effect of hollow polyester fibres on mechanical properties...

Fibers and Polymers 2009, Vol.10, No.4, 452-460

452

Effect of Hollow Polyester Fibres on Mechanical Properties of

Knitted Wool/Polyester Fabrics

A. Khoddami, C. M. Carr1, and R. H. Gong

1*

Department of Textile Engineering, Isfahan University of Technology, Isfahan, 84156-8311, Iran1School of Materials, the University of Manchester, Manchester, M60 1QD, UK

(Received July 4, 2008; Revised November 12, 2008; Accepted March 27, 2009)

Abstract: The physical and mechanical characteristics of hollow polyester fibres were compared with solid polyester fibresin order to establish their processing behaviour and performance characteristics. The effects of hollow fibres on fabric proper-ties were investigated by using microscopy and tests of tensile and bursting strength, pilling, abrasion resistance, watervapour permeability, and handle. The results show that tensile strength of hollow polyester fibres and yarns are negativelyaffected by the cavity inside the fibre. Hollow fibres also have higher stiffness and resistance to bending at relaxed state. Fab-rics made from hollow polyester/wool blends and pure wool fabrics show three distinguishable steps in pilling. During pill-ing, hollow fibres break before being pulled fully out of the structure, leading to shorter protruding fibres. Microscopy studiesshowed that the breakdown of hollow fibres started during entanglement by splitting along the helical lines between fibrils.KES results showed that the friction between fibres and the fibre shape are the most important parameters that determine thefabric low stress mechanical properties. However, in some aspects, the hollow structure of the fibre does not have a signifi-cant effect.

Keywords: Hollow fibre, Knitted fabric, Pilling, Wool/polyester, Mechanical property

Introduction

Hollow fibre production by changing the shape of the

spinning nozzle is a physical modification of polyester (PET)

during fibre production to achieve new properties [1-4].

Synthetic fibres for general commercial application are mostly

solid filament or solid fibre yarns. Hollow fibres have benefits

for specific applications due to the larger fibre surface/volume

ratio [1].

A change in the shape of the cross-section in man-made

fibres affects many physical characteristics such as sorption,

dyeability, touch, pilling resistance, abrasion, weight, bulk,

thermal properties, insulation capacity, glistening, lustre,

covering and opaqueness [1,4,5]. Fibre cross-section shape

also affects the fabric hand [6,7] and the changed hand of the

hollow fibres can be conveniently utilized in wool/polyester

blended yarns [3]. Furthermore, hollow fibres must have

sufficient mechanical qualities for the selected end uses. In

this research, the natural properties of wool are combined

with hollow polyester fibres to develop novel products with

enhanced performance. In this paper, the results on the fabric

mechanical properties and fabric hand are presented.

Experimental

Solid and hollow polyester fibres (hole diameter to fibre

diameter ratio of 25%), and Super-wash treated wool were

supplied and spun by Bulmer & Lumb, Bradford, UK. Yarns

were knitted using Stoll weft flat knitted machine in the

University of Manchester. The material properties are listed

in Table 1. The yarns were top-dyed commercially with

different colours using HT methods by Bulmer & Lumb. It is

noteworthy that the yarn samples were manufactured in

industrial scale. Therefore, chosing hollow and solid polyester

fibre fabrics with the same shade was unfortunately impossible.

Sodium carbonate (from Tennents) and non-ionic detergent,

Alcapol NFC (from Ciba) were used for washing and

relaxation of the knitted fabrics.

The knitted samples were washed with a 0.5 g/l non-ionic

detergent, pH 8-9 (sodium carbonate) at 40-50 ºC for 30

minutes. The fabrics were then washed off at 35-40 ºC for 45

minutes and cooled gradually, and finally rinsed cold and air

dried without any tension.

Fabric mechanical properties were compared by measur-

ing fibre and yarn tensile strength, yarn-on-yarn dry abrasion,

fabric bursting strength, pilling, abrasion resistance, hand,

and water vapour permeability. Fibre topography was analysed

after pilling and abrasion tests using SEM (Hitachi S-3000

N).

Fibre tensile testing was performed in accordance with BS

3411:1971 on an Instron 5564 with a sample length of 20

mm and crosshead speed of 10 mm/min. Breaking force and

elongation at break of yarns were measured according to BS

2062:1995, with gauge length of 250 mm, crosshead speed

of 250 mm/min, and 50 tests for each sample. The results of

tensile tests are reported by confident limit of 95 %.

