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Air-jet texturing of filament feed yarns of different shrinkage potential
V K Kothari & V K Yadav
Department of Textile Technology, Indian Institute of Technology, Hauz Khas, New Delhi I IO 0 1 6, India Received 10 February 1998; revised received and accepted 23 April 1998
The possibility of feeding filament yarns with different shrinkage potential in air-jet texturing has been studied. Paral
lel-end air-jet texturing of filament yams with different shrinkage potential results in decrease of bulk with the increase in shrinkage difference level initially, but then increases with further increase in shrinkage difference. Instability of air-jet tex
tured yarns also first decreases and then increases with the increasing shrinkage difference. The study suggests that shrink
age difference in the feeder yarn is not an effective way to increase the bulk of air-jet textured yams.
Keywords: Air-jet texturing, Filament feed'yam, Shrinkage potential, Textured yarn 1 Introduction
Techniques of using differential shrinkage for pro
ducing bulk in the final yam and fabric had been used by several researchers and some of these techniques were exploited commercially. High bulk acrylic yam could be cited as one of the examples. Use of differ
ent shrinkage yarns in air-jet texturing has been tried by a few workers'·J. Piller" 2 used parallel-end air-jet texturing of different shrinkage potential yams and reported higher loop frequency, greater cover, and warm and full hand in the resultant yams after shrink
age. Piller1.4 has also reported that it is not only the shrinka.ge value of feed yams which decides the shrinkage properties of resultant textured yams but also the shrinkage force and the shrinkage work. He produced different shrinkage in the modified yams by varying draw ratio and drawing temperature and ob
tained a direct relationship between physical bulk and shrinkage force multiplied by the amount of shrink
age. In the present work, a very low shrinkage yam has been combined with high shrinkage yams pro
duced by changing the hot-pin temperature alone to study the effect of difference in yam shrinkage on the resultant air-jet yarn properties.
2 Materials and Methods 2.1 Materials
Two semi-dull partially-oriented polyester yams of circular cross-section of 1 25/ 1 00 and 1 26/34 deniers were used for the study. Draw ratios used were 1 .564 and 1 .632, resulting in dra�n yam deniers of 80/ 1 00 and 80/34 respectively. Different shrinkage level yarns for each POY (partially-oriented yam) were
produced by varying the hot-pin temperature on the Eltex AT/HS air texturing machine. Hot-pin tem
perature was varied from 60°C to 140°C in steps of 20°C to produce 5 yams of different shrinkage levels.
A low shrinkage yam was produced by drawing POY at 140°C hot-pin temperature and post heat-stabilizing it at 200°C and 15% overfeed.
Parallel-end air-jet textured yams were produced on Eltex AT/HS air texturing machine. Low shrink
age yam was fed directly to the texturing zone feed roller, whereas the POY was fed to drawing feed roller where it was drawn at different hot-pin tem
peratures to induce different shrinkage potential in one of the ends of the two ends fed to the jet. Tex
tured yarns were then post heat-stabilized sequen
tially on the machine. All textured yams were heat
stabilized at constant tension. Following air-jet tex
turing parameters were kept at constant level:
Overfeed to the air-jet Texturing nozzle type Water application Winding underfeed Air pressure Mechanical stretch Stabilizing temperature Winding tension Winding speed
: 25%
: HemaJet with T3 l 0 core : I litrclh at 1 bar water pressure : 0.7 %
: 9 bar : 4.7 % : 200°C : 4 cN : 300 mlmin
In case of both POYs, an assembled yam package having low shrinkage and drawn yam was also pro
duced for measurement of bulk and % increase in lin
ear density and is referred to as the parent yam sam
ple.
