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Fibers and Polymers 2009, Vol.10, No.4, 452-460
452
Effect of Hollow Polyester Fibres on Mechanical Properties of
Knitted Wool/Polyester Fabrics
A. Khoddami, C. M. Carr1, and R. H. Gong
1*
Department of Textile Engineering, Isfahan University of Technology, Isfahan, 84156-8311, Iran1School of Materials, the University of Manchester, Manchester, M60 1QD, UK
(Received July 4, 2008; Revised November 12, 2008; Accepted March 27, 2009)
Abstract: The physical and mechanical characteristics of hollow polyester fibres were compared with solid polyester fibresin order to establish their processing behaviour and performance characteristics. The effects of hollow fibres on fabric proper-ties were investigated by using microscopy and tests of tensile and bursting strength, pilling, abrasion resistance, watervapour permeability, and handle. The results show that tensile strength of hollow polyester fibres and yarns are negativelyaffected by the cavity inside the fibre. Hollow fibres also have higher stiffness and resistance to bending at relaxed state. Fab-rics made from hollow polyester/wool blends and pure wool fabrics show three distinguishable steps in pilling. During pill-ing, hollow fibres break before being pulled fully out of the structure, leading to shorter protruding fibres. Microscopy studiesshowed that the breakdown of hollow fibres started during entanglement by splitting along the helical lines between fibrils.KES results showed that the friction between fibres and the fibre shape are the most important parameters that determine thefabric low stress mechanical properties. However, in some aspects, the hollow structure of the fibre does not have a signifi-cant effect.
Keywords: Hollow fibre, Knitted fabric, Pilling, Wool/polyester, Mechanical property
Introduction
Hollow fibre production by changing the shape of the
spinning nozzle is a physical modification of polyester (PET)
during fibre production to achieve new properties [1-4].
Synthetic fibres for general commercial application are mostly
solid filament or solid fibre yarns. Hollow fibres have benefits
for specific applications due to the larger fibre surface/volume
ratio [1].
A change in the shape of the cross-section in man-made
fibres affects many physical characteristics such as sorption,
dyeability, touch, pilling resistance, abrasion, weight, bulk,
thermal properties, insulation capacity, glistening, lustre,
covering and opaqueness [1,4,5]. Fibre cross-section shape
also affects the fabric hand [6,7] and the changed hand of the
hollow fibres can be conveniently utilized in wool/polyester
blended yarns [3]. Furthermore, hollow fibres must have
sufficient mechanical qualities for the selected end uses. In
this research, the natural properties of wool are combined
with hollow polyester fibres to develop novel products with
enhanced performance. In this paper, the results on the fabric
mechanical properties and fabric hand are presented.
Experimental
Solid and hollow polyester fibres (hole diameter to fibre
diameter ratio of 25%), and Super-wash treated wool were
supplied and spun by Bulmer & Lumb, Bradford, UK. Yarns
were knitted using Stoll weft flat knitted machine in the
University of Manchester. The material properties are listed
in Table 1. The yarns were top-dyed commercially with
different colours using HT methods by Bulmer & Lumb. It is
noteworthy that the yarn samples were manufactured in
industrial scale. Therefore, chosing hollow and solid polyester
fibre fabrics with the same shade was unfortunately impossible.
Sodium carbonate (from Tennents) and non-ionic detergent,
Alcapol NFC (from Ciba) were used for washing and
relaxation of the knitted fabrics.
The knitted samples were washed with a 0.5 g/l non-ionic
detergent, pH 8-9 (sodium carbonate) at 40-50 ºC for 30
minutes. The fabrics were then washed off at 35-40 ºC for 45
minutes and cooled gradually, and finally rinsed cold and air
dried without any tension.
Fabric mechanical properties were compared by measur-
ing fibre and yarn tensile strength, yarn-on-yarn dry abrasion,
fabric bursting strength, pilling, abrasion resistance, hand,
and water vapour permeability. Fibre topography was analysed
after pilling and abrasion tests using SEM (Hitachi S-3000
N).
Fibre tensile testing was performed in accordance with BS
3411:1971 on an Instron 5564 with a sample length of 20
mm and crosshead speed of 10 mm/min. Breaking force and
elongation at break of yarns were measured according to BS
2062:1995, with gauge length of 250 mm, crosshead speed
of 250 mm/min, and 50 tests for each sample. The results of
tensile tests are reported by confident limit of 95 %.
