MERINO FOR PERFORMANCE ACTIVEWEAR

MERINO FOR
PERFORMANCE
ACTIVEWEAR
MERINO FOR
PERFORMANCE
ACTIVEWEAR
Usage of Merino active wear is growing rapidly, worldwide,
supported by strong consumer endorsement and objective
evidence of performance. Merino apparel and hosiery offers
a means of enhancing wearer physical performance and
comfort when engaged in physical activity, and avoids the
use of non-sustainable synthetic fibres.
WHAT PERFORMANCE
CHARACTERISTICS
ARE IMPORTANT IN
ACTIVEWEAR?
In addition to normal textile characteristics, the following
attributes are particularly important for fabrics utilised in
active wear.
• An ability to actively manage heat and moisture flows
from the body under a variety of conditions (hot, cold,
dry and wet)
• Suppression of odour
• High abrasion resistance and durability
• Ease of laundering
• Softness and flexibility
WHY IS THE ABILITY
TO MANAGE HEAT
AND MOISTURE
FLOWS IMPORTANT IN
ACTIVEWEAR?
The ability to manage heat and moisture flows has a major
influence on the thermal state of the body, on human
performance and on a users’ perceptions of their physical
condition.
With respect to thermal comfort, the required attributes of
fabric differ greatly depending on the intended end use. By
way of example, sedentary activity in a cold environment will
require fabric insulation and moisture transfer requirements
quite different to those required of a garment designed for
sporting use in a warm or temperate climate. Generally,
active wear fabrics are designed to promote heat and
moisture flows away from the body.
How fabrics regulate heat and moisture flows are
intrinsically linked. To illustrate this, consider the case of
active sportswear. Such apparel should ideally support the
thermoregulation of the athlete by promoting evaporative
heat transmission (Pessenhofer et al. 1991). Such heat
transmission arises through conversion of liquid sweat
to water vapour at the skin surface, the efficiency of
which is dependent upon the temperature of the skin and
surrounding air, the relative humidity of the air on either side
of the fabric, air interchange from under the fabric, and the
ability of the fabric to pass water through it in vapour form.
The latter is mediated by fabric, but driven by concentration
gradients existing between the environment above the skin
surface and that exterior to the garment. Failing to promote
such dissipation will lead to a rise in core body temperature
and contribute to cessation of physical activity through
exhaustion.
Three principle modes of moisture (either liquid or vapour)
flow in Merino textiles exist (Massie and Mehta, 1980).
• Water vapour transport through fibres (by absorption/
desorption).
• Water vapour transport through air spaces in the fabric
structure.
• Liquid water transport through fabrics (along fibre
surfaces via capillary action).
Water vapour absorption is an intrinsic fibre quality and
hence independent of fabric structure (Massie and Mehta,
1980). Wool is able to actively absorb moisture from the
atmosphere and/or body – with its absorption properties
being much greater than most synthetic fibres (Figure 1).
160
Heat of sorbtion (energy release in kJ)
HOW DO MERINO FIBRES
TRANSPORT WATER
VAPOUR THROUGH THEIR
STRUCTURE?
140
120
100
80
60
40
20
0
18
Nylon
Polyester
Figure 2. Heat of sorption of wool and other synthetic fibres (Collie and
Johnson, 1998).
16
14
% moisture by fibre weight
Wool
This energy release is referred to as ‘heat of sorption’
and occurs in all fibres to some extent, but is particularly
pronounced in wool. The extent to which the processes of
absorption and desorption occur is governed by the relative
humidity of the surrounding environment and existing
moisture content of the fibre. The higher the ambient
humidity, the greater the absorption of water (Leeder 1984).
The reason Merino gives off heat when it absorbs water as
either liquid or vapour relates to:
12
10
8
6
4
2
0
Wool
Nylon
Polyester
Fibre
Acrylic
Polypropylene
Figure 1. Moisture absorbance of wool and synthetic fibres (Collie and
Johnson, 1998).
Wool owes its absorption characteristics to its chemical
building blocks, amino acids, which are hydrophilic. This
means they attract and absorb water molecules, with such
water becoming associated with the amorphous regions of
the intercellular cement and the fibre matrix. This interaction
with water occurs in a rather special manner.
Firstly, as the hydrogen bonds that bind the water molecules
are reversible, water can also be released in a process
known as desorption. Secondly, a wool fibre will absorb up
to 35% of its own weight in water at a high humidity, before
feeling wet (Leeder 1984; Collie and Johnson 1998). In
comparison, most man-made fibres are able to absorb less
than 5% of their weight in moisture at the same humidity
(Leeder 1984).
