Moisture management performance of functional yarns based on wool fibres

Abstract

Blends of wool and moisture management fibres such as Coolmax and Finecool have been prepared to produce innovative yarns with specific functionalities. These yarns have been used to produce knitted fabrics and their performance is evaluated, including vertical and horizontal wicking. The drying capability of the fabrics has been assessed by drying rate testing under two different conditions, namely standard conditions (20±2°C and 65±3 % RH) and, in an oven at 33±2°C to simulate the body skin temperature. The influence of wool fibre proportion on the performance of each blend is analyzed. It is observed that the Coolmax based fabrics show the best capillarity performance, and the wool based fabrics show low water absorption performance but good drying rate.

Full text

Indian Journal of Fibre & Textile Research
Vol. 34, December 2009, pp. 315-320
Moisture management performance of functional yarns based on wool fibres
Raul Fangueiroa, Pedro Gonçalves, Filipe Soutinho & Carla Freitasb
School of Engineering, University of Minho, 4800-058 Guimarães, Portugal
Received 16 October 2008; revised received and accepted 4 March 2009
Blends of wool and moisture management fibres such as Coolmax and Finecool have been prepared to produce
innovative yarns with specific functionalities. These yarns have been used to produce knitted fabrics and their performance
is evaluated, including vertical and horizontal wicking. The drying capability of the fabrics has been assessed by drying rate
testing under two different conditions, namely standard conditions (20±2ºC and 65±3 % RH) and, in an oven at 33±2ºC to
simulate the body skin temperature. The influence of wool fibre proportion on the performance of each blend is analyzed. It
is observed that the Coolmax based fabrics show the best capillarity performance, and the wool based fabrics show low
water absorption performance but good drying rate.
Keywords: Coolmax fibre, Drying capability, Finecool fibre, Functional yarns, Wicking performance, Wool
1 Introduction
Wool remains a premium apparel fibre with an
impressive set of technical attributes. For carpets and
rugs, wool remains the benchmark of quality and
performance with which other fibres are compared1.
The unique physical and chemical structures of wool
create a range of natural characteristics that have been
proved ideal for apparel, upholstery fabrics and
carpets2. These characteristics are warmth and
coolness, breathability, moisture absorption and
buffering, resilience, low odour, odour absorption,
softness, flame resistance, biodegradability and
recyclability, resistance to soiling and staining2. These
special characteristics of wool can be exploited in a
worsted suit or knitted outerwear or enhanced to create
novel apparel fabrics. Wool is increasingly being used
in technical applications in which its unique properties
and the opportunities for specific enhancements can be
profitably utilised1.
The versatility of wool has been demonstrated by a
number of innovative apparel products entering the
sportswear marketplace. These products, which
combine different fibres and structures, include the
Icebreaker and SportWool ranges. Icebreaker uses fine
merino wool for comfort and warmth in outerwear,
mid-layer, and underwear garments, while SportWool
combines the best features of wool and polyester fibres
in a bi-layer fabric, suitable for highly active sports.
Both products involve the use of technical data to
demonstrate the benefits they offer to the wearer1.
Liquid transporting and drying rate of fabrics are
two vital factors affecting the physiological comfort of
garments3-5. The moisture transfer and quick drying
behaviour of textiles depend mainly on the capillary
capability and moisture absorbency of their fibres.
These textiles are especially used in sport garments
next to the skin or in hot climates. In essence, the
human body generates heat more quickly during
exercise or vigorous activity. The body’s cooling
system attempts to dissipate this extra heat by
producing perspiration. Perspiration should be removed
readily from the skin surface or from the micro climate
just above it, for maintaining comfortably cool and dry
conditions.
Wicking is the spontaneous flow of the liquid in a
porous substance, driven by capillary forces.
Washburn6 proposed the well-known Lucas–Washburn
kinetics equation to describe the relationship between
wicking length and wicking time. Crow and Randall7,
Kissa8, Weiyuan et al. 9 investigated wetting and
wicking behaviour of textiles. As capillary forces are
caused by wetting, wicking is a result of spontaneous
wetting in a capillary system. Wicking takes place only
in wet fabrics and the contact angle decides the
wicking behaviour.
According to Sailen2, wool is highly moisture
absorbent because its constituent keratin is very rich in
amino acids which easily bind together the water
molecules. Wool can absorb water vapour (30% of its
own weight) without feeling wet2.
_______________________
aTo whom all the correspondence should be addressed.
E-mail: rfang@det.uminho.pt
bPresent address: Fiação da Graça SA, Lugar da Veiga, 4700-
670
Padim da Graça, Portugal.