Yarn-on-yarn abrasion resistance was evaluated by equip-

ment built at the University of Manchester [8]. The test

essentially involves subjecting two yarn sections, wrapped

helically together, to a reciprocating motion under tension

until failure.

Bursting strength was tested according to BS 13938-*Corresponding author: [email protected]

DOI 10.1007/s12221-009-0452-7

Effect of Hollow Polyester Fibres on Mechanical Properties Fibers and Polymers 2009, Vol.10, No.4 453

1:1999 on a Mullen Burst Tester with sample area of 50 cm2,

20 seconds time to burst and 10 tests per sample.

The pilling ratings were studied according to BS 12945-

2:2000 by a Martindale Abrasion Tester on scoured and

relaxed sample under 9 KPa pressure and different number

of rubs including 125, 500, 1000, 2000, 5000, and 7000.

Pilling resistance was determined by comparison with

standard pictures in a light cabinet.

The abrasion resistance was measured on a Martindale

Wear & Abrasion Tester according to BS 12947-2: 1999.

The mass loss during abrasion was measured according to

BS 12947-3: 1999 on scoured and relaxed samples under 9

KPa pressure. The occurrence of one broken thread (observed

under Vickers Zoomax Light Microscope) was considered as

the end point. It should be mentioned that when pilling was

observed on the specimen, the test was continued without

cutting off the pills.

The fabric hand was tested using the Kawabata Evaluation

System (KES). Four tests were carried for each KES

parameter. Water vapour permeability of fabrics was carried

out in accordance with BS 7209-1990 using an Equiptex

Water Vapour Permeability Tester on conditioned samples.

The water temperature was 20±2 ºC and its surface height to

fabric was 1 cm. After establishing equilibrium (1 hr), weight

measurements were done after 6 and 24 hrs.

The Water Vapour Permeability (WVP) in g/m2/day was

calculated by the following formula:

WVP = 24M/At (1)

Where

M is the loss in mass of the assembly over the time period

t (in g);

t is the time between successive weighing of the assembly

(in hr);

A is the area of exposed test fabric (internal area of the test

dish) (in m2).

The Water Vapour Permeability Index is given by:

I = {(WVP)f / (WVP)r}×100 (2)

Where

(WVP)f is the mean Water Vapour Permeability of the

fabric under test;

(WVP)r is the Water Vapour Permeability of the reference

fabric (a high tenacity polyester woven with monofilament).

Results and Discussions

The tensile properties of hollow fibres are compared with

those of solid fibres in Table 2. Hollow fibres tend to have

lower tenacity, with the other tensile properties affected by

the dyeing process, high temperature top dyeing. In parti-

cular the black fibres appear to have lower tenacity but

higher elongation. Yarn and fabric properties are shown in

Table 3. Solid fibre blended yarns have the highest tenacity

while the pure wool yarn has the lowest tenacity. As can be

seen the yarn produced from hollow fibres have lower

tenacity and wear resistance. The reason for the differences

in tenacity will be discussed further along with the pilling

results.

The lower resistance to abrasion of the hollow fibre yarns

may be attributed to the higher surface friction of the hollow

Table 1. Properties of materials used and knitted fabric construction parameters

Wool fibre

(micron)

Polyester fibre

(dtex)

Yarn count

(Nm)

Twist (tpm)

single two-fold

Blend composition (%)

wool PES

Knit

structure

Knit density (per cm)

wale course

21.5 3.3 28/2 430 220 (ZS) 60 40 Plain 5 8

Table 3. Mechanical properties of yarns and knitted fabrics

SampleYarn tenacity

(cN/tex)

Yarn elongation

(%)

Yarn on yarn abrasion

(cycles)

Fabric bursting strength

(kPa)

Fabric abrasion resistance

(1,000 cycles)

SP/W* Black 31.80 ± 0.56 12.95 ± 0.22 19400 ± 420 1078 ± 61 40.7 ± 0.65

SP/W Charcoal 31.03 ± 0.56 11.78 ± 0.15 16200 ± 260 1117 ± 65 37.2 ± 0.86

HP/W** Brown 25.34 ± 0.69 12.16 ± 0.56 5700 ± 60 1045 ± 34 19.9 ± 0.35

HP/W Charcoal 27.86 ± 0.57 13.56 ± 0.24 5500 ± 180 1048 ± 37 15 ± 0.23

HP/W Darkblue 25.04 ± 0.68 12.89 ± 0.58 6100 ±230 1031 ± 25 23.95 ± 0.40

Wool 14.28 ± 0.31 7.539 ± 0.51 − 845 ± 41 12.5 ± 0.57

*SP/W: solid polyester/wool blends fabric, **HP/W: hollow polyester/wool blends fabric.