In addition to these moisture absorption properties, wool
has an important differentiator in apparel usage in that an
appreciable quantity of heat is also generated as water is
absorbed into the fibre (Figure 2); and then lost again as
the garment dries (Leeder 1984) – effectively warming and
cooling the wearer when needed the most.
• water vapour condensing within the fibre (releasing its
latent heat of condensation)
• water disrupting existing bonding networks and
structure within the fibre, forming new chemical bonds
(with an associated energy release).
Put simply, addition of a polar molecule like water alters
the internal chemistry of Merino to release energy as heat.
Conversely, removing water (eg. by drying) requires the
opposite – an input of energy.
These moisture absorption and desorption characteristics
provide additional important functional characteristics to
wool garments. For example:
The importance of this becomes apparent if one considers
that under resting conditions the body may lose 0.5 litres
of water through perspiration each day, however during
strenuous exercise this can increase to up to 1 litre per
hour. If transmission of moisture (in vapour or liquid form) is
impeded, it can build up against the skin, creating wetness
or clamminess for the wearer.
• When a wool fabric experiences a sudden change
in the environment associated with its wearer, such
as increased activity leading to sweating, wool acts
as a buffer, absorbing the extra moisture quickly and
dissipating it gradually (Leeder 1984). The same occurs
for the external environment, where wool acts as a buffer
to changes in atmospheric humidity (Onions 1962). As a
result, wool can prevent the ‘clamminess’ that can occur
in environments of high humidity (Collie and Johnson,
1998). Supporting this, studies have shown that wool
fabrics still provide a similar level of performance as
polypropylene or nylon fabrics of a similar construction
with respect to perceived comfort, skin temperature
and core body temperature (Rodwell et al. 1965, Rodahl
et al. 1973, Holmer 1985, Bakkevig and Nielsen 1994)
(Bakkevig and Nielsen 1994), despite wool tcontaining
greater levels of moisture. This benefit is most likely
conferred because of the energy released (heat of
sorption) when wool absorbs that moisture.
Because wool fabrics are porous/lofty/bulky and not
completely impermeable to air, they also provide an avenue
for moisture transmission through air spaces between
the fibres and yarns. Such water vapour dispersion can
be further enhanced by movement of the wearer, which
causes a ‘pumping’ of air close to the skin through to the
outside of the garment, both through the fabric itself and
through openings at collars, sleeves, etc (Leeder 1984).
In this respect, design and fit of the garment are also very
important.
HOW DO MERINO FABRICS
TRANSPORT LIQUID
MOISTURE THROUGH
THEIR STRUCTURE?
• In cold climates, where the relative humidity indoors
in winter is generally lower than outdoors, wool
garments conditioned (equilibrated) in a dry indoor
environment immediately begin producing heat when
taken outdoors, buffering the wearer against the sudden
temperature drop they experience. On exposure to a
saturated atmosphere, the heat produced by a kilogram
of dry wool as it takes up 35% water vapour is about 960
kJ, equivalent to the heat output from an electric blanket
over 8 hours. This effect occurs quite quickly, typically
in the first 2-5 minutes and then decreases until the
moisture content of the wool reaches equilibrium with
the higher relative humidity of the atmosphere.
Just as the ability of individual fibres to absorb water in
vapour form is important, a fabric’s ability to allow water
vapour to pass through it is also critical to managing body
temperature and maintaining comfort - especially when the
wearer is participating in athletic activity.
Surface Energy ( relative units)
HOW DO MERINO FABRICS
TRANSPORT WATER
VAPOUR THROUGH THEIR
STRUCTURE?
The interior of the wool fibre has a greater affinity for water
than the exterior of the fibre, but both have the capacity to
transport water in one form or another. The degree of water
repellence of a fibre is determined by its surface energy,
with higher surface energies found in fibres that are more
easily wetted and promote the wicking of water along their
surfaces. Polyester, acrylic and nylon all have higher surface
energy values than wool (Leeder 1984), but a lesser ultimate
capacity for moisture (Figure 3). Polypropylene has a similar
surface energy to wool and (all other things being equal)
could be expected to have similar wicking
properties to wool.
40
30
20
10
0
Nylon
Acrylic
Polyester
Wool
Figure 3. Fibre surface energies of various fibres (Leeder, 1984).
