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Thermo-physiological comfort
of a PES fabric with incorporated
activated carbon
Part II: wear trials
R. Splendore
Associazione Tessile e Salute, Biella, Italy
F. Dotti
Dipartimento di Scienze dei Materiali e Ingegneria Chimica,
Politecnico di Torino, Torino, Italy
B. Cravello
Associazione Tessile e Salute, Biella, Italy, and
A. Ferri
Dipartimento di Scienze dei Materiali e Ingegneria Chimica,
Politecnico di Torino, Torino, Italy
Abstract
Purpose – The purpose of this paper is to consider the thermal-physiological comfort performances
of a sport shirt made of a polyester (PES) fabric with incorporated activated carbon. After having
characterized the modified PES fabric in Part I, the results of a wear trial campaign are shown and
discussed in this work.
Design/methodology/approach – The wear trials have been carried out under a controlled
physical activity. A short-and-intense effort and an intermittent effort of milder intensity were carried
out twice by each volunteer: once wearing a shirt made of the modified PES fabric and the other one
wearing an analogous shirt made of a conventional PES fabric.
Findings – When sweating was moderate, the modified PES shirt was judged as more comfortable
on the average. As the effort became harder, the modified PES fabric turned out to be less
comfortable than the conventional one. In the final recovery stage, the conventional PES was still
more comfortable than the modified PES. This behaviour was justified according to the findings of
Part I: at the beginning, the prevailing effect was the adsorbing ability of carbon particles that buffer
sweat impulses, giving the user a pleasant dry sensation. Then, when sweating became intense,
the lower evaporative cooling of the modified PES fabric became the key factor governing the
physiological comfort of the garment. This is confirmed by a slightly higher skin temperature
measured during the modified PES fabric trials. Finally, a post-exercise chill sensation was felt with
the modified PES fabric, due to a longer drying time.
Originality/value – The paper presents a comprehensive study of the thermo-physiological comfort
of a fabric containing activated carbon particles.
Keywords Wear trial, Thermo-physiological comfort, PES, Activated carbon, Thermal testing,
Fabric testing, Clothing
Paper type Research paper
The current issue and full text archive of this journal is available at
www.emeraldinsight.com/0955-6222.htm
The authors gratefully acknowledge the Piemonte Regional Government, which financed this
work within the HITEX project (D.G.R No. 227-4715).
Thermo-
physiological
comfort
283
Received 16 December 2010
Revised 23 February 2011
Accepted 23 February 2011
International Journal of Clothing
Science and Technology
Vol. 23 No. 5, 2011
pp. 283-293
qEmerald Group Publishing Limited
0955-6222
DOI 10.1108/09556221111166220
1. Introduction
The performances of fabrics for sport and active wear have been continuously improved
in recent years and nowadays a variety of fabrics are available on the market in order to
satisfy the needs of the most demanding customers (Buirski, 2005). Sweat absorption and
rapid drying are two critical functions that must be fulfilled by a sportswear fabric.
To keep the wearer’s body dry, fabrics should be able to wick moisture away from skin
and distribute it over the surface, reducing drying times (Wong and Li, 2004). A variety of
technological solutions have been proposed to improve the liquid management of
hydrophobic fibres such as polyester (PES): for instance, a structured cross-sectional
shape distributing liquid on a wider surface is the principle exploited in Coolmaxe
technology. Using micro-fibres is another way to enhance liquid management since the
finest the fibre diameter, the larger the yarn surface area (Umbach, 1993). Finally,
a number of chemical treatment such as enzymatic and alkali treatments can be carried
out to obtain a hydrolyzed PES (Hsieh, 1998; Zeronian et al., 2003). Recently, the inclusion
of activated carbon particles derived from recycled coconut shell has been presented on
the market as an effective way to modify moisture absorption of a man-made fibre.
Thanks to their huge surface on which a liquid can be absorbed, activated carbon
particles provide moisture adsorption and odour control. In Part I, a conventional and a
carbon-particle containing PES fabrics have been compared as far as the comfort-related
properties are concerned and a double effect has been observed due to carbon particle
inclusion: fabric hydrophilicity dramatically increased but, on the other hand, drying
time lengthened (Splendore et al., 2010). These two effects act in opposite directions as far
as comfort is concerned: a hydrophilic behaviour is desired for absorbing sweat but liquid
must be quickly evaporated to provide cooling. However, fabricphysical characterization
does not provide an exhaustive comfort evaluation. In Figure 1, the five-level system for
the analysis of the physiological properties of textiles and garment proposed by Umbach
(1988) is shown. Three out of five levels involve the subjective evaluation of a panel
Figure 1.
