2007, Piran, Slovenia

Clothing
THE INTERACTION BETWEEN PHASE CHANGE MATERIALS
AND PHYSIOLOGICAL EFFECTOR MECHANISMS
Hilde Færevik*, Maria Le Thi*, Arne Røyset**, Randi Eidsmo Reinertsen*
*SINTEF Health Research, NO-7465 Trondheim, Norway
**SINTEF Materials and Chemistry, NO-7465 Trondheim, Norway
Contact person: hilde.ferevik@sintef.no
INTRODUCTION
Phase-change materials (PCM) are characterized by their ability to absorb energy
when they change from a solid to a liquid state and to release heat as they return to the
solid phase. PCM used in clothing go through the phase change at temperatures close
to the thermally neutral temperature of the skin, 28-32° C. During the phase change,
the temperature of the PCM does not change, and PCM thus have the ability to
stabilise body temperature. Hence, PCM are potentially capable of reducing thermal
stress and providing improved thermal comfort when protective clothing is worn.
During periods of heat stress, the potential cooling contribution provided by PCM
should be identified and evaluated as a part of the total heat exchange mechanism
through the clothing system, together with the capacity of the body to maintain
thermal neutrality and comfort. If PCM has a cooling effect, this will affect the
temperature-regulating system, and postpone the activation of the body’s own effector
mechanisms that facilitate heat loss.
The aim of this study was to investigate the effect of PCM in a protective clothing
ensemble used in a warm environment (27° C, 50% RH). We hypothesised that the
time course of physiological thermoregulatory heat defence mechanisms will follow
the dynamics of temperature development in the PCM. The hypothesis was
investigated through the following predictions: i) PCM will suppress (but not prevent)
vasodilatation and sweat production during the phase change period of the PCM; ii) At
the point in time when all the PCM has changed to a liquid state and there is no more
capacity to absorb excess heat from the body, we will observe a temperature rise at the
location of the PCM together with a rise in skin temperatures and sweat production;
iii) Subjective ratings of thermal comfort and thermal sensations will change to less
comfortable and sensation of higher temperatures after the end of the phase change
period.
METHODS
Experiments were carried out using PCM microcapsules in fabrics (Outlast 341
Clemmons). The effect of Outlast PCM microcapsules in fabrics is 60J•kg -1 .
The test subjects (six men) were dressed in protective clothing with integrated zones
of PCM immediately on entering the climatic chamber (air temperature 27±0.5º C,
50±5% RH, air velocity 1.5 m•s -1 ). Before the test they rested for 20 minutes in a
preparation room to stabilize their body temperatures. The test protocol comprised
120 minutes rest in a sitting position. Heat production was measured every 15
minutes. Temperatures, moisture and heart rate were recorded every minute.
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