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CHAPTER 9
MODIFICATION OF POLYESTER COTTON WEFT
KNITTED FABRICS BY ALKALI TREATMENT
9.1 INTRODUCTION
In the last few years there has been increasing interest in the surface
modification of poly (ethylene terephthalate) whose use is quite wide spread
in the textile industry with an annual production 36 million tons, (Guebitz and
Cavaco - Paulo 2008). Apart from the excellent physical - chemical properties
of polyester, increased hydrophilicity is essential for many applications
ranging from textiles (Zeronian and Collins 1989) medical (East and Rahman
2009) and electronics (Guebitz and Cavaco - Paulo 2008). Alkaline treatment
is used to increase hydrophilicity of PET based textile materials, (Zeronian
and Collins 1989). However, this leads to formation of pit-like structures
(Brückner et al 2008) which results in weight loss and leads to reduced fibre
strength. Alkaline hydrolysis of polyester cotton blends on the other hand
results in an improvement in hydrophilicity and less weight loss (Shet et al
1982).
In contrast, PET is successively degraded from the chain ends.
While the alkaline hydrolysis of polyester cotton fabrics holds greater
potential, the other properties such as mechanical and comfort have not been
investigated in detail. In most previous studies changes of PET surface
properties like hydrophilicity, absorbency and tensile properties have been
studied while the low stress mechanical properties of polyester cotton fabrics
132
following alkaline hydrolysis have not been assessed. Thus, in this study for
the first time, the alkaline hydrolysis of polyester cotton fabrics has been
studied. Jeddi and Otaghsara (1999) investigated the correct relaxation
treatment of 100% cotton blended polyester cotton and 100% polyester
knitted fabrics. They concluded that the correct relaxation state for polyester
cotton was achieved by chemical relaxation treatment. Their results showed
that the effect of mechanical relaxation decreased as the percentage of
polyester increased. Montazer and Sedhigi (2006) have looked at the
optimisation of hot alkali treatment of polyester cotton fabric with sodium
hydrosulfite. Lilkemark and Asnes (1971) have found that treatment of fabrics
containing polyester cotton with strong alkali imparts pigment soil - release
properties equivalent those obtained by conventional soil release finishes.
9.2 MATERIALS AND METHODS
These have already been discussed in chapter 3
9.2.1 Fabric Production
The knitted fabrics were produced in a weft knitting machine. The
simplest single jersey fabrics was produced using a needle gauge of 28 and
dia 17 inches
In all three types, samples were produced. The geometrical
properties of knitted fabrics are given in the Table 9.1. Figure 9.1 illustrates
the GSM of fabrics.
133
Table 9.1 Geometrical properties of knitted fabrics.
Fabric W/cm C/cm SD (cm²) GSM Thickness (mm)
35/65 P/C 21 22 462 142 0.43
50/50 P/C 20 21 420 139 0.44
65/35 P/C 19 23 437 135 0.42
W – Wales, C- Courses, SD – Stitch Density,
GSM
124
126
128
130
132
134
136
138
140
142
144
35/65 50/50 65/35P/C blend
GSM
GSM Untreated
GSM Treated
Figure 9.1 GSM of the fabric
9.2.2 Sodium hydroxide treatment of fabrics
The fabric (30cm x 30 cm), in tubular form, and conditioned at 65%
RH and 25oC was weighed accurately. It was immersed in 25% aqueous
sodium hydroxide for two mins at room temperature and then padded twice to
obtain uniform distribution of alkali in the fabric. This concentration was used
because it was used by the industry. The padded sample held between two
ceramic frames was heated in an oven fitted with a blower at 60oC for
15 mins. At the end of the treatment, the fabric was carefully washed with tap
water to remove hydrolyzed products as well us untreated alkali. Washing
was continued with distilled water. Residual alkali in the fabric was removed
by immersion in 1% aqueous hydrochloric acid for 5 mins. This was followed
by thorough rinsing with distilled water. Samples were left overnight in
GS
M
134
distilled water to ensure the complete removal of the acid and washings
continued if necessary, until the rinsed water was neutral to litmus. The
samples were air dried, conditioned for 48 hrs at 65% RH, 250
C and
weighed again. Each treatment was done in duplicate. Control samples were
treated similarly for 15 min, except that water instead of sodium hydroxide
was used as padding liquor.
