ORIGINAL CONTRIBUTION

Development of Knitted Warm Garments from Speciality JuteYarns

Alok Nath Roy

Received: 10 September 2012 / Accepted: 1 January 2014 / Published online: 21 January 2014

� The Institution of Engineers (India) 2014

Abstract Jute-polyester blended core and textured poly-

ester multifilament cover spun-wrapped yarn was produced

using existing jute spinning machines. The spun-wrapped

yarn so produced show a reduction in hairiness up to

86.1 %, improvement in specific work of rupture up to

9.8 % and specific flexural rigidity up to 23.6 % over

ordinary jute-polyester blended yarn. The knitted swatch

produced out of these spun-wrapped yarn using seven

gauge and nine gauge needle in both single jersey and

double jersey knitting machines showed very good

dimensional stability even after three washing. The two-ply

and three-ply yarn produced from single spun-wrapped

yarn can be easily used in knitting machines and also in

hand-knitting for the production of sweaters. The thermal

insulation value of the sweaters produced with jute-poly-

ester blended spun-wrapped yarn is comparable with

thermal insulation value of sweaters made from 100 %

acrylic and 100 % wool. However, the hand-knitted

sweaters showed higher thermal insulation value than the

machine-knitted sweaters due to less packing of yarn in

hand knitted structure as compared to machine knitting.

Keywords Blended yarn � Polyester �Spun-wrapped yarn � Thermal insulation value

Introduction

The thermal insulation ability of a textile fabric is sub-

stantially independent of the nature of the fibre but is a

function of the state of aggregation of fibre in the fabric [1].

One of the important factors which govern the thermal

insulation behaviour of fabric is how much immobile air

the fabric can entrap in its structure. The higher the air

entrapped, the higher is the thermal insulation value. The

capacity of the fabric to entrap immobile air is largely

dependent on its physical bulk and in turn the physical bulk

of the yarn as well as the fabric constructional parameters.

Attempts has been made by various researchers [2–8] to

produce jute fibre based bulked yarn with the view to

produce diversified products as woven or knit wear, blan-

kets, carpets etc. with improved thermal insulation property

either by chemical modification of fibre or by adopting

different yarn bulking technique. However, the works

reported above are mainly related to bulk yarn and woven

fabric development only. Reports on the development of

knitted fabric/products from jute based yarns are scanty.

Jute, a natural ligno-cellulosic fibre has tremendous

potential for the manufacture of diversified products

including warm garments due to its natural look, rigidity,

strength, thermal insulation property, heat of wetting and

coarseness. However, some work is needed to make yarn

softer and smoother for knitting process (without any

cumbersome chemical process), where yarns passes

through the needles in very acute angle. For this, some

compatible fibre having much smooth surface may be

mixed with jute to some extent. Attempt has been made in

the present work to develop knittable jute-polyester blen-

ded yarns—both single and plied. Efforts have also been

made to reduce yarn hairiness. The developed yarns were

used to produce knitted fabric and sweaters with different

needle parameters. The properties (viz. weight/unit area,

bulk density, thermal insulation value, dimensional stabil-

ity) related to apparels realized by the knitted fabric/

sweaters have also been reported here. The aim of the work

A. N. Roy (&)

National Institute of Research on Jute and Allied Fibre

Technology, ICAR, Kolkata, West Bengal, India

e-mail: a_n_royin@yahoo.co.in

123

J. Inst. Eng. India Ser. E (September 2013–February 2014) 94(2):61–65

DOI 10.1007/s40034-014-0026-0

is to develop warm garment having reasonable thermal

insulation property at much cheaper cost than wool without

any chemical treatment.

Materials and Methods

Materials

Jute fibre (Corchorus olitorius) of TD-3 grade [9] having

fineness 2.1 tex, tenacity 30 cN/tex and extension at break

of 1.7 %; Polyester staple fibre (average fibre length

110 mm, fineness 4 tex) top (sliver) of variable cut length

having tenacity of 39 cN/tex and elongation at break of

21 % and textured polyester multifilament (34 filaments)

having fineness of 9 tex, tenacity of 35 cN/tex and exten-

sion at break of 24 % were used for the study.

