A study on the thermal properties of 100% modal & viscose fabrics

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National Journal of Multidisciplinary Research and Development
1264
National Journal of Multidisciplinary Research and Development
ISSN: 2455-9040
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Volume 3; Issue 1; January 2018; Page No. 1264-1267
A study on the thermal properties of 100% modal & viscose fabrics
R Divya1, Dr. G Manonmani2, Payal Kothari3
1 Assistant Professor, Department of Costume Design and Fashion, PSG College of Arts and Science, Coimbatore, Tamil Nadu, India
2 Department of Home Science, Mother Teresa University, Kodaikanal, India
3 Department of Costume Design and Fashion, PSG College of Arts and Science, Coimbatore, Tamil Nadu, India
Abstract
The thermal comfort properties of fabric structures made from Modal yarns. 100% Modal is spun into yarns of identical linear
density. Each of the yarns produced was converted to single jersey knitted fabrics, cross tuck fabric, cross miss fabric & twill
fabric. The thermal conductivity of the fabrics was generally found to decrease with increase in the proportion of Modal fibre. The
water vapour permeability and wicking of the fabrics were observed to increase with increase in Modal fibre content. Statistical
analysis also indicates that the results are significant for water vapour permeability of the fabrics. Wicking test was also done
which gives fabric absorbency of water that how much it takes.
Keywords: modal fabric, thermal conductivity, air permeability
Introduction
Knitting is a method of forming fabric from a single strand of
yarn, using two needles. The resulting fabric has given more
than woven fabric. It is a technique to turn thread or yarn into
a piece of cloth. Knitted fabric consists of horizontal parallel
courses of yarn which is different from woven cloth as said by
Prakash. C (2012). The courses of threads or yarn are joined
together by interlocking loops in which a short loop of one
course of yarn or thread is wrapped over another course.
Fabric can be formed by hand or machine knitting, but the
basic principle remains exactly the same i.e. pulling a new
loop through the old loop. A knitted fabric consist of forming
yarns into loops, each of which is typically only released after
a succeeding loop has been formed and intermeshed with it so
that a secure ground loop structure is achieved by Koushik.
C.V.
Modal is a wood pulp based cellulosic fiber, made out of pure
wooden chips from the beech tree, technically as the European
Schneider Zelkova tree. While viscose rayon can be obtained
from the wood pulp from a number of different trees, Modal
uses only beech wood thus it is essentially a variety of viscose
rayon; a generic name for modified viscose rayon fiber that
has high tenacity and high wet modulus.
Modal was first developed by Austria based Lenzing AG Com
pany who trademarked the fabrics’ name, but now many manu
facturers make their own versions. It was initially imported
from Czech Republic, Slovakia, Hungary and Germany; but n
ow for Indian market, it is catered to by Len
zing, Austria, which has tied up with Rajasthan Textile Mills.
Thermal properties: Physical property of a solid body related
to application of heat energy is defined as a thermal property.
Thermal properties explain the response of a material to the
application of heat. Important thermal properties are
 Heat capacity
 Thermal expansion
 Thermal conductivity
 Thermal stresses
 Air Permeability
 Water Vapour Permeability
Heat capacity
External energy required to increase temperature of a solid
mass is known as the material’s heat capacity, it is defined as
its ability to absorb heat energy. Heat capacity is not an
intrinsic property i.e. it changes with material volume/mass.
Specific heat - For comparison of different materials, heat
capacity has been rationalized. Specific heat is heat capacity
per unit mass. It has units as J/kg-K or Cal/kg-K. With
increase of heat energy, dimensional changes may occur.
Hence, two heat capacities are usually defined. Heat capacity
at constant pressure, Cp, is always higher than heat capacity at
constant volume; Cv. Cp is only marginally higher than Cv.
Heat is absorbed through different mechanisms: lattice
vibrations and electronic contribution.
Thermal expansion: Increase in temperature may cause
dimensional changes. Linear coefficient of thermal expansion
(α) defined as the change in the dimensions of the material per
unit length.
Thermal conductivity: It is ability of a material to transport
heat energy through it from high temperature region to low
temperature region. Heat energy transported through a body
with thermal conductivity. It is a microstructure sensitive
property and has units as W/m.K.
Thermal stresses: Stresses due to change in temperature or due
to temperature gradient are termed as thermal stresses.