Yarn-on-yarn abrasion resistance was evaluated by equip-
ment built at the University of Manchester [8]. The test
essentially involves subjecting two yarn sections, wrapped
helically together, to a reciprocating motion under tension
until failure.
Bursting strength was tested according to BS 13938-*Corresponding author: hugh.gong@manchester.ac.uk
DOI 10.1007/s12221-009-0452-7
Effect of Hollow Polyester Fibres on Mechanical Properties Fibers and Polymers 2009, Vol.10, No.4 453
1:1999 on a Mullen Burst Tester with sample area of 50 cm2,
20 seconds time to burst and 10 tests per sample.
The pilling ratings were studied according to BS 12945-
2:2000 by a Martindale Abrasion Tester on scoured and
relaxed sample under 9 KPa pressure and different number
of rubs including 125, 500, 1000, 2000, 5000, and 7000.
Pilling resistance was determined by comparison with
standard pictures in a light cabinet.
The abrasion resistance was measured on a Martindale
Wear & Abrasion Tester according to BS 12947-2: 1999.
The mass loss during abrasion was measured according to
BS 12947-3: 1999 on scoured and relaxed samples under 9
KPa pressure. The occurrence of one broken thread (observed
under Vickers Zoomax Light Microscope) was considered as
the end point. It should be mentioned that when pilling was
observed on the specimen, the test was continued without
cutting off the pills.
The fabric hand was tested using the Kawabata Evaluation
System (KES). Four tests were carried for each KES
parameter. Water vapour permeability of fabrics was carried
out in accordance with BS 7209-1990 using an Equiptex
Water Vapour Permeability Tester on conditioned samples.
The water temperature was 20±2 ºC and its surface height to
fabric was 1 cm. After establishing equilibrium (1 hr), weight
measurements were done after 6 and 24 hrs.
The Water Vapour Permeability (WVP) in g/m2/day was
calculated by the following formula:
WVP = 24M/At (1)
Where
M is the loss in mass of the assembly over the time period
t (in g);
t is the time between successive weighing of the assembly
(in hr);
A is the area of exposed test fabric (internal area of the test
dish) (in m2).
The Water Vapour Permeability Index is given by:
I = {(WVP)f / (WVP)r}×100 (2)
Where
(WVP)f is the mean Water Vapour Permeability of the
fabric under test;
(WVP)r is the Water Vapour Permeability of the reference
fabric (a high tenacity polyester woven with monofilament).
Results and Discussions
The tensile properties of hollow fibres are compared with
those of solid fibres in Table 2. Hollow fibres tend to have
lower tenacity, with the other tensile properties affected by
the dyeing process, high temperature top dyeing. In parti-
cular the black fibres appear to have lower tenacity but
higher elongation. Yarn and fabric properties are shown in
Table 3. Solid fibre blended yarns have the highest tenacity
while the pure wool yarn has the lowest tenacity. As can be
seen the yarn produced from hollow fibres have lower
tenacity and wear resistance. The reason for the differences
in tenacity will be discussed further along with the pilling
results.
The lower resistance to abrasion of the hollow fibre yarns
may be attributed to the higher surface friction of the hollow
Table 1. Properties of materials used and knitted fabric construction parameters
Wool fibre
(micron)
Polyester fibre
(dtex)
Yarn count
(Nm)
Twist (tpm)
single two-fold
Blend composition (%)
wool PES
Knit
structure
Knit density (per cm)
wale course
21.5 3.3 28/2 430 220 (ZS) 60 40 Plain 5 8
Table 3. Mechanical properties of yarns and knitted fabrics
SampleYarn tenacity
(cN/tex)
Yarn elongation
(%)
Yarn on yarn abrasion
(cycles)
Fabric bursting strength
(kPa)
Fabric abrasion resistance
(1,000 cycles)
SP/W* Black 31.80 ± 0.56 12.95 ± 0.22 19400 ± 420 1078 ± 61 40.7 ± 0.65
SP/W Charcoal 31.03 ± 0.56 11.78 ± 0.15 16200 ± 260 1117 ± 65 37.2 ± 0.86
HP/W** Brown 25.34 ± 0.69 12.16 ± 0.56 5700 ± 60 1045 ± 34 19.9 ± 0.35
HP/W Charcoal 27.86 ± 0.57 13.56 ± 0.24 5500 ± 180 1048 ± 37 15 ± 0.23
HP/W Darkblue 25.04 ± 0.68 12.89 ± 0.58 6100 ±230 1031 ± 25 23.95 ± 0.40
Wool 14.28 ± 0.31 7.539 ± 0.51 − 845 ± 41 12.5 ± 0.57
*SP/W: solid polyester/wool blends fabric, **HP/W: hollow polyester/wool blends fabric.