9.3 RESULTS AND DISCUSSION
9.3.1 Yarn Properties
These are listed in 9.2
Table 9.2 Yarn characteristics
Blend 35/65 P/C 50/50 P/C 65/35 P/C
Tenacity cN/Tex (Uster TensoJet 4) 19.11. 23.06 25.77
Tenacity, CV% 7.7 8.5 9.6
Elongation % 5.81 7.85 8.88
Elongation, C V% 7.9 9.9 9
U% 12.43 12.42 11.72
Thin places / km 30 29 15
Thick places / km 215 195 118
Neps / km 319 239 157
Total imperfection / km 564 463 290
Hairiness (uster) 6.52 5.7 5.26
S3 ( Zweigle G565) 2258 2130 807
9.3.2 Weight loss
Table 9.3 shows the moisture content % moisture regain % and
weight loss %. It is interesting to note that the weight loss shows an increase
135
with increase in polyester content in the fabrics. This is due to hydrolysis and
is in agreement with the findings of Shet et al (1982). Figure 9.4 illustrates the
trend.
9.3.3 Moisture sorption
Table 9.3 shows the moisture regain and moisture content values of
control and treated samples. Figures 9.2 and 9.3 illustrates the trend. It is also
interesting to note that the values agree with those reported by Shet et al for
woven fabrics. Cotton rich (35/65) blend showed a higher value of moisture
content and regain. It is a well known fact that this is due to swelling of cotton
fibers.
Table 9.3 Moisture Absorption values of fabrics
P/CSample
Type
Moisture
Content (%)
Moisture
Regain (%)
Weight
loss (%)
65/35U 2.07 2.1 -----
T 2.56* 2.63* 5.97
50/50U 3.11 3.19 ----
T 3.47* 3.59* 1.97
35/65U 3.72 3.83 ----
T 4.1* 4.28* 1
* Significant at 95% level.U – Untreated. T- Treated. P- Polyester .C- Cotton.
136
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
35/65 50/50 65/35
P/C Blends
Moisture
Content %
Untreated Treated
Figure 9.2 Moisture content of the fabric
MOIS TU R E R EGAIN
0
1
2
3
4
5
65/35 50/50 35/65
p/c b le nds
% untreated
treated
Figure 9.3 Moisture Regain of the Fabric
9.3.4 Tensile properties
LT values do not show any specific trend. The tensile properties are
the tensile energy (WT) tensile resilience (RT) and extensibility (EM). The
different tensile properties of the weft knitted fabrics control and treated with
alkali as measured by the KES F systems are shown in Table 9.4.
Mo
istu
re
Co
nte
nt
%
Mo
istu
re R
eg
ain
%
137
The tensile energy (WT) is defined as the energy required for
extending the fabric and reflects the ability of the fabric to withstand external
stresses during extension. It is apparent that following alkaline treatment, WT
values show a decrease. In all the cases course way WT values are higher than
those of the wale way.
0
1
2
3
4
5
6
7
35/65 50/50 65/35
P/C Blends
Weight Loss %Weight Loss %
(Treated sample)
Figure 9.4 Weight loss % of the Fabric
EMT follows the same trend as WT as both are interrelated; WT is
also closely related to the fabric flexibility, softness, gentleness, smoothness
and compactness. Matsudaira et al (1994) have characterized the quality of
polyester fiber fabrics and silk fabric using the tensile properties.
The treated fabrics become less extensible and more resilient under
tensile deformation as shown by the decrease in elongation and the increase in
tensile resilience. RT, the tensile resilience, refers to the ability of fabric to
recover after applying the tensile stress. A lower value of RT implies that the
fabric is not recovering. It shows that the alkali treatment has improved the
recovery in 35/65 and 50/50 blends. With an increase in polyester, the values
of RT show an increase; LT values show a decrease in treated fabrics. LT and
WT are inversely related and this may be due to lower cohesive force between
yarns. The differences in RT between the control and treated samples in
respect of 65/35 polyester cotton blends are less as compared to the 35/65 and
Wei
gh
t L
oss
%
138
50/50 polyester cotton blended fabrics. This shows that the recovery of 35/65
polyester cotton blended fabric is poor compared to other fabrics. Fabric
extension is maximum in 35/65 blend and minimum in 65/35 blend. When the
polyester blend component increases in the blend, the effect of alkaline
treatment appears to the quite significant. Among the three types of fabrics,
the 35/65 polyester cotton blended fabric shows the maximum elongation.
In the case of 65/35 polyester cotton blend, the caustic-reduced
fabrics have a high resilience and this is noticed in 50/50 blend also.
