Value Added Knits From Ramie-Cotton Blended Yarns Spun Using Short

Chattopadhyay et al
ID #01
Value Added Knits From Ramie-Cotton Blended Yarns Spun Using Short
Staple (Cotton) Spinning System
ID Number: 01
Sajal Kumar Chattopadhyay1, Shaymal Kumar Dey2, Bindu Venugopal3 and Amar
Chaphekar4
1,3,4
Central Institute for Research on Cotton Technology, (ICAR), Adenwala Road, Matunga,
Mumbai 400 019, India and 2National Institute of Research on Jute and Allied Fibre Technology,
12 Regent Park, Kolkata 700 040, India
drskchattopadhyay@gmail.com
Abstract
In India, many of the natural ligno-cellulosic fibres are considered as low value fibres useful
only for manufacturing industrial ropes and fabrics for packaging. Ramie is one such natural
ligno-cellulosic bast fibre obtained by decortication of bark from canes of the plant, followed by
degumming of ramie fibres. The present paper reports an exploratory study on the possibility of
utilizing Indian ramie fibre in blends with cotton using cotton spinning system. A two stage
degumming method has been optimised. Ramie fibre could be blended with cotton to an extent of
35% for spinning of acceptable yarn qualities for production of 24.6 and 14.7 tex (30s and 40s
Ne) ring yarns. The knitting and garmenting trials of the blended yarns on commercial knitting
machines were also found satisfactory.
INTRODUCTION
In India, many of the natural ligno-cellulosic fibres are considered as low value fibres useful only
for manufacturing industrial ropes and fabrics for packaging. However, with the increasing
concern world over for ecological preservation, sustainable resources like vegetable fibres
originating from plants that are safe, biodegradable and recyclable are gaining importance in
recent years. Ramie is one such natural ligno-cellulosic strong, lustrous and fine bast fibre
obtained from the inner bark of Boehmeria nivea (L) Gaud. The fibres are embedded in the cells
of bast that lies between the outer bark and the woody core of the stem. The spinnable fibres are
obtained by decortication and degumming. It is not normally possible to spin the fibre with 2030% adhered gum, which therefore, needs to be removed by the process of degumming. Various
methods of degumming have been reported in the literature for the removal of gums from crude
ramie fibres. These include both chemical[1-3] and microbial[4-6] methods.
Attempts have been made by various researchers to spin ramie in blends with jute, silk, viscose
and polyester fibres using jute and woollen spinning systems[7-9]. Any efforts to develop
appropriate technologies for the production and processing of ramie either alone or in blends
with other fibres for producing finer yarn with improved properties can widen the application of
ramie fibre.
The present paper reports an exploratory study on the possibility of utilizing Indian ramie fibre in
blends with cotton using commercial cotton machinery for producing ring spun blended yarns.
The knitting and garmenting trials of the blended yarns on commercial knitting machines have
also been reported.
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DESCRIPTION OF THE ACTUAL WORK
The chemical degumming of decorticated ramie fibre (R 67-34 variety) was optimised at
NIRJAFT (National Institute of Research on Jute and Allied Fibre Technology). In one set of
experiments, decorticated ramie fibre was treated with 1.5% NaOH at 100 °C for 90 minutes.
The resultant sample was coded as NIR-1. In a second set, decorticated ramie fibre was first
treated with 1.5% NaOH at 100 °C for 60 minutes and then again treated with NaOH of varying
concentration, viz., 3.0%, 6.0%, 15.0% and 18.0% at 100 °C for 30 minutes and the resultant
fibre samples were coded as Sample NIR-2 to NIR-5. The schematic diagram of various
treatments carried out is given in the flowchart (Fig. 1).
Ist set
Decorticated ramie fibre
2nd Set
Decorticated ramie fibre
1.5% NaOH
100 °C
90 minutes
1.5% NaOH
100 °C
60 minutes
3.0% NaOH
100 °C
30 min
NIR-1
6.0% NaOH
100 °C
30 min
NIR-2
NIR-3
15.0% NaOH
100 °C
30 min
NIR-4
8.0%NaOH
100 °C
30 min
NIR-5
Fig. 1. Ramie fibre degumming flowchart
Gum content of ramie fibre was determined by using test methods as reported earlier[10]. The
ramie fibre samples were evaluated for fibre fineness and bundle strength following standard test
procedures.
