Indian Journal of Fibrc & Textile Research Vol. 27, Junc 2002, pp. 149-155

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1£) 7

Influence of arn str ctun;, sizing ingredient and type of sizing on properties and performance of sized yarm : Part III - A s,tudy of ~ttritiQ..n during ~eaving

for air-jet, r~ng and rotor _arnJ; on a modern high speed weaving machine

I A K /::engupta: P Pratihar & P q'-Ki~othia '-- r I \ - I

Ahmedabad Textile Industry's Rescarch Association, Ahmedabad 380015 \

and

'~ ~ernekar & M M Alamgir Sayeed

_Department of Textile Engineering, M S University of Baroda, Vadodara 390 OO~

Received II September 2000; revised received alld accepted 8 Jalluary 2001

'- How best the yarns of a g ivcn spinning system can be sized with optimum cost to overcome attritive forces acting on warp yarns during weaving has been studied. Polyester/vi scose (70:30) yarns (30s) obtained from the three spinning sys tems, viz. air-jet, ring and rotor, were sized with cold brand PV A and tested for abras ion and tensile properties. Using these yarns in warp, a plain weavc fabric was woven on a Dornier Rapier loom. The yarns were then unravelled from the fabric and tested for the abrasion and tensile properties. It is observed that among the ring, rotor and air-jet yarns, the excellent abrasion resis tance is obtained with air-jet yarn at higher size concentration and slow rate of drying. This is because at higher concentration there is good size film formation on the yarn surface and at slow rate of drying more outward si ze migration takes place, resulting in beller size encapsul at ion. An air-jet yarn whose strength properties are derived from the tightness and compression of the surface wrappings is , therefore, protected from the abrasion forces, . caused during weaving, by thi s size fihn for a longer duration. . ~;

Keywords : Air-jet yarn, Ring yarn, Rotor yarn, Sizing, Weav ing

1 Introduction During the process of weaving, the warp yarn is

subjected to complex mechanical forces due to repeated extension, abrasion and bending. Warp yarns under a state of dynamic loading on a loom should withstand flexure and buckling in heald eyes, cyclic stress imposed by shedding, and the frictional force arising due to the abrasion of yarns with reed wires, picking element, heald eyes, warp stop motion and whip roll 1. Repeated loading and unloading under small stress often cause stress concentration at some places and thus decrease resistance of a material to its failure, even when the imparted stress intensity is well below the ultimate strength of the material under static load . The capacity of the material to sustain failure gradually dimini shes with the increase in number of stress cycles because the damage caused is cumulative. This phenomenon of decreased resistance of a material to cyclic stress is called fatigue2

a To whom all the correspondence should be addressed . Phonc: 6307921 ; Fax: 0091-079-6302879; E- mail : aitraad l @sancharnel.in

Weaving tension is, in general, not more than about 20% of the strength of the unsized yarns3

.4. Yarn breaks on a loom occur even though the tension during weaving is 5-12% of the average yarn breaking strengths. Thus, it appears reasonable to suppose that the yielding of warp yarns during weaving is perhaps not entirely dependent on strength and abrasion resistance in individual yarns, but depends also on cumulative damage due to tensile fatigue of relatively small forces combined with abrasion action6

•7

. In practice, it is difficult to detect the initiation and the propagation of accumulated fatigue damage and generally there is no prior indication of impending failure. So, the study of individual yarn for its abrasion and tensile properties before and after imparting some fatigue will be of great importance.

Spun yarns are made by twisting together staple fibres which are laid discontinuous in length along the length of the yarn. The principle of twist insertion is different in different spinning systems, viz. ring, rotor and air-jet. Therefore, the types of fibre migration and hence the structures of ring, rotor and air-jet yarns cliffer accordingly. Rotor spinning is advantageous for

150 INDIAN J. FIBRE TEXT. RES., JUNE 2002

coarser yarns « 30s count). Air-jet spinning is suitable for yarns of 30s - 60s count, whereas ring spinning can be used for yarns of all counts. Rotor yarn is weaker than air-jet yarn, which is weaker than ring yarn of the same count; the per cent difference between rotor and ring yarns being more for finer counts. Ring yam is, however, substantially more hairy than rotor and air-jet yarns.

