Post on 24-Jul-2020
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Chapter 4
Influence of twist and blend ratio on characteristics of tencel-
polyester and tencel-cotton blended ring-spun yarns
4.1 Introduction
Tencel is amongst the strongest and stiffest regenerated cellulosic fibre ever
produced. It combines the advantages of both natural and synthetic fibres. It has the
softness of silk, the absorbency of cotton, and is fully biodegradable as well as highly
durable too. Its strength exceeds cotton and can even compete with a typical normal
polyester staple. Further, the strength is much less affected by wetting than other
made cellulosic fibres. Tencel‘s high strength leads to very strong yarns and fabrics,
and its high wet strength gives trouble free processing for both yarns and fabrics in
the wet state during sizing, dyeing and finishing of light weight fabrics. Besides, its
high modulus particularly in wet state, leads to very low shrinkage in water which
makes the garments truly launderable.
Tencel fibre also blends well with other natural or synthetic fibres such as
cotton, linen, polyester, lycra or wool, adding drape, comfort and performance to the
fabrics. The versatility of this fibre produces excellent fabrics for both men‘s and
women‘s casual and tailored wear, as well as lingerie in women, jersey and knitwear.
Although there are many papers, highlighting the advantage of tencel fibre [7-21,
111], only few reports have been published on the performance of tencel blended
yarns [51,112] and fabrics [113]. Kilic and Okur [51] investigated the structural,
physical and mechanical properties of cotton-tencel and cotton-promodal blended
ring, compact and vortex spun yarns and concluded that with increasing ratio of tencel
or promodal fibre content in the blend decreases unevenness, imperfection, diameter
and roughness value, but increases breaking force, elongation, density and shape
value. Kilic and Sular [112] studied the frictional properties of cotton-tencel yarns
produce on different spinning systems with different twist factors and test parameters.
They observed that yarn-to-yarn friction decreases, while yarn-to-metal and yarn-to
ceramic friction increase with the increasing ratio of tencel in the blended yarn for all
the input tensions. With the twist level, no systematic change is observed in yarn
frictional properties. Many researchers studied the influence of twist factor on the
characteristics of ring spun yarns [54, 55, 74, 76-88]. The present study, therefore,
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aims at investigating the quality aspects of tencel-polyester and tencel-cotton ring-
yarns spun with different blend ratios and twist factors.
4.2 Experimental
Ring yarns of 29.5 tex were spun from tencel and its blend with polyester and
cotton fibres using different blend ratios and tex twist factor as discussed in Section
3.2.1 in Chapter 3. The fibre specifications of tencel, polyester and cotton fibres are
also mentioned in Table 3.1 in Chapter 3.
All the yarns were tested for single strand strength, breaking extension, yarn
irregularity, hairiness and flexural rigidity. The test procedures for all yarn properties
are given in Section 3.2.2 in Chapter 3.
4.3 Results and Discussion
The influence of three experimental factors, viz. fibre type, blend ratio and
twist factor, on the yarn characteristics was analysed for significance using ANOVA.
The significance of independent variables and their interactions on the yarn
characteristics were tested at a 99% confidence level i.e. probability level of 0.01. A
probability (p) value smaller than 0.01 leads to the conclusion that the independent
variable had a significant effect on the dependent variable. The results of the ANOVA
test are reported in Table 4.1.
The hypothesis to be tested in the study were determined as follow:
H0: No significant difference exists between average yarn properties.
The alternative hypothesis was as follows:
H1: Significant difference exists between average yarn properties.
If the F-ratio equals or exceeds the critical value, the null hypothesis (H0) is rejected.
It means if F-ratio is greater or equal to critical value than difference is statistically
significant and if it is less than critical value, than difference is said to be non-
significant. It is observed from Table 4.1 that main factors have strong influence on
most of the properties. The interaction effect of fibre type and blend ratio is
significant on all the properties. However, the interaction effect of blend ratio and
twist factor is mostly insignificant. Fibre type and twist factor interaction is
significant for tenacity and very short hairs only.