Procedure for the analysis
of the physiological
properties of textiles
and garment
Level 1
Biophysical analysis of textiles (skin model)
Level 2
Biophysical analysis of garment (manikin)
Level 3
Controlled wear test in climatic chamber,
physiological data/subjective ratings
Level 4
Limited field test
Level 5
Field test
IJCST
23,5
284
of people who tested the garment both in a controlled environment and in field. Using
human subjects to evaluate clothing will reduce control but it is the only way toprovide a
realistic and comprehensive comfort evaluation (Parson, 2003). The user performance
tests are especially needed when level 1 findings did not give a univocal response about
comfort, as it happened for the fabrics investigated in this work.
Two long-sleeved shirts, one made of the carbon-containing PES fabric and the other
one of a conventional PES fabric, were worn by four volunteers (two men and two
women, about 30 year old) during two physical tests, one short and intense and the other
one intermittent and milder. All subjects were healthy and exercises regularly. To study
the effect of a protract contact between skin and a carbon-particle-including fabric,
a patch test was carried out and skin physiological parameters investigated. Residual
detergent, a responsible of textile-induced dermatitis (Belsito et al., 2002), may be present
in a larger amount on a carbon-particle-containing fabric than in a conventional
one as carbon particles tends to retain detergent. The aim of the work was to evaluate
whether carbon particle inclusion would increase the overall comfort of the garment
both on an objective and subjective evaluation scale.
2. Materials and experiments
The conventional PES and the modified PES fabrics have the same honeycomb structure.
This knitting construction is frequently used in sportswear because it provides space
between skin and textile, thus avoiding a “clingy” sensation in case of sweating. A detailed
characterization of the two fabrics is presented elsewhere (Splendore et al., 2010). The
fabric characterization pointed out that the modified PES fabric has an enhanced
hydrophilicity with respect to the conventional one but, on the other hand, water
desorption is slow and the drying time of the active carbon containing fabric is longer than
that of the conventional PES. Moreover, thermal resistance and water vapour resistance of
the modified fabric are slightly worse with respect of conventional PES.
In Figure 2, a picture of two long-sleeved shirts tailored with the two fabrics is
shown. The tailoring of the two items is the same.
2.1 Patch tests
Patch tests were carried out with an internal standardized method to evaluate any
change in skin physiology of the four volunteers due to a protract contact with the
fabrics. Transepidermal water loss (TEWL), pH, moisture content and erythema index
were measured by means of the Cutometer MPA580 on two delimited areas on the
inner forearm at time zero. An area was subsequently covered with a 4 £4cm
2
fabric
sample while the other one was let free from any covering. After 24 hours, the fabric was
removed and skin parameters were evaluated again on both areas. In order to take into
account daily variability, the uncovered area was used as a control zone in the
following way: for each skin parameter, the value measured on the test area
immediately after the removal of the fabric was divided by the value measured on the
control area at the same time. Skin parameters were evaluated into the climatic
chamber at 238C and 50 per cent of relative humidity.
2.2 Wear trials
A wear trial campaign was conducted in a climatic chamber with temperature and
relative humidity set to 278C and 60 per cent, respectively. The temperature was set
to quite a high value, so that the sweating was abundant. An athletic performance
Thermo-
physiological
comfort
285
depends on personal training level, kind of training, environmental conditions and
clothing configuration. In this work, the environmental conditions were fixed, while the
personal training level, the kind of training and the clothing configuration were
assumed as factors in a general full factorial design. The software Minitab 15 was used
for randomizing the runs. The four volunteers involved in the wear trials, though being
all amateurs, have different training levels. Thus, four levels were assigned to this
factor. The clothing configuration factor has two levels as two shirts were used in the
trials, one containing active carbon particles and the other one without them. Finally,
each volunteer trained according to two kinds of training: a short-and-intense one and
a long-and-milder one. A summary of the design of experiments is shown in Table I.