Failure of warp yarns on looms is basically due to the combination of slippage and breakage of fibres . The purpose of sizing of warp yarn is, therefore, to increase resistance to slippage of fibres as well as to protect fibres at the surface from getting ruptured due to the friction between yarn and different parts of the loom along the path of the yarn .

The type of size and the sizing processes are different for different types of yarns. Some yarns may need higher size penetration, some may need better surface coating and some may have requirements of similar extent for both. The present study was, therefore, aimed at finding out how best the yarn of a given spinning system can be sized for getting excellent performance during weaving.

2 Materials and Methods 30s polyester/viscose (70:30) nng (TM 4 .5),

rotor(TM 5.0) and air-jet yarns were sized on a Calaway laboratory sizing machine at ATIRA using 5% and 9% PYA cold brand, each separately at two drying temperatures (70°C and 140°C).

All the samples of both unsized and sized yarns were tested for tensile and abrasion properties. Out of the above-mentioned sized yarns, the yarns sized with 9% at 70°C and with 5% at 140°C were selected for weaving trials, as these are the two extreme conditions with respect to size migration and penetration . The size concentration of 9% at 70°C shows the maximum size encapsulation while 5% size concentration at 140°C shows the maximum size penetration as well as more size entrapment inside the yarns. These six sets of sized yarns, each comprising 50 ends, were mounted simultaneously on a weaver' s beam behind the Dornier Rapier loom at ATIRA. A plain weave fabric was woven using the following fabric construction: ends/inch, 80; pickslinch, 63 ; and weft count 32s (100% cotton)

The sized warp yarns, both not-woven and woven, were tested for tensile and abrasion properties. For testing woven warp yarns, these were carefully unravelled from the fabric and only those portions were tested which had undergone through total

weaving stress and abrasion from back rest to fell of the cloth on the loom.

All the tensile tests were carried out on Uster Tensorapid-3 and the abrasion tests on Zweigle G 55l.

3 Results and Discussion Table 1 shows the values of tensi le strength and

elongation for unsized and sized warp yarns. Table 2 gives the numbers of abrasion strokes till break of the sized yarns. Table 3 shows the tensi le strength and elongation values of sized yarns which are not-woven, woven and both subjected to 35 abrasion strokes . Table 4 shows the per cent loss in strength and elongation due to weaving alone and due to 35 abrasion strokes on both not-woven and woven warp yams. Table 5 shows the values of total abrasion strokes to break the not-woven the woven warp yarns and the calculated per cent reduction in the number of abrasion strokes due to weaving of the yarns. Fig. 1 shows the per cent gain in yarn strength after sizing. Fig. 2 shows the per cent loss in tensile strength of unsized and sized warp yarns due to 35 abrasion strokes. Fig. 3 shows the average values of tensile strength given in Table 3. Fig. 4 shows the numbers of abrasion strokes till yarn breaks for not-woven and woven warp ends. Fig. 5 shows the per cent reduction in these strokes due to weaving.

3.1 Effect of Sizing on Tensile Properties

From Table I and Fig.l, it is observed that among these three types of yarns, the increase in tensi Ie strength after sizing is maximum in rotor yarns , closely followed by air-jet yarns but it is significantly lower in ring yarns. This type of difference between rotor and ring yarns was also observed in 6s cotton yarn8

. Table I also shows that among the yarns sized with 9% and 5% PYA cold at the same temperature (70°C or 140°C), there is no significant difference in their tensile strengths. This, however, does not mean that 5% PYA cold is the optimum add-on for these yarns as for this, the results of abrasion tests need to be considered. It is also observed that in all the 6 cases, the increase in tensile strength is higher for the yarns dried at 140°C than for the y" rn s dried at 70°C, though to a less extent in ring yarns as compared to rotor and air-jet yarns .

The per cent loss in elongation after sizing is significantly lower in case of ring yarns than· that in the cases of rotor and air-jet yarns; between the latter two, the per cent loss is of about similar order.