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Table 4.1 − ANOVA test results
Process
variables
F–ratio
Tenacity Breaking
extension
Work of
rupture
Unevenness Imperfection Flexural
rigidity
Hairiness
Thin
places
Thick
places
Neps Total 1mm 2mm S3
A 528.11
(8.10)
4005.58
(8.10)
4281.2
(8.10)
1246.91
(8.10)
99.39
(8.10)
145.4
(8.10)
2239.6
(8.10)
1004.15
(8.10)
4.61
(8.10)
323.2
(8.10)
139.0
(8.10)
118.6
(8.10)
B 16.76
(4.43)
162.25
(4.43)
325.81
(4.43)
38.30
(4.43)
19.84
(4.43)
5.45
(4.43)
119.05
(4.43)
51.79
(4.43)
531.02
(4.43)
166.4
(4.43)
334.5
(4.43)
719.6
(4.43)
C 6.19
(4.10)
52.03
(4.10)
19.77
(4.10)
7.26
(4.10)
6.01
(4.10)
0.13
(4.10)
15.39
(4.10)
4.98
(4.10)
67.43
(4.10)
117.4
(4.10)
74.73
(4.10)
49.78
(4.10)
A*B 86.39
(4.43)
549.69
(4.43)
734.24
(4.43)
170.17
(4.43)
19.84
(4.43)
16.43
(4.43)
337.80
(4.43)
142.73
(4.43)
16.93
(4.43)
49.54
(4.43)
15.35
(4.43)
9.29
(4.43)
A*C 8.51
(4.10)
0.69
(4.10)
4.10
(4.10)
1.69
(4.10)
6.01
(4.10)
0.35
(4.10)
3.41
(4.10)
2.23
(4.10)
0.57
(4.10)
9.14
(4.10)
5.78
(4.10)
2.79
(4.10)
B*C 1.12
(2.94)
5.03
(2.94)
4.34
(2.94)
1.93
(2.94)
1.00
(2.94)
1.63
(2.94)
0.67
(2.94)
0.91
(2.94)
2.11
(2.94)
0.84
(2.94)
0.76
(2.94)
1.16
(2.94)
R2 .9811 .9972 .9977 .9908 .9442 .9306 .9952 .9892 .9923 .9892 ,9899 .9940
Figures in parentheses indicate critical value
A—Fibre type; B—Blend ratio; C—Tex twist factor
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4.3.1 Tenacity
Table 4.2 shows the results of the tensile test. The results show that there are
marked differences between the yarns spun with different twist factors. For tencel-
polyester yarns, increasing tex twist factor from 23.93 to 33.50 leads to an increase in
tenacity which later drops with further increase in twist factor to 47.85 (Fig. 4.1). The
initial increase in yarn tenacity with increase in twist factor is attributed to the effect
of improved fibre cohesion which outweighs the effect of obliquity, however, a
further increase in cohesion due to twist is leveled off by the decrease due to well
known obliquity effect. Further, yarn tenacity increases as the tencel content in the
mix increases (Fig. 4.2) and the effect is significant for tencel-cotton mix too.
In case of tencel-cotton blends, the yarns exhibit highest tenacity when spun at
a twist factor of 38.28. This shift of optimum twist factor can be attributed to the
presence of short fibres in cotton. The optimum twist factor for 100% polyester and
tencel yarns are 33.5 and 28.71 respectively. The tencel-polyester yarns shows an
optimum twist factor at 33.50 i.e. equivalent to 100% polyester yarn when proportion
of polyester is 50% or more, whereas it is at 28.71 which is equivalent to 100% tencel
yarn when tencel proportion predominates irrespective of blend ratio used. The
optimum twist factor for 100% cotton yarn is at 43.07. The tencel-cotton blended
yarns shows optimum twist factor at 38.28, which is in between their respective
optimum twist factors.
