Dynamic Moisture Vapor Transfer Through Textiles

Abstract

This study investigates new techniques for measuring the influence of fiber, type on fabric surface vapor pressure and temperature, which are related to sensations of cloth ing comfort. Microfine hygrometry and thermometry are used to measure dynamic changes in moisture vapor pressure and temperature on both surfaces of a two-layer fabric assembly under simulated body-clothing conditions. Findings show that fiber type significantly influences transient, comfort-related variables such as changes of inner surface vapor pressure and temperature. Polyester double layer assemblies exhibit the lowest inner surface temperature, but a much higher concentration of moisture vapor. Cotton assemblies show the slowest rate of inner vapor pressure accumulation with the highest inner surface temperature rise. Mixed fabric layers of cotton and polyester reveal moderate inner surface temperature peaks and moderate vapor pressure changes. Using a completely different methodology, this study reinforces other findings that fiber type and finish are indeed important to understanding transient changes in moisture vapor and temperature within fabric and clothing assemblies and their interior microclimates.

Clothing, Textiles, and Human Performance

“…Addition of either a microporous membrane or laminating substrate in an assembly resulted in increased vapour pressure and increased temperature, and in the assemblies tested, the cotton outer layer could thus not absorb moisture vapour [232]. The smaller the space the larger the impedence.…”

“…Dillcrences in the properties of materials arranged in single and in multiple layers and measured in the laboratory have beeti reported (e.g. [232] on fabric layers with various microporous films; [233] on thermal properties of different structures and weights of cotton; [234] on thermal protective performance of single and multiple-layer fabric assemblies). Interactions betw^een and among effects of the various layers are evident, thus predicting the performance of humans wearing garments made from these types of fabrics is problematic.…”

“…Similarly, a semi-permeable film positioned between two fabric layers of an assembly of materials (knitted cotton, knitted polyester) has been shown to influence vapour pressure and temperature changes on both surfaces of the assembly, when arranged to simulate bodyclothing conditions [232]. Addition of either a microporous membrane or laminating substrate in an assembly resulted in increased vapour pressure and increased temperature, and in the assemblies tested, the cotton outer layer could thus not absorb moisture vapour [232].…”

“…The smaller the space the larger the impedence. Physical properties in the assembly such as the pore size of the film w^ere shown to be far more important to moisture transfer in the fabric film fabric assembly than the hydrophilicity of the film [232]. Although linked to transient comfort variables for wearers of garments, by 2000. this work had been restricted to tests carried out on a simulated sweating skin model.…”

“…These differences were ignored in the discussion. Three commercially a\ailable microporous polytetrafluoroethylene (PFTE) membranes and one non-porous pohurethane copohmer laminate were included in the trials [232].…”