Investigation of the Two-Bar Warp-Knitted Fabric
Structure Effect on Luster Value
Saeed Ajeli, PhD, Zoleykhah Ahmadvand
Department of Textile Engineering, Isfahan University of Technology, Isfahan, Isfahan IRAN
Correspondence to:
Saeed Ajeli email: [email protected]
ABSTRACT
Consumer points of view determine economical
value of fabrics. Fabric luster plays a momentous role
in attracting people's attention, especially for clothing
and domestic purposes. Luster is defined by intensity
of both specular and diffuse light reflection off of a
surface. There are various methods for measuring
surface luster. Gloss. Luster is described as the ratio
of specular reflection in one angle to diffuse
reflection in another angle.
describe its performance rather than specular. Luster
or gloss is defined based on the specular diffuse
reflection ratio of light. Although luster has been a
common perception among people, physically
measuring and associating it to psychological aspects
are rather difficult [1,2,3].
Angular photometer has been widely applied to
measure light scientifically. It measures the amount
of light reflected from a surface in different
directions. In other words, luster is specified by
reflected light intensity in all possible angles.
Textiles luster is stated by the difference between
specular and diffuse light reflection off different parts
[4,5,6].
Two-bar warp knitted polyester fabrics such as
Tricot, Locknit, Satin, reverse Locknit and Sharkskin
in three different densities were provided. A mini
gloss apparatus was applied to measure fabric
specular reflection in the angle of sixty degrees,
before and after disperse dying with different colors
of white, blue and yellow. Results suggest that luster
is a function of knitted fabric type, color and density.
Enhancement of technical back luster resulted from
longer underlap of the front bar. However, it did not
change the technical face luster significantly. Density
increased in all knitted fabrics and caused the luster
to decrease. Dark color fabrics showed lower luster
compared to light ones.
Keywords: luster, light reflection, warp knitted
structure, underlap, knitting density
According to Hunter's visual survey, six distinct
groups of gloss can be categorized among which
specular is of great importance. This apparatus
measures specular gloss with one light source and
one detector with the reflectance angle the same as
the incidence angle [7,8,9]. Recently, Smith has also
declared both physical and psychological difficulties
of gloss measurement. Based on his theory, practical
gloss measurement is of five methods: Single-angle
visual, Double-angle visual, Angular photometry,
Polar, and Specific.
INTRODUCTION
Luster is classified as a surface property. It refers to
specular reflection where incidence and reflection
angles are the same. Based on the definition of gloss,
the highest amount of reflected light is ascribed to the
most lustrous surface. A perfect specular surface is
able to reflect all light in accordance with the law of
reflection, while Opaque surfaces are recognized by
their minimal gloss. Opaque surfaces reflect light so
that gloss in all visual sides is the same and
independent of incidence angle. Since a rough
surface reflects light in all possible directions
irregularly, diffuse reflection is the best word to
Comparing surface luminescence to that of a standard
lamp, Smith provided a photometry method in order
to measure the luster of textile materials [10].
Thomas Preston conducted some research on material
luster and conceived that fabric luster is completely
different from that of individual fibers. He also
expressed that fabric luster depends on both fiber
luster and fabric finishing treatment [11]. In 2004, the
effect of other parameters such as yarn twist and
woven fabric types, including plain, twill and satin,
on fabric luster were studied [12]. Some research
focused on procedures by which decreasing specular
reflection and consequently luster fabric decline were
Journal of Engineered Fibers and Fabrics
Volume 9, Issue 2 – 2014
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favorable [13]. As studies show, various complex
tools have been invented for measuring luster and
gloss [14,15,16]. Moreover, some scientists have
utilized image analysis for evaluating textile luster
[17,18].
EXPERIMENTAL
Two-bar warp knitted fabrics with Tricot, Locknit,
reverse Locknit, three and four-needle Satin, and
three and four-needle Sharkskin structure were
prepared in three tight, medium and low densities,
see Figure 1. All samples were knitted on a Liba
tricot machine with 28 needles per inch using flat, 8.3
tex monofilament polyester. The positive feed
mechanism was used for controlling the delivery and
tension of the warp yarn while being knitted. Fabrics
specifications are provided in Table I.
The connection of knitted structure and fabric
mechanical properties has been taken into account in
many articles. This project studied the effect of twobar warp knitted parameters, such as the number of
underlaps and knitting density, on the specular gloss
of fabrics.