Methods

Preparation of Yarn

Jute fibre was sprayed with 30 % oil-in-water emulsion

(containing glycerin—1.5 % and castor oil—6 %), passed

through a jute softener machine and stored in a bin for

piling or conditioning for a period of 24 h. Castor oil was

used in place of conventional mineral (batching oil) to

make the knitted products human skin friendly and free

from unwanted odor. The fibres were then successively

passed through roller and clearer type jute carding

machines (breaker card followed by a finisher card). The

finisher card sliver was blended with polyester sliver at first

drawing stage to get a jute/polyester (75/25) blended sliver

which was then processed through second and third

drawing frame of commercial scale jute drawing machines.

The sliver from the third drawing machine was used to spin

spun wrapped yarn [10] with jute/polyester blended core

wrapped with 9 tex polyester multifilament and also

ordinary yarn of 138 tex on Mackie’s standard apron-draft

flyer (Baxter) spinning machine. The spun-wrap yarn pro-

duced was made two-ply and three-ply with 10 and 7.5 tpm

respectively.

Preparation of Knitted Fabric Sample

Knitting of fabrics from spun-wrapped yarns was suc-

cessfully made in automatic flat bed both single-jersey and

double jersey knitting machines. Jute/polyester blended

spun-wrapped single yarns were first knitted into small

swatch of 30 cm 9 30 cm with seven gauge (seven nee-

dles per inch) and nine gauge (nine needles per inch)

needles to study the shrinkage behaviour. After that some

knitted products e.g., ladies and gents sweaters, both

machine knitted (used seven gauge needle for three-ply

yarn and nine gauge needle for two-ply yarn) and hand

knitted, were developed from two-ply to three-ply spun-

wrapped yarn.

Evaluation of Tensile Properties of Yarn

The tensile properties, such as tenacity, elongation-at-

break, initial modulus and specific work of rupture of yarns

were evaluated using a computer-aided Instron tensile

tester (Model 4411) after conditioning at 65 ± 2 % RH

and 27 ± 2 �C for 48 h. The gauge length and cross-head

speed were maintained at 610 and 300 mm/min respec-

tively as per the IS: 1670–1970 method [11].

Measurement of Hairiness of Yarn

The hairiness of yarns was measured using NIRJAFT jute

yarn hairiness meter following a standard method [12] at a

yarn speed of 45 cm/s (27 m/min). The instrument is based

on the principle of counting the number of protruding fibres

from the yarn surface by optico-electronic method. Three

hair-length settings 3, 5 and 7 mm were selected. The

number of hairs protruding from the yarn surface at three

hair-length settings was recorded separately. An average of

fifty such readings for each yarn at each hair-length setting

was taken and the average value of hairiness of each hair-

length interval per 135 cm of yarn length was converted to

number of hair per 100 m of yarn length.

Measurement of Bending Rigidity of Yarn

The bending rigidity of yarn, expressed as specific flexural

rigidity, was measured by the ring-loop method, for which

a mandrel of 3.12 cm diameter was used for the preparation

of a yarn ring [8]. The yarn ring was gently hung on a hook

of standard size and the undistorted diameter was mea-

sured. A load of 0.004 g/tex was then suspended on the

yarn ring for 60 s and the diameter of the distorted ring was

measured. The calculation of flexural rigidity of yarn was

carried out by the method given by Beevers [13].

Measurement of Dimensional Changes on Washing

of the Knitted Fabrics

The dimensional change of the knitted fabrics on washing

was evaluated as per BS 4923–1973 [14]. All the knitted

fabric swatch developed from single (spun-wrapped) yarn

were washed in plain water at 60 �C temperature for

30 min in a horizontal rotating-cage type washing machine

provided with automatic reversing motion. After washing,

water was drained out and fabric samples were rinsed for

5 min. Fabrics were then taken out and dried in air laying

62 A. N. Roy

123

flat on a glass surface. The washing and drying process

were repeated for another two cycles. The length and

breadth of fabrics were then measured removing the

wrinkles without stretching the fabric samples. Dimen-

sional change of the fabrics was expressed as the per-

centage reduction in length and width value from its initial

value.