SENGUPTA el al.: PROPERTIES AND PERFORMANCE OF SIZED YARNS: PART 11\ 151

Table I-Tensile properties of 30s polyester/viscose (70:30) warp yarns before and after sizing with PYA cold

Property Ring Rotor Air-jet Average % of Average %01' Average %of

unsized unsized unsized

Tensile Strength . g Unsized 418 277 288 Sized with 9% PY A

cold and dried at 70°C 473 113.2 336 121 .3 334 116.0 140°C 484 115 .8 383 138.3 383 133.0

Sized with 5% PYA cold and dried at 70°C 472 112.9 333 120.2 341 118.4 140°C 492 117.7 356 128.5 360 125.0

Elongation-at-break. %

Unsized 13 .03 11.55 11.97

Sized with 9% PYA cold and dried at

70°C 10.24 78.6 8.05 69.7 8.37 69.9 140°C 10.30 79.0 8.23 71.3 7.72 64.5

Sized with 5% PY A cold and dried at

70°C 10.42 80.0 7.79 67.4 9. 19 76.8 140°C 9.87 75.7 7.60 65 .8 7.76 64.8

Table 2 - Number of abrasion strokes to break the 30s polyester/viscose (70130) sized (PY A cold) and unsized yarns

Yarn Average CY% Minimum Maximum Ring Rotor Air-jet Ring Rotor Air-jet Ring Rotor Air-jet Ring Rotor Air-jet

Unsized 49 41 34 18.4 20.4 24.2 33 31 23 64 55 48

Sized with 9% PYA cold and dried at

70°C 99 174 182 35.9 28 .8 24.9 45 103 102 163 276 269 140°C 101 171 198 32.6 30.3 21.2 62 94 133 158 283 284

Sized with 5% PYA cold and dried at

70°C 72 141 58 19.8 32.2 18.5 53 86 41 93 241 80 140°C 95 124 78 30.7 41.3 25 .9 59 68 51 155 220 117

Minimum and maximum arc average of 5 respective values of 5 sets with each set having 20 test values of 20 threads mounted at a time on the instrument.

3.2 En'cel of Sizing on Abrasion Propcl'ties

Table 2 shows that the total number of abrasion strokes till yarn break in the uns ized state decreases in the order: ring yarns > rotor yarns> air-jet yarns . However, in case of sized yarns (Fig. 4) with 9% PV A cold the total number of abrasion strokes decreases in the order: air-jet yarns> rotor yarns> ring yarns , and with 5% PV A cold it is rotor yarns> ring yarns> air-jet yarns. I n all the cases, 9% PV A cold Fi g. 1- Per ce nt gain in strength after sizing

152 INDIAN J. FIBRE TEXT. RES ., JUNE 2002

sized yarns show better result than 5% PYA cold sized yarns of respective types. Drying at 140°C has shown better results than drying at 70°C for both air­jet and ring yarns and, to a greater extent, with 5% size than with 9% size.

The above results indicate that among these three types of yarns sized and dried under similar conditions, the highest and the lowest increase in abrasion resistance is obtained respectively for (i) air­jet and ring yarns when the size concentration is high (9%) and hence the good size coating, and (ii) rotor and air-jet yarns when the size concentration is low (5%) and hence the good size penetration . The higher retention of size within the yarn dried at 140°C has shown improvement for air-jet and ring yarns but surprisingly, contrary to expectations, not for rotor yarns.

3.3 Effect of Weaving and Abrasion Strokes on Tensile Properties of Warp Yarns

3.3.1 ElTect of Weaving From the data given under the columns a and c in

Table 3 and e in Table 4, it is observed that in the woven sized warp yarns the values of tens ile strength and elongation are slightly reduced in case of ring and rotor yarns but are slightly improved in case of air-jet yarns. Since weaving cannot improve these properties, the order of difference observed in the values of these properties after weaving can be considered within the range of normal variability of these yarn characteristics in a given sized yarn sample and hence not sign ificant. However, from the trends of the results, it can be said that due to weaving there may be a marginal loss in tensile strength and elongation of sized ring and rotor yarns but a negligible loss in sized air-jet yarns.

