Thermal Insulation and Porosity-From Macro- to Nanoscale

Porosity of textiles is one of the main factors influencing their thermal conductivity and insulation. Porosity in textile fabrics is the combination of fiber porosity, yarn packing density, and voids due to fabric construction. It is shown that assemblies from very fine fibers tend to suppress radiation and convection heat transfers because of huge total surface area, which restricts the free flow of air passing through them. For effective thermal insulation especially at low temperatures, it should be selected sufficiently high thickness of textile layer as well. Porosity is therefore decisive parameter for the evaluation of thermal comfort expressed in special units clo. The main aim of this chapter is the prediction of the effect of porosity of fabrics and fibers on the thermal conductivity and insulation. The changes of thermal comfort due to the use of hollow fibers and multilayer corrugated nonwovens are described. The thermal properties of highly porous aerogel structures are discussed. Enhancement of insulation by their inclusion into textiles is investigated as well.