The degummed ramie fibres were cut into 40 mm staple length on a staple cutter machine and
blended with DCH.32 cotton having 2.5% span length of 33 mm, micronaire value of 2.9 µg/inch
(0.114 tex), bundle tenacity of 26.6 g/tex and uniformity ratio of 45%. The Improved
Microspinning Technique developed at CIRCOT was adopted for carrying out spinning
optimisation trials. The degummed ramie sample was blended in the proportions of 35%, 50%
and 65% with DCH.32 cotton adopting flock-blending method. All the blends were spun to 14.7
tex (40s Ne) yarn using the ring spinning system. The list of spinning trials is given in Table I.
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TABLE I. List of Spinning Trials on Cotton-Ramie Blends (14.7 Tex Ring Yarn)
S.No.
1 to 5
Blend Code
NIR-1 to NIR-5
6
7
8
MP-1
MP-2
MP-3
Fibres Used In Blends
Ramie
degummed
under
chemical conditions:Cotton
Ramie (NIR-3):Cotton
Ramie (NIR-3):Cotton
Ramie (NIR-3):Cotton
different
Blend Composition (%)
35:65
35:65
50:50
65:35
Based on the results of these optimisation trials, bulk blending trials were undertaken keeping the
cotton each to ramie blend ratio of 65:35 and spun to 24.6 and 19.7 tex (24s and 30s Ne) yarn on
the ring spinning system. Pure cotton sample was also spun to identical count for comparison
purpose.
Further, yarn samples were suitably waxed and identically knitted into single jersey fabric on a
25.4 cm (10 inch) diameter, 8 feeder knitting machine at 37 rpm with 9 needles per cm. This was
followed by commercial knitting, finishing and garment making trials.
TESTING OF YARN AND FABRIC SAMPLES
All the yarn samples were tested for lea strength and linear density on a computerised lea tester.
They were tested for various tensile properties by using Uster Tensorapid automatic tensile
tester. Yarn unevenness (U%) and imperfections were tested on an electronic evenness tester.
The knitted fabrics were evaluated for various dimensional properties, such as courses per cm
(C), wales per cm (W) and loop length (l). The loop shape factor and stitch density were
calculated as,
Stitch density = C x W
C
W
Tightness factor =
Loop shape factor =
(1)
(2)
yarn tex
(3)
l
Tightness factor11 (TF) of the knitted fabrics was determined by the following formula.
Besides, fabrics were tested for bursting strength with a diaphragm type bursting tester as per the
standard method. Shrinkage testing was done after wet relaxation using a wetting agent (0.5%) at
room temperature as per CIRCOT procedure. Air permeability was determined by Prolific Air
Permeability tester as per the standard procedure and the results were expressed in terms of
m3/m2/min.
RESULTS
i)
Effect of Degummed Ramie Fibre Properties on Blended Yarn Quality
Five degummed ramie fibre samples prepared by various chemical treatments were used in
the study. The properties of fibres are given in Table II. It can be seen from the table that
with decrease in residual gum content, the fibres become finer and weaker. The sample
NIR-1 has the highest bundle tenacity of 47.5 g/tex, but the fibres remained the coarsest
(1.06 tex), while sample NIR-5 having the lowest bundle tenacity of 19.1 g/tex was the
finest (0.67 tex). The properties of cotton-ramie blended yarns produced using the above
ramie fibres are presented in Table III. It can be seen that initially the lea CSP and single
yarn breaking tenacity increase due to increase in fibre fineness, reach optimum values (for
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sample NIR-3) and, there after drop down (Fig. 2). As the gum is removed, fibres become
finer resulting in higher realisation of the blended yarn strength due to increase in the
number of fibres in the yarn cross-section. However, this will be offset by the fall of fibre
strength resulting from the decreased interfibre cohesion. Thus, the optimum degumming
treatment will be determined by the combined effect of fibre fineness and bundle tenacity
resulting in optimum tenacity realisation in the blended yarn. Unevenness of all the cottonramie blended yarns is on a higher side compared to similar cotton yarns probably due to
migration of coarser ramie fibre to the surface. This explanation is supported by SEM
photographs of the blended yarn sample (Fig. 3).