Table 2. Polyester fibre tensile properties
SampleTenacity
(cN/dtex)
Elongation
(%)
Solid white fibres 41.6 ± 0.31 12.3 ± 0.22
Solid black fibres 40.6 ± 0.53 16.4 ± 0.46
Hollow white fibres 39.1 ± 0.42 10.4 ± 0.34
Hollow black fibres 37.1 ± 0.71 21.6 ± 0.68
454 Fibers and Polymers 2009, Vol.10, No.4 A. Khoddami et al.
fibres, or to the greater contact area or inherent weakness of
the hollow fibres [2,4,9].
The pure wool fabric has much lower bursting strength in
comparison with polyester/wool blended fabrics. This is
likely due to the greater elongation of the blended yarns
[10]. During the bursting strength test, fabric starts to fail
from the direction with the lowest breaking extension. The
reason for this phenomenon is that, when the fabric is
stressed in all the directions in the test, the fabric direction
with thr lowest elongation at break is the one that will fail
first. Consequently, this direction is not necessarily the
direction with the lowest strength. Therefore it was expected
that the wool fabric would have the lowest bursting strength
as it has the lowest extension. In addition, using hollow
polyester fibres increased the fabrics bursting strength
significantly as compared with the pure wool fabric.
The fabric pilling performance is compared in Table 4. At
low levels of mechanical action, no pills formed and the only
visible change was fuzz formation. After 500 rubs, however,
the entanglement phase started, with pills forming. After
higher mechanical abrasion, the apparent pilling was reduced
and with pill removal becoming the predominant process.
These three steps can be clearly seen for samples composed
of 100% wool, and the hollow polyester/wool fabrics with
dark blue and brown colours. Also the results show that the
hollow fibre samples have lower pilling tendency and higher
rate of pill wear-off than solid fibre samples. The differences
between the two types of polyester fibres can be seen in
Figures 1 to 5, with Figure 1 indicating the high pill density
of solid polyester fibre fabrics resulted from the high abrasion
resistance and strength of polyester fibres. The solid fibre
fabrics are less affected by the pill wear-off. Although some
wool fibres can be observed in the pills, the main component
is polyester, with multiple fibre splitting fatigue resulting in
the wear-off of the wool fibres.
With hollow fibres having lower strength than the solid
polyester fibres, the associated effect is that pill wear-off is
faster for hollow fibres. After 5000 rubs, their pilling ap-
pearance is clearly better (Figure 2, as compared with Figure
1). It was reported that the greater the breaking strength and
Table 4. Pilling performance of knitted fabrics
Sample \ number of rubs 125 500 1000 2000 5000 7000 Average
SP/W Black 5 4 3-4 2-3 3 2-3 3.5
SP/W Charcoal 5 5 3 2-3 1-2 1 3.0
HP/W Brown 5 5 4-5 3-4 5 5 4.7
HP/W Charcoal 5 5 4-5 3-4 4 4 4.3
HP/W Darkblue 5 4-5 4-5 3-4 4-5 5 4.5
Wool 5 4 3-4 4 5 5 4.4
Figure 1. Pilling of solid polyester/wool fabrics after 7000 rubs.
High pill density on the fabric surface is evident with solid polyester
fibres as a main component, with multiple wool fibre splitting
resulting in the wear-off the wool fibres.
Figure 2. Pill wear-off on the surface of brown hollow polyester/
wool fabric after 5000 rubs.
Effect of Hollow Polyester Fibres on Mechanical Properties Fibers and Polymers 2009, Vol.10, No.4 455
the lower the bending stiffness of the fibres, the more likely
they can be pulled out of the fabric structure and producing
long protruding fibres [10]. But hollow fibres with lower
breaking strength and high bending stiffness will tend to
break before being pulled fully out of the structure leading to
shorter protruding fibres (Figures 3, 4). This means that
many protruding fibres can not reach the “critical height” for
the for fibre entanglement and pill formation. The break
down of hollow fibres commences during entanglement by
splitting along the helical lines between fibrils and is
continued along the fibre axes and finished with bushy ends
(Figure 5).
The fibre break develops along the axial splits, due to
either repeated bending, or bending and twisting (Figure 6).
