209

CHAPTER 7

DESIGN AND DEVELOPMENT OF MULTILAYERED

HOSPITAL TEXTILES

7.1 INTRODUCTION

This part of the research work deals with design and development

of multi layered knitted and woven fabrics for hospital textiles and analysis of

their comfort characteristics. Tri-layered knitted and woven fabrics were

developed using the fibres like lyocell, bamboo charcoal, bamboo and micro

polyester in different combinations.

The tri-layer fabric comprise of two fabric layers joined together by

a connecting yarn. The tri-layer weft knitted fabric is soft, with good thermal

conductivity and wickability, which appeals to the comfort properties of the

user. This fabric possesses certain exceptionally good functional

characteristics, such as moisture absorbency, where the moisture from the

body is absorbed by the base layer, passed through the connecting layer and

gets evapourated from the top layer.

7.2 Production of Multi layered structure

Four types of tri-layer fabrics were constructed from lyocell, bamboo

charcoal, bamboo and micro polyester yarns in two different combinations.

The fibre composition of the different types of multi layered fabrics produced

are given in the Table 7.1.

210

Table 7.1 Composition of Multi layered structures

S.No Multi layered

fabric

Top layer Connecting

Layer

Bottom

Layer

1 Knitted fabric 1

BC:L/MP/L

Bamboo

charcoal

/Lyocell

Micro polyester Lyocell

2 Knitted fabric 2

B/MP/L

Bamboo Micro polyester Lyocell

3 Woven fabric 1

BC:L/MP/L

Bamboo

charcoal/

Lyocell

Micro polyester Lyocell

4 Woven fabric 2

B/MP/L

Bamboo Micro polyester Lyocell

7.2.1 Production of Weft Knitted Tri-layer Fabrics

Weft knitting machine with two sets of needles has the ability to

create two individual layers of fabric that are held together by tucks. Such a

fabric was referred as a double-faced fabric, also called as tri-layer fabric.

Doubleface fabrics can be produced on dial and cylinder machines. It requires

the use of at least three different yarns for each course of visual fabric. 1)

Yarn for the cylinder needles, 2) Yarn for the dial needle, 3) A binding yarn,

connecting the two layers. The distance between the two fabrics can be

manipulated by dial height adjustment, ultimately determining the amount of

yarn being put between the two fabrics. The degree of space or height

between the two fabric faces is determined in the circular knitting machine by

the setting of the dial height relative to the machine cylinder.

Sequence of operation in knitting tri-layer fabric is given in the

Figure 7.1.

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Figure 7.1 Knitting sequence of Tri-layer fabric

a) Tucking on dial and cylinder needles at the same feeder

b) Tucking on the dial and cylinder needles on feeders 1 and 4

on low and high butt needles alternately (this connects the

two layers together)

c) Knitting dial needles with dial yarn at feeders 2 and 5 on low

and high butt needles alternately

d) Knitting cylinder needles with cylinder yarn at feeders 3 and

6 on low and high butt needles alternately

The details of knitting machine used for knitting tri-layer fabric is

given in the Table 7.2.

Table 7.2 Parameters of knitting machine

Feeders 72

Number of needles 32*18

Diameter 32”

Gauge 18

Machine speed 20-25 rpm

Machine Make Germany

Company Fomaco

212

The cam diagram used for the production of multi layered knitted

fabric is shown in the Figure 7.2 below.

Front layer back layer middle layer

Figure 7.2 Cam arrangements to knit Tri-layer structure

The tri-layer knitted fabrics were produced in two fibre

combinations such as bamboo charcoal / micropolyester / lyocell and bamboo

/ micropolyester / lyocell. In bamboo charcoal / micropolyester / lyocell

combination, the top layer contains bamboo charcoal and lyocell yarns and

the bottom layer contains lyocell yarn, and the micro polyester acts as the

connecting layer. Similarly in the bamboo / micropolyester / lyocell

combinations, the top layer contains bamboo yarn and the bottom layer

contains lyocell yarn, and the micro polyester acts as the connecting layer.

7.2.2 Production of Woven Tri-layer Fabrics

The tri-layer woven fabric was produced in a sample loom using

three warp sheets and two types of weft yarns. In bamboo charcoal / micro

polyester / lyocell combination fabric, the top layer contains bamboo charcoal

yarn in warp direction and lyocell yarn in the weft direction. Lyocell is

introduced in the weft direction to ensure maximum moisture spreading along

the width of the fabric, so that the wetness is transferred away from the body

213

of the patient. The bottom layer is made of lyocell to ensure rapid absorption

of water from the inner layer and faster drying. The connecting layer is made

of micro polyester warp which interweaves with the face and back weft

alternatively, assisting in moisture transfer from the inner layer to the outer

layer. Micro polyester with high wicking ability acts as an efficient medium

to transfer moisture from the inner layer to the outer layer. The weave

structure is given in the Figure 7.3.