Polyester cotton 65/35 fabrics show higher resilience than the other blends.
The low tensile resilience of cotton rich fabrics, namely 35/65 and 50/50 may
be a contributor towards that low crease resistance Figures 9.5 - 9.8 illustrate
the trends obtained.
Table 9.4 Tensile properties
35/65 P/C 50 P/C 65/35 P/C
Un
TreatedTreated
Un
TreatedTreated
Un
TreatedTreated
LT –1 0.72 0.65* 0.64 0.42* 0.48 0.65*
LT-2 0.72 0.44 0.67 0.69 0.44 0.34
Mean 0.72 0.55* 0.65 0.55* 0.46 0.50
WT-1 15.53 12.10* 12.35 7.55* 6.96 9.21*
WT-2 28.76 16.90* 23.77 22.19* 10.33 8.57*
Mean 22.14 14.51 18.05 14.87 8.64 8.89
RT-1 (%) 34.70 26.32* 36.50 50.65* 33.80 34.57
RT-2 (%) 25.21 40.19* 41.65 36.20* 70.14 69.71
Mean (%) 29.55 33.31 39.07 43.42 51.97 52.14
EM-1 (%) 17.15 14.79 15.48 14.50 11.56 11.27
EM-2 (%) 31.75 30.38 28.32 25.57* 18.62 19.79
Mean (%) 24.45 22.58 21.91 20.01 15.09 15.53
*Significant at 95% level.
139
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
35/65 50/50 65/35
P/C Ble nd
LC
Untreated
Treated
Figure 9.5 Tensile Property (Linearity)
TE N S ILE PR OPE R T IE S- E N ER GY
0
5
10
15
20
25
35/65 50/50 65/35
P /C BLEND
W T
(g.cm /cm 2)
Untreated
Treated
Figure 9.6 Tensile Property (Energy)
TEN S ILE PR OPER T Y - R ESILIEN C E
0
10
20
30
40
50
60
35/65 50/50 65/35
P/C BLENDS
RT %
Untreated %
Treated %
Figure 9.7 Tensile Property (Resilience)
LT
35/65 65/35
35/65 65/35
WT
(g
.cm
2/c
m
35/65 65/35
RT
%
140
TE N S ILE P ROP E R TY - E LON GATION
0
5
10
15
20
25
30
35/65 50/50 65/35
P /C BLENDS
EM T %
Untreated %
Treated %
Figure 9.8 Tensile Property (Elongation %)
9.3.5 Bending Properties
The bending properties of fabric have a significant effect on both
the handle and tailoring performance. It is apparent from Table 9.5 that the
wale way bending rigidity is higher than that of the course way and the
alkaline hydrolysis treatment has lowered the bending rigidity. This means
that the fabrics have become more flexible. With the increase in polyester
content, the bending rigidity values of fabrics show a decrease after treatment.
The greatest decrease was in 65/35 blend which accounted for 31.25%.
Bending hysteresis (2HB), unlike bending rigidity, shows an increase
following alkaline hydrolysis treatment which is due to higher frictional
restraint. Values of 2HB/B are provided, which show that they are higher
compared to control. The higher the value of 2HB/B, the poorer the recovery
and on this basis 35/65 blend shows poor recovery. Thus although bending
rigidity values show a drop, bending hysteresis shows an increase following
alkaline hydrolysis treatment. Generally speaking, course way values of
2HB/B are higher implying that the recovery is poorer. This may be due to the
larger number of threads compared to wales. The larger the number of
threads, the larger the number of contacts and hence higher restraint. The
65/35 35/65
EM
T %
141
significance of 2HB/B has been discussed by Grosberg and Swani (1966) act
length in that frictional restraint is directly related to residual stresses in a
fabric. Alkaline hydrolysis treatment has increased 2HB and this may be due
to increased clustering of fibers as a result of the treatment Figures 9.9 and
9.10 illustrate the trends obtained.