Measurement of Thermal Insulation Property of Knitted

Fabrics

Thermal insulation property of knitted fabric was measured

in terms of thermal insulation value (TIV) in an instrument

developed by NIRJAFT. The instrument gives the TIV in

‘tog’ [15] and is based on the principal of measuring the

energy put into the heater to maintain a steady temperature

differential through the thickness of the fabric. The test

fabric is placed between two plates at different tempera-

tures and the rate of heat flow through the fabric at steady

state is determined.

Determination of Bulk Density of Knitted Fabrics

The weight per unit area of fabric was divided by thickness

of the knitted fabric to get the fabric bulk density. Hence

the fabric bulk density expressed in Table 1 is weight of

the fabric per unit volume.

Results and Discussion

Yarn Properties

Tensile and other physical properties of the yarns i.e. sin-

gle, two-ply, and three-ply yarns have been given in

Table 2. It is noted from Table 2 that the tenacity, exten-

sion at break and work of rupture of the spun-wrapped yarn

is higher and initial modulus is lower than those of the

ordinary yarn, but the strength CV % is slightly higher in

case of spun-wrapped yarn. The reason may be due to the

slight disturbance created in the twist-propagation while

feeding the covering element in the front roller nip during

yarn formation. However, the strength CV % and extension

CV % of two-ply and three-ply yarns were found to be

lower than that of the single yarn due to the averaging

action. It is also noted that three-ply yarn tenacity is higher

than the single or two-ply yarn. This is due to better

compaction and averaging action in three-ply yarn due to

twisting and folding respectively.

Evaluation of bending rigidity of different yarn samples

revealed that specific flexural rigidity of spun-wrapped

yarn is lower than that of the corresponding ordinary spun

yarn (Table 2). Similar trend of result was reported earlier

by the authors [10]. The reduction of specific flexural

rigidity of spun-wrapped yarn, both single and plied helps

in easy bending of these yarns around the knitting needle

during knitting.

It is also observed from Table 2 that hairiness of spun-

wrapped yarn is much lower in case of all the hair-lengths

than the corresponding ordinary jute/polyester blended

yarn, which may be due to laying and binding of the hairs

on the yarn surface by the filament during yarn formation.

The yarn hairiness is marginally increased in the plied

yarn. This may be attributed to extensive rubbing of yarn

with various machine parts in the subsequent processing.

However, the hairiness of the folded yarn is still much less

than that of ordinary yarn. Thus the reduction in yarn

hairiness and specific flexural rigidity enables the spun-

wrapped yarns to be processed through knitting machines

with appropriate needle gauges.

Fabric Properties

Dimensional changes of the knitted fabrics on washing

have been furnished in Table 3. Table 3 shows that the

maximum dimensional change of the fabrics along any

direction is 1.32 % even after three washings, which is

marginal and acceptable in case of knitted fabrics. Single

Table 1 Thermal insulation property of sweaters made from jute-based spun-wrapped, wool and acrylic yarns

Sr.

no.

Product details Fabric weight

(gm/m2)

Thickness

(mm)

Bulk density

(gm/cm3)

Thermal insulation

value (tog)

1 Machine knitted sweater made from three ply 138 tex spun wrapped jute

yarn (knitted with seven gauge needle)

702 2.278 0.31 0.583

2 Machine knitted sweater made from two ply 138 tex spun wrapped jute

yarn (knitted with nine gauge needle)

598 1.965 0.30 0.420

3 Hand knitted sweater made from two ply 138 tex spun-wrapped jute yarn 620 2.740 0.23 0.733

4 Hand knitted sweater made from three ply 138 tex spun wrapped jute

yarn

570 2.950 0.19 0.820

5 Sweater made from 100 % wool (machine knitted commercial) 458 1.575 0.29 0.428

6 Sweater made from 100 % acrylic (machine knitted commercial) 402 1.682 0.24 0.420

Development of Knitted Warm Garments 63

123

jersey fabrics shows less dimensional change than double

jersey fabrics knitted with needles of similar gauge, due to

lesser complexity in knitted structure of the former. Simi-

larly fabrics knitted with lower (coarser) gauge needles

show lower dimensional change than those knitted with

higher (finer) gauge needle due to lesser number of loops

per unit area of the fabric knitted with coarser gauge

needle.