82 INDIAN J . FIBRE TEXT. RES., JUNE 1 999 2.2 Yarn Shrinkage
All drawn yarn series and · low-shrinkage yams were tested for hot-air shrinkage of single yam as per the ASTM Test Method 05 104-90 (ref. 5). From the conditioned yarn package, a 120 yd skein was pre
pared on a hand dri ven wrap reel. From this, 5 yams of approx. 70 cm length were cut at random. These cut lengths were clamped from the top of vertical measuring stand and a load of 0. 1 gf/den was applied to the other end. Two marks (50 cm apart) were then made on the suspended yam. All such five yams were then grouped together by fixing a Teflon tape at their tips and were placed in a relaxed state in a hot-air oven maintained at 120 ± 2°C for 30 min. These were then allowed to cool down under laboratory atmos
pheric conditions. The distance between the two marked points was measured under the same load of 0. 1 gf/den and recorded as L. Shrinkage in yam was calculated as follows:
50 -L Shrinkage (%) = --x 1 00
50 2.3 Tensile Properties
Tensile properties of all textured yams were meas
ured in accordance with the ASTM Test Method D2256-95a (ref. 6). Instron (Model 4301 ) tensile testing machine working on CRE principle and fitted with pneumatic jaws and a load cell of 1 kgf was used. All measurements were made in a straight con
figuration of the specimen at 250±3 mm gauge length with a pretension of 0.06 gflden. Jaw speed of 300 mrnlmin was used. Ten readings per sample were used to obtain the averages of tensile properties.
2.4 Physical Bulk
Physical bulk of air-jet textured yams was meas
ured using the modified Ou Pont method suggested by Sengupta et al. 7• Cylindrical package was wound under a fixed tension level of 4 cN at a speed of 300 rnImin for 30 min. Physical bulk of the textured yam was calculated as follows:
Density of parent yarn package (g/ cm3)
Physical h u l k ( % ) =------'--- x 1 00 Density of textured yarn package
(g/ cm3) 2.5 Instability
A method suggested by Ou PontS was used for the instability measurement of air-jet textured yams. A basic load of 0.0 I gflden was applied to the yam and
a mark was made at 100 cm distance from the clamp.
Yam was then subjected to a load of 0.5 gf/den for 30 s. The permanent extension in the length of the yam, measured 30 s after the heavy load has been removed, was taken as a measure of instability. Ten readings were taken from a sample package to esti
mate instability and between each successive readings nearly 5 m yam was unwound from the package and discarded.
2.6 Yarn Count
Skeins were prepared on a motorized wrap reel of 1 m girth. Five skeins of 1 00 m each were prepared from each package and weighed on an electronic bal
ance capable of measuring to an accuracy of 1 mg.
The yam denier was calculated as follows:
Weight of 1 00 m skein in grams
Yarn denier = x 9000
1 00
3 Results and Discussion
3.1 Relationship between Hot-Pin Temperature and Shrinkage
Fig. 1 shows the effect of hot-pin temperature on the hot-air shrinkage of drawn yams. Shrinkage de
creases with the increase in drawing temperature in a non-linear fashion. As the drawing temperature is increased there is an increased mobility of molecular chains, helping them in orienting in the direction of draw. Increased orientation increases the crystallinity by better packing of molecular chains in their most thermally stable positions. Shrinkage, which is due to
80 50
• ft
: 30
�
�
en 20
1 0
Yarn �ni�r
(> 1 28/34 o 1 2 5 / 1 00
o ����-L�� __ �L-��
40 80 80 1 00 1 20
Fig. l-Effect of hot-pin temperature on the hot-air shrinkage of drawn POY yarns
y:
the rearrangement of molecular chains into new ther
modynamically favourable configurations when an external heat is applied, is prevented by the increased crystallinity at higher drawing temperatures. The only shrinkage is due to the relaxation of residual strain in the molecular chains where the thermally-induced crystallisation has failed to take place. Similar results were also obtai ned by Piller 4 and Sengupta et al. 3.
3.2 Relationship between Hot-Air Shrinkage and Properties of Air-Jet Textured Yarns
Table I shows the properties of parallel-end air-jet textured 'yarns produced from POY of 126/34 and
1 251 1 00 deniers at constant winding tension. It has been shown earlier' that as the shrinkage increases (reducing drawing temperature), the flexural rigidity of filaments decreases due to the less compact mo
lecular structure of filaments. This lowering of flex
ural rigidity should help in better loop formation due to easy bending of filaments as they emerge out of the nozzle 9. This is supported by the findings of 'other researchers·1. 10.1 1 which show a lower loop size, lower yarn core and overall diameter, higher loop frequency and higher physical bulk for yarns having filaments of lower flexural rigidity.