Figure 7.3 Weave structure of Tri-layer woven fabric

In the bamboo / micro polyester / lyocell combination fabric,

bamboo yarn is used in the top layer and lyocell yarn in the bottom layer. The

connecting layer is made of micro polyester warp. The four tri-layer fabrics

produced were tested for fabric parameters and comfort properties and are

given in the Table 7.3 and Table 7.4.

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Table 7.3 Parameters of Tri-layer Fabrics

Sam

ple

.N

o

En

ds(

or)

wale

s/in

ch

Pic

ks(

or)

cou

rse/

inch

Fab

ric

wei

gh

t

(g/m

2)

Fab

ric

thic

kn

ess

(mm

)

Wa

rp S

tren

gth

(kg

f)

Warp

Elo

ngati

on

(%)

Wef

t S

tren

gth

(kg

f)

(%)

BC/MP/L (Knit) 15.74 9.5 306 .73 Bursting strength 63kgf

B/MP/L (Knit) 15.74 9.5 248 .75 Bursting strength 55kgf

BC/MP/L

(Woven)

27.6 20 162 .60 130 24.75 80 28.75

B/MP/L (Woven) 27.6 20 174 .53 193 23.91 100 33.83

215

Table 7.4 Comfort properties of Tri-layer Fabrics

Ab

sorp

tio

n(s

ec)

Sam

ple

No

Air

per

mea

bil

ity

Th

erm

al

con

du

ctiv

ity

W/M

/K

Wa

ter

va

po

ur

per

mea

bil

ity

(g/m

2/d

ay

)Face Back

Sp

rea

din

g a

rea

Fa

ce (

cm2)

Sp

rea

din

g a

rea

Back

(cm

2)

Ver

tica

l w

ick

ing

(Wa

rp)

) (c

m)

Ver

tica

l w

ick

ing

(Wef

t) )

(cm

)

Inp

lan

e w

ick

ing

(g

/cm

2)

(5s)

Inp

lan

e w

ick

ing

(g/c

m2)

(10s)

BC/L/MP

(KNIT)77.84 0.0361 2556.56 1.548 3.944 3.52 3.94 15.0 11.0 2.07 3.45

B/L/MP

(KNIT)65.55 0.0316 2543.88 3.924 4.100 3.14 4.90 10.0 11.5 1.97 2.08

BC/L/MP

(WOVEN)31.13 0.0314 2228.67 1.998 2.136 7.50 9.50 12.0 10.0 1.06 1.56

B/L/MP

(WOVEN)20.75 0.0418 2193.82 4.220 4.120 9.00 11.00 8.5 9.0 2.02 2.78

216

7.3 RESULTS AND DISCUSSION

The comfort properties of the multilayered fabrics were analyzed

and are discussed below.

7.3.1 Air Permeability of multi layered fabrics

Air permeability is a measure of the amount of air passing through

a fabric and the air permeability of the tri-layer fabrics are shown in the

Figure 7.4.

Figure 7.4 Air permeability of multilayered fabrics

Better air permeability is noticed in the case of bamboo charcoal/

lyocell / micro polyester tri-layer fabrics in both woven and knitted structures.

The bamboo lyocell combination has comparatively lower air permeability.

The higher air permeability of bamboo charcoal combination may be

attributed to the highly porous structure of bamboo charcoal. Compared to

woven tri-layer fabrics, knitted fabrics have higher air permeability due to the

loop structure. Obviously, the multi layered structures have lower air

permeability than the single layered structures.

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7.3.2 Thermal conductivity of multilayered fabrics

The thermal conducting behaviour of multi layered fabrics is shown

in the Figure 7.5.

Figure 7.5 Thermal conductivity of multilayered fabrics

The bamboo charcoal fabrics exhibit higher thermal conductivity

when compared to bamboo/lyocell combinations. Bamboo charcoal as well as

bamboo fibers have very good thermal conductivity required for human

comfort. The woven tri-layer fabric made of bamboo charcoal / lyocell

combination has higher thermal conductivity values than the remaining three

fabrics. The thermal conductivity of tri-layer fabric remains similar to that of

single layered fabrics.