The wear trials were replicated once. Thus, the total number of runs was 16.
The observations were collected under the same environmental conditions in the same
laboratory, thus they are all included in one single block.
The volunteers acclimatized for 30 min; the test procedure was explained in detail
prior the test taking place. Temperature sensors were attached at different body
locations (chest, shoulder-blade, deltoid, elbow) and the basal temperature of the
bare-breasted subjects was measured for 10 min before the volunteer wears the shirt.
The bare-breast phase was aimed at ensuring that the basal physiological skin
Number of factors 3
Name of the factors Personal training level; clothing configuration; kind of training
Levels of factors 4; 2; 2
Replicates 1
Blocks 1
Total runs 16
Table I.
Summary of the design
of experiments
Figure 2.
The two long-sleeved shirt (a) (b)
Notes: (a) Made of carbon-particle containing PES; (b) made of conventional PES
IJCST
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temperature was approximately the same in the two wear trials for each subject.
Then, the subject rested for 10 min before starting the physical activity wearing the
clothing configuration under investigation. The clothing configuration included the
long-sleeved shirt under investigation, cycling shorts, short socks and gym shoes.
Two trial sets were carried out by each volunteers in different days, one simulating an
intense-and-short strain and the other one a intermittent strain of medium intensity.
In the first case, the subject cycled on a cyclo-ergonometer Tunturi Bike T6 (Eve srl,
Milan) according to the VO
2
max test. Starting from 30 W, the pedal resistance increased
by 20 W every 2 min so that the strain increased stepwise. In this test, the volunteer must
reach his/her anaerobic threshold and then he/she must continue cycling in anaerobic
conditions for some minutes, according to his/her endurance. This phase was followed
by a recovery phase during which the volunteer cycled at 30 W for 5 min. Finally,
the volunteer rested for 30 min.
In the second wear trial, an intermittent physical effort was performed: the pedal
resistance was set to 90 W and a 10-min cycling activity was repeated three times.
The volunteer stayed at rest for 10 min between one cycling phase and the next one.
Finally, a 30 min rest followed.
A questionnaire was prepared to monitor the volunteers sensations during the
different steps of the VO
2
max test. The questionnaire, reported in the Appendix,
was answered after 6 and 12 min from the beginning of the physical activity,
in correspondence of a mechanical power of 65 and 110 W, respectively, and after
15 and 30 min from the end of the physical activity.
3. Results and discussion
The statistical analysis of the patch test data was generated using Minitab 15.
The analysis of variance (ANOVA) was used to test the effect of the fabric and that
of the subject on physiological skin parameters. The results are shown in Table II.
The p-values are well above the significant level, except for pH. This means that
pH is the only skin parameter influenced by the fabric. Nevertheless, pH values remain
within a physiological limit for both fabrics; that is, none of the two fabrics cause any
pathological change in skin pH.
The upper body skin temperature profiles are shown in Figures 3 and 4 for the two
sets of wear trials.
An upper body skin temperature was defined in the following way:
TUB ¼0:357 · TShoulder þ0:357 · TChest þ0:143 · TDeltoid þ0:143 · TElbow ð1Þ
where the weights take into account the relative extension of the skin areas. The upper
body skin temperature rather than the mean skin temperature defined in the UNI EN
Variable Factor: fabric
TEWL 0.314
pH 0.000
Moisture content 0.341
Erythema index 0.172
Note: p-values in the ANOVA
Table II.
Patch test results
Thermo-
physiological
comfort
287
ISO 9886 has been used in this work because the upper body skin temperature is
supposed to be more influenced by the shirt than the mean skin temperature.
In Figure 3, the temperature trend in the VO
2
max test is shown. When the subject
wore the shirt at 10 min, skin temperature increased and reached an approximately
steady value. In the first 10 min of activity (from 20 to 30 min), when the physical effort
was of mild to medium intensity, the temperature stayed almost constant. Then,
a steep increase in skin temperature was shown in correspondence to the recovery phase
Figure 4.
Upper body skin
temperature in the
three-cycle test
0 102030405060
Time (min)
70 80 90 100
33.50
33.00
32.50
Upper body skin temperature (°C)
32.00
Modified PES
PES
Note: Mean value among the volunteers
Figure 3.