Irrespective of the mechanisms of moisture transport
through textile structures, those made of wool have been
shown by Holmer (1985) to absorb more liquid than those of
nylon (245g vs 198g of sweat) or polyester (Li et al 1992).
WHAT DETERMINES HOW
WARM A GARMENT FEELS?
The skin has nerve endings that will detect even minute or
brief temperature changes, and the degree of coolness or
warmth felt by the wearer will depend on how well fabric
conducts heat away from the skin. Heat has a natural
tendency to move from warmer to cooler regions, and
losses by the human body occur in a number of different
ways:
• Radiation
• Conduction
• Convection
• Evaporative cooling
Radiation is the primary mechanism by which the body
emits and absorbs heat, with up to half of body heat
loss occurring through this means. Heat also transfers
from the body to objects, via conduction, because the
temperature of clothing fabrics is typically between that of
the environment and that of the skin. Because warm air is
lighter than cold air, it rises and is replaced by cooler air,
with the resulting convection currents also carrying heat
away from the body. Finally, evaporative cooling (of sweat)
also allows the body to dissipate excess heat. Conduction
and convection account for 15-20% of heat loss to the
environment.
The thermal resistivity (R) of a fabric is a measure of its
insulating properties – and hence of its relative warmth.
Thermal resistivity is influenced by a range of factors, but the
key ones are:
• The fabric surface;
• The fibres contained in the fabric; and,
• The air trapped in the fabric, yarn or in the
fibres themselves.
To summarise, when the environment temperature exceeds
skin temperature, the body will gain heat through radiation
and conduction and only lose heat through evaporative
cooling. When the environment temperature is lower than
skin temperature, the body will lose heat to the environment
through radiation, conduction, convection and, if active,
through sweat evaporation.
HOW DOES MERINO
APPAREL PERFORM IN
TERMS OF THERMAL
RESISTANCE AND
WARMTH?
The key parameter determining the thermal resistance of
a fabric is the amount of air it traps in its interior - which is
strongly correlated with its thickness (Figure 4). Fibre type
is only of second order importance (Pierce and Rees 1946,
Holcombe and Hoschke 1983), although wool does have
some advantages over other fibres in this respect. Due
to the crimp of the fibres, wool fabrics have an inherent
bulkiness or loft as the fibres are unable to pack together
too closely in the yarn structure. The resilience or elastic
recovery of the wool fibre allows this bulkiness to be
maintained over time (Leeder 1984).
Thermal Resistance = 0.276 ( Fabric Thickness ) - 0.108
R = 0.976
1.2
Fabric Thermal Resistance ( tog )
Having said this, it is important to remember that the
moisture management characteristics of wool arise through
different mechanisms to those seen in synthetic fibres.
Typically, synthetic fibres rely solely on liquid water transport
for their water management characteristics – this being
dictated by the cross sectional shape of the fibre (eg hollow,
solid, round, trilobal, etc) and surface characteristics (which
govern how easily liquid will travel along the fibre surface).
Whilst wool also has the potential to ‘wick’ water in this way,
its superior moisture management characteristics arise
because of its capacity to also absorb/desorb water vapour
– a process that staves off the need to wick liquid water
away (Leeder 1984).
1.0
0.8
0.6
Cotton
Polyester/Cellulosic
Polyvinlychloride
Wool
Other
0.4
0.2
0
0
1.0
2.0
3.0
4.0
5.0
Fabric Thickness (mm)
Figure 2. Influence of fibre type and fabric thickness on thermal resistance
of underwear.
Air permeability has been found to increase as mean fibre
diameter increases (van der Merwe and Gee 1985) and
Merino garments are able to be manufactured in a variety of
thicknesses, structures and micron ranges in order to tailor
the insulative effect to the intended end use.
Illustrating this, heat transmission or dispersal can be
assessed by measuring fabric surface temperature (Figure
5). In a study by Pessenhofer et al. (1991), fabric surface
temperatures were higher for wool, indicating improved heat
dispersal characteristics, while measures of retained heat
were significantly lower for wool than for polypropylene.
WHAT OTHER
IMPROVEMENTS IN
PHYSICAL PERFORMANCE
RESULT FROM WEARING
MERINO?
In addition to the examples cited above, a study (Laing et
al 2007) comparing physiological responses of athletes
exercising while wearing single layers of Merino, polyester
or 50/50 Merino/polyester activewear (237±16 g/m2), under
hot and cold conditions, revealed the following statistically
significant differences
• A longer time to onset of sweating whilst wearing
merino single jersey fabric (Figure 6).