Also, the individual portions of the split can break to give
many splits (Figure 7). Furthermore, the axial splits can
occur from tensile fatigue (Figure 8), or peeling by surface
shear, failure by surface wear creating peeled fibres (Figure
9). The other type of fibre break down can be found in
Figure 10. Figure 10(A) shows a wool fibre with a split end;
Figure 3. Pill wear-off on the surface of charcoal hollow polyester/
wool fabrics after 7000 rubs.
Figure 4. Breakage of hollow polyester fibres during entanglement.
(A) charcoal and (B) brown hollow polyester/wool fabrics after
5000 rubs.
Figure 5. Breakage steps of brown hollow polyester fibre after
5000 rubs. (A) start of fibre breakage along helical lines between
fibrils, (B-H) continued splitting along the fibre axes, and (I) bushy
end of breakage.
456 Fibers and Polymers 2009, Vol.10, No.4 A. Khoddami et al.
Figure 10(B) shows a failure adjacent to a knot which is
likely to be caused by flexural fatigue. As can be seen from
Figures 4 and 5, splits along the hollow polyester fibre can
be extremely long. This is a consequence of the fact that the
axial crack in this fibre type runs much more closely parallel
to the fibre axis. The phenomenon is a characteristic of the
highly oriented, highly crystalline, linear polymer fibres
[11].
Figures 11 and 12 show the tensile breakage of hollow and
solid polyester fibres respectively. It is clear that the tensile
strength of hollow polyester fibres is adversely affected by
the cavity inside the fibre which acts as a weak point where
the failure can be initiated.
In the case of wool which has low breaking strength, pills
will be easily removed and detached from the fabric. But for
fabrics containing solid polyester fibres, the pills will tend to
remain in place. Therefore, even after 7000 rubs their pilling
ratings are quite high. In conclusion it can be stated that the
higher the tensile strength and abrasion resistance of the
fibre, the higher the pilling tendency of the fabric. This is
mainly controlled by pill wear-off.
Figure 6. Biaxial rotations and flex fatigue of polyester fibres after
5000 rubs. (A) hollow brown sample, (B) solid black sample, (C-
D) solid charcoal sample, and (E-F) solid charcoal sample.
Figure 7. Long bushy ends of split hollow polyester fibre after
7000 rubs.
Figure 8. Tensile fatigue of solid black polyester/ wool blend
knitted fabric after 7000 rubs.
Figure 9. Wool fibre peel after 5000 rubs in blend fabric with solid
black polyester fibres.
Figure 10. Wool fibre breaks after 5000 rubs in blend fabric with
polyester fibres. (A) hollow charcoal, after 7000 rubs and (B) solid
black sample, after 5000 rubs.
Effect of Hollow Polyester Fibres on Mechanical Properties Fibers and Polymers 2009, Vol.10, No.4 457
The results of abrasion test, Table 3 and Figure 13, show
the significant effects of fibre type. The ability of a fibre to
resist repeated distortion is very important to its abrasion
resistance. Therefore high elongation, elastic recovery and
work of rupture are considered to be the key factors for a
good degree of flat abrasion resistance in a fibre rather than
high strength [10]. Polyester fibres are considered to have
good abrasion resistance and a comparison of the hollow and
solid polyester fibres indicated that the hollow fibres have
lower abrasion resistance, which may be related to their
shape. Compared with solid fibres of the same linear density,
hollow fibres are stiffer, more resistant to bending and torsion
[4] and have a relatively poor resistance to flexural strain
[3,9]. Therefore they abraded faster than the comparable
solid polyester fibres.
Measuring the mass loss during abrasion also demon-
strated the higher rate of hollow fibre removal during abrasion
(Figure 13). While these fibres were broken between 15,000
to 24,000 rubs, the minimum abrasion for solid fibres was
37,000 rubs. Furthermore, it is evident that the dyeing
processes have a significant effect on fibre properties. The
abrasion resistance of hollow polyester/wool fabric with
dark blue colour is at least 8000 rubs higher than similar
samples with the charcoal colour which may be related to
the dyeing period at high temperature. The mass loss during
abrasion is also compatible with the rubs to break; a higher
weight loss during abrasion correlates to a lower number of
rubs to break. The results also revealed the great improve-
ment of wool abrasion resistance by blending with hollow
and solid polyester fibres.