Thermal stresses in a constrained body will be of compressive
nature if it is heated, and vice versa. Engineering materials can
be tailored using multi-phase constituents so that the overall
material can show a zero thermal expansion coefficient. Eg.:
Zerodur - a glass-ceramic material that consists of 7080%

National Journal of Multidisciplinary Research and Development
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crystalline quartz, and the remaining as glassy phase. Sodium-
zirconium-phosphate (NZP) have a near-zero thermal
expansion coefficient.
Air Permeability: The air permeability is a very important
factor in the performance of some textile materials.
Especially, it is taken into consideration for clothing,
parachutes sails, vacuum cleaners, fabric for air bags and
industrial filter fabrics. The air permeability is mainly
dependent upon the fabric’s weight and construction.
Water vapour permeability: Water vapor permeability is a
measure of the passage of water vapor through the material. It
is also known as water vapor transmission rate (WVTR) or
moisture vapor transmission rate (MVTR). It is the mass of
water vapor transmitted through a unit area in a unit time
under specified conditions of temperature and humidity.
Breathability or also referred to as Water Vapor Permeability
can be described as the ability of a fabric to allow
moisture vapor to be transmitted through the material.
Wicking
Moisture transfer properties and drying rate of fabrics are two
major factors affecting the physiological comfort of garments.
Moisture transfer and quick dry behavior of textiles depend
mainly on the capillary capability and moisture absorbency of
their fibers. These characteristics are especially important in
sport garments next to the skin or in hot climates. In these
situations, it is critical that textiles are able to absorb large
amounts of perspiration, draw moisture to the outer surface
and keep the body dry. Therefore, in order to optimize these
functionalities in sport clothing, and to support moisture
management claims, it is necessary to determine the wicking
behavior and quick drying capability of functional fabrics.
Methodology
Flow Chart
MSJ -Modal Single Jersey
MTW - Modal Twill
MCT - Modal Cross Tuck
MCM - Modal Cross Miss
Fabric Production
(Production of Weft Knitted Fabric with 0.30cm Loop Length)
The following stitch combination of fabrics are produced for
our study
 Knit Stitch - Single Jersey
 Knit and Tuck - Cross Tuck
 Knit and Miss - Cross Miss
 Knit, Tuck & Miss - Knitted Twill
Single Jersey
Jersey fabric is a type of knit textile made from cotton or a
cotton and synthetic blend. Some common uses for jersey
fabric include t-shirts and winter bedding. The fabric is warm,
flexible, stretchy, and very insulating, making it a popular
choice for the layer worn closest to the body. Jersey also tends
to be soft, making it very comfortable.
Tuck and miss stitch
Apart from the knitted loop stitch the two most commonly
produced stitches are the tuck stitch and the miss stitch (float
stitch).
Tuck
A tuck stich is composed of a held loop, one or more tuck
loops and knitted loops. It is produced when a needle holding
its loop also receives the new loop. The tuck loop assumes an
inverted U-shaped configuration.
Miss
A miss stitch or float stich is composed of a held loop, one of
more float loops and knitted loops. It is produced when a
needle holding its old loop fails to receive the new yarn that
passes, as a float loop to the back of the needle, and to the
reverse side of the resultant stitch.
Twill
Twill is a type of textile weave with a pattern of diagonal
parallel ribs (in contrast with a satin and plain weave). This is
done by passing the weftthread over one or more warp threads
then under two or more warp threads and so on, with a "step,"
or offset, between rows to create the characteristic diagonal
pattern [1]. Because of this structure, twill generally drapes
well.
Thermal comfort characteristics of samples
The air permeability of the knitted fabric structures were
measured with the Air Permeability Tester following the
ASTM D 737 standard. Thermal conductivity is an intrinsic
property of material that indicates its ability to conduct heat.
Lee’s disk instrument was used to measure the thermal
conductivity according to Standard ASTM D1518, GB/T
11048-1989. The evaporative dish method based on BS
7209:1990 was used to determine the water vapour
permeability of the fabrics. A strip of 20 cm × 2.5 cm test
fabric at 20°C & 65% RH was suspended vertically with its
lower edge (0.5 cm) immersed in a reservoir of distilled water.
The rate of rise of the leading edge of the water was then
monitored for longitudinal wicking. The static immersion
method, which follows Standard BS 3449 [26] was used to
evaluate the amount of water absorbed by the fabric. (Journal

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of Engineered Fibers and Fabrics http://www.jeffjournal.org
Volume 12, Issue 1 – 2017)
Thermal Conductivity
Before testing the sample must be conditioned. Sample
conditioning is done by Humidity Chamber. Specifications of
Humidity Chamber are as follows;
 Machine Name – Humidity Cabinet
 Make- MAG Solvics PVT LTD, Coimbatore
 Serial No-7854670016
 Year-2017
 Capasity-20-90% RH
 Product Name-MAG-G0651
The conditioning process is as follows
 Keep the sample inside the cabinet tray.