• Lower heart rate during resting and walking whilst
wearing Merino in hot conditions (Figure 7).
• Lower heart rate during running and walking while
wearing Merino in cold conditions.
• Greater heat content of the body when wearing
polyester interlock fabric (under both hot and cold
conditions).
When assessed subjectively, subjects involved in the
investigation gave more positive responses to garment
comfort questions with respect to wool than they did for
polypropylene (Pessenhofer et al. 1991). Achievement
of higher levels of stress by athletes in wool garments
than by those in polypropylene garments indicates
that aerobic performance capacity, that is the supply of
energy through the oxidation of nutrients, is available to a
greater extent in the wool clothing. This can be important
in sporting competition, where only slight differences
in time and performance can be extremely important in
terms of outcomes (Pessenhofer et al. 1991). Wool also
exhibits favourable dynamic adaptation to the flow of
heat from the athlete to the environment. This is possibly
due to the loading of the fibre with moisture from the
massive generation of sweat that takes place following the
commencement of high-load activity (Pessenhofer et al.
1991).
• Greater stability of skin temperature under Merino
fabric.
• Greater stability in core temperature whilst running,
walking and resting in Merino (hot and cold conditions)
The performance of garments constructed from
50/50 Merino/polyester fabric exhibited performance
characteristics intermediate to those made from either
100% Merino or 100% polyester.
40
35
Minutes untill onset of sweating
Figure 5. Infra-red image taken of athlete after 30 minutes of exercise
wearing garment comprised half of merino (RHS of image, as viewed) and
half of polyester (LHS of image) – showing higher surface temperatures
with the merino half, indicative of more efficient heat release.
Wool
Polyester
30
25
20
15
10
5
0
_
_
+
+
89.6oF, 20 2%
R.H. 46.4oF, 40 2%
R.H.
Figure 6. Time to onset of sweating when exercising wearing merino vs
polyester base layer product.
160
60
Propensity for odour emission
Highest
40
Lowest
Wool
Polyester
140
100
80
20
_
+
89.6oF, 20 2%
R.H.
Walking
Running
Walking
Running
0
80
60
40
20
0
Polyester
Polypropylene
Merino
Figure 8. Propensity for odour emission by fabrics of similar construction
(SEMs indicated).
_
+
46.4oF, 40 2%
R.H.
Figure 7. Change in heart rate when exercising wearing merino vs polyester
base layer product.
HOW DOES MERINO
SUPRESS BODY ODOUR
COMPARED WITH OTHER
FIBRES?
Another key consideration with active apparel is its
propensity to build up unwanted body odours. Body odour
arises as the result of the build-up of bacteria and micro
organisms on the skin and/or in worn apparel/hosiery. One
of the key contributing factors to the build-up of bacteria
and body odour is sweat on the skin surface. The human
body has more than 3,000,000 sweat glands, which
continuously secrete moisture. Sweat by itself does not
have any odour. However, if sweat remains on the skin for a
period of time, bacteria are likely to proliferate, creating the
body odour that many find offensive. Such body odour is
due largely to volatile fatty acids produced by these bacteria
as a waste product.
Apparel fabrics constructed from Merino fibre have been
found (McQueen et al 2007a,b) to exhibit a significantly
lower propensity for odour emission after wear than
polyester fabrics of a similar weight and construction
(Figure 8).
Further supporting this, a study carried out by researchers
at the of (WRONZ), who used a panel of human noses to
compare the effect of different fibre types on odour – asking
each participant to rank the odour of used socks in a series
of pairwise comparisons (Burling-Claridge 1998). The
research found that the odour generated on wool socks in
active use was significantly less objectionable than that of
other fibres (Figure 9).
4.0
Propensity for odour emission
Lowest
Highest
Heart beats per minute
120
100
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Polyester
Acrylic Polypropylene Cotton
Merino
Figure 9. Propensity for odour emission from socks constructed of differing
fibres (Burling-Claridge 1998).
HOW DOES MERINO
APPAREL PROTECT FROM
ULTRAVIOLET RADIATION?
Ultraviolet (UV) radiation is a component of the solar
radiation that comes from our sun and to which many
people are exposed whilst engaged in active pursuits.
