms are uniquely inconsistent and, hence, inherently in-
compatible to keep constant and consistent tension among the individual strands. Thus, in view of the above hypothesis, which, incidentally, has not yet been validated due to the difficulties experienced in constantly monitoring individual yarn running tensions of several warp yarn strands simultaneously during weaving, extra care was taken to ensure a nearperfect consistency of tension of individual yarn strands, especially during warping.
A loom beam was prepared using a so-called "dummy" West Point slasher with no conventional yarn sizing. The warp sheet was continuously and uninterruptedly washed with boiling water in the size box containing an aqueous solution of I % detergent and 0.1 % non-ionic wetting agent (Triton X-IOO) with 0.01 % antifoaming agent (Patco Antifoam TWB ). Beside setting the yarn twi st torque, the washing treatment was also intended to partly lubricate the yarn surface (during squeezing) with natural cotton sugars/waxes, which presumably got dissolved in the boiling water. The warp sheet was dried under a nominal tension by passing it over three drying cans steam heated at 1160 C (240 F). The dried yarn was very lightly «0.001 %) lubricated with a molten paraffin wax by means of a kiss roller and then wound onto a loom beam using a minimum of four lease rods in the leasing section of the slasher. The total yarn stretch was 0 .8% and the moisture regain of the yarn was controlled around 6%. After about 89m (97yd) of the warp had been prepared in this manner, the remaining 60m (66 yd) was slashed normally using a 6% solution of Du Pont Elvanol T-25. The reason for providing a length of sized warp was to provide, beside a control , sufficient warp to ensure that any crossed ends or other defects were eradicated before the unsized portion was reached .
2.2 Modification of Weaving Machinery and Conditions The critical loom components, viz . reed, heddles
and drop-wires, were coated with teflon and the drag and whip rolls were polished to minimize unnecessary yarn abrasion. The warp was woven on a 52 inch wide "Draper model X-P" loom equipped with a 16-jack Staubli dobby. The loom was operated at its normal speed of 190 ppm. The sized portion of the warp was woven into 18.9 ends/cm and 17.3 picks/cm (48 endslinch and 43 pickslinch) 211 right hand twill fa bric with a 30 tex yarn in both the warp and filling directions.
At the end of the sized portion of warp, the number of picks was temporarily reduced to 7 .9 picks/cm
120 INDIAN 1. FIBRE TEXT. RES., JUNE 2004
(-20 pickslinch) to optimize running tension for the size-free warp. Weaving was continued through a transition zone of untreated warp of about 3 m until the warp that had been washed and dried was reached. The weaving was further continued and the pick density was gradually increased to 17.3 picks/cm. A total of about 50 m of size-free warp was woven .
The weaving was monitored for performance (yarn fai lures/breakages and their causes and sources), yarn condition (specially in the shed region) , and any abnormal lint/fly generation. Photographs of the yarn hairiness in the shed region were taken to record any excessive yarn abrasion or abnormality during weaving. After weaving, the fabric was si mply scoured and then bleached with hydrogen peroxide.
3 Results and Discussion Table 2 shows the yarn test data. The greige yarn
has excellent properties, even better than those of a typical (carded) cotton ring-spun yarn which generally is - 20% stronger than an equivalent rotor-spun carded yarn . The yarn strength consistency, as expressed by the standard deviation values of breaking strength and tenacity, is also very good, which indeed is critical for efficient weaving. The yarn hairiness, although not objecti vely measured, was subjective ly considered to be significantly less than that of a similar ring-spun yarn. The wet-cleaned and dried yarn shows more than 20% increase in its breaking strength compared to that of the greige yarn. The yarn shrinkage, which most likely uccurred during washing, perhaps contributed to the increased yarn strength .