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Table 4.2 − Influence of blend ratio and twist factor on tenacity of tencel-polyester
and tencel-cotton ring- spun yarn
Fibre
type
Blend
ratio
Tenacity, cN/tex
23.93a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a
Tencel:
Polyester
0:100 35.1 35.3 35.4 34.6 33.8 30.5
25:75 28.1 28.7 29.9 28.5 27.5 27.2
50:50 26.1 26.7 26.8 26.0 24.0 22.4
75:25 23.9 25.4 23.9 23.3 22.6 21.5
100:0 22.4 23.4 23.3 22.0 20.7 19.3
Tencel:
Cotton
0:100 10.5 14.9 17.7 18.2 18.9 18.9
25:75 12.9 16.5 18.8 20.5 19.5 19.1
50:50 15.3 18.6 19.7 20.7 20.2 19.5
75:25 18.5 20.5 21.0 20.8 19.5 20.2
100:0 22.4 23.4 23.3 22.0 20.7 19.3
a Tex twist factor
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Fig. 4.1 − Variation in tenacity with tex twist factor of tencel blended ring spun yarns
[(a) Tencel-polyester, and (b) Tencel-cotton]
0
10
20
30
40
50
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
10
20
30
40
50
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COT
Tex twist factor
Ten
acit
y,
cN/t
ex
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Fig. 4.2 − Variation in tenacity with blend ratio of tencel blended ring yarns spun at
different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
10
15
20
25
30
35
4023.93 TF 28.71 TF 33.50 TF
38.28 TF 43.07 TF 47.85 TF
10
15
20
25
30
35
40
0 25 50 75 100
23.93 TF 28.71 TF 33.50 TF
38.28 TF 43.07 TF 47.85 TF
Tencel in blend, %
Ten
acit
y,
cN/t
ex
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4.3.2 Breaking Extension
As expected, the tencel-polyester yarns exhibit higher breaking extension than
their tencel-cotton counterparts due to higher breaking extension of polyester fibre
(Table 4.3). The maximum breaking extension of 100% polyester, 100% cotton and
100% tencel yarns are found to be at twist factor of 47.85. The blended yarns also
show their maximum breaking extension at the highest twist factor i.e. 47.85. For all
fibre-mix, the breaking extension increases with the increase in twist factor (Fig. 4.3).
As more twist is inserted, the constituent fibre follows close spiral path within the
yarn. When such yarns are stretched, the spiral extends initially in place of the fibres
extension. This causes increased extension of the yarn with increase in twist factor. In
the case of tencel-polyester yarns, the breaking extension increases with the increase
in polyester content. Similarly, for tencel-cotton yarns, the breaking extension
increases with the addition of tencel fibre in the mix (Fig. 4.4). For both the fibre mix,
the yarn breaking extension is dominated by the presence of more extensible fibre.
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Table 4.3 − Influence of blend ratio and twist factor on breaking extension of tencel-
polyester and tencel-cotton ring-spun yarn
Fibre
type
Blend
ratio
Breaking extension, %
23.93a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a
Tencel:
Polyester
0:100 12.00 12.73 13.08 13.51 14.59 14.88
25:75 9.90 10.34 11.08 11.24 11.64 12.25
50:50 8.84 9.27 9.64 9.78 9.79 9.68
75:25 7.96 8.30 8.48 8.36 8.59 8.67
100:0 7.16 7.22 7.25 7.29 7.27 7.46
Tencel:
Cotton
0:100 4.03 4.79 5.29 5.78 6.05 6.13
25:75 4.20 5.33 5.65 6.35 5.96 6.33
50:50 5.09 5.62 6.22 6.25 6.51 6.52
75:25 5.76 6.19 6.34 6.56 6.63 7.35
100:0 7.16 7.22 7.59 7.29 7.27 7.46
a Tex twist factor
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Fig. 4.3 − Variation in breaking extension with tex twist factor of tencel blended ring
spun yarns [(a) Tencel-polyester, and (b) Tencel-cotton]
0
4
8
12
16
20
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
4
8
12
16
20
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COT
Tex twist factor
Bre
akin
g e
xte
nsi
on
, %
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Fig. 4.4 − Variation in breaking extension with blend ratio of tencel blended ring
yarns spun at different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
4
6
8
10
12
14
16
23.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
4
6
8
10
12
14
16
0 25 50 75 100
23.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
Tencel in blend, %
Bre
akin
g e
xte
nsi
on
, %
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4.3.3 Work of Rupture
It is evident (Table 4.4) that tencel-polyester fibre mix yarns have higher work
of rupture than tencel-cotton mix yarns (Fig. 4.5). In regards to tencel content, work
of rupture reflects a similar trend as yarn tenacity and breaking extension. The work
of rupture for tencel-polyester blended yarns is maximizes at around 33.5 tex twist
factor and the same is at 38.28 tex twist factor for tencel-cotton blended yarn. These
are intermediate values of twist factor that maximizes work of rupture for 100 %
tencel, polyester and cotton yarn. The data indicate a sizeable increase in work of
rupture with increased twist factor up to certain level (Fig. 4.6). Further increase in
twist factor beyond that level, however, lowers the work of rupture. The same
comment could be made on the decisive effect of higher twist factor.