INDIAN J. FIBRE TEXT. RES., DECEMBER 2009
316
This paper reports the development and optimization
of functional yarns based on wool fibres for different
applications. In this study, wool is combined with
moisture management materials to create intimate
blends of different fibres. These new blended yarns
with different percentages of wool and functional fibres
were then used to produce knitted fabrics and the
performance of these structures was evaluated. Two
main evaluation methods (vertical wicking and
horizontal wicking) for studying the liquid transfer
behaviour through textile materials were used. Drying
capability testing was carried out at two different
conditions, namely standard (20±2ºC and 65% RH)
and at 33ºC to simulate the body skin temperature.
These two parameters play an important role on the
performance of clothing for professional sport players.
The influence of different fibres in each sample
produced has also been evaluated.
2 Materials and Methods
2.1 Materials
Wool fibres (19µ) with Basolan treatment were
combined in different proportions with moisture
management fibres: Finecool (2.4 dtex) and Coolmax
(2.4 dtex).
Yarns with 100% the same material, blends with
50% of wool and 50% of moisture management
fibres, and blends with 75% of wool and 25% of
moisture management fibres have been developed and
produced. All the yarns produced have a linear
density of 20 tex with 630 turns/m of twist.
Table 1 shows the dimensional properties of single
jersey knitted fabrics, produced on a circular weft
knitting machine (E28 gauge).
2.2 Methods
2.2.1 Vertical Wicking Testing
Vertical wicking testing was performed on the
apparatus as shown in Fig. 1. Five specimens of
200×25mm size cut along wale-wise and course-wise
directions were prepared. The specimens were
suspended vertically with their bottom ends dipped in
a reservoir of distilled water. In order to ensure that
the bottom ends of the specimens can be immersed
vertically with 30mm depth into the water, the bottom
end of each specimen was clamped with a clip
(Fig. 1). The wicking heights, measured after every 30
s till 5 min, were recorded as a direct evaluation of the
fabric wicking ability.
2.2.2 Horizontal Wicking Testing
Figure 2 shows the apparatus used to evaluate the
horizontal wicking rate under standard environmental
conditions (20±2ºC and 65±2 % RH). In the horizontal
Table 1 − Dimensional properties of knitted fabrics produced
Fabric Cover
factor (K)
Aerial
mass
g/m2
Density
(wales ×
courses)/cm
Thickness
mm
Wool 15.68 155.23 16 ×20 0.68
Polyester 16.86 168.73 14 × 22 0.67
Wool/Polyester
(50:50)
16.28
147.67
14 × 20
0.64
Finecool 16.64 158.91 14 × 21 0.71
Wool/Finecool
(50:50)
15.79
164.11
15 × 19
0.66
Wool/Finecool
(75:25)
17.12
161.53
16 × 19
0.68
Coolmax 16.40 163.49 15 × 19 0.63
Wool/Coolmax
(50:50)
16.18
154.68
14 × 20
0.61
Wool/Coolmax
(75:25)
16.76
160.89
16 × 20
0.71
Fig. 1 − Vertical wicking apparatus
Fig. 2 − Horizontal wicking apparatus