Table 2. Polyester fibre tensile properties

SampleTenacity

(cN/dtex)

Elongation

(%)

Solid white fibres 41.6 ± 0.31 12.3 ± 0.22

Solid black fibres 40.6 ± 0.53 16.4 ± 0.46

Hollow white fibres 39.1 ± 0.42 10.4 ± 0.34

Hollow black fibres 37.1 ± 0.71 21.6 ± 0.68

454 Fibers and Polymers 2009, Vol.10, No.4 A. Khoddami et al.

fibres, or to the greater contact area or inherent weakness of

the hollow fibres [2,4,9].

The pure wool fabric has much lower bursting strength in

comparison with polyester/wool blended fabrics. This is

likely due to the greater elongation of the blended yarns

[10]. During the bursting strength test, fabric starts to fail

from the direction with the lowest breaking extension. The

reason for this phenomenon is that, when the fabric is

stressed in all the directions in the test, the fabric direction

with thr lowest elongation at break is the one that will fail

first. Consequently, this direction is not necessarily the

direction with the lowest strength. Therefore it was expected

that the wool fabric would have the lowest bursting strength

as it has the lowest extension. In addition, using hollow

polyester fibres increased the fabrics bursting strength

significantly as compared with the pure wool fabric.

The fabric pilling performance is compared in Table 4. At

low levels of mechanical action, no pills formed and the only

visible change was fuzz formation. After 500 rubs, however,

the entanglement phase started, with pills forming. After

higher mechanical abrasion, the apparent pilling was reduced

and with pill removal becoming the predominant process.

These three steps can be clearly seen for samples composed

of 100% wool, and the hollow polyester/wool fabrics with

dark blue and brown colours. Also the results show that the

hollow fibre samples have lower pilling tendency and higher

rate of pill wear-off than solid fibre samples. The differences

between the two types of polyester fibres can be seen in

Figures 1 to 5, with Figure 1 indicating the high pill density

of solid polyester fibre fabrics resulted from the high abrasion

resistance and strength of polyester fibres. The solid fibre

fabrics are less affected by the pill wear-off. Although some

wool fibres can be observed in the pills, the main component

is polyester, with multiple fibre splitting fatigue resulting in

the wear-off of the wool fibres.

With hollow fibres having lower strength than the solid

polyester fibres, the associated effect is that pill wear-off is

faster for hollow fibres. After 5000 rubs, their pilling ap-

pearance is clearly better (Figure 2, as compared with Figure

1). It was reported that the greater the breaking strength and

Table 4. Pilling performance of knitted fabrics

Sample \ number of rubs 125 500 1000 2000 5000 7000 Average

SP/W Black 5 4 3-4 2-3 3 2-3 3.5

SP/W Charcoal 5 5 3 2-3 1-2 1 3.0

HP/W Brown 5 5 4-5 3-4 5 5 4.7

HP/W Charcoal 5 5 4-5 3-4 4 4 4.3

HP/W Darkblue 5 4-5 4-5 3-4 4-5 5 4.5

Wool 5 4 3-4 4 5 5 4.4

Figure 1. Pilling of solid polyester/wool fabrics after 7000 rubs.

High pill density on the fabric surface is evident with solid polyester

fibres as a main component, with multiple wool fibre splitting

resulting in the wear-off the wool fibres.

Figure 2. Pill wear-off on the surface of brown hollow polyester/

wool fabric after 5000 rubs.


the lower the bending stiffness of the fibres, the more likely

they can be pulled out of the fabric structure and producing

long protruding fibres [10]. But hollow fibres with lower

breaking strength and high bending stiffness will tend to

break before being pulled fully out of the structure leading to

shorter protruding fibres (Figures 3, 4). This means that

many protruding fibres can not reach the “critical height” for

the for fibre entanglement and pill formation. The break

down of hollow fibres commences during entanglement by

splitting along the helical lines between fibrils and is

continued along the fibre axes and finished with bushy ends

(Figure 5).