KES-F mechanical properties of knitted fabrics before and
after relaxation were measured. The results indicate that
after relaxation, there is an increase in extension (EM) for all
the samples (Tables 5 and 6). In general extensibility of the
solid polyester fibre samples are higher than the comparable
samples based on hollow fibres. The changes in these
properties indicate that the friction between fibres has been
reduced by the relaxation shrinkage process which makes
fabrics more extensible with better elastic recovery. But the
differences between hollow and solid polyester fibres show
that the friction between solid fibres is lower than hollow
fibres which can be related to the shape of fibres, because in
Figure 11. Tensile breaks of hollow polyester fibres.
Figure 12. Tensile breaks of solid polyester fibres.
Figure 13. Percentage mass loss during abrasion test.
458 Fibers and Polymers 2009, Vol.10, No.4 A. Khoddami et al.
general these fibres have greater outside surface area, result-
ing in a greater frictional contact area.
The tensile properties of the wool fabric changed greatly
after relaxation. The EM and RT (recovery) increased
significantly. However, blending wool with polyester fibres
especially hollow fibres reduced the effects of relaxation on
the tensile properties.
It is expected that bending rigidity and bending hysteresis
of all the samples will decrease after scouring, but the grey
samples were so unstable that it was impossible to measure
their bending properties accurately. The results from the
relaxed samples clearly show that the bending stiffness of
hollow fibre fabrics is much higher than that of the solid
fibre fabrics. These hollow fibres have the same linear den-
sity as the solid fibres, therefore, they are stiffer and more
resistant to bending and torsion [44,12].
The shear properties of all the samples were reduced by
scouring. This is mainly due to decreasing inter-yarn friction.
In general, shear rigidity and hysteresis of hollow fibre fabrics
are greater than solid fibre fabrics. The effects of different
Table 5. KES-F Mechanical properties of knitted relaxed fabrics
SP/W Black SP/W Charcoal HP/W Brown HP/W Charcoal HP/W Darkblue Wool
Tensile
EM (%) 16.85 15.71 15.99 14.55 14.98 22.71
LT 0.894 0.919 0.912 0.960 0.979 0.904
WT (g·cm/cm2) 3.75 3.40 3.66 3.50 3.64 5.07
RT (%) 47.97 48.58 49.40 48.77 50.86 52.94
BendingB (g·cm2/cm) 0.0834 0.1036 0.1217 0.1221 0.1169 0.0494
2HB (g·cm/cm) 0.1235 0.1506 0.1878 0.1917 0.1627 0.0606
Shear
G (g./cm·deg) 0.39 0.38 0.42 0.43 0.42 0.32
2HG (g./cm) 1.71 1.61 1.94 1.94 1.92 1.33
2HG3 (g./cm) 1.75 1.63 2.01 1.97 1.98 1.36
Surface
MIU 0.229 0.224 0.225 0.223 2.000 0.244
MMD 0.0189 0.0177 0.0183 0.0199 0.0190 0.0195
SMD (µm) 11.9 10.9 13.7 13.8 13.9 14.0
Compression
LC 0.360 0.340 0.367 0.364 0.355 0.391
WC (g·cm/cm2) 0.812 0.836 0.829 0.833 0.844 0.820
RC (%) 48.23 48.27 46.98 48.04 46.82 47.22
ConstructionT (mm) 0.799 0.810 0.822 0.813 0.835 0.956
W (mg/cm2) 22.10 22.13 21.88 21.58 21.95 23.73
Table 6. KES-F Mechanical properties of knitted fabrics before relaxation
SP/W Black SP/W Charcoal HP/W Brown HP/W Charcoal HP/W Darkblue Wool
Tensile
EM (%) 13.77 14.81 12.19 11.10 11.70 16.47
LT 0.956 0.931 1.042 1.028 0.994 0.968
WT (g·cm/cm2) 3.19 3.46 3.13 2.82 2.86 3.89
RT (%) 40.23 40.73 44.45 39.21 34.46 39.16
Shear
G (g./cm·deg) 0.49 0.46 0.50 0.51 0.55 0.47
2HG (g./cm) 3.11 2.68 3.06 3.31 3.72 3.22
2HG3 (g./cm) 3.19 2.72 3.12 3.35 3.75 3.20
Surface
MIU 0.242 0.245 0.245 0.237 0.242 0.241
MMD 0.0209 0.0212 0.0216 0.0225 0.0225 0.0223
SMD (µm) 13.5 13.7 12.2 13.4 14.2 13.8
Compression
LC 0.344 0.352 0.368 0.334 0.348 0.390
WC (g·cm/cm2) 0.865 0.872 0.910 0.808 0.876 0.884
RC (%) 44.50 45.46 44.50 45.51 44.92 44.57
ConstructionT (mm) 0.613 0.621 0.630 0.628 0.677 0.884
W (mg/cm2) 21.10 21.68 20.95 20.03 20.05 21.80
Effect of Hollow Polyester Fibres on Mechanical Properties Fibers and Polymers 2009, Vol.10, No.4 459
colours during dyeing on shear properties are not significant
because the dyeing operation generally produced fabrics
with low yarn interactions regardless of colour [13].