FANGUEIRO et al.: PERFORMANCE OF FUNCTIONAL YARNS BASED ON WOOL FIBRES
317
wicking apparatus, a tiny water drop contact with the
horizontally placed specimen (200mm×200mm) was
provided, leading to the water absorption by wicking
and wetting through the pores. The water was supplied
continuously from a reservoir by siphoning. The
reservoir was kept on an electronic balance, which
enables to record the water mass absorbed by the fabric.
Because the mass absorbed by the sample is related to
the sample thickness, water absorption per unit of
thickness is used to evaluate the horizontal wicking
ability. The wicking was measured after every minute
till 10 min.
2.2.3 Drying Rate Testing
Quick drying capability of the fabric was evaluated
by its drying rate. The specimen of the size 200×200
mm2 was put on the plate of the balance and the dry
weight was recorded as f
w (g). The weight of water
previously added in fabric was equal to 30% of the
dry weight and then the wet weight was recorded
as o
w (g). The change in weight of water [ i
w (g)] at
regular intervals was continuously recorded. The
remained water ratio (RWR) was calculated using the
following equation to express the change in water
weight remained in the specimen over the time for
drawing the evaporating curve from 100% to 0%:
%100
)(
)(
(%) RWR
0
×
−
−
=
f
fi
ww
ww … (1)
In order to assess the quick drying capability of the
fabric in different conditions, two testing conditions,
namely standard condition (20±2ºC and 65±5 % RH)
and at 33±2ºC temperature were chosen. For the first
condition, the mass of water [wi (g)] has been measured
after every 5 min continuously for next 60 min. For the
second condition, the mass of water [wi (g)] has been
recorded continuously after every 1 min till the next 5
min, and in the next 30 min after every 5 min.
3 Results and Discussion
3.1 Wicking Ability
3.1.1 Horizontal Wicking
Figure 3 shows the results obtained for horizontal
wicking testing. Considering that during intense
physical activity, when the body starts perspiration,
quick moisture transportation is important; the results
have been analyzed after the first minute. The
performance ranking of fabrics (from the best to the
worst) is shown below:
Coolmax > Finecool > Polyester > Wool /
Coolmax (75:25) > Wool / Coolmax (50:50) > Wool /
Finecool (75:25) > Wool / Finecool (50:50) > Wool /
Polyester (50:50) > Wool.
It can be seen that the fabric with 100% Coolmax
fibres shows the best performance. Moreover, the
fabrics with 25% and 50% of Coolmax show better
performance than those with the same amount of
Finecool. Fabric with 100% wool presents the poorest
behaviour.
For fabrics produced with 100% of the same
material, it is possible to easily identify the trends of
horizontal wicking behaviour, as the diameter of the
fibres in the yarn structure is constant. When different
fibres are blended, their diameters vary according to
the fibres density, leading to the different
arrangements in the yarn and consequently different
wicking channels.
3.1.2 Vertical Wicking
Figure 4 shows the results obtained for vertical
wicking in the course-wise and wale-wise directions.
Based on the findings at 1st min, performance ranking
(from the best to the worst) is shown below:
Course-wise direction: Coolmax > Polyester >
Wool / Finecool (75:25) > Wool / Coolmax (50:50) >
Finecool > Wool / Coolmax (75:25) > Wool /
Finecool (50:50) > Wool / Polyester (50:50) > Wool
Wale-wise direction: Coolmax > Polyester > Wool
/ Finecool (75:25) > Wool / Coolmax (50:50) >
Finecool > Wool / Coolmax (75:25) > Wool /
Polyester (50:50) > Wool / Finecool (50:50) > Wool
It is found that the 100% Coolmax fabric shows the
best performance in both directions, and for all the
other fabrics the results are very similar in both
Fig. 3 − Horizontal wicking curve