Table II. Fibre Properties of Chemically Degummed Ramie Fibre
Sample Code Properties
NIR-1
NIR-2
NIR-3
NIR-4
NIR-5
Fibre Fineness (Tex)
Bundle Tenacity, 3.2 mm gauge (g/tex)
Residual Gum Content (%)
1.06
47.5
4.45
0.85
34.1
5.23
0.83
25.7
5.08
0.70
20.7
4.97
0.67
19.1
4.82
Table III. Properties of Cotton-Ramie Blended Yarns (14.7 Tex Ring Spun)
Blend
Code
CSP
1
2
3
4
5
NIR-1
NIR-2
NIR-3
NIR-4
NIR-5
1758
1853
1951
1924
1902
Uneven
ness
(U%)
18.9
18.4
20.5
19.6
19.1
Breaking
Work (gf.cm)
200.2
197.5
223.8
279.5
238.2
Breaking
Force
(gf)
171.5
183.8
189.1
185.2
174.8
2000
Breaking
Tenacity
(gf/tex)
11.6
12.5
12.8
12.5
11.8
Breaking
Elongation (%)
4.40
4.15
4.62
5.61
4.80
13
12.5
Lea CSP
1900
12
1800
11.5
CSP
Br. Tenacity (gf/tex)
S.
No.
Tenacity (gf/tex)
1700
11
NIR-1
NIR-2
NIR-3
NIR-4
NIR-5
Chemical Treatment Code
Fig. 2. Effect of Degumming on Lea CSP and Breaking Tenacity of Cotton-Ramie Blended Yarn
(14.7 tex ring)
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Fig. 3. SEM Depicting Longitudinal View of Cotton-Ramie Blended Ring Yarn
ii)
Effect of Blend Proportions on Cotton-Ramie Blended Yarn Quality
The optimised degummed ramie fibre sample, NIR-3 was used to study the effect of
proportion of ramie fibre in the blended yarn. The properties of various blended yarns are
presented in Table IV. It can be seen that as the proportion of ramie fibres in the blend
increases, various tensile properties, elongation and evenness of the blended yarns
decrease (Fig. 4 (a) and 4 (b)). This is due to the increase in the number of coarser and
stiffer ramie fibres in the yarn cross-section. It is to be noted that ramie can be added to
an extent of 35% in the blend for production of 14.7 tex (40s Ne) yarn suitable for
knitting.
Table IV. Properties of Cotton-Ramie Blended Ring Yarns (14.7 Tex)
S.
No.
Blend
Code
1
2
3
MP-1
MP-2
MP-3
Blend
Composition
(R:C)
35:65
50:50
65:35
CSP
Unevenness
(U%)
1850
1326
858
19.6
23.7
25.6
Breaking
Work
(gf.cm)
232.6
165.0
82.5
Breaking
Force
(gf)
180.3
144.5
92.5
Breaking
Tenacity
(gf/tex)
12.2
9.79
6.25
Breaking
Elongation (%)
4.81
4.12
3.28
1850
12
10
Lea CSP
1600
8
1350
6
1100
4
850
Lea CSP
Br. Tenacity (gf/tex)
600
5
(50R:50C)
MP2
Blend Code
4.5
4
3.5
Br. Elongation (%)
2
0
( 35R:65C)
MP1
Br. Elongation %
14
Br. Tenacity (gf/tex)
2100
(65R:35C)
MP3
(a)
Unevenness (U%)
3
( 35R:65C)
MP1
(50R:50C)
MP2
26
25
24
23
22
21
20
19
18
17
16
Unevenness (U%)
R=Ramie, C=Cotton
(65R:35C)
MP3
Blend Code
(b)
Fig. 4. Effect of Ramie Fibre Proportion on (a) Lea CSP and Br. Tenacity and (b) Br. Elongation
and Unevenness (14.7 Tex) of Blended Yarns
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iii)
a)
b)
c)
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Bulk Trials on Blending Ramie with Cotton
Based on the results of these optimisation trials, bulk blending trials were undertaken
keeping the cotton each to ramie blend ratio of 65:35 and spun to 24.6 and 19.7 tex (24s
and 30s Ne) yarn on the ring spinning system. Pure cotton sample was also spun to
identical count for comparison purpose. Yarn properties of the samples are given in Table