Relaxation shrinkage decreases the friction coefficient
(MIU) and its variation (MMD) of polyester/wool blend
fabrics. This may be due to the tighter and more compact
structure of the fabrics after shrinkage making the gaps in
the fabric and the surface variation smaller.
The surface roughness (SMD) of hollow fibre based fabrics
increased after scouring while the solid polyester/wool fibre
fabrics showed lower surface roughness. The larger diameter
and higher bulk of the hollow fibres produce result in higher
SMD, demonstrating that the fabric hand is dependent on
fibre cross-section.
It is generally expected that fabrics have higher energy of
compression (WC) after scouring, but here the trend is
decreasing. This may be due to the more compact structure
after relaxation. The recovery after compression (RC) of all
the samples increased. This is compatible with the reduction
of friction between yarns and fibres due to the release of
internal fabric tension. As already mentioned hollow fibres
have more friction, consequently fabrics with these fibres
have lower RC.
In any relaxation process the thickness of fabrics increases.
This is shown in this study as well. Also, it was found that
the thicknesses of hollow fibre fabrics are higher than that of
the solid fibre fabrics. Clearly, the increased fibre external
dimension of the hollow fibres is a factor. In fact, the greater
fabric thickness is one of the reasons to use hollow fibres as
this leads to greater thermal insulation.
The permeability to water vapour, the thermal insulating,
and water transport are some of the basic factors affecting
thermal comfort. These properties can be influenced by
suitable choice of fibre cross-sectional shapes, the formation
of cavities or micro-cavities in the fibres and other modifi-
cations to fibre geometry. They can also be influenced by
fibre blending and fabric construction [3]. The results of
water vapour permeability tests, Table 7, indicate that
relaxation resulted in a more compact structure and conse-
quently a reduction in the water vapour permeability of
fabrics. This effect is greater than the influence of the type of
fibre. In this aspect, fabric and yarn structure is more
important than the constituent fibres.
Conclusion
Solid polyester fibre fabrics have higher tensile and burst-
ing strength, and better abrasion resistance. However, by
using hollow fibres in the fabrics, the extent of pilling, a
serious fabric appearance defect for high strength synthetic
fibre fabrics was reduced by about 40%, a result of faster pill
wear-off, due to the differences in the physical properties of
the constituent fibres.
The use of hollow fibres resulted in lower extensibility,
tensile and compressional resilience, greater bending and
shear stiffness and hysteresis. Accordingly the results indi-
cate that by using hollow fibres, it is possible to produce a
fabric similar to that base on solid polyester fibres but with
higher stiffness and rougher texture. The fabric and yarn
structures control the overall fabric handle and water vapour
permeability. The use of hollow fibres increases fabric thick-
ness. This should increase the thermal resistance.
Acknowledgements
Financial support of the Iran’s Ministry of Science, Research
and Technology, and Bulmer & Lumb Company to afford
fibres and yarns is gratefully appreciated.
Table 7. Water vapour permeability of knitted samples before and after scouring & relaxation
State of fabric SampleWVP*
After 6 hr
I**
After 6 hr
WVP
after 24 hr
I**
After 24 hr
Relaxed
SP/W Black 1100 90.424 1350.515 90.086
SP/W Charcoal 1121.650 92.203 1387.113 93.324
HP/W Brown 1095.876 90.085 1357.474 91.330
HP/W Charcoal 1104.124 94.192 1356.186 94.301
HP/W Darkblue 1096.907 93.580 1345.103 93.530
Wool 1138.144 92.385 1367.698 93.940
Before
relaxation
SP/W Black 1201.031 101.229 1399.485 98.204
SP/W Charcoal 1178.3505 99.317 1380.155 96.848
HP/W Brawn 1239.175 104.444 1425.515 100.031
HP/W Charcoal 1200.00 101.142 1400.515 98.277
HP/W Darkblue 1191.753 100.447 1407.732 98.783
Wool 1147.423 96.711 1381.186 96.920
*: Water vapour permeability, **: Water vapour permeability index.
460 Fibers and Polymers 2009, Vol.10, No.4 A. Khoddami et al.
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