Table 3 -Tensile properti es of 30s polyester/viscose (70: 30) sized (PVA cold) warp yarns before and after weaving and a lso after 35 abrasion strokes

Yarn Si ze conc. Dry ing Tensile strength, g Elongation, % (PVA cold ) temp. a b c d a b c

% °C

Ring 9 70 473 205 446 104 10.24 3.2 1 9.64 5 140 492 271 435 145 9.87 4.52 9 .20

Rotor 9 70 336 279 308 216 8.05 4.54 7.89 5 140 356 170 323 101 7.60 3.21 7.27

Air-jet 9 70 334 278 345 258 8.37 3.92 9.52 5 140 360 247 369 221 7.76 3. 13 8.25

a = Parent sized yarn b = Parent sized yarn subjected to 35 abrasion strokes c = Yarn removed from fabri c d = Yarn removcd from fabric and then subjected to 35 abrasion strokes

Tablc 4-Per cent loss in strength and elongation of 30s polyes ter/viscose (70:30) sized (PV A cold) warp yarns due to weaving and abras ion strokes

Yarn Si ze conc . Drying % Reduction in tensile (PYA cold) temp. strength

% °C e f g

Ring 9 70 5.7 56.7 76.7 5 140 11.6 44.9 66.7

Rotor 9 70 S.3 17.0 29.9 5 140 9. 1 52.2 68.7

Air-jct 9 70 -3.3 16.8 25.2 5 140 -2.5 31.4 40.1

Referring to Table 3: e = % decay only due to weaving = rea - c) x 1001/ a f = % decay only due to 35 abrasion strokes in warp yarns not-woven =[ (a - b) x 1001/ a g = % decay onl y due to 35 abrasion strokes in woven warp yarns = I(c - d) x 1001/ c

% Reduction in elongation

e g

9.4 68 .7 78 .1 6.4 54.2 70.4

2.0 43.6 30.3 4.3 57.8 71.9

-13.7 53.2 32. 1 -6.3 59.7 22.2

d

2 .11 2.72

5.50 2.04

6.46 6.42

SENGUPTA el aJ.: PROPERTIES AND PERFORMANCE OF SIZED YARNS: PART 11/ 153

3.3.2 Effect of Abrasion Strokes

3.3.2.1 Unsizcd and Sized Not-woven Warp Yarns

Fig. 2 shows that in unsized yarns the per cent loss in tensile strength after 35 abrasion strokes is quite high (about 77%, 74% and 67% for ring, rotor and air-jet yarns respectively) . T his loss in sized yarns, as shown in column f of Table 4, is however considerably reduced with (i) 9% size to about 57% and 50% in ring yarns, 17% and 18% in rotor yarns and 17% and 32% in air-jet yarns, and (ii) 5% size to about 45 % and 45 % in ring yarns , 42% and 52% in rotor yarns and 21 % and 31 % in air-j et yarns, dried at 70°C and 140°C respectively . Thus, in this case the per cent reduct ion in tensile strength due to 35 abrasion strokes is less with better size encapsu lation (9% size, 70°C drying) in rotor and air-jet yarns and with better penetration and retention of size inside the yarn (5% size, 140°C drying) in ring yarns. The per cent loss in elongation, as shown in column f of Table 4, follows the trend similar to that of per cent loss in tensile strength.

3.3.2.2 Sized Woven Warp Yarns

It is observed from Fig . 3 and col umn d of Table 3 that after subjecting the woven sized warp yarns to 35 abras ion strokes, the tensile properties are much better for air-jet yarns than for the ring and the rotor yarns . It is also observed that between the yarns of the same spinning system, those having better size encapsulation (9% size, 70°C drying) show higher values of tensile properties than the yarns having better penetration and retention of size inside the yarn (5 % size, 140°C drying) for air-jet and rotor yarns ; however, for ring yarns the opposite is the case.