Overexposure to UV radiation can have harmful effects on
human health, ranging from moderate sunburn, through to
melanoma. The potential for a fabric to protect its wearer
from ultraviolet radiation is described as its Solar Protection
Factor (SPF) or, more commonly, its Ultraviolet Protection
Factor (UPF). UPF relates to the time taken before human
skin begins to redden after exposure to ultraviolet light –
and is usually measured on a scale of 0-50. Until recently
there was a widespread perception that clothing afforded
complete protection against such radiation, however, there
is an increasing understanding that this may not necessarily
be the case. Some fabric constructions perform much better
than others, as do some fibre types.
Many factors influence the level of ultraviolet protection a
garment provides. When radiation strikes a textile surface
some components are reflected, some are absorbed, and
some pass through it. The greater the amount of radiation
able to pass through the textile, the lower the UPF. The most
important of the factors influencing UPF are summarised
below:
• Fibre type (with the UPF being dictated by such things
as chemical composition, ecru colour, fibre cross
sectional shape, presence of delustrants, etc). Wool
typically has a much higher UPF than synthetic fibres
such as polyester.
• Fabric density (with denser knit/weave structures
conferring a higher UPF).
• Degree of stretch (with the UPF being lowered in a
stretched state).
• Fabric colour (with the UPF factor conferred being
dependent upon the amount of dyestuff present and the
chemistry of the dye itself – noting that darker colours
usually, but by no means always, result in a higher level
of protection being conferred).
• Whether the fabric is wet or dry (with the UPF
decreasing markedly when wet).
• Presence of UV absorbing finishes and/or optical
brightening agents (with a range of proprietary finishes
able to be applied to fabrics in order to increase the
UPF).
• Garment design
Merino wool affords excellent UV protection. Research by
Hilfiker et al (1996), Reinert et al (1997) and Haerri (2000)
has shown that wool absorbs radiation throughout the entire
UV spectrum, whereas untreated cotton, nylon, acrylic,
and silk are poor absorbers of UV. Polyester absorbs UV
predominantly at low wavelengths – but with little benefit as
these are the same wavelengths that the earth’s atmosphere
is also efficient at screening out.
In a study by Gamblicher et al (2001) more than half of
236 fabrics surveyed fell below the European standard for
ultraviolet protection of UPF >30. All 100 of the Merino
fabrics passed the test, with even the worst performing
fabric still having a UPF greater than 40 (Table 1). In
contrast, all of the linen samples, and 89% of the viscose
samples tested fell below the standard of UPF 30 – while
the other fabrics tested (nylon, polyester, cotton and blends
thereof) fared equally badly. For example 79% of the cotton
fabrics had a UPF ≤20.
Table 1. UPF Factor for 236 Summer fabrics (mean weight 158 g/m2).
UPF Factor
FIBRE:
0-10
10-20
20-30
30-40
40-50
50+
-
-
-
-
27
73
Cotton
28
28
21
-
7
14
Linen
31
52
20
-
-
-
Viscose
52
29
9
6
2
1
Polyester
2
4
2
2
11
22
Nylon
44
19
-
-
-
38
Blends
-
10
12
14
19
46
Wool
KEY POINTS
Heat and Moisture Management
• Merino fibre has a hydrophobic (water repelling) exterior
and hydrophilic (water loving) interior that confer its
unique moisture management properties , resulting in
enhanced wearer comfort and performance.
• In contrast to most synthetic fibres, wool has the
capacity to remove large amounts (up to 35% of its own
weight) of moisture from the skin surface, before the
fibre even begins to feel wet.
• A fabric’s ability to allow the transmission of water
vapour through its structure will significantly affect the
comfort of the wearer. The ability of Merino fabrics to do
this surpasses that of synthetics.
• The chemical structure of Merino fibre means that it
has the ability to absorb and desorb moisture and to
gain and release heat depending on the external and
internal environment - thus buffering wearers against
environmental changes.
• As it absorbs moisture, Merino fibre releases a small
but perceptible amount of heat. In an apparel or hosiery
application this prevents the wearer from chilling in wet,
cool conditions. In hot conditions the reverse effect
occurs, affording a natural means of buffering the
body’s microclimate.
Odour Supression/Ease of care
• Body odour arises as a by-product of bacteria, which
proliferate in warm moist environments (e.g, when sweat
is allowed to remain on the skin for a period of time).
• Merino fibre, through its complex chemical and physical
structure, resists the development and proliferation of
odour to a much greater extent than synthetic materials
or cotton.
• Merino apparel and hosiery is readily laundered to
remove soil or other contaminants of potential relevance
to health - and efficient shrink resist processes are
employed to enable full machine washability.