Increasing yarn shrinkage potential in feed yams would have the following effects on air-jet textured yarn produced at constant winding tension:
- Decreasing the flexural rigidity of drawn feed yarn.
- Increasing the overfeed in the stabilizing zone to compensate for increased tension due to higher shrinkage.
- Decreasing the loop size and compacting the yam structure due to shrinkage in individual filaments.
- Bulging out of low shrinkage potential fila
ments under the action of shrinkage forces in the shrinkable component.
The net effect on the yam properties depends on the relative dominance of each of the above factors at a given shrinkage value. Since the overall effect on the properties of the resultant air-jet textured yams depends on the interaction between the two compo
nents of the feed yam, all the results would be dis
cussed with respect to the shrinkage difference in the feed yams entering the jet.
Fig. 2 shows the effect of shrinkage difference in the feed yarn' on the physical bulk. It is observed that the physical bull( increases after a initial drop with the increase in shrinkage difference. Initially, as the shrinkage difference increases the compaction due to the shrinkage of one of the ends, it has more effect counteracting the effect of smaller loops due to lower flexural rigidity filaments of one of the ends and re
duction in loop size due to its shrinkage. The net ef
fect of these two factors is the decrease in physical bulk. This decrease in bulk continues till the increase in bulk due to smaller loops and greater disorienting effect in the yam matrix, making the core open, and bulging out of low shrinkage yams start to have over
riding effect over the factors causing a reduction in bulk. Thus, bulk increases after a certain shrinkage value, due to opening of the yam structure and bulg
ing out of the low shrinkage component. The way by
Table I-Properties of air-jet differential shrinkage yarns produced from POY of 1 26/34 and 1 2511 ()() deniers
Drawing Shrinkage Shrinkage Physical Instability Increase in Tenacity Breaking
temperature % difference bulk % linear density gf/den elongation
°C % % % %
Yarns made from 126/34 denier POY
60 42.4 42.2 263 4. 1 22.54 1 .98 40.9
80 35.4 35.2 257 3.5 2 1 .2 1 1 .9 1 37.9
1 00 20.0 1 9.8 252 1 .5 1 7.96 2.01 33.6
1 20 1 0.8 1 0.6 266 1 .6 1 5.80 2. 1 2 32.6
1 40 7.8 7.6 275 1 .6 14.85 2.36 34.5
Yarns made from 125/100 denier POY
60 59.4 59 2 1 0 3.6 1 8.56 1 .85 42.3
80 53.2 52.8 207 2.7 1 7.3 1 1 .88 37.2
1 00 25.6 25.2 208 1 .7 14.33 1.94 39.0
1 20 7.8 7.4 220 1 .4 1 2. 1 1 2. 1 2 37. 1
140 7.6 7.2 230 2. 1 1 0.5 1 2.24 37.5
84 INDIAN J. FIBRE TEXT. RES., JUNE 1999
X
� '5
.l2
'i u
'i l!!o
� 11.
300
250
200
1 50
1 00
0
Yarn �nifr
6 1 28/34 o 1 2 5 / 1 00
o 1 0 20 30 40 50 80 Shrlnk8g8 difference , Yo
Fig. 2-Effect of shrinkage difference in feed yams on physical bulk of air-jet textured yarns
5
4
X 3
>-
� :a
.. •
2
oS •
1
o
o
o
Yarn denier A 1 28/34 o 1 25/ 1 00
o 1 0 20 30 40 50 80 Shrinkage dlff.rence, X
Fig. 3-Effect of shrinkage difference in feed yams on instability of air-jet textured yarns
which the bulk increases after reaching a minimum is unable to yield higher physical bulk than the lowest shrinkage difference yam in present range of shrink
age values.
Fig. 3 shows the effect of shrinkage difference in
feed yarn on instability. Initially, the increase in shrinkage difference makes the yam core compact,
resulting in reduction in instability. But after a certain
value of shrinkage difference, the internal disorienta
tion of the yam matrix and bulging out of the fila
ments of low shrinkage yam start to contribute in in
stability through reduction in the compactness of the structure.