Upper body skin
temperature in the
VO
2
max test
32.50
33.00
33.50
34.00
34.50
35.00
0 10203040506070
Upper body skin temperature (°C)
Time (min)
Modified PES
PES
Note: Mean value among the volunteers
IJCST
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(from 35 to 40 min). This means that the increase of the upper body skin temperature
shows some delay with respect to the production of metabolic heat (the time needed by
heat to reach the outer surface).
The upper body skin temperature in the three-cycle test is shown in Figure 4. Since
the intensity of the physical activity was lower, the maximum temperature reached
in the three-cycle test was lower by about 18C with respect to the VO
2
max test.
The temperature peaks are slightly higher for the modified PES fabric in both training
tests. Since the evaporative rate of the modified fabric is slower, as demonstrated by the
lengthening of the drying time, a lower amount of metabolic heat is removed during the
physical activity and this leads to a higher skin temperature. Moreover, the thermal
resistance of the modified fabric is slightly higher than that of PES fabric, as shown in
Part I, and this contributes to a more difficult heat removal.
It can be observed that a lower temperature is measured when wearing the modified
PES fabric at the end of the test in both the VO
2
max (Figure 3) and the three-cycle test
(Figure 4). This effect is due to a longer drying time of the modified PES fabric, that is
25 per cent longer as reported in Part I. The activated carbon particles made the fabric
more hydrophilic and this has the counterfeiting effect of drying time lengthening.
So the presence of a wet fabric in contact with skin keeps its temperature lower.
During the three-cycle test, the relative humidity of the thin air layer between skin and
garment has been evaluated via a small sensor, called smart button, that was positioned
on the chest and spaced out from skin and textile thanks to a small grid. The main aim of
the three-cycle test was exactly that of investigating the microclimate. In fact, in the VO
2
max test, the humidity sensor reached a saturation value and no interesting trends could
be observed. Owing to the bent position adopted by the wearer during cycling, the best
location for a microclimate measurement was found to be the chest. The humidity of the
microclimate increased dramatically at the beginning of the physical activity at 20 min.
Thus, unlike skin temperature which showed a delay, microclimate humidity is a prompt
signal that metabolic heat has begun to being produced. The increase in the microclimate
humidity is due to the sweat impulses occurring from the beginning of the physical
activity. As shown in Figure 5, microclimate humidity was found to be lower with the
modified PES shirt on. Thus, despite a similar water vapour permeability and a lower air
permeability, the modified PES fabric guarantees a drier microclimate thanks to the
carbon particle inclusion. This was confirmed by the wettability measurement that was
found to be greater for the modified PES than the conventional one.
The sensorial differences perceived by the volunteers when wearing the two shirts
during the VO
2
max were captured through the questionnaire reported in the Appendix.
For each question, a score was assigned to each answer: the lowest score was assigned to
the most uncomfortable sensation and the highest score to the most comfortable one.
The scores reported in Table III are the weighted sum of the subjects’ answers, where the
weights are the answers frequencies.
In the last row in Table III, the sum of the absolute differences was reported in order to
point out the entity of difference between the shirts scores. At rest, the scores obtained by
the modified fabric were generally better. As reported in Part I, the modified fabric has a
larger thermal diffusivity than the PES fabric. Thermal diffusivity is the transient state
thermal property describing the rate of temperature propagation through the material
(Hes and de Araujo, 1996). This property quantifies the cool feeling immediately after
Thermo-
physiological
comfort
289
putting a garment on. Thus, the better comfort sensation experienced in the first min of
the wear trial could be due to the higher thermal diffusivity of the modified PES fabric.
At 6 min, the clothing comfort (question 4) and humidity acceptability (question 2)
were better for the modified PES shirt while thermal acceptability (question 1) was
worse. This result reflects the modified fabric features that is slightly thicker and
more insulating than the conventional fabric and contains carbon particles that buffer the
sweat impulses keeping the body drier. At 12 min, the scores of the two shirts are more
similar to each other as shown by the small values of the absolute difference sum.