V. The following measures were adopted during bulk trials.
A thorough opening of stiffer ramie fibre component was more effectively achieved by the
use of improved beaters in the blowroom. These are better suited than the conventional
beaters for cotton ramie processing. Conventional beaters necessitate the ramie component
to be passed thrice for acceptable level of fibre opening.
During carding, the use of improved apron doffing system reduced the instances of card
web sagging and shedding of fibres as compared to doffing with the conventional doffer
comb.
Ramie fibre in blended sliver was observed to give more resistance during drafting
operation. This is due to the higher stiffness of ramie fibre. Hence, higher drafting pressure
was needed for satisfactory processing of ramie fibre blends.
Table V. Yarn Properties of Cotton-Ramie Blended Yarns and 100% Cotton Yarns (Bulk Trials)
Materials Properties
100% Cotton
65% Cotton:35% Ramie (NIR-3)
Blend Code
C1
C2
RC1
RC2
Nominal Tex (Ne)
Corrected CSP
Breaking Tenacity (g/tex)
Breaking Elongation (%)
Unevenness (U%)
Thick Places/km
Thin Places/km
Neps/km
Total imperfections/km
24.6 (24s)
2416
12.4
8.8
15.5
1532
216
1764
3512
19.7 (30s)
2385
15.3
5.6
17.4
1440
295
1614
3349
24.6 (24s)
2047
12.0
4.8
19.6
2780
981
2964
6725
19.7 (30s)
1956
11.7
4.4
20.8
3109
1494
4525
9127
iv)
Knitting Behaviour in Bulk Trials
Though the CSP of blended yarns were significantly lower, the knitting performance was
almost identical for all the yarn samples. No needle breakage occurred during knitting
and hence mechanical faults were almost absent in the knitted fabrics. The single jersey
fabric properties are given in Table VI. No mechanical fault was observed in blended
fabrics indicating that there was no damage to knitting elements. Cloudiness and
accumulation of trash particles resulting in spots were found more in blended fabrics.
This was mainly due to significantly higher U% and more imperfections in the blended
yarns. These spots were frequently observed in the blended fabrics, which may be due to
presence of considerably higher number of thick places in the blended yarns. Bursting
strength of blended fabric was much lower than that of the cotton fabric. This was mainly
because of weaker yarns from cotton/ramie blends. The area shrinkage of blended fabric
was much higher than 100% cotton of the same yarn count. It may be due to quick
relaxation of cotton fabric because of higher extensibility and pliability of cotton yarn.
Air-permeability of blended fabric was higher than 100% cotton indicating the suitability
of cotton/ramie blends for apparel fabrics.
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Table VI. Properties of Single Jersey Cotton-Ramie Blended Knitted Fabrics
Code
Yarn
Tex
C
(No./
cm)
W
(No./
cm)
Loop
length
(cm)
Stitch
density
(No./
2
cm )
Fabric
wt
(g/m2)
Area
Shrinkage
(%)
Bursting
strength
(kg/
2
cm )
Air
permeability
(m3/m2/
min)
Skewness
(%)
RC1
RC2
C1
C2
24.6
19.7
24.6
19.7
14.9
14.1
16.1
15.4
13.9
15.2
13.7
13.6
0.334
0.339
0.327
0.342
206
214
221
210
165
162
196
165
2.43
1.65
1.89
1.54
100
88
106
88
72
96
56
86
3.9
7.3
5.3
3.4
RC = 65% Cotton: 35% Ramie, C= 100% Cotton
(v)
Circular Knitting, Printing and Garment Making Trials
Commercial knitting trials of the cotton-ramie (65:35) blended 19.7 tex yarn was
successfully carried out. The knitting was done on a 24-gauge double jersey circular
knitting machine. In addition to plain and interlock design, a peanut design was also
produced. The plain and interlock designs were made on a 76 cm (30 inch) diameter
machine equipped with 36 feeders and running at 20 rpm, while the peanut design was
knitted on a 61 cm (24 inch) diameter machine having 24 feeders. The working of all the
yarns was quite satisfactory.
