A Comparative Study of NIR Diffuse Reflectance of Cottons Grouped According to Fiber Cross-Sectional Dimensions. Part III: Experimental

Abstract

In Part I of this series, a model was proposed to predict the comparative NIR reflectance of grouped cottons. In Part II of this series, the model's optical path was simulated. We report here the detailed examination of this model, its optical path, and cotton reflectance spectra in the wavelength range from 840 to 2500 nm. The premise that paired cottons with allowed nontrivial combinations of dimensional variables will produce the predicted comparative reflectance is verified experimentally, as is the premise that any number of cottons of the same perimeter with varying wall thickness will produce the predicted comparative reflectance. The critical assumption of a constant total fiber length in the optical path, for cottons of the same perimeter, is confirmed. Thus the log(1/ R) values are a function of a wall dimension (thickness or area) and perimeter. Finally, three distinct wavelength regions of the reflectance spectra are noted: <1440 nm, 1440 to 2100 nm, and ≥2100 nm. At wavelengths ≥ 2100 nm, significant absorption of photons out of the beam, caused by the cellulose in the fiber wall, controls the reflectance. At wavelengths <1440 nm, the log(1/ R) function is different and its cause unresolved. For some cottons, the intermediate band of wavelengths shows a transition in log(1/ R) values from the resolved to the unresolved function.

Cotton Fiber Quality Characterization with Light Scattering and Fourier Transform Infrared Techniques

“…It was employed to determine polarized-and spectral-light (410 nm to 690 nm) scattering of six different cotton samples. This light-scattering approach differs from the near-infrared (NIR) spectrometry work reported by Montalvo et al 5 and Thomasson and Shearer, 6 as no glass or any other medium was used to hold the samples. The laser light was incident directly on the sample, thereby eliminating any possible error due to refraction and multiple scattering from the sample holder.…”

“…The nominal wavelength used by Carter et al 7 was 6 lm. Montalvo et al 5 used NIR transmission spectroscopy spanning a wavelength spectrum of 850 to 2500 nm, and Thomasson and Shearer 6 used NIR reflectance spectroscopy (1100 to 2500 nm) for measurements on cotton fibers. Also, Buco and Montalvo 8 discussed the application of visible reflectance spectroscopy to cotton samples.…”

Cotton Testing

“…Likewise, micronaire was found to be a better guide to dye uptake than either of its components [115]. A series of papers [116][117][118] examined the relationship between diffuse reflectance of near-infra-red radiation on both fineness and maturity. The authors partitioned spectral variation into physical and chemical causes, and applied principal components analysis to refine their model.…”

Studies to Measure Cotton Fibre Length, Strength, Micronaire and Colour by vis/NIR Reflectance Spectroscopy. Part II: Principal Components Regression

“…On the other hand, MIC is a function of wall thickness and perimeter, both of which are sensed concurrently in the 1100-2498 nm region of the spectrum due to light absorption by the cellulosic wall of the fibre. [8][9][10][11] The primary spectral region for both colour measures is the 400-1100 nm region because radiation in the visible range senses electronic structures (i.e. colour functional groups) of molecules.…”