Table 4.4 − Influence of blend ratio and twist factor on work of rupture of tencel-
polyester and tencel-cotton ring-spun yarns
Fibre
type
Blend
ratio
Work of rupture x 10-3
, g/den
23.93a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a
Tencel:
Polyester
0:100 239.9 256.4 262.6 264.9 279.6 257.2
25:75 157.6 167.9 187.8 181.5 181.6 188.6
50:50 130.8 140.9 145.8 143.9 133.3 122.7
75:25 107.8 119.3 114.6 110.4 110.1 105.7
100:0 90.8 95.8 100.0 90.7 85.3 81.5
Tencel:
Cotton
0:100 24.0 40.5 53.0 59.6 64.8 65.6
25:75 30.6 52.9 60.0 73.7 66.0 66.5
50:50 44.2 59.2 69.3 73.2 74.4 71.9
75:25 60.2 71.9 75.4 77.4 73.3 83.9
100:0 90.8 95.8 100.0 90.7 85.3 81.5
a Tex twist factor
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Fig. 4.5 − Variation in work of rupture with blend ratio of tencel blended ring yarns
spun at different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
0
50
100
150
200
250
30023.93 TF 28.71 TF33.50 TF 38.28 TF43.07 TF 47.85 TF
0
50
100
150
200
250
300
0 25 50 75 100
23.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
Tencel in blend, %
Work
of
ruptu
re x
10
-3, g/d
en
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Fig. 4.6 − Variation in work of rupture with tex twist factor of tencel blended ring
spun yarns [(a) Tencel-polyester, and (b) Tencel-cotton]
0
70
140
210
280
350
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
70
140
210
280
350
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COT
Tex twist factor
Work
of
ruptu
re x
10
-3, g/d
en
-81-
4.3.4 Mass Irregularity
Yarn irregularity (U %) of tencel-polyester and tencel-cotton yarns vary from
8% to 11.5% and 10.1% to 15.3% respectively (Table 4.5). As expected, evenness is
least for 100% cotton yarns, which improves with the inclusion of tencel fibre in the
fibre-mix (Fig. 4.7). Yarn evenness also significantly improves with increase in
polyester fibre content in the tencel-polyester mix. This improvement in yarn
evenness, however, depends on the twist factor used. For all yarns except 100%
cotton, evenness deteriorates as the twist factor is increased (Fig. 4.8). With the
increase in twist factor, the drafting speed reduces as increase of twist is accomplished
by reducing front roller delivery. The decrease in drafting speed decreases dynamic
friction between the fibres which controls the nature of movement of fibres in drafting
field. The movement of floating fibres become more regular when frictional restrain
to sudden acceleration increases. A reduction in drafting speed exercises lesser control
on fibre movement due to decrease in dynamic friction between the fibres. Hence, a
decline in evenness is observed when twist factor is increased. Surprisingly, however,
evenness continuously improves with the increase in twist factor in 100 % cotton
yarn.