7.3.3 Water vapour permeability of multilayered fabrics

The amount of water vapour passing through the multi layered

fabrics is shown in the Figure 7.6. The tri-layer fabrics maintain the same

trend as the single layered fabrics in the water vapour management. The

highest water vapour permeability is observed in case of bamboo charcoal tri-

layer fabrics, which may be due to the presence of carbon particles in the fiber

218

and also the highly porous nature of bamboo charcoal leading to higher water

vapour permeability and higher water absorption.

Figure 7.6 Water vapour permeability of multilayered fabrics

The woven tri-layer fabric has lower water vapour permeability

than knitted fabrics.

7.3.4 Water absorbency of multi layered fabrics

The rate of water absrption, measured in face and back of the four

tri-layered fabrics are shown in the Figure 7.7.

Figure 7.7 Water absorption of multilayered fabrics

219

The bamboo charcoal fabrics were noticed to have higher water

absorbing tendency owing to the combination of three fibers having excellent

moisture absorbing and transporting property. Presence of bamboo charcoal,

micro polyester and lyocell leads to rapid absorption of moisture. Bamboo /

lyocell combination also has good moisture absorbing property. The tri-layer

fabrics exhibit very good water absorbency compared to single layered

structures, resulting in immediate transfer of moisture to inner layers and

hence gives a dry feel. This property is essential to keep the patient dry and

hence avoids problem created by wet skin.

7.3.5 Spreading area of multi layered fabrics

The extent to which a drop of water, spreads in warp and weft

direction or in course and wales direction of the fabric is shown in the Figure

7.8.

Figure 7.8 Spreading area of multilayered fabrics

In the Bamboo charcoal multi layer fabrics, the bamboo char coal

surface has lower spreading area when compared to the lyocell side of the

fabric. This trend has already been noticed in single layered structures.

Similar trend is seen in bamboo/lyocell union fabrics, lyocell side of the

fabric spreads more than the bamboo side of the fabric. Tri layer woven

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fabric spreads water to a greater extent and it exhibits more distribution of

water in the warp and weft direction.

7.3.6 Vertical wicking of multi layered fabrics

The height to which water is wicked in ten minutes, in both warp

and weft directions is shown in the Figure 7.9.

Figure 7.9 Vertical wicking of multilayered fabrics

The bamboo charcoal tri-layer fabric exhibits higher wicking

tendency due to the presence of bamboo charcoal and micro polyeater

combinations. Compared to single layered fabrics, multi layered structure has

almost 3 to 4 times increase in wicking height. The bamboo / lyocell

combination tri-layer structure shows lower wickability but still 3 to 4 times

higher than that of single layered structure.

7.3.7 Inplane wicking of multi layered fabrics

The amount of water absorbed along the plane of the multi layered

fabrics in five and ten seconds respectively are shown in the figure 7.10. The

bamboo charcoal/lyocell combination fabric absorbs more moisture when

compared to the bamboo/ lyocell fiber combination. This is again due to the

micro porous structure of bamboo charcoal and micro fiber combinations.

221

Figure 7.10 Inplane wicking of multilayered fabrics

When compared to single layered fabrics, the bamboo charcoal

combination tri-layer fabric absorbs around 250 times more water which is

exclusively due to the multi layer structure and combination of moisture

absorbent fibers. The bamboo fiber based multi layered structure shows

29 times more water absorption when compared to the corresponding single

layered structure. This higher absorbing tendency of the multi layered

structure results in absorption of more amount of sweat from the skin and

hence keeps the patient in comfort zone.

7.3.8 Drying rate of multi layered fabrics

The time taken to dry a fabric which is wetted with water of 30%

on the weight of the fabrics are shown in the Figure 7.11. Quick drying

capability of a fabric could be evaluated by its drying rate.

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Drying Rate

0

10

20

30

40

50

60

70

10 min 20 min 30 min 40 min

RW

R%

BC/L/MP (KNIT)

B/L/MP (KNIT)

BC/L/MP (WOVEN)

B/L/MP (WOVEN)

Figure 7.11 Drying rate of multilayered fabrics

From the figure, it is observed that bamboo charcoal fabrics have

faster drying rate and addition of lyocell delays the drying time of the fabrics

as the moisture content of lyocell fiber is more than the polyester based

bamboo charcoal yarns. But still the bamboo charcoal/ lyocell combination

dries faster than the bamboo/lyocell combinations.

7.4 DEVELOPMENT OF MULTILAYER COMBINATION

FABRICS

Three multi layered combination fabrics were developed by

combining three single layered fabrics together by arranging the fabrics one

over the other. Different combinations of fabric layers were prepared based on

their ability to complement and maximize the essential comfort properties of a

bed linen. Considering the moisture management property as the key factor,

various fabric combinations were analyzed and the following combination of

fabric layers were selected and tests were carried out to analyze the comfort

characteristics.