The fibre break develops along the axial splits, due to

either repeated bending, or bending and twisting (Figure 6).

Also, the individual portions of the split can break to give

many splits (Figure 7). Furthermore, the axial splits can

occur from tensile fatigue (Figure 8), or peeling by surface

shear, failure by surface wear creating peeled fibres (Figure

9). The other type of fibre break down can be found in

Figure 10. Figure 10(A) shows a wool fibre with a split end;

Figure 3. Pill wear-off on the surface of charcoal hollow polyester/

wool fabrics after 7000 rubs.

Figure 4. Breakage of hollow polyester fibres during entanglement.

(A) charcoal and (B) brown hollow polyester/wool fabrics after

5000 rubs.

Figure 5. Breakage steps of brown hollow polyester fibre after

5000 rubs. (A) start of fibre breakage along helical lines between

fibrils, (B-H) continued splitting along the fibre axes, and (I) bushy

end of breakage.


Figure 10(B) shows a failure adjacent to a knot which is

likely to be caused by flexural fatigue. As can be seen from

Figures 4 and 5, splits along the hollow polyester fibre can

be extremely long. This is a consequence of the fact that the

axial crack in this fibre type runs much more closely parallel

to the fibre axis. The phenomenon is a characteristic of the

highly oriented, highly crystalline, linear polymer fibres

[11].

Figures 11 and 12 show the tensile breakage of hollow and

solid polyester fibres respectively. It is clear that the tensile

strength of hollow polyester fibres is adversely affected by

the cavity inside the fibre which acts as a weak point where

the failure can be initiated.

In the case of wool which has low breaking strength, pills

will be easily removed and detached from the fabric. But for

fabrics containing solid polyester fibres, the pills will tend to

remain in place. Therefore, even after 7000 rubs their pilling

ratings are quite high. In conclusion it can be stated that the

higher the tensile strength and abrasion resistance of the

fibre, the higher the pilling tendency of the fabric. This is

mainly controlled by pill wear-off.

Figure 6. Biaxial rotations and flex fatigue of polyester fibres after

5000 rubs. (A) hollow brown sample, (B) solid black sample, (C-

D) solid charcoal sample, and (E-F) solid charcoal sample.

Figure 7. Long bushy ends of split hollow polyester fibre after

7000 rubs.

Figure 8. Tensile fatigue of solid black polyester/ wool blend

knitted fabric after 7000 rubs.

Figure 9. Wool fibre peel after 5000 rubs in blend fabric with solid

black polyester fibres.

Figure 10. Wool fibre breaks after 5000 rubs in blend fabric with

polyester fibres. (A) hollow charcoal, after 7000 rubs and (B) solid

black sample, after 5000 rubs.


The results of abrasion test, Table 3 and Figure 13, show

the significant effects of fibre type. The ability of a fibre to

resist repeated distortion is very important to its abrasion

resistance. Therefore high elongation, elastic recovery and

work of rupture are considered to be the key factors for a

good degree of flat abrasion resistance in a fibre rather than

high strength [10]. Polyester fibres are considered to have

good abrasion resistance and a comparison of the hollow and

solid polyester fibres indicated that the hollow fibres have

lower abrasion resistance, which may be related to their

shape. Compared with solid fibres of the same linear density,

hollow fibres are stiffer, more resistant to bending and torsion

[4] and have a relatively poor resistance to flexural strain

[3,9]. Therefore they abraded faster than the comparable

solid polyester fibres.

Measuring the mass loss during abrasion also demon-

strated the higher rate of hollow fibre removal during abrasion

(Figure 13). While these fibres were broken between 15,000

to 24,000 rubs, the minimum abrasion for solid fibres was

37,000 rubs. Furthermore, it is evident that the dyeing

processes have a significant effect on fibre properties. The

abrasion resistance of hollow polyester/wool fabric with

dark blue colour is at least 8000 rubs higher than similar

samples with the charcoal colour which may be related to

the dyeing period at high temperature. The mass loss during

abrasion is also compatible with the rubs to break; a higher

weight loss during abrasion correlates to a lower number of

rubs to break. The results also revealed the great improve-

ment of wool abrasion resistance by blending with hollow

and solid polyester fibres.