The knitted fabric samples were subjected to chemical finishing optimisation
experiments. Scouring, bleaching and softening treatments were optimised and carried
out in a single bath process. The following chemical processing was found suitable for
the type of garments (Fig. 5) produced in the study.
(a) Scouring and bleaching
Application steps:
(i)
Water-7 litres, ALLENDENT (wetting agent)-NI-0.5 g/l, temp-40°C, time-15 min, drain
the bath.
Water-7 litres, LUBASSIST-JET (Lubricating agent)-1 g/l, Acetic acid-0.5 g/l,
(ii)
MADSCOUR-BL (Scouring agent)-2.5 g/l, time-30 min, Hydrogen peroxide-9 g/l,
Caustic soda-3.0 g/l, temp-95°C, time-45 min, drain the bath.
(iii) Water-7 litres, Acetic acid-1 g/l, time-10 min, temp-85°C, drain the bath.
(iv)
Water-7 litres, time-10 min, temp-70°C, drain the bath.
Water-7 litres, Acetic acid-1 g/l, ARAPLEX-PH-0.5 g/l, time-10 min, drain the bath.
(v)
(vi)
Water-7 litres, White Tinopal 2B-0.3 g/l, temp-60°C, time-20 min, drain the bath.
(vii) Rinsing and drying of fabric.
(b) Softness treatment
Application by pad.
The following softeners were attempted,
DERMASIL-3780
(i)
HYDROSIL
(ii)
(iii) MICRODERM 8865
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Dermasil softness treatment was found better for such fabrics. It creates softness coupled with
smooth and silky hand while retaining the original water absorbency of fabric.
Fig.5. Assorted Knitwear Collection made from Cotton-Ramie Blended Yarns
CONCLUSIONS
In the present study, finer cotton-ramie blended yarns were successfully produced by adopting
commercial cotton spinning system, where the jute/flax spinning machines had failed. A blend
ratio of 65% cotton and 35% ramie produced 14.7 tex (40s Ne) ring yarn with adequate strength.
Knitting performance of the blended yarns on a laboratory scale was satisfactory. The following
main conclusions were made from the study:
Decorticated ramie fibre contains 20-30% gum. It is not possible to spin the fibre with
(i)
this adhered gum, which therefore, needs to be removed. In the present study, ramie fibre
was chemically degummed by an improved method.
The optimum degumming treatment (sample NIR-3) is determined by considering the
(ii)
combined effect of fibre fineness and bundle tenacity resulting in optimum tenacity for
the blended yarn.
(iii) A blend ratio of 65:35 for cotton each to ramie was found to give adequate CSP for
spinning to 14.7 Tex (40s Ne) ring yarns.
Though the CSP of blended yarns was significantly lower, the knitting performance was
(iv)
almost identical for all the yarn samples. No mechanical fault was observed in blended
fabrics that were knitted, indicating that there was no damage to knitting elements.
Air-permeability of blended fabric was higher than 100% cotton fabric, indicating the
(v)
suitability of cotton/ramie blends for apparel fabrics.
The area shrinkage of blended fabric was higher than that made from 100% equivalent
(vi)
cotton yarn.
(vii) Dermasil softness treatment was found better for such fabrics. It creates softness coupled
with smooth and silky hand while retaining the original water absorbency of the fabric.
Thus, by improved degumming method coupled with appropriate modification of the spinning
process and proper selection of cotton, finer cotton-ramie blended yarns can be produced by
adopting commercial cotton spinning system. These yarns can be used for production of knits on
commercial machines and variety of outerwear garments.
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ACKNOWLEDGEMENTS
This report forms a part of the R & D work carried out jointly by CIRCOT and NIRJAFT under
an AP cess fund project. The authors are thankful to Indian Council of Agricultural Research,
New Delhi for necessary financial support. The authors are also thankful to Director, CIRCOT,
Mumbai and Director, NIRJAFT, Kolkata for their valuable suggestions during the course of the
work.
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