A comparison of the va lues given in Tables 3 and 4 show that in all the six cases the per cent loss in

tensi le strength after 35 abrasion strokes (columns d and g) is substantially higher for woven warp yarns than for the not-woven warp yarns (colu mns b and f). With respect to elongation per cent also, the findings are similar in three cases (ring 9% & 5% and rotor 5% PY A cold); in the remain ing three cases (rotor 9% and air-jet 9% & 5% PYA cold) there appears to be some error of testing because the results show that after subjecting to the same number of abrasion strokes, the elongation at break is substantially higher for woven than for the not-woven sized warp yarn and this is not poss ibl e.

'" 80

~ 70 c Q) 60 -" (/) 50

-; ",0

~ 10 -' "* 20

10

m L-~ :

~-= . . L-:

. . : ~=.

[-:

Grey yam

o Ring yarn ~ Rotor yarn E;l Air:Jef yarn

- -

R "" r.7

.Ii·~. !---

l=-f F:=r-:~:-j ~:-~ m-::::: ~=-j : ~-={ 1:-=1

9%.70C 9%.140°C 5%.140°C

Fi g. 2 - Per cent loss in s tre ngth after 35 abrasion strokes

800 ,-----------------.-------~

500 t-- - ....... ;;--------------~

'" ~ ~~I-~~---~a-~~------------~ c Q)

~ 300r~~~-~~-I~_;~~--~-~--~~--~·-~~ .9! .~ 200 !!! > <t 100

9%.70°c 5%.140·C 9%.70°C 5%.140'1:: 9%.70't 5%.140°C Ring Ring RolDr Rotor Air·jet Air-jet

Fi g. 3-Effect of weav ing and abrasion strokes on te nsil e strength of sized warp yarns r E;a parent sized yarn , 0 parent sized ya rn subjected to 35 abrasion strokes, [SJ ya rn remo ved from fabric, and, !al yarn removed from fabric and then subjected to 35 abras ion strokes J

Table 5 - Effect of weav ing on number of abrasion strokes to break 30s po lyes ter / viscose (70:30) sized (PYA cold) warp ya rns

Yarn Size conc . Drying No. of abrasion strokes till break (PYA cold) temp. Average CY % Minimul1l Max illlum

% °C a b c a b a b a b

Ring 9 70 99 63 36.4 35.9 17.9 45 45 163 85 5 140 95 6 1 35.8 30.7 22.8 59 34 155 93

Rotor 9 70 174 107 38 .5 28.8 43.7 103 47 276 180 5 140 124 72 41.9 41.3 20 .1 68 47 220 94

Air-jet 9 70 182 169 7.1 24.9 24.7 102 107 269 258 5 140 78 69 I 1.5 25.9 34.5 5 I 40 11 7 11 7

a = Parent sized ya rn b = Yarn removed from fabri c c = % reduction in number of abras ion strokes = r(a - b) x I OOJ / a

154 INDI AN J. FIBRE T EXT . RES., JUNE 2002

100

",

~ 150 e u; c o

.~ 100

.0 .. '0 :v .0 ~O E :0 Z

~ Pwent sIzed yarm 0 Yarn removed from fabric

9%.700C 50/", ,140°C 9tJ/o,70oC 5%,140

oC 91l/o.70oe 5%.140

oC

Ring Ring Rotor Rotor AIr·jet Air-jet

Fig. -Effect o f weav ing on nUlll be r of abrasion strokes till break

_~ ~ o

e ::,s . Ui c ~o o

.~ ;:5

.!5 .. 20 c

.2 15

g 10 D

~ ~

9%)ot 5%. 140°C 9%.70°C 5"'/01, 140°C 9%.70°C 5%.1:10Q

C Ring RIng Ro\or Rotul Air-jet Air-jet

Fig. 5- Per cent reducti o n in abras ion strokes till break alkr weav ing

3.3 Effect of Weaving on Decay in Abrasion Rcsis ta nce

Table 5 and Figs 4 and 5 show that the extent as well as percentage of deteri orati on in the abras ion resistance of the sized warp yarns due to weaving is substantiall y lower for air-j et yarns than for ring and rotor yarn s, irrespecti ve o f whe th er the number of abrasion strokes ti II break of sized warp yarn before weav ing is higher or lower for air-j et yarns th an for ring and rotor yarns. Thi s deteri ora ti on is found to be less with 9% sizing at 70°C (i.e. more size add-on and encapsulation) than with 5% sizing at 140°C (i.e. less size add-on but more penetrat ion and retention of size inside the yarn ) in the cases o f air-j et and rotor yarns, but not signifi cantl y different in the case of ring yarn.