The machine knitted and hand knitted sweaters devel-

oped from jute based spun wrapped yarn, were tested in the

TIV tester for the determination of their thermal insulation

property. TIV values of the 100 % wool and 100 % acrylic

commercial sweaters were also measured under similar

conditions (i.e., at temp. of 28 �C and R. H. of 62 ± 2 %)

for comparison. The test results have been furnished in

Table 1. It can be noted from Table 1 that the thermal

insulation value in tog of sweaters made from jute based

spun-wrapped yarn is either same or higher than the tog

value of sweaters made from 100 % wool or 100 % acrylic

fibre. The fibres in jute yarn are observed [16] to reside

more near the surface than the core of the yarn and thus

produce higher packing density of fibres near the surface

than the core. As a result, there is lot of immobile air

entrapped in the core of the jute yarn, which may be the

general cause of higher thermal insulation property of jute

fabrics. Also jute yarns being coarser in nature, forms

numerous tiny air pockets at different bends of yarn in the

knitted structure and forms an air shield which may be the

reason behind higher TIV of sweaters made from jute yarn.

Hand-knitted structure shows much higher thermal insu-

lation value than that of machine knitted structure. This

may be due to less packing of yarn in hand knitted structure

as compared to machine knitting.

Conclusions

• Jute-polyester blended core and textured polyester

multifilament cover spun-wrapped yarn can be pro-

duced using existing jute spinning machines. The spun-

wrapped yarns show a reduction in hairiness up to

86.1 %, increase in specific work of rupture of 9.8 %

and reduction in specific flexural rigidity of 23.6 %

over ordinary jute-polyester blended yarn. The reduc-

tion of specific flexural rigidity of spun-wrapped yarns,

both single and plied, help in easy bending of yarns

around the knitting needle during loop formation

enabling smooth knitting.

• These spun-wrapped yarns can be successfully knitted

into fabric with seven gauge and nine gauge needle in

both single jersey and double jersey knitting machines.

The two-ply and three-ply yarns produced from spun-

wrapped single yarn can be easily used in knitting

machines and also in hand-knitting for the production

of sweaters.

Table 2 Physical properties of jute/polyester blended spun-wrapped yarn and ordinary yarn

Yarn details Yarn linear

density

(tex)

Yarn tenacity

(cN/tex)

Yarn

extension at

break (%)

Specific work of

rupture (mJ/tex-

m)

Initial

modulus

(cN/tex)

Hairiness no. of hair/

100 m of yarn at the

hair-length setting of

Specific flexural

rigidity (mN-mm2/

tex2) 9 104

3 mm 5 mm 7 mm

Jute/polyester

(75:25) blended

ordinary yarn

135 9.96 (15.78)a 1.79 (21.09)a 1.33 (28.20)a 268.23 2,518 913 577 119.21

Spun-wrapped yarn

(single)b139 10.02 (20.36) 2.04 (14.11) 1.45 (30.54) 89.56 350 69 28 91.08

Spun-wrapped yarn

(two-ply)

282 9.82 (17.02) 2.34 (12.05) 1.52 (21.10) 79.09 391 83 34 78.92

Spun-wrapped yarn

(three-ply)

435 10.08 (12.75) 2.94 (10.72) 1.98 (18.19) 83.64 454 98 40 76.65

a Values in the parenthesis denotes the CV %b 9 tex polyester filament yarn as covering element

Table 3 Dimensional changes of the fabrics on washing

Knitting particulars Fabric areal density

(g/m2)

Dimensional

change on

washing (%)

Length Width

Single

jersey

Seven machine

gauge

402 0.52 0.05

Nine machine

gauge

427 0.70 0.10

Double

jersey

Seven machine

gauge

455 1.11 0.10

Nine machine

gauge

497 1.32 0.12

64 A. N. Roy

123

• The knitted fabric produced out of spun-wrapped yarn

showed very good dimensional stability even after three

washings.

• The thermal insulation value of the sweaters produced

with jute-polyester blended spun-wrapped yarn is

comparable to or even sometimes higher than that of

sweaters made from 100 % acrylic and 100 % wool

ordinary yarn. However, the hand-knitted sweaters

show further increased thermal insulation value than

the machine-knitted sweaters.

Acknowledgments Authors are thankful to the National Institute of

Research on Jute and Allied Fibre Technology, Kolkata for their

suggestions and encouragement in carrying out the work.

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Development of Knitted Warm Garments 65

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