Linear density increases with the increasing shrinkage difference due to increasing overfeed in the heat-stabilizing zone in order to keep the yam tension constant, as the yam shrinkage increases. There is a drop in tenacity with increasing shrinkage difference.
This is probably due to (i) increasing linear density, (ii) increasing disorientation in the yam matrix, and (iii) decreasing tenacity of the drawn yamt2 of one of the ends. Elongation increases with shrinkage differ
ence after the initial drop. This is due to more instable structure obtained at higher shrinkage difference lev
els. There is an initial drop, except for 1 25/1 00 denier POY, which is due to initial compacting of yam structure on shrinkage, resulting in greater interlock
ing between the filaments.
The present study is confined to the effect of shrinkage difference between the feed yams on the properties of resultant air-jet textured yams. The shrinkage in filament sections forming the loops and that in the core would be different as they would be under different levels of tension and the microstruc
ture of these sections would change differently de
pending on whether it is free shrinkage or shrinkage under tension. The level of tension developed in dif
ferent sections in the core will vary considerably during the shrinkage process. These effects would be important in further understanding of the mechanical behaviour of air-jet textured yams.
3.3 Effect of Number of Filaments on Yarn Properties
It may be seen from Figs 2 and 3 that the yam made from 125/100 denier POY, though having a high number of low denier filaments which is advan
tageous in air-jet texturing, shows inferior results compared to yam produced from 1 26/34 denier POY.
Yam from 125/100 denier POY results in a large number of smaller size loops at greater frequency and a compact core. Lower flexural rigidity of finer fila
ments leads to lower bulk levels. Compact core structure also results' in lower effect of increasing shrinkage difference of the two components of feed yams.
At lower range of shrinkage difference, the yam from POY of 1 25/100 denier shows a higher instabil
ity due to a greater disorientation in the filaments of
lower flexural rigidity. At higher shrinkage differ
ence, the greater filament entanglement and higher inter-filament friction due to more specific surface leads to lower instability of finer denier air-jet tex
tured filament yarns.
Tenacity is lower and elongation is higher in yarns made from 1 25/ 1 00 denier POY due to greater obliq
uity in the yarn structure as compared to the yarns made from 1 26/34 denier POY, as the finer filaments of lower flexural rigidity lead to greater filament dis
orientation and entanglement in the texturing process.
4 Conclusions
Shrinkage potential in drawn yarns decreases as the drawing temperature increases. Bulk and instabil
ity first decrease and then increase with the increase in shrinkage difference between the two ends of feed yarns to air-jet texturing machine.
References
I Piller B. Melliand Textilber. 2 ( 1 979) 140. E 1 28.
2 Piller B. Melliand Textilber. 5 (1 980) 402. E649.
3 Sengupta A K. Kothari V K & Alagirusamy R. Chemie- fasernffext-Ind. 39/9 1 (6) ( 1 989) 73 1 . E84.
4 Piller B. Melliand Textilber. 4 ( 1 980) 3 1 9. E522.
5 Annual Book of ASTM Standards. Vol. 07.02 ( 1 995) 684.
6 . Annual Book of ASTM Standards. Vol. 07.01 ( 1 995) 601 . 7 Sengupta A K. Kothari V K & Rengasamy R S. Chemie-
fasern/Text-Ind. 40/92 ( 1 990) 998. E 1 1 3.
8 Technical Information. Taslan Bull. TS-4 ( 1 99 1 ).
9 Acar M. Chemiefasem/l'ext-Ind. 38/90(4) ( 1 988) 322. E35.
10 Bock G & Liinenschloss J in Textile machinery: Investing for the future (The Textile Institute. Manchester). 1 982. 1 -20.
I I Rengasamy R S. Kotban V K & Sengupta A K. Melliand Textilber. 7 1 ( 12) ( 1 990) 935. E421 .
12 Yadav V K . Studies on air-jet texturing of different types of feed yarns. M.Tech. thesis. Indian Institute of Technology.
Delhi. 1997.