B E N D IN G R IGID ITY
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
65/35 50/50 35/65
P /C BLENDS
g.cm 2
Untreated
Treated
Figure 9.9 Bending Rigidity
0.017
0.0175
0.018
0.0185
0.019
0.0195
0.02
0.0205
35/65 50/50 65/35
P/C BLENDS
2HB
( g .cm /cm 2)
Untreated
Treated
Figure 9.10 Bending Hysteresis
g.c
m2
/cm
2H
B
g.c
m/c
m
142
Table 9.5 Bending properties
35/65 50/50 65/35
Un
TreatedTreated
Un
TreatedTreated
Un
TreatedTreated
B -1 0.017 0.015 0.016 0.014 0.016 0.011*
B -2 0.008 0.006 0.006 0.007 0.006 0.004
Mean 0.012 0.010 0.011 0.010 0.011 0.007*
2HB -1 0.022 0.026 0.025 0.025 0.021 0.023
2HB -2 0.015 0.012 0.016 0.014 0.014 0.014
Mean 0.018 0.019 0.020 0.019 0.018 0.019
2HB1/B1 1.29 1.73 1.56 1.78 1.31 2.09
2HB2/B2 1.88 2.0 2.6 2 2.3 3.5
2HB-M/B-M 1.50 1.9 1.8 1.9 1.6 2.7
B/T 0.85 0.8 0.91 0.84 0.8 0.85
0.14 0.125 0.12 0.11 0.137 0.082
*Significant at 95% level
9.3.6 Shear Properties
The shear rigidity (G) reflects the ability of the fabric to resist shear
stress. Shear is an important property which determines the handle and drape
of fabrics. With the exception of 65/35 blend, it is apparent that shear rigidity
shows a slight increase in other blends. Unlike bending, it is interesting to
note that the course way values are higher than those of wale way. This is
principally due to greater contacts made. The treated fabrics show higher
values for shear rigidity and shear hysteresis. Shear hysteresis values show an
increase following alkaline hydrolysis which may be due to increases in
contact. Values of 2HG/G and 2HG3/G, which represent residual shear strain,
show an increase in all the cases implying that the recovery has reduced. The
greatest increase has occurred in 65/35 blend which is an indication of greater
frictional restrain Table 9.6. Figures 9.11- 9.13 illustrate the trends obtained.
143
S H E AR R IGID IT Y
0
0.2
0.4
0.6
0.8
1
1.2
65/35 50/50 35/65
P/C BLENDS
g.cm /cm
Untreated
Treated
Figure 9.11 Shear rigidity of the fabric
Table 9.6 Shear properties
35/65 50/50 65/35
Un
TreatedTreated
Un
TreatedTreated
Un
TreatedTreated
G-1 0.81 0.82 0.85 0.87 0.91 0.83*
G-2 0.87 0.87 0.88 0.94 1.07 1.00*
G-Mean 0.84 0.85 0.87 0.90* 0.99 0.92*
0.27 0.21 0.31 1.27 0.26 0.28
2HG -1 2.75 3.02* 3.00 3.58* 3.04 3.59*
2HG -2 3.04 3.82* 3.31 4.54* 3.78 4.91*
2HG- Mean 2.89 3.42* 3.15 4.06* 3.41 4.25*
0.25 0.28 0.27 0.26 0.28 0.28
2HG3-1 2.88 3.26* 3.22 3.85* 3.24 3.79*
2HG3-2 3.40 4.17* 3.61 4.83* 4.32 5.23*
2HG3-Mean 3.14 3.71* 3.42 4.34* 3.78 4.51*
0.33 0.34 0.36 0.38 0.4 0.42
2HG/G 3.4 4.02* 3.63 4.48* 3.45 3.33
2HG3/G 3.7 4.37* 3.93 4.78* 3.82 4.90*
2HG1/G1 3.4 3.67* 3.40 4.10 3.3 4.30*
2HG2/G2 3.4 4.35 3.74 4.83 3.54 4.89*
2HG-M/G-M 3.4 4.03* 3.63 4.48* 3.44 4.62
2HG3.1/G1 3.5 3.9* 3.80 4.40* 3.6 4.54*
2HG3.2/G2 3.9 4.76* 4.08 5.14* 4.04 5.2*
2HG3-M/G-M 3.7 4.37* 3.93 4.78* 3.82 4.9*
* Significant at 95% level
g/c
m
144
0
1
2
3
4
5
35/65 50/50 65/35
P /C BLENDS
2HG
g/cm
hysteris is at 0.5 °
Untreated
hysteris is at 0.5 °
Treated
Figure 9.12 Shear Hysteresis of the fabric at 0.5° (G/cm)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
35/65 50/50 65/35
P/C Blends
G/Cm
hysterisis at 3.0 °
Untreated
hysterisis at 3.0 °
Treated
Figure 9.13 Shear Hysteresis of the fabric at 3.0° (g/cm)
9.3.7 Compression properties
Unlike the tensile, bending, shear and surface properties, only a
single parameter is obtained for the compression properties. With the
exception of 65/35 polyester cotton blended knitted fabric, WC values show a
decrease for treated fabrics. An increase in WC (Compression energy) is an
indication of an improvement in handle of fabrics and thus alkaline hydrolysis
treatment for 65/35 blend has led to a better handle.
