| Heat barriers or insulators are defined as those materials or combinations of materials, with air or evacuated spaces, which will retard the transfer of heat with reasonable effectiveness under ordinary conditions. The manufacture of heat barrier or insulating materials has become a major industry since 1990. Insulating materials are used in many different applications and at a variety of temperatures. Many of the heat barrier materials being employed use some form of textile fibers or fabrics. One of the most used fabric structures is nonwoven fabrics, and in particular, needle-punched nonwoven fabrics. However, the traditional nonwoven insulators are limited in temperature range to less than 150{dollar}spcirc{dollar}C. This research is an attempt to extend the temperature range of needled nonwoven fabrics to approximately 450{dollar}spcirc{dollar}C.; The heat blocking potential of a material is known to be a function of fiber thermal properties, fabric porosity, fiber packing density, and operating temperature. This research focuses on development and evaluation of a heat barrier fabric for use at approximately 450{dollar}spcirc{dollar}C. The fabric structure being studied is a multi-layered, glass/ceramic, needle punched nonwoven. Ceramic/glass structures are entangled using needles having differing numbers of bars. The effective thermal conductivity of each sample is measured using the guarded hot plate method. Finally, through statistical analysis, an attempt is made to relate effective thermal conductivity and air permeability of the fabric structures. |