This result could be ascribed to the difficulty of the subject in detecting any difference
between the two shirts when the volunteer is psychologically involved in a hard physical
work. The main difference was observed in the recovery phase 15 min after the end of the
physical activity: it is noteworthy that the conventional PES fabric was felt much more
transpiring (question 3) than the modified one at that time. This outcome is attributable
to the fact that the modified fabric stays wet for a longer time after the end of the physical
activity and this feature brings an occlusive sensation to the wearer. Finally, 30 min after
the end of the physical, activity both shirts were dry again and the modified PES obtained
a better score on humidity acceptability as it happened at the beginning of the test.
From the experiments under two sorts of training, conclusions concerning the
possible end-uses of the modified PES can be drawn: this material with its superior
ability to remove sweat from skin is suitable for sports activities of soft-to-medium
intensity in a cool-to-mild environment. Its use is not recommended during intense
physical training in a hot environment, when thermoregulation becomes of primary
importance, due to the slow desorption of the liquid from the active carbon particles
which reduces the heat rate from the body.
4. Conclusion
In this work, thermo-physiological comfort of a sport long-sleeve shirt has been
investigated via wear tests. A hard and a medium intensity physical activity were
Figure 5.
Humidity of the
microclimate in the
three-cycle test
50.0
55.0
60.0
65.0
70.0
75.0
80.0
0 102030405060708090100
Relative humidity (%)
Time (min)
Modified PES
PES
Note: Mean value among the volunteers
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At rest just before the
beginning of the test
6 min after the beginning
of the VO
2
max test
12 min after the
beginning of the
VO
2
max test
15 min after the end of the
VO
2
max test
30 min after the end of
the VO
2
max test
Mod. pes Pes Abs. diff. Mod. pes Pes Abs. diff. Mod. pes Pes Abs. diff. Mod. pes Pes Abs. diff. Mod. pes Pes Abs. diff.
Q1 – Thermal
acceptability 3.5 3.25 0.25 2.5 3.25 0.75 1.5 1.5 02 3.25 1.25 3.75 3.5 0.25
Q2 (ex5) –
Humidity
acceptability 3.75 4 0.25 3.5 3 0.5 1.5 1.25 0.25 1.75 1.75 03.25 2.5 0.75
Q3 – Clothing
transpiring feature 4.5 3.75 0.75 33 01.5 1.5 01.5 3.25 1.75 2.25 3 0.75
Q4 – Clothing
comfort 3.75 3.25 0.5 3 2.75 0.25 2 2.25 0.25 2.5 2.75 0.25 3 2.5 0.5
Sum 1.75 1.5 0.5 3.25 2.25
Note: Abs. diff.– absolute difference
Table III.
Results of the
questionnaire
Thermo-
physiological
comfort
291
carried out in a quite warm and humid climate (278C and 60 per cent RH). The results
were interpreted also in the light of the fabric physical measurements presented in Part I.
The modified PES fabric was generally judged as more comfortable at rest and under a
moderate physical activity thanks to the carbon particle inclusion that adsorb sweat
impulses. The carbon including fabric turned out to be less comfortable at the end of the
physical activity due to the lengthening of the drying time which brings about an
unpleasant post-exercise chill sensation.
According to the results of the physical characterization (Part I) and the wear
tests (Part II), the modified PES seems to be ideal for realizing sportswear to be used in
mild conditions as far as the physical effort and climatic conditions are concerned.
For the fabric to be used in sportswear for extreme conditions, the liquid
management of the modified PES should be improved with the aim of speeding up the
fabric drying time. This goal should be achieved only by promoting the desorption rate
of water from the active carbon containing PES. Up to now, we could not find any data
on this issue in literature.
References
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Appendix
Questionaire for thermo-physiological comfort assessment of clothing
Date: ___________________________Hour: ____________
Subject no. __ __________________________
Item of clothing ____________________________________
(1) How do you judge your thermal comfort condition?
Acceptable (1) Just acceptable (2) Hardly acceptable (3) Non acceptable (4)
(2) How do you judge your humidity condition?
Acceptable (1) Just acceptable (2) Hardly acceptable (3) Non acceptable (4)
(3) How do you judge your clothing ?
Non
Transpiring (1) Transpiring
(5) I don't
know
(4) How do you feel your clothing on the skin ?
Comfortable Fairly comfortable Slightly uncomfortable Uncomfortable
Corresponding author
A. Ferri can be contacted at: ada.ferri@polito.it
Thermo-
physiological
comfort
293
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