In this section, the structural properties such as unevenness, imperfections, hairiness, and mechanical properties such as breaking strength and elongation of RS, CS, and DCS yarns were evaluated comparatively in this part, respectively.
Yarn unevenness (U%)
The mass or weight variation per unit length of yarn is defined as unevenness or irregularity (Demiryürek et. al 2014). A percent U value is calculated via mathematical methods that detect changes in the yarn's unit length. The unevenness values (U%) and statistical test (ANOVA and DUNCAN) results of the hybrid yarns produced in this study were given in Fig. 3 and Table 4-5, respectively. As shown in Fig. 3, yarns with OCVH sheath fibers provided the highest unevenness values (from 19.41 to 19.60), while yarns with CT sheath fibers provided the lowest (from 10.07 to 10.78).
Fiber length and length variations are the main causes of yarn unevenness (Aydoğdu et al. 2020; Demiryürek et al. 2018). Low fiber-to-fiber cohesion in the yarn occurs in the yarn structure due to the characteristics of hemp fiber such as being short, having poor uniformity difference, and high fiber length variation (Liu et. al 2011). Furthermore, using viscose fiber in the yarn structure reduces yarn unevenness values because the crimped cross-
section of the viscose fiber a generates higher surface area, i.e., more fiber-to-fiber friction (Aydoğdu et al. 2020;
Demiryürek et al. 2018). Therefore, the observation of the highest U% values in yarns containing OCVH sheath
fibers could be attributed to the low fiber-to-fiber friction in the yarn primarily due to less homogeneity between
three fibers that causes low fiber-to-fiber friction. Secondly, the decreased ratio of viscose from 70% (VH) to 35
% (OCVH) might cause low friction forces between fibers and result in high unevenness. As for the effect of the core component, the core component either slightly decreased or increased the yarn unevenness values in CS and DCS yarns, regardless of the sheath fiber type. This result, which is in accordance with the statistical findings, could be attributed to the greater effect (84.16%) of the sheath fibers on the unevenness. ANOVA results indicated that sheath fiber type (p=0.000) and sheath fiber type & core component type (p=0.004) were statistically significant at a level of 5% while core component type (p=0.437) was not statistically significant on the yarn unevenness values. As a result, yarns containing different sheath fiber blends resulted in different yarn unevenness values. On the contrary, yarns formed from the identical sheath fiber blend with or without core component gave similar unevenness values. The unevenness values of yarns were compared using the DUNCAN test as seen in Table 5. According to the results, CT, VH, and OCVH yarn types were significantly different from each other. However, core component types (R, L, and LT) were not significantly different from each other, statistically.
Table 4
ANOVA findings for yarn unevenness values.
Source
|
Type III sum of squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
659.667a
|
8
|
82.458
|
818.472
|
0.000
|
Intercept
|
10729.870
|
1
|
10729.874
|
106503.511
|
0.000
|
Sheath fiber type
|
657.580
|
2
|
328.791
|
3263.543
|
0.000
|
Core component type
|
0.171
|
2
|
0.085
|
0.847
|
0.437
|
Sheath fiber type * Core component type
|
1.914
|
4
|
0.479
|
4.750
|
0.004
|
Error
|
3.627
|
36
|
0.101
|
|
|
Total
|
11393.168
|
45
|
|
|
|
Corrected total
|
663.294
|
44
|
|
|
|
a. R Squared = .995 (Adjusted R Squared = .993)
|
Table 5
DUNCAN findings for yarn unevenness values.
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra, and T: T400)
Yarn unevenness
|
|
Group
|
N
|
1
|
2
|
3
|
Sheath fiber type
|
|
|
|
|
CT
|
15
|
10.322
|
|
|
VH
|
15
|
|
16.497
|
|
OCVH
|
15
|
|
|
19.505
|
Sig.
|
|
1.000
|
1.000
|
1.000
|
Core component type
|
|
|
|
|
R
|
15
|
15.397
|
|
|
L
|
15
|
15.398
|
|
|
LT
|
15
|
15.528
|
|
|
Sig.