UV Protection
• UV radiation reaching earth from the sun can have
deleterious effects on human health when overexposure
occurs.
• Merino fibre is a very efficient absorber of potentially
harmful UV-A and UV-B radiation.
• Fabric construction is also a key determinant of the
extent to which textiles will protect a wearer from UV
radiation.
• Summer-weight Merino garments have been
consistently shown to offer a higher degree of UV
protection than fabrics constructed of
competing materials.
REFERENCES
Bakkevig, M. K and Nielsen, R. 1994. Impact of wet underwear on
thermoregulatory responses and thermal comfort in the cold. Ergonomics,
37, 1375-89.
Burling-Claridge, G. R., 1998. Odour production in active sportwear.
WRONZ Confidential report.
Collie, S. R. and N. A. G. Johnson, 1998. The benefits of wearing wool
rather than man-made fibre garments. Lincoln, Christchurch, New Zealand,
WRONZ.
Gambichler, T., Rotterdam, S., Altmeyer, P., and Hoffmann, K., 2001.
Protection against ultraviolet radiation by commercial summer clothing:
need for standardised testing and labeling, BMC Dermatology, 1: 6.
Hilfiker, R., Kaufmann, W., Reinert, G., and Schmidt, E., 1996. Textile
Research Journal, 66: 2, 61.
Holcombe, B. V., and Hoschke, B. N., 1983. Dry heat transfer characteristics
of underwear fabrics. Textile Research Journal, 53, 368-74.
Holmer, I. 1985. Heat exchange and thermal insulation compared in woollen
and nylon garments during wear trials, Textile Research Journal, 55: 9,
511-8.
Laing, R. M., Sims, S. T., Wilson, C. A., Niven, B. E., and Cruthers, N. M.,
2007. Differences in wearer response to garments for outdoor activity.
Ergonomics, 1-19.
Leeder, J., 1984. Wool - Nature’s Wonder Fibre, Australasian Textile
Publishers.
Li, Y., Holcombe, B. V., and Apcar, F., 1992. Moisture buffering behaviour of
hygroscopic fabric during wear. Textile Research journal, 62: 11, 619-27.
Massie, D. S. and Mehta, P. N., 1980. Moisture transport properties of
underwear fabrics. Ilkley, Yorkshire, UK, International Wool Secretariat,
Technical Centre.
McQueen, R.H., Laing, R.M., Brooks, H.J.L., and Niven, B.E., 2007a. Odor
intensity in apparel fabrics and the link with bacterial populations. Textile
Research Journal, 77, 449-56.
McQueen, R.H., Laing, R.M., Wilson, C.A., Niven, B.E., and Delahunty,
C.M., 2007b. Odor retention on apparel fabrics: Development of test
methods for sensory detection. Textile Research Journal, 77, 645-52.
Onions, W. J., 1962. Wool. An Introduction to its Properties, Varieties, Uses
and Production. Interscience Publishers: 46-63.
Pessenhofer, H., B. Kohla, et al., 1991. Influencing energy readiness
and thermal regulation of humans during physical stress on a bicycle
ergometer by clothing made from various textile materials. Graz, Austria,
Physiologiches Institut, Karl-Franzens Universitat.
Pierce, F. T and Rees, W. H. 1946. Heat transfer through moist fabrics.
Journal of the Textile Institute, 37, T181-204.
Reinert, G., Fuso, F., Hilfiker, R., and Schmidt, E., 1997. Textile Chemist and
Colorist, 29: 12, 36.
Rodahl, R., Giere, A., Staft, P. H., and Wedin, B., 1973. A physiological
comparison of the protective value of nylon and wool in a cold environment,
in A. Borg and J. H. Veghte (eds.), The Physiology of Cold Weather Survival
(AGARD Report No 620) 53-8.
Rodwell, E. C., Renbourn, E. T., Greenland, J., and Kenchington, K. W. L.,
1965. An investigation of the physiological value of sorption heat in clothing
assemblies. Journal of the Textile Institute, 56, 624-45.
Van der Merwe, J. P. and E. Gee, 1985. The Effect of Fibre Physical
Properties on Woollen Processing Performance and on Yarn and Plain
Knitted Fabric Properties. Proceedings of the 7th International Wool Textile
Research Conference. Tokyo. 2: 95-104.
This report was prepared by the New Zealand Merino Company
Limited, funded by WR Inc.