The weaving performance of the size-less warp was surprisingly good in the sense that not one yarn, out of the 1900 comprising the warp, failed or broke during the entire production of about 50 m of fabric . The improved yarn strength and the stabi lized yarn twist torque, along with somewhat improved yarn lubricity, appear to have helped in the satisfactory performance of the yarn during weaving. Considering the potential damage from the shuttle abrasion and the need for a much larger shed size than that requi red for a modern weaving machine, this performance was considered to be very encouraging . Inspection of the warp during weaving showed a considerable increase in hairiness, especially as the yarn moved towards the cloth-fe ll. The hairiness in the reed-swing region became markedly visible, probably due to the close proximity of the shed's two components/layers in the region. In the vicinity of the cloth-fell , protruding fi-
Parameter Table 2- Yarn properti es
Value Greige yarn
Skein test data Yarn number Count strength product
Single yarn tensile properties
Mean breaking load Mean tenacity C V of breaking load Mean elongation- at- break C V of e longation-at-break
Evenness test data Non-uniformity (CV) I mperfections/ 1000 m
Thin places ( - 50%) Thick places ( + 50%) Neps ( + 200%)
29.7 tex 127.7 kN/tex
494.7 cN 16.58 cN/tex 6.1 % 6.85 % 5.2 %
12.8 1 %
2.2 5.5 2.2
Washed yarn (taken from the loom beam)
Single-strand breaking strength 597.6 (50 41.1; CV 6.9 %) Single-strand breaking elongation 3.5 % (S 00.46; CV 13.5 %)
bers from both layers of the shed are too close to each other to visibly increase the density of projecting fibers in the region. Interes tingly, however, abso lutely no fiber-to-fiber or yarn-to-yarn entanglement was ever observed. In other words, the increase in yarn hairiness apparently did not interfere with either the shed formation or the filli ng insertion. It appears that the increased hairiness resulting from the excessive abrasion of the size-free, washed and dried warp may not be as detrimental and critical as previously thought in case of conventionally sized or sub-sized warp yarns. In fact, it seems that the tradi tional warp size due to its adhes ive nature may actually be responsible for causing some inter-fiber or inter-yarn entanglements which , in turn, may cause certain yarn fai lures in slashing and weaving, especiall y when the size is improperly applied, dried and/or damaged (during weaving). In the absence of conventional size and any other adhesive contaminant (s uch as cotton's natural sugars, waxes, etc.), the washed size-free warp proved to be completely free of any "fiber c linging" and/or "yarn entanglements" that generally cause significant problems in weaving and fab ric quality . Interestingly, the amount of lint collec ted from beneath the loom was also minimal, despite the excess ive yarn abrasion hairiness that occurred during weaving. Based on the observations made from thi s weavi ng exercise using a fly-shuttle loom, there is reasonable expectation that a simil arly prepared rotor yarn can be woven successfully on a high speed weav ing machine of more modern technology, such as a fl ex ible rapier
SA WHNEY et al.: SUCCESSFUL W EAV ING TRIAL WITH SIZE-FREE COTTO W ARP 12 1
weaving machine. A series of similar weaving trial s usi ng differently prepared rotor- and ring- spun cotto n yarns are scheduled fo r e ither a Somet or a Pi gnone/Sultex rapi er weaving machine in order to determine scope of s ize-free weaving. The hand of the greige-s tate fabric was smooth , presumably due to the increased hairiness generated during weaving. However, the bleached fabric felt abnormally harsh . Thi s perhaps was due to the unique combination of the structure of the rotor yarn and the re lati vely open construction of the fabric , which permitted substantial shrinkage of the fabric during the wet finishing treatment. The sized section of the fabric, after the usual scouring and desizing, also yielded a similar harsh hand . This confirmed that the inherent rotor yarn structure in conjunctio n with the excessive fabric shrinkage was the culprit of the harsh hand.
4 Conclusions Although it is somewhat premature to accurately
assess the true impact of the preliminary work on size-free weaving conducted so far, early results are positive and encouraging. It is believed that the sizefree weaving of an appropriately prepared, washed and dried cotton warp of consistent quality is feasibl e for certain types of fabrics and weaving conditions, which , in itself, is an exciting prospect for future research on the subject. Still the relative effect or impact of the various factors involved in this exploratory size-free weaving trial is not exactly known.
A good and consistent basic yarn quality , coupled with the described yarn preparation and weaving modifications, seems to considerably assist weaving of cotton yarns without the traditional warp sizing. Continuing studies with different types of fibers, yarns and weaving machines will give a fundamental understanding of the process of size-free weaving. If
successful , the size-free weaving offers sig ni ficant savings as well as improved ecolog ical balance fo r cotton textil e processing, since the elimination of sizing process is highly des irab le from standpoi nts of cost reduction and removal of a source of polluti on and wasted energy .
Acknowledgement The authors would like to thank the staff of the Pi
lot Plants of the SRRC Colton Textile Engineering (CTE) and T extil e Finishing Chemistry (TFC) Un its for their considerable assistance in process ing the various fi bel'S, yarns and fabrics studied . Special thanks are due to Mr. Jim Sandberg and Mr. Jerome Jeanpierre for help in the mechanical processing of the various material s.
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8 Vincent J J & Robinson D M, The s iz ing of a s ingle worsted warp yarn, Text Ill st Ind, 9 (7) ( 1971 ) 181 - 184.
9 Vincent J J & Gandhi K L, Singeing as a substitute for s izing, Text IlIstllld, 12 (1)(1974) 17.