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Lyocell terry pile with Lyocell twill fabric (LP/LT)

Lyocell terry pile with micro polyester twill fabric(LP/MPT)

Lyocell terry pile with cool finished single jersey knitted

fabric (LP/K)

Two layers of lyocell terry pile structures were used as base layer

over which three different fabrics were tried as top layers. Terry pile structure

is selected as the base layer because of its higher absorbing tendency and

resilience. For the top layer, the fabrics having smooth surface such as

lyocell twill, micro polyester twill woven fabrics and a single jersey cotton

fabric treated with cool finish were used. The fabric parameters of the multi

layer combination fabrics are shown in the Table7.5.

Table 7.5 Parameters of Tri-layer combination Fabrics

S.No Fabric type

Yarn

count

(Ne)

Fabric

structure

Ends

/cm

Picks

/cm

Fabric

weight

g/m2

Fabric

thickness

(mm)

1 Lyocell 30 Terry Pile 10 7 240 0.310

2 Lyocell 30 Twill 11 9 150 0.135

4 Cotton(cool

finish)

30 Single

jersey

7.87

wpcm

9.8

cpcm

150 0.150

5 Micro-

polyester

32Twill

11.8 9 70 0.140

The above listed multilayered combination fabrics were tested and

analyzed for their comfort properties and the reslts are given in the Table 7.6.

From the table it is clear that the multilayered combination fabrics having

lyocell terry pile with lyocell twill combination, has higher air permeability

followed by the fabric with lyocell pile with micropolyester twill combination

fabrics.

224

Table 7.6 Properties of Tri-layer combination Fabrics

S .

No

Air

per

mea

bil

ity

(cm

3/c

m2/s

)

Th

erm

al c

on

du

ctiv

ity

(w/m

/k)

Wat

ervap

our

per

mea

bil

ity

(g/m

2/d

ay)

Wat

er A

bso

rpti

on

(sec

)

Spre

adin

gar

ea

(cm

2)

Ver

tica

l w

ickin

g

(War

p)

) (c

m)

Ver

tica

l w

ickin

g

(Wef

t) )

(cm

)

Inp

lan

e w

ick

ing

(g/c

m2)

(5s)

Inp

lan

e w

ick

ing

(g/c

m2)

(10s)

Fri

ctio

nal

Fac

tor

(sta

tic)

Fri

ctio

nal

Fac

tor

(dy

nam

ic)

Lyocell pile

with knitted

cotton

51.89 0.0361 2838.5 3 1.60 3.0 3.4 0.013 0.015 9.64 8.74

Lyocell pile

with Lyocell

Twill

73.26 0.0373 3015.91 5 0.58 3.2 3.8 0.014 0.22 8.04 7.11

Lyocell pile

with

micropolyester

twill

88.96 0.0382 5410.9 5.5 0.59 3.4 4.0 0.017 0.025 8.24 7.42

Thermal conductivity is found to be higher for lyocell pile and cool

finished knitted fabric combination, followed by lyocell pile and lyocell twill

combination. This shows that these two combinations can conduct away heat

from the body easily and keeps the patient cool. All the three combinations

exhibited very good water absorbency resulting in immediate transfer of

moisture to inner layers and ensures dry feel. Regarding the water spreading

area, lyocell pile and cool finish combination immediately spreads the drop of

water to maximum extent and proves its water management ability. Lyocell

pile, micro polyester twill combination shows higher wicking tendency due to

more inter fibrillar capillary space.

An analysis of all the overall performance of these fabrics ensures

that the lyocell pile and lyocell terry combination proves to be a suitable

225

combination for hospital textiles in all aspects likes air permeability, thermal

conductivity and moisture management property.

7.5 CONCLUSIONS

Based on the analysis of the multi layered knitted and woven

fabrics made of bamboo charcoal / lyocell / micro polyester combinations and

bamboo / lyocell / micro polyester combinations, the following conclusions

are arrived:

Higher air permeability, water vapour permeability, water

absorbing tendency, wicking tendency and faster drying rate

are noticed in the case of bamboo charcoal /micro polyester /

lyocell tri-layer fabrics for both woven and knitted structures.

The woven tri-layer fabric made of bamboo/lyocell

combination has higher thermal conductivity value.

Generally, multi layered structures have better moisture

management properties when compared to single layered fabrics. The knitted

multilayered fabric is a more suitable choice for hospital textile application

because of its comfort and elongation characteristics. Similarly, multilayered

bed sheets made of lyocell twill: lyocell pile combination proves to be a

suitable combination for hospital textiles. Hence use of multi layered fabrics

can improve the comfort properties of hospital textiles.