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Table 4.5 − Influence of blend ratio and twist factor on work of rupture of tencel-
polyester and tencel-cotton ring-spun yarns
Fibre
type
Blend
ratio
Unevenness, U%
23.93a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a
Tencel:
Polyester
0:100 8.78 8.95 9.04 9.17 9.19 9.23
25:75 8.87 8.95 9.16 9.26 9.26 9.46
50:50 9.30 9.27 9.45 9.54 9.51 9.64
75:25 9.37 9.59 10.19 10.22 10.30 10.51
100:0 10.13 10.51 10.65 10.87 11.23 11.52
Tencel:
Cotton
0:100 15.30 15.17 14.57 14.43 14.12 14.14
25:75 12.44 12.29 11.87 11.81 13.07 13.20
50:50 11.66 11.59 11.40 11.70 12.06 12.36
75:25 11.05 11.35 11.42 11.56 11.72 11.68
100:0 10.13 10.51 10.65 10.87 11.23 11.52
a Tex twist factor
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Fig. 4.7 − Variation in unevenness with blend ratio of tencel blended ring yarns spun
at different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
8
9
10
11
12
13
14
15
16
17
23.93 TF 28.71 TF 33.50 TF
38.28 TF 43.07 TF 47.85 TF
8
9
10
11
12
13
14
15
16
17
0 25 50 75 100
23.93 TF 28.71 TF 33.50 TF
38.28 TF 43.07 TF 47.85 TF
Tencel in blend, %
(a)
(b)
Unev
ennes
s, U
%
(b)
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Fig. 4.8 − Variation in unevenness with tex twist factor of tencel blended ring spun
yarns [(a) Tencel-polyester, and (b) Tencel-cotton]
0
4
8
12
16
20
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
4
8
12
16
20
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COTUnev
ennes
s, U
%
Tex twist factor
-85-
4.3.5 Imperfections
As can be observed form Table 4.6, the frequency of imperfections in the
tencel-polyester yarns increases with increase in tencel content in the mix (Fig 4.9). In
the case of tencel-cotton yarns, an increase in proportion of tencel fibre in the mix
leads to a marked reduction in imperfection indices on account of increase in the
proportion of long fibres in the mix, which allows better control of fibre movement
during drafting. In regards to twist factor, the yarn imperfections (Fig 4.10),
particularly neps and thin places, show a continuous increase with the increase in
twist factor. This is in agreement with the observation by Simpson and Fiori [55]. The
increase in dynamic friction between fibres in the drafting field, as stated above, with
decrease in twist is responsible for improvement in uniformity and imperfections.
-86
-
Table 4.6 − Influence of blend ratio and twist factor on imperfection of tencel-polyester and tencel-cotton ring-spun yarns
Fibre
type
Blend
ratio
Thin places/ km Thick places/ km Neps/ km Imperfections/ km
23.93a 28.71a 33.50a 38.28a 43.07a 47.85a 23.93a 28.71a 33.50a 38.28a 43.07a 47.85a 23.93a 28.71a 33.50a 38.28a 43.07a 47.85a 23.93a 28.71a 33.50a 38.28a 43.07a 47.85a
Tencel:
Polyester
0:100 0 0 0 0 0 0 1 0 0 1 0 2 2 4 4 6 6 8 3 4 4 7 6 10
25:75 0 0 0 0 0 0 4 0 4 2 0 4 8 12 12 24 20 24 12 12 16 26 20 28
50:50 0 0 0 0 0 0 16 8 6 4 0 4 32 32 40 40 52 56 48 40 46 44 52 60
75:25 0 0 0 0 0 0 12 10 8 8 6 4 48 64 68 76 72 76 60 74 76 84 78 80
100:0 0 0 0 0 0 0 30 28 20 12 14 12 56 52 56 52 80 92 86 80 76 64 94 104
Tencel:
Cotton
0:100 6 8 10 18 24 26 48 60 76 80 100 128 276 304 328 328 356 396 330 372 414 426 480 550
25:75 4 6 8 10 12 18 36 32 48 56 68 76 236 252 236 252 268 284 276 290 292 318 348 378
50:50 0 2 4 4 6 12 56 44 42 40 22 24 156 148 172 184 192 192 212 194 218 228 220 228
75:25 0 0 2 0 4 4 56 64 48 36 32 16 104 128 108 128 132 176 160 192 158 164 168 196
100:0 0 0 0 0 0 0 30 28 20 12 14 12 56 52 56 52 80 92 86 80 76 64 94 104
a Tex twist factor
-87-
Fig. 4.9 − Variation in imperfection with blend ratio of tencel blended ring yarns spun
at different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
0
100
200
300
400
500
60023.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
0
100
200
300
400
500
600
0 25 50 75 100
23.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
Tencel in blend, %
Imper
fect
ion/k
m
-88-
Fig. 4.10 − Variation in imperfection with tex twist factor of tencel blended ring spun
yarns [(a) Tencel-polyester, and (b) Tencel-cotton]
0
150
300
450
600
750
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
150
300
450
600
750
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COT
Tex twist factor
Imper
fect
ions/
km
-89-
4.3.6 Flexural Rigidity
Among 100% tencel, polyester and cotton yarns, the former shows highest
flexural rigidity followed by polyester and the cotton yarns (Table 4.7). The yarns
follow the order in which tensile modulus and linear density of individual fibres exist.