Tricot
Satin
Locknit
Reveres Locknit
Sharkskin
FIGURE 1. Five standard two-bar warp knitted schema (each unit includes loop head, arms and underlap).
TABLE I. Sample specifications and symbol of each knitting type.
Number of underlap
Run-in (cm/rack)
FB
BB
FB
BB
Loose
Tl
1
1
202
189
Tricot
Medium
Tm
1
1
165
145
Tight
Tt
1
1
141
129
Loose
Ll
2
1
225
192
Locknit
Medium
Lm
2
1
182
145
Tight
Lt
2
1
160
131
Loose
S3l
3
1
261
198
Three needles satin
Medium
S3m
3
1
224
150
Tight
S3t
3
1
209
130
Loose
S4l
4
1
306
195
Four needles satin
Medium
S4m
4
1
261
151
Tight
S4t
4
1
245
132
Loose
RLl
1
2
201
221
Reveres locknit
Medium
RLm
1
2
160
180
Tight
RLt
1
2
142
162
Loose
SH3l
1
3
205
256
Three needles Sharkskin
Medium
SH3m
1
3
162
216
Tight
SH3t
1
3
144
211
Loose
SH4l
1
4
210
306
Four needles sharkskin
Medium
SH4m
1
4
161
261
Tight
SH4t
1
4
150
252
Note: FB:front guide bar; BB: back guide bar; CPC: course per cm; WPC: wale per cm. a1 rack = 480 courses
Fabric structure
Density
Journal of Engineered Fibers and Fabrics
Volume 9, Issue 2 – 2014
Fabric code
33
CPC
WPC
12.0
16.2
20.6
11.8
16.2
22.0
11.6
16.4
19.8
12.2
16.8
21.6
12.0
16.6
21.0
12.2
17.2
21.2
11.0
17.0
22.0
13.2
14.0
13.6
13.0
16.6
15.8
14.0
16.4
16.4
14.8
15.8
15.2
13.2
15.2
14.2
13.2
13.6
13.4
12.4
13.2
12.6
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TABLE II. Results of different samples luster.
structure code
Tl
Tm
Tt
Ll
Lm
Lt
S3l
S3m
S3t
S4l
S4m
S4t
RLl
RLm
RLt
SH3l
SH3m
SH3t
SH4l
SH4m
SH4t
Blue
course
3.17
3.30
2.70
3.32
3.50
3.12
4.20
4.72
4.27
4.92
5.27
4.30
3.37
2.90
2.87
3.05
3.02
3.00
3.25
3.67
3.27
wale
3.20
3.10
2.70
3.37
3.60
3.27
4.15
5.15
5.15
4.82
5.32
4.45
3.20
2.80
2.85
3.00
2.90
2.72
3.25
2.87
2.85
Technical Back
Yellow
Course
wale
3.52
3.20
3.35
2.87
3.05
3.00
3.52
3.30
3.30
3.32
3.05
3.02
4.17
3.90
2.60
3.30
2.60
2.75
3.80
3.75
3.20
3.17
2.77
2.92
3.72
3.62
3.12
3.15
2.60
2.65
3.75
3.52
3.12
3.07
2.92
2.70
3.77
3.70
3.32
2.92
3.00
2.55
White
course
wale
1.60
1.77
1.35
1.25
1.12
1.07
1.80
1.85
2.00
2.05
1.97
2.22
2.62
2.60
3.42
3.90
2.57
2.72
3.47
3.25
3.32
3.67
2.42
3.00
1.80
1.55
1.20
1.17
1.65
1.20
2.17
1.60
1.82
1.47
1.52
1.32
2.25
1.72
1.95
1.67
1.95
1.57
Blue
course
2.82
2.22
2.12
3.17
3.15
2.62
3.85
4.30
4.35
4.75
5.40
3.82
2.47
2.32
2.27
2.62
2.70
2.55
3.12
2.95
2.90
wale
3.05
2.22
2.02
3.20
3.27
2.77
3.72
4.67
4.85
4.90
5.42
4.22
2.42
2.27
2.22
2.57
2.35
2.30
2.67
2.32
2.25
Technical Face
Yellow
course
wale
2.12
1.85
1.57
1.62
1.30
1.10
2.02
2.02
1.72
1.77
1.57
1.65
2.05
2.05
1.30
1.42
1.30
1.60
2.17
2.55
1.70
1.92
1.52
1.62
1.87
1.87
1.47
1.50
1.17
1.17
2.02
2.20
1.37
1.37
1.37
1.32
2.05
1.90
2.22
1.70
1.32
1.10
White
course
wale
3.12
2.87
2.60
2.67
2.35
2.40
3.22
3.20
2.85
2.95
2.65
2.67
3.05
3.02
2.37
2.87
2.37
2.47
3.32
3.52
2.60
2.70
2.47
2.65
3.27
3.32
2.65
2.72
2.32
2.32
3.22
3.20
2.47
2.62
2.55
2.35
3.05
2.87
2.82
2.50
2.30
2.25
Having washed in a soap-water solution of 300 C for
thirty minutes, samples were relaxed and dried on a
flat plane. Samples were dyed in two similar baths.
