An Investigation of the Relationship between Cotton Fineness and Light Scattering from Thin Webs as Measured by Near-Infrared Transmission Spectroscopy

Abstract

Near-infrared transmission spectroscopy (NITS) is applied to thin cotton webs to measure fiber fineness (expressed either as specific surface—the external surface area per unit weight of fiber—or as cross-sectional perimeter). We report here the development and successful testing of a mathematical model that predicts a linear relationship between fineness and light-scattering intensity (optical density, log 1/ T) by a thin cotton web. With a thin web of fibers in the light beam, absorption of photons out of the beam is negligible. When the detector is placed several inches from the web, only the photons passing between the fibers strike the light detector. Photons that strike a fiber are scattered out of the light beam and away from the detector. Thus the fineness of the fiber controls the propagation of light to the detector. The premise that specific surface is proportional to optical density when the weight of fiber in the light beam is constant is shown experimentally (probability, p < 0.0045). Also, the premise that perimeter is proportional to optical density when the total length of fiber in the light beam is constant is shown experimetally ( p < 0.0070). These results are based on analysis of 9 cottons; 810 webs were produced, computer sorted by weight, and the scatter spectra recorded for 360 webs.