|
|
0.293
|
|
|
Yarn imperfections
Imperfections are defined as the cumulative amount of thin -50%, thick +50%, and neps +200% per kilometer of yarn length (Jabbar et. al. 2018). Yarn imperfection values and statistical analysis outcomes (ANOVA and DUNCAN) were displayed in Figs 4-6 and Table 6-11, respectively. There were no thin places (-50%) detected in the yarns for CT sheath fiber. While there were some thin places in VH sheath blended yarns, they grew significantly in OCVH sheath fiber yarns. (Fig. 4). Yarn imperfection is highly influenced by fiber characteristics (Malik et al. 2012). A larger rate of thin places could be noticed in the yarns containing OCVH sheath fibers due to the non-uniform fineness and length of hemp fibers, as well as the increase in fiber variety in the blend. Using core components boosted yarn thin place values, with the exception of CT yarns, regardless of sheath fiber. Moreover, this increase was much more in DCS yarns. This could be attributed to the two different core components in the yarn structure reducing the sheath fiber ratio and the core components couldn't be wrapped uniformly. The sheath fiber type (p=0.000) and core component type (p=0.035), as well as the interacting effect of these two factors (p=0.042) on thin places, were statistically insignificant at the 5% level, according to ANOVA results (Table 6). According to the DUNCAN test results for thin places (Table 9), where the difference between VH and OCVH fiber types was statistically significant, the difference between CT and VH fiber types was insignificant. When the core components were investigated, the difference between R and L core components was statistically insignificant, however, the difference between L and LT core types was statistically significant.
According to Fig. 5, OCVH and VH sheath fibers had much higher thick places (+50%) than yarns spun entirely of CT sheath fibers. This could be due to the non-homogeneousness structure between fibers. Hemp fibers are coarser than CT, OC, and V. Determining the thick places values of yarns containing OCVH and VH sheath fibers, the thick places values of the OCVH yarns were slightly greater than the VH yarns. This could be attributed to the increased fiber variety in the yarn structure which decreases the length uniformity in yarns with OCVH sheath fibers. When the effect of the core component was evaluated, there was no obvious tendency on yarn thick place values. According to the ANOVA results (Table 7), sheath fiber type (p=0.000) had a statistically significant effect on the yarn thick places although core component type (p=0.435) and the interactive effect of these two components (p=0.526) did not.
In this study, neps were measured at +200% levels. It was observed that neps content per kilometer was increased with the usage of hemp fiber and the increase of fiber variety in the blend, regardless of the core component (Fig. 6). This could be owing to the physical properties of hemp fiber and the usage of various fibers in the blend, resulting in a less homogenous distribution in the yarn cross-section. The use of core component in all yarns, except for the OCVHLT sample, slightly decreased the yarn neps values. ANOVA results revealed that sheath fiber type had a statistically significant effect on yarn neps values (p=0.000). But, core component type (p=0.348) and the intersection of these factors (p=0.650) had no statistically significant effect on yarn neps values (Table 8 and Table 11). Comparing thick place and neps values of the yarns formed from OC, VH, and OCVH sheath fiber, the difference between thick place and neps values for all fiber types was statistically significant, whereas, for yarns containing R, L, and LT core components, the difference of all core types for thick place and neps values were statistically insignificant according to the DUNCAN test results given on Table 10 and Table 11.
When the yarn imperfection results were evaluated together, it could be said that thin places, thick places, and neps were increased with the hemp fiber presence in the blend, and this increase was also more noticeable when hemp and organic cotton fiber were used together in the blend, as reported for yarn unevenness. The effect of core component usage and core component type on yarn imperfection varied depending on sheath fiber blends.
Table 6
ANOVA findings for yarn thin places values.
Source
|
Type III sum of squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
1562360.000a
|
8
|
195295.000
|
37.603
|
0.000
|
Intercept
|
822151.250
|
1
|
822151.250
|
158.301
|
0.000
|
Sheath fiber type
|
1466625.833
|
2
|
733312.917
|
141.195
|
0.000
|
Core component type
|
38132.500
|
2
|
19066.250
|
3.671
|
0.035
|
Sheath fiber type * Core component type
|
57601.667
|
4
|
14400.417
|
2.773
|
0.042
|
Error
|
186970.000
|
36
|
5193.611
|
|
|
Total
|
2571481.250
|
45
|
|
|
|
Corrected total
|
1749330.000
|
44
|
|
|
|
a. R Squared = .893 (Adjusted R Squared = .869)
|
Table 7
ANOVA findings for yarn thick places values.
