Thermal and moisture behavior of a multi-layered assembly in a pneumatic compression device

Abstract

The objective of this research was to determine the effect of multiple layers of materials typical of those used in air pneumatic compression devices (which require air impermeable layers to function) on thermal and water vapor resistance. The experimental set-up included: (a) single layers of two next-to-skin knit fabrics in both relaxed and extended conditions, (b) two layers of silicone, and (c) a multi-layered assembly comprised of a next-to-skin fabric and two layers of silicone. Structural properties (thickness, mass) dominated thermal resistance of the multi-layered assembly, and the silicone layers rendered this assembly impermeable to water vapor as expected. Results confirmed the need for some form of 'ventilation' to facilitate water vapor transfer from a potential user’s skin to the environment. By creating 18 circular vents across the silicone layers (each vent 314 mm2), which formed ventilation of ∼2% of total surface area, the water vapor resistance of the multi-layered assembly dropped significantly from very high (but non-measurable) to below ∼300 m2 Pa/W, although ventilation did not improve the thermal resistance of the multi-layer arrangements. Results of this research will enable manufacturers of pneumatic compression devices to develop devices comprised of a multiple layer arrangements i.e. a knit fabric next-to-skin layer and silicone layers with optimized vents across the silicone layers, so that the user can continue the compression treatment with an acceptable microenvironment.

Material, structure, and design of textile-based compression devices for managing chronic edema

“…whether they are relaxed or extended also have an effect on the physical and performance properties of fabrics, given that extended fabric exhibit thinner and more open up the fabric structure resulting in less resistance to thermal and water-vapor transfer, more permeable to water-vapor, more permeable to air compared to relaxed fabrics. 69,70 For compression products, knitted fabric is the most prevalent fabric structure. Knitted fabric is a two-dimensional structure made up of natural yarn and/or synthetic filament.…”

“…whether they are relaxed or extended also have an effect on the physical and performance properties of fabrics, given that extended fabric exhibit thinner and more open up the fabric structure resulting in less resistance to thermal and water-vapor transfer, more permeable to water-vapor, more permeable to air compared to relaxed fabrics. 69,70…”

“…145 The effect of multi-layer assemblies composed of a wool-based next-to-skin knit layer (in extended conditions to simulate the end-use or application), and outer two silicone layers with and without vents across the silicone layers on thermal and moisture behavior of a potential PCD was investigated. 69,70 Water vapor resistance of the multi-layered assembly dropped significantly by forming ventilation of ∼2% of total surface area, allowing it to create an acceptable microenvironment for the user. Although, this study was the limit examination of the thermophysiological properties of single layer material/s, and multi-layer assemblies using a sweating guarded hot plate.…”

“…Properties critical to selection of materials and their performance are that they are light in weight, puncture resistant (in case of PCDs), sufficiently flexible to allow conformation to the body shape, air and water-vapor permeable, and that they exhibit low thermal and water-vapor resistance. 13,58,69 Other factors include presence of frictional properties and response to repeated cycle without wrinkles occurring. A further requirement is that compression devices must not abrade the affected or adjacent skin.…”