Infrared emittance of fibrous materials

A theory of the IR emittance of fibrous materials has been developed. The theory predicts the IR spectral emittance of a matte of randomly arrayed cylindrical fibers as a function of the optical constants of the fiber material, the fiber diameter, the packing density of the fibers, the packing of the fibers within fiber bundles, the reflectance of the substrate, and the thickness of the fabric layer. Theoretical simulations were made and compared with experimental measurements of the IR emittance of polypropylene samples. Both the theory and the experimental data confirm the validity of the concept that fabrics can be tailored by a proper choice of the above parameters so as to obtain an emittance distinctly different from unity.