KES-F mechanical properties of knitted fabrics before and

after relaxation were measured. The results indicate that

after relaxation, there is an increase in extension (EM) for all

the samples (Tables 5 and 6). In general extensibility of the

solid polyester fibre samples are higher than the comparable

samples based on hollow fibres. The changes in these

properties indicate that the friction between fibres has been

reduced by the relaxation shrinkage process which makes

fabrics more extensible with better elastic recovery. But the

differences between hollow and solid polyester fibres show

that the friction between solid fibres is lower than hollow

fibres which can be related to the shape of fibres, because in

Figure 11. Tensile breaks of hollow polyester fibres.

Figure 12. Tensile breaks of solid polyester fibres.

Figure 13. Percentage mass loss during abrasion test.


general these fibres have greater outside surface area, result-

ing in a greater frictional contact area.

The tensile properties of the wool fabric changed greatly

after relaxation. The EM and RT (recovery) increased

significantly. However, blending wool with polyester fibres

especially hollow fibres reduced the effects of relaxation on

the tensile properties.

It is expected that bending rigidity and bending hysteresis

of all the samples will decrease after scouring, but the grey

samples were so unstable that it was impossible to measure

their bending properties accurately. The results from the

relaxed samples clearly show that the bending stiffness of

hollow fibre fabrics is much higher than that of the solid

fibre fabrics. These hollow fibres have the same linear den-

sity as the solid fibres, therefore, they are stiffer and more

resistant to bending and torsion [44,12].

The shear properties of all the samples were reduced by

scouring. This is mainly due to decreasing inter-yarn friction.

In general, shear rigidity and hysteresis of hollow fibre fabrics

are greater than solid fibre fabrics. The effects of different

Table 5. KES-F Mechanical properties of knitted relaxed fabrics

SP/W Black SP/W Charcoal HP/W Brown HP/W Charcoal HP/W Darkblue Wool

Tensile

EM (%) 16.85 15.71 15.99 14.55 14.98 22.71

LT 0.894 0.919 0.912 0.960 0.979 0.904

WT (g·cm/cm2) 3.75 3.40 3.66 3.50 3.64 5.07

RT (%) 47.97 48.58 49.40 48.77 50.86 52.94

BendingB (g·cm2/cm) 0.0834 0.1036 0.1217 0.1221 0.1169 0.0494

2HB (g·cm/cm) 0.1235 0.1506 0.1878 0.1917 0.1627 0.0606

Shear

G (g./cm·deg) 0.39 0.38 0.42 0.43 0.42 0.32

2HG (g./cm) 1.71 1.61 1.94 1.94 1.92 1.33

2HG3 (g./cm) 1.75 1.63 2.01 1.97 1.98 1.36

Surface

MIU 0.229 0.224 0.225 0.223 2.000 0.244

MMD 0.0189 0.0177 0.0183 0.0199 0.0190 0.0195

SMD (µm) 11.9 10.9 13.7 13.8 13.9 14.0

Compression

LC 0.360 0.340 0.367 0.364 0.355 0.391

WC (g·cm/cm2) 0.812 0.836 0.829 0.833 0.844 0.820

RC (%) 48.23 48.27 46.98 48.04 46.82 47.22

ConstructionT (mm) 0.799 0.810 0.822 0.813 0.835 0.956

W (mg/cm2) 22.10 22.13 21.88 21.58 21.95 23.73

Table 6. KES-F Mechanical properties of knitted fabrics before relaxation

SP/W Black SP/W Charcoal HP/W Brown HP/W Charcoal HP/W Darkblue Wool

Tensile

EM (%) 13.77 14.81 12.19 11.10 11.70 16.47

LT 0.956 0.931 1.042 1.028 0.994 0.968

WT (g·cm/cm2) 3.19 3.46 3.13 2.82 2.86 3.89

RT (%) 40.23 40.73 44.45 39.21 34.46 39.16

Shear

G (g./cm·deg) 0.49 0.46 0.50 0.51 0.55 0.47

2HG (g./cm) 3.11 2.68 3.06 3.31 3.72 3.22

2HG3 (g./cm) 3.19 2.72 3.12 3.35 3.75 3.20

Surface

MIU 0.242 0.245 0.245 0.237 0.242 0.241

MMD 0.0209 0.0212 0.0216 0.0225 0.0225 0.0223

SMD (µm) 13.5 13.7 12.2 13.4 14.2 13.8

Compression

LC 0.344 0.352 0.368 0.334 0.348 0.390

WC (g·cm/cm2) 0.865 0.872 0.910 0.808 0.876 0.884

RC (%) 44.50 45.46 44.50 45.51 44.92 44.57

ConstructionT (mm) 0.613 0.621 0.630 0.628 0.677 0.884

W (mg/cm2) 21.10 21.68 20.95 20.03 20.05 21.80


colours during dyeing on shear properties are not significant

because the dyeing operation generally produced fabrics

with low yarn interactions regardless of colour [13].