Source
|
Type III sum of squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
57595635.078a
|
8
|
7199454.385
|
537.813
|
0.000
|
Intercept
|
112875842.222
|
1
|
112875842.222
|
8432.044
|
0.000
|
Sheath fiber type
|
57529295.244
|
2
|
28764647.622
|
2148.775
|
0.000
|
Core component type
|
22838.544
|
2
|
11419.272
|
0.853
|
0.435
|
Sheath fiber type * Core component type
|
43501.289
|
4
|
10875.322
|
0.812
|
0.526
|
Error
|
481915.200
|
36
|
13386.533
|
|
|
Total
|
170953392.500
|
45
|
|
|
|
Corrected total
|
58077550.278
|
44
|
|
|
|
a. R Squared = .992 (Adjusted R Squared = .990)
|
Table 8
ANOVA findings for yarn neps values.
Source
|
Type III sum of squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
79460008.244a
|
8
|
9932501.031
|
391.828
|
0.000
|
Intercept
|
154610629.606
|
1
|
154610629.606
|
6099.246
|
0.000
|
Sheath fiber type
|
79341753.678
|
2
|
39670876.839
|
1564.979
|
0.000
|
Core component type
|
55189.211
|
2
|
27594.606
|
1.089
|
0.348
|
Sheath fiber type * Core component type
|
63065.356
|
4
|
15766.339
|
0.622
|
0.650
|
Error
|
912568.900
|
36
|
25349.136
|
|
|
Total
|
234983206.750
|
45
|
|
|
|
Corrected total
|
80372577.144
|
44
|
|
|
|
a. R Squared = .989 (Adjusted R Squared = .986)
|
Table 9
DUNCAN findings for yarn thin places values
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra, and T: T400).
Yarn thin places
|
|
Group
|
N
|
1
|
2
|
Sheath fiber type
|
|
|
|
CT
|
15
|
0.167
|
|
VH
|
15
|
15.000
|
|
OCVH
|
15
|
|
390.333
|
Sig.
|
|
0.576
|
1.000
|
Core component type
|
|
|
|
R
|
15
|
103.000
|
|
L
|
15
|
129.000
|
129.000
|
LT
|
15
|
|
173.500
|
Sig.
|
|
0.330
|
0.099
|
Table 10
DUNCAN findings for yarn thick places values
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra and T: T400).
Yarn thick places
|
|
Group
|
N
|
1
|
2
|
3
|
Sheath fiber type
|
|
|
|
|
CT
|
15
|
76.333
|
|
|
VH
|
15
|
|
1875.800
|
|
OCVH
|
15
|
|
|
2799.400
|
Sig.
|
|
1.000
|
1.000
|
1.000
|
Core component type
|
|
|
|
|
R
|
15
|
1557.100
|
|
|
L
|
15
|
1582.033
|
|
|
LT
|
15
|
1612.200
|
|
|
Sig.
|
|
0.227
|
|
|
Table 11
DUNCAN findings for yarn neps values
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra and T: T400).
Yarn neps
|
|
Group
|
N
|
1
|
2
|
3
|
Sheath fiber type
|
|
|
|
|
CT
|
15
|
49.100
|
|
|
VH
|
15
|
|
2305.733
|
|
OCVH
|
15
|
|
|
3205.933
|
Sig.
|
|
1.000
|
1.000
|
1.000
|
Core component type
|
|
|
|
|
R
|
15
|
1804.100
|
|
|
L
|
15
|
1876.667
|
|
|
LT
|
15
|
1880.000
|
|
|
Sig.
|
|
0.226
|
|
|
Yarn hairiness
Yarn hairiness is one of the important yarn parameters, which is used for yarn production quality control. It is usually characterized by the number of free fibers (fiber loops, fiber ends) protruding from the compact body of yarn towards the outer yarn surface (Tyagi 2010). The Uster hairiness values (H) of yarns spun were shown in Fig. 7 and the statistical test results (ANOVA and DUNCAN) were given in Tables 12 and 13. The yarns created from VH blended fibers had the lowest hairiness values (From 6.94 to 7.28). The hairiness values increased when OC and H fibers were combined in the blend. The type of fiber and blending ratio are the main factors affecting yarn hairiness. Owing to their non-uniform fineness and length, OC and H fibers did not bind properly in the yarn body (Malik et al. 2012) which results in an increase in hairiness. Therefore, the viscose fiber presence in the blend reduced hairiness. As for the effect of the core material, no clear trend in the values was observed and the results changed depending on the sheath fiber type. ANOVA test results display that sheath fiber type (p=0.000), core component type (p=0.000), and sheath fiber type*core component type (p=0.000) had a statistically significant effect on the yarn hairiness values. The hairiness values of yarns were compared using the DUNCAN test as shown in Table 13. According to the findings, CT, VH, and OCVH yarn types were significantly different from each other. The core component types of R and L were not significantly different from each other, whereas the L and LT core types of yarn were significantly different from each other.
