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Phase Change Material in Hiking Boots Does Not Minimise the Risk of Cold Injury

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The present study compared the thermal insulation properties of identical hiking boots, incorporating a layer of either Sympatex or a layer of Outlast Phase Change Material PCM. PCM contains paraffin filled microcapsules, which change their state of aggregation with temperature. During heating, PCM liquefies and absorbs a certain amount of energy. Conversely, during cooling PCM changes from a liquid to a solid state and releases thermal energy. Specifically, we evaluated whether PCM offers any significant protection against peripheral cooling and subsequent cold injury to the feet. Subjects 20 males and 20 females participated in three trials. In two of these trials they immersed their booted feet, wrapped in a thin plastic bag, in 30 C for 15 min, followed by 3 hrs in 15 C water. On one occasion they wore boots with a PCM layer PCM, and on the other, identical boots, but without a PCM layer Control. At regular intervals we monitored tympanic temperature Tty, average skin temperature of the arm, chest, thigh and calf Tsk, foot temperature 6 sites, and heat flux from the skin of the foot 6 sites. Thermal insulation of the boots was determined separately with a thermal foot manikin. There was no change in Tty and Tsk during the three trials. There were no differences in any of the foot skin temperatures or heat flux measurements between the Outlast and Sympatex boots. The thermal insulation of the boots was 0.167 sq m KW for the Sympatex and 0.163 sq m KW for the Outlast boot. Phase change material does not offer any significant improvement in thermal protection, and thus does not minimize the risk of cold injury.

Subject Categories:

  • Biomedical Instrumentation and Bioengineering
  • Protective Equipment
  • Stress Physiology
  • Test Facilities, Equipment and Methods

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