2H
G3
g/c
m
hysteresis at 3.0°
Untreated
hysteresis at 3.0°
Treated
65/35 35/65
2H
G g
/cm
hysteresis at 0.5°
Untreated
hysteresis at 0.5°
Treated
145
Table 9.7 Compression properties
35/65 50/50 65/35
Un
TreatedTreated
Un
TreatedTreated
Un
TreatedTreated
LC 0.38 0.35* 0.38 0.38 0.344 0.34
2.1 2.4 2.1 2.5 2.5 2.4
WC 0.32 0.26* 0.37 0.31* 0.284 0.33*
1.2 1.5 1.2 1.4 1.3 1.2
RC % 46.0 43.9* 43.3 45.7* 46.556 46.30
1.1 1.2 1.1 1.2 1.1 1.2
T (mm) 0.84 0.76 0.91 0.83 0.795 0.85*
2.1 2.2 2.1 2.2 2.2 2.3
W (mg.cm2) 13.9 13.9 14.3 14.10 14.24 13.39
1.4 1.7 1.4 1.3 1.2 1.4
* Significant at 95% level
It is interesting to note that the fabric thickness To increased in a
significant manner for 65/35 P/C blend after the alkaline hydrolysis treatment
and this reflects the fact that alkali treated fabric became fuller than the
untreated fabric. The increase in thickness could be due to decrease of inner
strains of the yarns that result in relaxation of fabric structure and as a
consequence, fabric swells. Figures 9.14-9.18 illustrates the trend. The 50/50
blend had the highest compressibility when untreated.
It may be noted that the larger the compressibility of untreated
fabric, the lower the compressibility after alkaline hydrolysis. As expected,
the increase in the thickness caused by alkaline hydrolysis treatment was
accompanied by significant change in compressional energy WC. In fact, WC
increased resulting in fluffier or soft fabrics. Thus may be due to higher
degree of treatment. While 35/65 and 50/50 blends showed a change in RC
(i.e., % energy loss due to compressive hysteresis), the 65/35 blend did not
show any significant change. With the exception of 35/65 blend, no
significant changes were noticed in compressional linearity, LC (i.e. linearity
of fabric compression, thickness curve).
146
0.31
0.32
0.33
0.34
0.35
0.36
0.37
0.38
0.39
0.4
35/65 50/50 65/35
p/c b le nds
L C
compress ion( L C)
Untreated
compress ion( L C)
Treated
Figure 9.14 Compression Properties- Linearity
0
0.1
0.2
0.3
0.4
35/65 50/50 65/35
p/c b le nds
W C
g.cm /cm ²
Energy ( W C) Untreated
Energy ( W C) Treated
Figure 9.15 Compression Properties –Energy
C OMPR ES SION - R ES IL IEN C E
41
42
43
44
45
46
47
35/65 50/50 65/35
p/c b le nds
RC (%)
Resilience ( R C)
Untreated
Resilience ( R C)
Treated
Figure 9.16 Compression Properties –Resilience
WC
(g.c
m/c
m2)
RC
%L
C
147
C OMP R E S SION - T H IC K N E S S
0.65
0.7
0.75
0.8
0.85
0.9
0.95
65/35 50/50 35/65
p/c b le nds
m m Untreated
Treated
Figure 9.17 Compression Properties –Thickness
C OMP R E S S ION - W E IGH T
12.8
13
13.2
13.4
13.6
13.8
14
14.2
14.4
14.6
65/35 50/50 35/65
p/c b le nds
M g/cm ²
W eight of actually
tested fabric in
Mg/cm ² Untreated
W eight of actually
tested fabric in
Mg/cm ² Treated
Figure 9.18 Weight of the Fabric
9.3.8 Surface properties
MIU reflects the fabric smoothness, roughness and crispness and
SMD constitutes the geometric smoothness and lower value of these
parameters are Desirable. It is apparent that, with the exception of 50/50
polyester blend, there is a reduction in MIU. In all the cases, SMD values
show an increase implying that the fabrics have become rougher. The surface
of the treated fabric became harsher after treatment of alkaline hydrolysis.