The flexural rigidity of tencel fibre is highest due to being coarsest and having higher
individual modulus. The tencel yarn therefore shows highest flexural rigidity too (Fig
4.11). The same argument can be extended to 100% polyester and cotton yarns. The
blended yarns show flexural rigidity values which are in between their 100%
constituent yarns. Furthermore, the flexural rigidity of all the yarns shows an
ascending trend with the increase in twist factor (Fig 4.12). The expected increase in
yarn compactness due to increase in inter fibre cohesion could impair the freedom of
fibre movement and hence a high flexural rigidity.
Table 4.7 − Influence of blend ratio and twist factor on flexural rigidity of tencel-
polyester and tencel-cotton ring-spun yarns
Fibre
type
Blend
ratio
Flexural rigidity x 10-3
, g.cm2
23.93a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a
Tencel:
Polyester
0:100 2.30 2.87 2.87 3.11 3.15 3.22
25:75 3.01 3.03 3.23 3.33 3.47 3.71
50:50 2.94 3.09 3.36 3.71 3.89 4.84
75:25 3.93 4.55 4.71 4.67 5.26 5.66
100:0 4.93 5.04 5.22 5.66 5.51 5.80
Tencel:
Cotton
0:100 2.29 2.34 2.55 2.69 2.96 2.29
25:75 2.89 2.94 3.60 3.88 3.99 2.89
50:50 3.72 4.22 4.42 4.57 4.83 3.72
75:25 4.83 4.73 5.21 5.44 5.74 4.83
100:0 5.04 5.22 5.66 5.51 5.80 5.04
a Tex twist factor
-90-
Fig. 4.11 − Variation in flexural rigidity with blend ratio of tencel blended ring yarns
spun at different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
1
2
3
4
5
6
7
23.93 TF 28.71 TF 33.50 TF
38.28 TF 43.07 TF 47.85 TF
1
2
3
4
5
6
7
0 25 50 75 100
23.93 TF 28.71 TF 33.50 TF
38.28 TF 43.07 TF 47.85 TF
Tencel in blend, %
(a)
Fle
xura
l ri
gid
ity x
10
-3, g.c
m2
-91-
Fig. 4.12 − Variation in flexural rigidity with tex twist factor of tencel blended ring
spun yarns [(a) Tencel-polyester, and (b) Tencel-cotton]
0
2
4
6
8
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
2
4
6
8
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COT
Tex twist factor
Fle
xura
l ri
gid
ity x
10
-3, g.c
m2
-92-
4.3.7 Hairiness
100% polyester yarn shows minimum hairiness followed by 100% cotton and
100% tencel yarns. The blended yarn shows intermediate value of hairiness (Table
4.8). The lowest value of hairiness for polyester yarn can be ascribed to long length,
low linear density and devoid of short fibres. The tencel yarn shows highest amount
of hairiness (Fig 4.13). Even though cotton is finest among the three, the presence of
short fibres in it leads to large number of hairs. With increase in twist factor, hairiness
decrease monotonically for all the yarns (Fig 4.14). This can be ascribed to the
reduction in length of spinning triangle.