Relaxation shrinkage decreases the friction coefficient

(MIU) and its variation (MMD) of polyester/wool blend

fabrics. This may be due to the tighter and more compact

structure of the fabrics after shrinkage making the gaps in

the fabric and the surface variation smaller.

The surface roughness (SMD) of hollow fibre based fabrics

increased after scouring while the solid polyester/wool fibre

fabrics showed lower surface roughness. The larger diameter

and higher bulk of the hollow fibres produce result in higher

SMD, demonstrating that the fabric hand is dependent on

fibre cross-section.

It is generally expected that fabrics have higher energy of

compression (WC) after scouring, but here the trend is

decreasing. This may be due to the more compact structure

after relaxation. The recovery after compression (RC) of all

the samples increased. This is compatible with the reduction

of friction between yarns and fibres due to the release of

internal fabric tension. As already mentioned hollow fibres

have more friction, consequently fabrics with these fibres

have lower RC.

In any relaxation process the thickness of fabrics increases.

This is shown in this study as well. Also, it was found that

the thicknesses of hollow fibre fabrics are higher than that of

the solid fibre fabrics. Clearly, the increased fibre external

dimension of the hollow fibres is a factor. In fact, the greater

fabric thickness is one of the reasons to use hollow fibres as

this leads to greater thermal insulation.

The permeability to water vapour, the thermal insulating,

and water transport are some of the basic factors affecting

thermal comfort. These properties can be influenced by

suitable choice of fibre cross-sectional shapes, the formation

of cavities or micro-cavities in the fibres and other modifi-

cations to fibre geometry. They can also be influenced by

fibre blending and fabric construction [3]. The results of

water vapour permeability tests, Table 7, indicate that

relaxation resulted in a more compact structure and conse-

quently a reduction in the water vapour permeability of

fabrics. This effect is greater than the influence of the type of

fibre. In this aspect, fabric and yarn structure is more

important than the constituent fibres.

Conclusion

Solid polyester fibre fabrics have higher tensile and burst-

ing strength, and better abrasion resistance. However, by

using hollow fibres in the fabrics, the extent of pilling, a

serious fabric appearance defect for high strength synthetic

fibre fabrics was reduced by about 40%, a result of faster pill

wear-off, due to the differences in the physical properties of

the constituent fibres.

The use of hollow fibres resulted in lower extensibility,

tensile and compressional resilience, greater bending and

shear stiffness and hysteresis. Accordingly the results indi-

cate that by using hollow fibres, it is possible to produce a

fabric similar to that base on solid polyester fibres but with

higher stiffness and rougher texture. The fabric and yarn

structures control the overall fabric handle and water vapour

permeability. The use of hollow fibres increases fabric thick-

ness. This should increase the thermal resistance.

Acknowledgements

Financial support of the Iran’s Ministry of Science, Research

and Technology, and Bulmer & Lumb Company to afford

fibres and yarns is gratefully appreciated.

Table 7. Water vapour permeability of knitted samples before and after scouring & relaxation

State of fabric SampleWVP*

After 6 hr

I**

After 6 hr

WVP

after 24 hr

I**

After 24 hr

Relaxed

SP/W Black 1100 90.424 1350.515 90.086

SP/W Charcoal 1121.650 92.203 1387.113 93.324

HP/W Brown 1095.876 90.085 1357.474 91.330

HP/W Charcoal 1104.124 94.192 1356.186 94.301

HP/W Darkblue 1096.907 93.580 1345.103 93.530

Wool 1138.144 92.385 1367.698 93.940

Before

relaxation

SP/W Black 1201.031 101.229 1399.485 98.204

SP/W Charcoal 1178.3505 99.317 1380.155 96.848

HP/W Brawn 1239.175 104.444 1425.515 100.031

HP/W Charcoal 1200.00 101.142 1400.515 98.277

HP/W Darkblue 1191.753 100.447 1407.732 98.783

Wool 1147.423 96.711 1381.186 96.920

*: Water vapour permeability, **: Water vapour permeability index.


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