 The chamber door has to be closed after keeping the
sample inside. The sample can be seen from outside
through inspection glass of humidity cabinet.
 Conditioning Fabric: 21±2 ˚C or 27 ± 2˚C
 Relative humidity (RH): 65±2% in chamber for 24 hours
before testing.
 ASTM-1777 standard for the sample conditioning.
After conditioning the required sample is ready to test for the
Thermal Conductivity Tester.
Air Permeability Test
Air permeability was measured in accordance with ASTM
D737-04 [22], by the Tex-Test air permeability tester (FX3300,
Switzerland). The air permeability is expressed as the quantity
of air in cubic centimetres passing through a square centimetre
of fabric per second (cm3/sec∙cm2). The air permeability tests
were done at a test pressure drop of 100 Pa (20 cm² test area).
The average of five measurements was used for comparison.
The air permeability is a very important factor in the
performance of some textile materials. Especially, it is taken
into consideration for clothing, parachutes sails, vacuum
cleaners, fabric for air bags and industrial filter fabrics. The
air permeability is mainly dependent upon the fabric’s weight
and construction.
Results and discussion
In this study, the results on the thermal comfort properties of
air permeability, & thermal conductivity, has been seen and
discussed.
Air Permeability Test
Air permeability test of Modal fabric
The test result of regenerated cellulosic fabric of Modal 100%
of different structure is shown in the table & figure.
Table 1: Air permeability of Modal fabric.
Sample Specification
Air permeability (cm3/cm2/sec)
MCT
275.6
MTW
310
MSJ
241.2
MCM
289.8
Fig 1: Air permeability of Modal fabric.
From the above result it is clear that the fabric of modal from
the four structures in the test of the air permeability of bi-layer
knitted fabrics can decrease with increased stitch density and
thickness. So it is conclude that Air permeability of Modal
Twill gives good result compared to single jersey, cross miss,
cross tuck.
Thermal Conductivity of Modal fabric
Table 1: Thermal Conductivity of Modal fabric - Insulation rate
Sample
MCT
MCM
MSJ
MTW
Insulation Rate T.R
14.15%
18.31%
15.07%
11.36%
Fig 2: Thermal Conductivity of Modal fabric - Insulation rate

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1267
Among the four structural variation of modal cross tuck,
modal cross miss, modal twill, modal single jersey. The
insulation rate of thermal conductivity of modal cross miss
gives good result among the other knit structure.
Table 2: Thermal Conductivity of Modal fabric – Heat Transfer
Coefficient HTC
Sample
MCT
MCM
MSJ
MTW
Heat Transfer Coefficient HTC
64.11
46.95
59.23
81.97
Fig 3: Thermal Conductivity of Modal fabric - Heat Transfer
Coefficient HTC
In heat transfer coefficient among the modal single jersey,
modal twill, modal cross miss, modal cross tuck it is seen that
modal twill gives the good performance then the other one.
Thermal Conductivity of Modal fabric - CLO VALUE
Table 3: Thermal Conductivity of Modal fabric – CLO VALUE
Sample
MCT
MCM
MSJ
MTW
CLO Value
0.1
0.13
0.11
0.07
Fig 4: Thermal Conductivity of Modal fabric - CLO VALUE
Thermal conductivity of CLO VALUE among the modal 4
structure of single jersey, twill, cross miss, cross tuck the
result is seen that modal cross miss gives the good result.
Summary & Conclusions
A “Warm - cool feeling” is a very important property, as a
result of which a human can feel comfort or discomfort in
various activities and environmental conditions. This feeling
could be achieved by using different types of yarns. It was
determined that higher air permeability is characterized for
knits manufactured only from pure yarns.
The thermal comfort properties of single jersey fabrics made
from yarns of 100% Modal yarns were investigated.
It is observed that the parameters of air permeability, and
thermal conductivity are significantly affected by the Moisture
Vapour Transport.
However if the wearer performs mild activities, skin wetness
is very low and thermal comfort is managed by skin
temperature. The fabrics’ of air permeability and thermal
conductivity are determining properties for thermal comfort,
Fabrics must have high air permeability and low thermal
resistance. Modal fabrics with single jersey structure fulfill
these requirements as well as offering the advantages cited at
the outset of this work.
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