Table 12
ANOVA findings for yarn hairiness values.
Source
|
Type III Sum of Squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
41.372a
|
8
|
5.172
|
99.901
|
0.000
|
Intercept
|
2804.028
|
1
|
2804.028
|
54166.666
|
0.000
|
Sheath fiber type
|
19.542
|
2
|
9.771
|
188.750
|
0.000
|
Core component type
|
5.787
|
2
|
2.894
|
55.900
|
0.000
|
Sheath fiber type * Core component type
|
16.043
|
4
|
4.011
|
77.478
|
0.000
|
Error
|
1.864
|
36
|
.052
|
|
|
Total
|
2847.264
|
45
|
|
|
|
Corrected total
|
43.236
|
44
|
|
|
|
a. R Squared = .957 (Adjusted R Squared = .947)
|
Table 13
DUNCAN findings for yarn hairiness values
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra and T: T400).
Yarn hairiness
|
|
Group
|
N
|
1
|
2
|
3
|
Sheath fiber type
|
|
|
|
|
CT
|
15
|
|
|
8.685
|
VH
|
15
|
7.072
|
|
|
OCVH
|
15
|
|
7.924
|
|
Sig.
|
|
1.000
|
1.000
|
1.000
|
Core component type
|
|
|
|
|
R
|
15
|
|
8.154
|
|
L
|
15
|
|
8.141
|
|
LT
|
15
|
7.387
|
|
|
Sig.
|
|
1.000
|
0.873
|
|
Yarn tenacity
Tenacity is the breaking force of yarn per unit linear density (Jabbar et. al. 2018). The tenacity values and statistical test results (ANOVA and DUNCAN) of the yarns spun were presented in Fig. 8, Table 14, and 15, respectively. While the yarns formed with CT sheath fiber had the highest tenacity, OCVH yarns containing 3 different sheath fibers had the lowest tenacity value, regardless of the core component, as shown in Fig. 8. Moreover, VH yarns had nearly the same tenacity values as CT yarns, which could be explained by the fact that hemp fiber had a higher tenacity value (45 cN/tex) than other fibers (OC: 32 cN/tex and V: 25 cN/tex) in the blend and the hemp/viscose fiber blend had a synergistic effect in the yarn structure. Considering all yarn properties, the lowest tenacity value of OCVH yarns might be due to the incompatibility of three different sheath fibers in the yarn structure and the inability to achieve a homogeneous distribution in the yarn structure due to low fiber-to-fiber friction. Since this sheath part of the yarn carries more of the load than the core component, sheath fibers contribute more to the tensile properties of the yarn in CS yarns (Aydoğdu et al. 2020; Das et al. 2013; Qadir et al. 2014; Babaarslan 2001) As a result, the CS yarns' tenacity characteristics varied depending on the sheath fiber types. When the role of the core component on yarn tenacity was examined, it was discovered that the Lycra core component increased or did not change the tenacity. On the other hand, using Lycra & T400 core components together negatively affected the strength of all yarns. This could be due to the reduced proportion of sheath fibers, which has a major effect on strength, as a result of using two core components and thus being unable to cover the core components uniformly.
When the tenacity values of the yarns spun were evaluated statistically, the ANOVA findings revealed that sheath fiber type (p=0.000), core component type (p=0.000), and the intersection of these factors (p=0.004) all had a statistically significant effect on the yarn tenacity values. The tenacity values of yarns were compared using the DUNCAN test as seen in Table 15. According to the findings, the CT, VH, and OCVH yarn types were significantly different from each other. The core component types of R and L were not significantly different from each other, even though the L and LT core types of yarns were significantly different from each other.
Table 14
ANOVA findings for yarn tenacity values.