Baths were filled with yellow and blue disperse dyes
respectively. Components of bathes are as below:
FIGURE 3: Schematic image of mini gloss model 101N.
FIGURE 2. Dying diagram of polyester fabrics.
RESULTS AND DISCUSSION
Since there was no significant difference between
course and wale luster values in all samples as shown
in Table II, the average amount of those directions
were used in analyzing technical face and back luster
measured data.
After dying, dried samples were ironed calmly in
order to prevent fabrics curl. Luster measurement
was carried out by mini gloss 101N apparatus made
in Sdl-international Company in the angle of sixty
degree. Specular gloss of fabrics was determined
before and after dying. For each sample, the luster of
technical face and back in two course and wale
directions were measured. Tests were performed
three times for each knitted sample to define an
acceptable CV (coefficient variation). Experimental
results are shown in Table II.
Journal of Engineered Fibers and Fabrics
Volume 9, Issue 2 – 2014
The Effect of Knitted Structure on Luster Value
As Figure 3 illustrates, in Tricot, Locknit, and three
and four-needle Satin, whose front-bar underlaps are
variable, longer underlaps on technical back of
fabrics increase luster value. This is due to yarn
number increase between course and wale and also
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longer parallel yarns on the technical back of the
fabric shown in Figure 5. On the contrary, in Tricot,
Reverse Locknit, and three and four-needle Sharkskin
fabrics, whose back-bar underlaps are variable,
longer underlaps; did increase fabric luster value.
This can be attributed to the fact that front-bar yarn
covers back-bar yarn on the technical back of a
fabric. Front-bar underlaps in the above structures are
as equal as one needle, as illustrated in Figure 5.
As Figure 4 depicts, loop geometry (legs and
overlap) in all knitted types on the technical face of
fabrics is the same. This point is also illustrated in
Figure 5. As a result, Figure 4 clearly does not show
any difference in the luster value.
FIGURE 3. The effect of knitted structure on technical back luster
value.
FIGURE 5. Schematic image of all fabrics technical back and face.
The Effect of Density on Luster Value
According Figures 6 and 7, density increases in most
of the knitted types decreases luster value, since flat
yarns of arms and underlaps are shortened the on
technical face and back of fabrics, respectively.
Mentioned issue can be observed better on technical
the face of fabrics owing to the geometry similarity
of all knitted structures.
FIGURE 4. The effect of knitted structure on technical face luster
value.
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FIGURE 9. The effect of color on technical face luster value.
FIGURE 6. The effect of density on technical back luster value.
CONCLUSION
A fabric luster value is an outstanding parameter
according to its usage in various fields especially
textile and ornamental ones. This study evaluated
standard two-bar warp knitted polyester fabrics in
different structures, densities, and colors. Mini gloss
measurement results indicate the influence of the
three parameters on fabrics luster value.
Longer underlaps increase fabrics luster on their
technical backs. But, the luster value of the technical
face of fabrics is the same. While, density increase
causes luster value to decline on both the technical
face and back of fabrics. Furthermore, dark colors
like blue, decrease fabric luster.
FIGURE 7. The effect of density on technical face luster value.
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The Effect of Samples Color on Luster Value
Among white, yellow and blue colors, the most and
least lustrous samples were the white and blue ones,
respectively. Samples with yellow color placed in
between those colors. This can be clearly viewed in
Figures 8 and 9.
FIGURE 8. The effect of color on technical back luster value.
Journal of Engineered Fibers and Fabrics
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AUTHORS’ ADDRESSES
Saeed Ajeli, PhD
Zoleykhah Ahmadvand
Department of Textile Engineering
Isfahan University of Technology
Daneshgah St.
Isfahan, Isfahan 84156-83111
IRAN
Journal of Engineered Fibers and Fabrics
Volume 9, Issue 2 – 2014
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