4 Conclusions The study of tensile and abrasion properti es of 30s

PlY ring, rotor and air-jet grey, sized and sized woven warp yarn s using 9% and 5% PY A co ld sizing at 70°C and 140°C and th at of the tensi Ie propert ies after some limited abras ion strokes on sized and sized woven warp yarns reveals that the sizing parameters need to be vari ed and ca refu II y controlled for

opti mUIll performance when the yarns of di fferent structures are used.

On the who le, considering the sum effec t of vari ous vari ab les studi ed and disregarding a few results that are not in conformity because of inherent variabilit y faced in vari ous aspects in thi s 'type of study, the f indings show th at to get the max imum abrasion res istance and minimum loss in tensile properties during weav ing, the sizing requirements for air-j~, rotor and ring warp yarn s are as follows:

• A ir-jet yarn s, as compared to rotor and ri ng yarns, are poorest in abras ion res istance in unsized state and therefore need more a good size fi lm adhered to yarn surface than to a good penetrati on of the size into the yarn. Thi s is so becau se the strength and durability of an air-jet yarn are obtained mainly from the tightness and compress ion of the surface bands and hence the bands on the surface have to be gi ven maximum protection from getting loose during weav ing by a good size film f irmly adhered onto the yarn surface. Th is requires the use of the ingred ients which have good film forming property, hi gh adhes ive power and high v iscos ity, and the sizing needs to be clone w ith size pas te of high concentrati on at lower dry ing temperatures .

• Rotor yarns rank between rin g and air-j et yarns in abrasion res istance and are the poores t in tensi Ie strength in grey form. These yarns have bundl es of parallel fibres without good interl ocking in the core and the wrapper f ibres which keep intac t the fibres of the yarn core. The rotor yarns, therefore, require more of size penetration and less of size coating on the yarn surface than the air-jet yarn s. Therefore, for good weavabi lity, the rotor yarn s need to be sized w ith ingredients vvhi ch have low viscos ity using higher temperature for dry ing of sized yarn s and the size concentrati ons which can give the required add-on con sideri ng the type or sizing ingred ient , count of ya rn , type of fibres, fabric construction and type of weav ing machine.

• Grey ring yarn s, as compared to grey rotor and air­j et yarn s, are the best in abrasion resistance as we ll as in tens i Ie strength and have by rar the most uniform twi sted structure from core to surrace. For good weavability, the ring yarns therefore require size coa ting and size penetrati on of more or less similar order and hence the sizing pa rameters in bet ween of those suggested 1'0 1' rotor and ai r-j et yarns.

SENGUPTA et a/.: PROPERTIES AND PERFORMANCE OF SIZED YARNS: PART III 155

References Trauter J, Rcutlingen Abrasion Tester, Text Prax /111, 30 ( 1975) 1939.

2 Tillloshenko S, Strength of Materia/s , Part II: Advanced (Van Nostrand Rei nhold, New York) , 1978.

3 Faasen N J & Van Harten K, J Text IlI st , 57 (1966) T269-T2 85.

4 King D E, Weil H A, Condo FE & Ratherford H A, Text Res J, 22 (1952) 567-573.

5 Leblanc M, Illd Text, 69 (1952) 361-364. 6 Lord P R, Text Rec, 83 (1966) 56-58; 59-60. 7 Milovidov N N, Tech Textilld, USSR, 1 (1964) 75-79. 8 Sengupta A K, Pratihar P, Killlothi P D, Vernekar S &

Alaillgir Sayeed M M, Indian J Fibre Text Res, 27 (2002) 59.