Recent work by Tavanai (2009) using atomic microscope, has shown that the
surface of polyester fiber has become rough following weight reduction and
the present results are in agreement with his results (Figures 9.19-9.12).
mg
/cm
2
WEIGHT
mm
148
0.18
0.19
0.2
0.21
0.22
0.23
0.24
35/65 50/50 65/35
p/c ble n ds
M IUM IU Untreated
MIU Treated
Figure 9.19 Surface Properties- Coefficient of Friction
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
35/65 50/50 65/35
P/C Blends
MMD
MMD Untreated
MMD Treated
Figure 9.20 Surface Properties- Mean Deviation of Coefficient of
Friction
Table 9.8 Surface Properties
35/65 50/50 65/35
Un
TreatedTreated
Un
TreatedTreated
Un
TreatedTreated
MIU-1 0.19 0.21 0.23 0.23 0.22 0.20
MIU-2 0.20 0.18 0.22 0.22 0.22 0.20
Mean 0.20 0.20* 0.22 0.22 0.22 0.20*
MMD-1 0.01 0.01 0.01 0.01 0.00 0.01
MMD-2 0.01 0.00 0.01 0.00 0.01 0.01
Mean 0.01 0.01 0.01 0.01 0.00 0.01
SMD-1 (µm) 2.62 3.48 4.06 4.81 2.80 2.85
SMD-2 2.23 1.74 2.49 2.29 2.09 2.64
Mean 2.42 2.61* 3.28 3.55* 2.45 2.75*
0.85 0.8 0.91 0.84 0.8 0.85
SMD/T 28 32 36 42 31 33
* Significant at 95% level
MM
D
149
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
35/65 50/50 65/35
P/C Blends
MMD
MMD Untreated
MMD Treated
Figure 9.21 Surface Properties - Geometrical Roughness
9.3.9 Handle Force
Table 9.11 gives the value of handle force of the fabric samples
from which it is evident that following alkaline hydrolysis the handle has
improved. It is interesting to note that 65/35 polyester cotton blend shows a
drop of 60% in handle force which is quit encourage Figure 9.25 illustrates
the trend obtained.
Table 9.9 Withdrawal force (N)
Type of
fabric
P/C
(35/65)
P/C
(65/35)
P/C
(50/50)
Control 2.606 1.53 2.83
Treated 0.976 0.616 1.457
9.3.10 Total hand Value
Table 9.11 gives the primary and total hand values of the knitted
fabrics. It is interesting to note that THV shows a progressive increase with
increase in polyester content. Alkaline hydrolysis treatment has led to an
improvement in the handle of all fabrics. Figure 9.24 shows the trend.
SM
D
SMD untreated
SMD treated
150
Thus, the knitted fabrics containing 65/35 blend exhibit an
exceptionally good handle in comparison with 35/65 and 50/50 blends. We
used Kawabata’s primary hand equation for women’s dress materials to
evaluate the different tactile qualities of the experimental fabrics. The higher
the value of the primary hand quality within the 0-10 range, the greater is the
intensity of the particular hand tactile feeling. It is observed that alkaline
hydrolysis treatment makes the fabrics smoother (numeri) fuller and softer
(fukurami) and less stiff.
Table 9.10 Primary and total handle values
Sample Primary handle values
Koshi Numeri Fukurami THV
PC 65/35 normal 0.52 9.27 2.03 3.29
PC 65/35 Alkali Treated 0.24 8.83 2.92 3.46
PC 35/65 Normal -1.19 7.81 3.04 1.67
PC 35/65 Alkali
Treated-0.48 8.29 1.69 1.95
PC 50/50 Normal -0.62 7.28 2.80 1.62
PC 50/50 Alkali
Treated0.02 7.89 2.60 2.35
THV- Total Hand Value
9.3.11 Thermal Insulation Value or Heat keeping ratio
That there is no difference in the Thermal Properties in the various
types of knitted fabrics can be seen (Figure 9.24).