Source
|
Type III sum of squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
262.043a
|
8
|
32.755
|
66.952
|
0.000
|
Intercept
|
8949.834
|
1
|
8949.834
|
18293.591
|
0.000
|
Sheath fiber type
|
242.592
|
2
|
121.296
|
247.930
|
0.000
|
Core component type
|
10.214
|
2
|
5.107
|
10.439
|
0.000
|
Sheath fiber type * Core component type
|
9.237
|
4
|
2.309
|
4.720
|
0.004
|
Error
|
17.612
|
36
|
.489
|
|
|
Total
|
9229.490
|
45
|
|
|
|
Corrected total
|
279.655
|
44
|
|
|
|
a. R Squared = .937 (Adjusted R Squared = .923)
|
Table 15
DUNCAN findings for yarn tenacity values
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra, and T: T400).
Yarn tenacity
|
|
Group
|
N
|
1
|
2
|
3
|
Sheath fiber type
|
|
|
|
|
CT
|
15
|
|
|
16.711
|
VH
|
15
|
|
14.525
|
|
OCVH
|
15
|
11.071
|
|
|
Sig.
|
|
1.000
|
1.000
|
1.000
|
Core component type
|
|
|
|
|
R
|
15
|
|
14.339
|
|
L
|
15
|
|
14.488
|
|
LT
|
15
|
13.431
|
|
|
Sig.
|
|
1.000
|
0.700
|
|
Yarn breaking elongation
The percentage increase in yarn length before breaking is referred to as breaking elongation (Jabbar et. al. 2018). The breaking elongation values and statistical test results (ANOVA and DUNCAN) of yarns spun were shown in Fig. 9 and Tables 16 and 17. Due to having good elongation property of viscose fiber (20%) compared to other fibers, yarns containing viscose fiber (VH and OCVH) had the highest elongation values, as expected, while yarns including CT sheath fiber had the lowest elongation values, regardless of the core component. Decreasing viscose fiber ratio (from %70 to 35%) and usage of the hemp and organic cotton fibers in OCVH yarns, the breaking elongation decreased (Fig. 9), as well. The reason why the lowest elongation was seen in CT yarns could be due to the characteristic elongation feature of the CT fiber (5.3%). When the effect of the core component on the elongation values was evaluated, it was seen that the core component negatively affected the elongation values in CS and DCS yarns, except for CT sheath fiber yarns. This controversial result might be due to the fact that the less flexible sheath fibers did not wrap the core components well. As to the effect of the core filament type, Lycra gave significantly higher elongation values than the Lycra & T400 core filaments. A possible reason for this could be the fiber elongation feature of the core filaments. Lycra is a polyurethane fiber, which means it has a higher elongation than the semi-elastic T400 polyester filament. Sheath fiber type (p=0.000), core component type (p=0.000), and the intersection of these parameters (p=0.000) all exhibited statistically significant effects on yarn breaking elongation values, according to ANOVA results. The DUNCAN test was conducted to compare the breaking elongation values of yarns, as illustrated in Table 17. The VH and OCVH yarn types were observed to be significantly different from one another, while the CT and OCVH fiber types were not. The three core component types (R, L, and LT) differed significantly from each other.
Table 16
ANOVA findings for yarn breaking elongation values.
Source
|
Type III sum of squares
|
df
|
Mean square
|
F
|
Sig.
|
Corrected model
|
571.233a
|
8
|
71.404
|
231.694
|
0.000
|
Intercept
|
4647.387
|
1
|
4647.387
|
15079.944
|
0.000
|
Sheath fiber type
|
335.362
|
2
|
167.681
|
544.095
|
0.000
|
Core component type
|
40.885
|
2
|
20.442
|
66.332
|
0.000
|
Sheath fiber type * Core component type
|
194.986
|
4
|
48.746
|
158.174
|
0.000
|
Error
|
11.095
|
36
|
0.308
|
|
|
Total
|
5229.715
|
45
|
|
|
|
Corrected total
|
582.327
|
44
|
|
|
|
a. R Squared = .981 (Adjusted R Squared = .977)
|
Table 17
DUNCAN findings for yarn elongation values
(CT: Cotton, OC: Organic cotton, V: Viscose, H: Hemp, L: Lycra and T: T400).
Yarn elongation
|
|
Group
|
N
|
1
|
2
|
3
|
Sheath fiber type
|
|
|
|
|
CT
|
15
|
8.151
|
|
|
VH
|
15
|
|
14.022
|
|
OCVH
|
15
|
8.314
|
|
|
Sig.
|
|
0.428
|
1.000
|
|
Core component type
|
|
|
|
|
R
|
15
|
|
10.531
|
|
L
|
15
|
|
|
11.101
|
LT
|
15
|
8.855
|
|
|
Sig.
|
|
1.000
|
1.000
|
1.000
|