INDIAN J. FIBRE TEXT. RES., DECEMBER 2009
318
course-wise and wale-wise directions. The fabric with
75% wool and 25% Finecool gives very good results,
better than that of the fabric with 100% Finecool in
both directions. 100% wool fabric shows the poorest
results.
3.2 Drying Rate
Figure 5 shows the results obtained for drying rate
both at standard conditions and at 33ºC temperature.
Based on the results at 5 min, performance ranking
(from the best to the worst) is shown below:
At 33ºC temperature: Finecool > Wool > Wool /
Polyester (50:50) > Coolmax > Wool / Coolmax
(50:50) > Polyester > Rest
Standard conditions: Wool / Polyester (50:50) >
Wool / Finecool (50:50) > Coolmax > Wool > Wool /
Finecool (75:25) > Finecool > Rest
It is observed that the fabric with 100% Finecool
fibres shows the best performance under both the
conditions. The fabric with 50% wool and 50%
polyester shows better performance than that of the
100% polyester fabric.
Analyzing the behaviour in both conditions, one
can observe that, as expected, for the same material
and considering the same testing time, the RWR is
lower for the skin conditions as the heat provided by
the environment enables quicker evaporation. As a
consequence, the slope of the RWR vs time curve is
higher than that obtained under normal conditions.
Moreover, the curve shows an inflection point at
about 15 min, corresponding to a lower evaporation.
In fact, the first part of the behaviour, represented by
higher slope, corresponds to the moisture release from
fabric and the second part of the curve, with a lower
slope, corresponds to the moisture release from fibres.
3.3 Influence of Amount of Fibre
Figures 6-8 show the performance of different
blends, depending on the different percentages of
wool and functional fibres. It is observed that in
horizontal wicking, the increase in amount of wool in
the fabrics leads to a decrease in the absorption.
However, the fabrics with 75% wool and 25%
functional fibre show better performance than that of
fabrics with 50% wool and 50% functional fibre. In
vertical wicking, similar conclusions may be
observed. However, in this case, fabrics with 75%
wool show poor performance than those of fabrics
with 50% wool. For horizontal wicking, Coolmax
Fig. 4 − Vertical wicking curves
Fig. 5 − Drying rate (a) at standard conditions, and (b) at 33ºC
temperature

FANGUEIRO et al.: PERFORMANCE OF FUNCTIONAL YARNS BASED ON WOOL FIBRES
319
gives better performance for all proportions of
functional fibre (100, 75 and 25%). In vertical
wicking, the trend is similar but fabric with
wool/Finecool (75:25) shows the best performance.
However the performance is very similar in course-
wise and wale-wise directions for all other
proportions of different fibres.
In the drying rate performance, the variation in the
amount of different fibres used in the blends leads to
different behaviour for both the testing conditions. It
is observed that the decrease in amount of Coolmax in
the blends is directly related to the decrease in drying
rate for both testing conditions. For Finecool, it is not
possible to detect a clear trend. For standard
conditions, fabric with 50% Finecool shows very
good behaviour, however it gives worst performance
for human body testing conditions.
4 Conclusions
Fabrics with Coolmax fibres show the best
capillarity performance, i.e. they can transport quickly
the humidity (perspiration) from the skin to the
environment. Finecool fabrics show higher drying
rate, i.e. high capacity to dry after wet. Wool fibre
based fabrics show low water absorption
performance, but a good drying rate. The increase in
the percentage of wool fibre in the fabrics is directly
related to the decrease in water absorption
performance, however it does not lead to an increase
in the drying rate.
The findings help in designing the most suitable
combination of wool/functional fibres for end-uses,
where moisture management is an important issue.
The quantity of functional fibres can also be
optimized to produce the economical products of the
market demands.
Fig. 6 − Influence of type of fibre at the end of 1st min in the
horizontal wicking
Fig. 7 − Influence of type of fibre at the end of 1st min in the
vertical wicking
Fig. 8 − Influence of type of fibre at 5 min on the drying rate [(a)
standard conditions, and (b) 33ºC temperature]

INDIAN J. FIBRE TEXT. RES., DECEMBER 2009
320
Acknowledgement
The authors are thankful to the IAPMEI – Instituto
de Apoio às Pequenas e Médias Empresas, for funding
this project under the framework of PRIME
Programme – I&DT Projects.
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