151
Table 9.11 Heat keeping ratio and Tog value
Sample Heat keeping ratio Tog value
Without specimen - 0.83
PC 65/35 normal 20.00 1.04
PC 65/35 Alkali Treated 20.00 1.03
PC 35/65 Normal 19.17 1.02
PC 35/65 alkali Treated 18.32 1.01
PC 50/50 Normal 19.17 1.02
PC 50/50 Alkali Treated 19.17 1.02
17
17.5
18
18.5
19
19.5
20
20.5
35/65 50/50 65/35
P /C BL ENDS
He a t
Ke e p in g
Ratio
Heat keeping ratio Untreated
Heat keeping ratio Treated
Figure 9.22 Thermal Insulation Value- Heat Keeping Ratio
0.99
1
1.01
1.02
1.03
1.04
1.05
35/65 50/50 65/35
p/c blends
Tog
ValueTOG VALUE Untreated
TOG VALUE Treated
To
g V
alu
e
Hea
t K
eep
ing
Ra
tio
Figure 9.23 Tog Total hand Value
152
0
0.5
1
1.5
2
2.5
3
3.5
4
35/65 50/50 65/35
p/c ble nds
THVTHV Untreated
THV Treated
Figure 9.24 Total Hand Value of blended knitted fabric before and
after alkaline hydrolysis treatment.
0
0.5
1
1.5
2
2.5
3
35/65 50/50 65/35
p/c blends
Withdrawal
Force
(Newton)
Withdrawal force in (N)
Control
Withdrawal force in (N)
Treated
Figure 9.25 Withdrawal Force
9.3.12 Wickability
Figures 9.26-9.28 show the wickability of knitted fabrics before and
after hydrolysis from which it is noticed that wickability has improved in all
the cases in treated fabrics.
Table 9.12 shows the linear regression analysis carried out on the
data as shown in Figures 9.26 - 9.28.
Wit
hd
ra
wal
Force
(N)
TH
V
153
65/35 H VsT
0
2
4
6
8
10
12
14
0 5 10 15 20 25 30 35
Time in minutes
Wic
kin
g h
eig
ht (c
m)
Normal course way Normal wals way
Alkali Treated coarse way Alkali Treted wales way
c
65/35 H2 Vs T(s)
0
20
40
60
80
100
120
140
160
0 5 10 15 20 25 30 35
Time in minutes
Wicking h
ight(cm
)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated wales way
65/35 H Vs T1/2
0
2
4
6
8
10
12
14
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
Time in minutes
Wic
kin
g h
eig
ht(cm
)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated wales
65/35 logeH Vs loge
T
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Time in minutes
Wic
kin
g h
eig
ht(cm
)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated wales way
c
Figure 9.26 Wickability of knitted fabric 65/35(Wicking)
154
50/50.H VsT
0
2
4
6
8
10
12
14
16
0 5 10 15 20 25 30
Time in minutes
Wic
kin
g h
eig
ht (c
m)
Normal coarse way Normal wales way
Alkali Treated coarse way alkali Treated wales way
50/50 H2 Vs T
0
20
40
60
80
100
120
140
160
180
200
0 5 10 15 20 25 30 35
Time in minutes
Wicking height (c
m)
Normal coarse way Normal wals way
Alkali Treated coarse way Alkali Treated wales way
50/50 H VsT1/2
0
2
4
6
8
10
12
14
16
0 1 2 3 4 5 6
Time in minutes
Wic
kin
g height (c
m0
Normal coarse way Normal Wales way
Alkali Treated coarse way Alkali Treated wales way
50/50 logeH Vs loge
T
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Time in minutes
Wic
kin
g h
eig
ht(cm
)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated wales way
Figure 9.27 Wickability of knitted fabric 50/50 (Wicking)
155
35/65 H VsT
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35
Time in minutes
Wic
kin
g heig
ht (c
m)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated wales way
c
35/65 H2 VsT
0
20
40
60
80
100
120
140
0 5 10 15 20 25 30 35
Time in minutes
Wic
kin
g hig
ht (c
m)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated wales way
35/65H VsT1/2
0
2
4
6
8
10
12
0 1 2 3 4 5 6Time in minutes
Wic
kin
g h
eig
ht (c
m)
Normal coarse w ay Normal w ales w ay
Alkali Treated coarse w ay Alkali Treated w ales w ay
35/65 logeH Vs loge
T
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Time in minutes
Wic
kin
g h
eig
ht(cm
)
Normal coarse way Normal wales way
Alkali Treated coarse way Alkali Treated Wales Way
Figure 9.28 Wickability of knitted fabric 35/65 (Wicking)
156
Table 9.12 show the linear regression analysis carried out on the data.