-93-
Table 4.8 − Influence of blend ratio and twist factor on hairiness of tencel-polyester and tencel-cotton ring-spun yarns
Fibre
type
Blend
ratio
Hairs/10m
≥ 1mm ≥ 2mm ≥ S3
23.93a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a 23.93
a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a 23.93
a 28.71
a 33.50
a 38.28
a 43.07
a 47.85
a
Tencel:
Polyester
0:100 956 736 688 634 650 585 78 51 45 40 34 33 17 11 11 10 8 8
25:75 1075 800 787 780 702 675 91 56 55 52 47 37 20 12 12 12 11 11
50:50 1229 1008 974 914 887 864 135 91 80 75 70 69 31 20 17 15 15 8
75:25 1428 1152 1126 1101 1101 1079 179 129 125 120 111 107 43 31 28 27 26 25
100:0 1949 1670 1573 1463 1343 1341 338 278 249 230 220 212 109 96 85 53 81 77
Tencel:
Cotton
0:100 1923 1548 1208 1148 1076 1006 248 151 103 88 86 77 59 31 22 20 20 19
25:75 1734 1379 1240 1152 1001 973 188 140 112 99 83 80 39 33 26 23 23 20
50:50 1613 1330 1238 1059 1060 958 190 139 121 103 95 85 44 29 25 25 23 22
75:25 1694 1345 1281 1186 1133 1074 240 162 144 137 132 128 61 39 37 37 36 34
100:0 1949 1670 1573 1463 1343 1341 338 278 249 230 220 212 109 96 85 53 81 77
a Tex twist factor
- 94 -
Fig. 4.13 − Variation in hairiness with blend ratio of tencel blended ring yarns spun at
different twist factors [(a) Tencel-polyester, and (b) Tencel-cotton]
0
25
50
75
100
125
23.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
0
25
50
75
100
125
0 25 50 75 100
23.93 TF 28.71 TF
33.50 TF 38.28 TF
43.07 TF 47.85 TF
Tencel in blend, %
Hai
rs/1
0m
, S
3
- 95 -
Fig. 4.14 − Variation in hairiness with tex twist factor of tencel blended ring spun
yarns [(a) Tencel-polyester, and (b) Tencel-cotton]
0
30
60
90
120
150
0:100 TEN/PET 25:75 TEN/PET 50:50 TEN/PET
75:25 TEN/PET 100:0 TEN/PET
0
30
60
90
120
150
23.93 28.71 33.50 38.28 43.07 47.85
0:100 TEN/COT 25:75 TEN/COT 50:50 TEN/C0T
75:25 TEN/COT 100:0 TEN/COT
Tex twist factor
Hai
rs/1
0m
, S
3
- 96 -
4.4 Conclusions
4.4.1 Tensile behavior of tencel-polyester and tencel-cotton ring-spun yarns is
predominantly influenced by fibre composition and twist factor. Higher tencel content
results in less strength, reduced breaking extension and reduced work of rupture of
tencel-polyester yarns. However, for tencel-cotton yarns, there is an increase in
strength, breaking extension and work of rupture with the increase in proportion of
tencel fibre in the mix. Generally, the yarn strength and work of rupture increase
initially and then decrease with the increase in twist factor, and the optimum twist
factor shifts towards higher side as proportion of cotton in tencel-cotton mix
increases. Further, the breaking elongation of tencel blended yarns increases
consistently with the increasing twist factor.
4.4.2 The fibre composition as well as constituents of the mix markedly affects the
mass irregularity, which tends to improve with increase in polyester content in the
tencel-polyester mix. In the case of tencel-cotton yarns, mass irregularity increases
with the increase in proportion of cotton fibre. Generally, the tencel-polyester yarns
are more even and have fewer imperfections than the equivalent tencel-cotton yarns.
Twist factor has been found to change mass irregularity possibly due to change in
dynamic friction between fibres in the drafting field as speed of drafting alters with
twist.
4.4.3 Blending of tencel fibre either with polyester or cotton substantially increases
the yarn flexural rigidity. Higher twist factor has a deleterious effect on yarn rigidity.
4.4.4 Invariably, the yarns made with a tencel-polyester mix show less hairiness as
compared to tencel-cotton yarns, which further reduces with increase in polyester
content in the fibre-mix. Higher twist factor also results in considerable reduction in
hairs in all length groups.
4.4.5 In general, all tencel blended yarns produced with low level of twist are more
uniform, having less imperfection and flexible but less extensible and hairy. However,
tencel-polyester yarns are stronger at low twist level whereas tencel-cotton blended
yarns are stronger at high twist level.