Table 9.12 Linear regression analysis
65/35 50/50 35/65
N C W y = 0.2436x + 2.2179 y = 0.2614x + 2.1 y = 0.2321x + 0.6036
R2 = 0.8049 R2 = 0.8447 R2 = 0.9781
N W W y = 0.2457x + 1.7143 y = 0.265x + 1.9107 y = 0.2371x + 0.6571
H VsT R2 = 0.8772 R2 = 0.8647 R2 = 0.9665
A T C W y = 0.3286x + 4.0286 y = 0.3171x + 4.6429 y = 0.3036x + 3.7179
R2 = 0.7115 R2 = 0.6342 R2 = 0.711
A T W W y = 0.3229x + 4.1714 y = 0.3621x + 4.4821 y = 0.2879x + 2.225
R2 = 0.6899 R2 = 0.7085 R2 = 0.8573
H2VsT N C W y = 2.3077x + 7.2071 y = 2.6124x + 5.1607 y = 1.7621x - 4.2339
R2 = 0.9585 R2 = 0.9827 R2 = 0.978
N W W y = 2.3019x + 1.5093 y = 2.6119x + 3.5839 y = 1.8301x - 3.8736
R2 = 0.9646 R2 = 0.982 R2 = 0.9785
A T C W y = 4.5284x + 27.468 y = 4.3723x + 38.636 y = 3.8584x + 23.503
R2 = 0.9072 R2 = 0.8218 R2 = 0.9045
A T W W y = 4.4404x + 29.448 y = 5.5454x + 33.64 y = 3.8584x + 23.503
R2 = 0.8899 R2 = 0.9068 R2 = 0.9045
H VsT1/2 N C W y = 1.5413x + 0.5429 y = 1.6257x + 0.401 y = 1.3333x - 0.516
R2 = 0.975 R2 = 0.9881 R2 = 0.9745
N W W y = 1.4961x + 0.2278 y = 1.6324x + 0.2422 y = 1.3679x - 0.5071
R2 = 0.9837 R2 = 0.9926 R2 = 0.9715
A T C W y = 2.1566x + 1.5015 y = 2.1463x + 1.98 y = 1.9942x + 1.3885
R2 = 0.9271 R2 = 0.8786 R2 = 0.9268
A T W W y = 2.1362x + 1.6292 y = 2.3749x + 1.7039 y = 1.78x + 0.3995
R2 = 0.9135 R2 = 0.9217 R2 = 0.9901
logH VslogT N C W y = 0.6006x + 0.069 y = 0.6265x + 0.0817 y = 0.5892x - 0.0454
R2 = 0.961 R2 = 0.9537 R2 = 0.9827
N W W y = 0.6146x + 0.0891 y = 0.6322x + 0.0688 y = 0.5989x - 0.0423
R2 = 0.9439 R2 = 0.9665 R2 = 0.9811
A T C W y = 0.6957x + 0.1718 y = 0.6974x + 0.1863 y = 0.6798x + 0.1546
R2 = 0.8555 R2 = 0.8327 R2 = 0.8745
A T W W y = 0.699x + 0.1663 y = 0.7277x + 0.1759 y = 0.6471x + 0.092
R2 = 0.8646 R2 = 0.8583 R2 = 0.9458
157
9.4 CONCLUSION
While tensile resilience shows a higher value for 65/35 polyester
cotton blended fabric, a lower value for 35/65 PC blends is noticed. While
there is a reduction in WT, EMT shows only marginal changes. Bending
hysteresis and shear hysteresis values show a significant increase in the fabric
following alkaline hydrolysis. The thermal properties were unchanged and the
65/35 blend exhibited good handle.
Three polyester cotton blend weft knitted fabrics were subjected to
alkaline hydrolysis treatment. They were evaluated with the KES - F and the
other testing instruments. The properties of the treated fabrics were compared
with those of the untreated ones. It was noticed that major changes occurred
in the low stress mechanical behavior of the treated fabrics. Among the
properties most affected by alkaline hydrolysis treatment are tensile
elongation (EM %), tensile resilience (RT %), shear rigidity (G), shear
hysteresis (2HG), compression resilience (RC %), linearity of the
compression curve (LC), surface friction (MIU) and surface roughness
(SMD). A few of these properties changed by as much as 30 % after alkaline
hydrolysis treatment. There was not much difference in thermal insulation
property. The results provide evidence to conclude that alkaline hydrolysis
treatment affected the low stress mechanical properties significantly. The
thermal comfort performance was unchanged. It is apparent that the 65/35
polyester cotton blended knitted fabric exhibits an exceptionally good handle
following alkaline hydrolysis. This work will be useful for developing new
products in functional aspects using polyester/cotton blended yarns.
