Near infrared (NIR) techniques for the measurement of cotton-polyester (PET) blend content have concentrated on yarn slivers and greige fabrics rather than the more difficult application to dyed or printed fabrics. The need for a robust and rapid measurement of the fiber content in dyed cotton-PET fabrics has been expressed by several organizations. Investigations were initiated to develop NIR techniques to measure the cotton content of dyed blend fabrics. NIR measurements were made on dyed or pigmented cotton-PET fabrics that comprised a wide range of cotton content, fabric parameters, and patterns/colors. The samples were analyzed on two NIR instruments at two locations with various reflectance NIR sampling systems. Significant spectral differences were observed for 100% cotton and 100% PET samples, and these spectral differences carried over to the dyed cotton-PET samples with changing cotton content. The impacts of significant differences in baseline were minimized with the use of advanced chemometric normalization techniques. Rapid (less than 5 minutes) and accurate NIR measurements of the blend content in dyed cotton-PET fabrics were developed, with a NIRlaboratory method agreement normally within ± 3.0% cotton for nearly 90% and higher of the validation samples.

Two of the important cotton fiber quality and processing parameters are fiber maturity and fineness. Fiber maturity is the degree of development of the fiber’s secondary wall, and fiber fineness is a measure of the fiber’s linear density and can be expressed as mass per unit length. A well-known method for fiber maturity and fineness is a cross-section image analysis and microscopy measurement. In general, typical cross-section image analysis and microscopy methods for fiber maturity and fineness can be slow and tedious to perform. Much interest has been shown in improved and rapid routine measurements of fiber maturity and fineness in the laboratory. The Cottonscope® is a new small footprint instrument for measuring fiber maturity and fineness, consisting of a longitudinal measurement of weighted fiber snippets in water using polarized light microscopy and image analysis. A program was implemented to assess the potential and capabilities of the Cottonscope to measure cotton lint maturity and fineness and to determine the major operational impacts on the Cottonscope results. The measurement was fast and easy to perform. The major operational impact on the Cottonscope results was environmental conditions (room temperature and relative humidity), and its impact was a concern for fineness only. Very good method agreement was observed between the Cottonscope and image analysis and microscopy method for maturity and fineness, with moderate coefficients of determination, R²s, and low residuals. Recommended operational protocols for routine Cottonscope measurements were developed.

A key cotton fiber quality property is micronaire, which acts as an indicator of the fiber’s maturity and fineness. Previous studies have demonstrated the ability of Near Infrared (NIR) instrumentation to measure these cotton properties with varying degrees of success, but these studies did not provide conclusions on the capabilities of NIR spectroscopy as a general technique for these analyses. Recent advances in NIR technology could result in improved measurements of these cotton properties. A comparative investigation was implemented to determine the capabilities of modern commercial bench-top and portable NIR systems to monitor cotton fiber micronaire, maturity, and fineness in order to gain insight as to the “universality” of the NIR measurements for these fiber properties. Cotton samples were analyzed on five commercial systems and an older, custom-built system. Very good spectral agreement was observed between the portable and bench-top NIR units. The rapid and simultaneous measurement of cotton micronaire, maturity, and fineness by multiple commercial systems was demonstrated and compared favorably to the custom system, but without the delay and cost in building custom units. For the bench-top NIR systems, all end-state criteria were successfully meet. The “universal” nature of the NIR measurement of these cotton fiber properties was validated for commercial NIR systems. As expected, the NIR results for the portable NIR units were normally not as good as those for the bench-top instruments, but they were very acceptable for demonstrating the potential for the portable units to measure these cotton fiber properties.

The Cottonscope simultaneously measures a cotton fiber’s maturity and fineness using a small amount of fiber sample. A program of testing was devised to establish the potential and capabilities of the Cottonscope to rapidly and accurately measure maturity and fineness of small quantities of near-isogenic cotton lines (NILs), and to examine the use of the Cottonscope maturity distributions for breeder applications. Cottonscope measurements were performed on mature and immature fibers of varying days post-anthesis (DPA) from two pairs of NILs (MD 52ne versus MD 90ne; TM-1 versus the low maturity im). The patterns of cotton maturity and fineness during cotton fiber development of each NIL measured by the Cottonscope were compared to those measured by more conventional methods (e.g. the Advanced Fiber Information System (AFIS), an older and currently more widely used method). The Cottonscope maturity and fineness results were much more responsive to increasing DPA than the AFIS results, and the patterns of Cottonscope maturity values were consistent with those of the Fibronaire micronaire. Comparisons of the Cottonscope maturity distributions among the NILs demonstrated that the maturity distribution for im was very different and exhibited much lower maturity values compared to the distributions of other lines. The results demonstrated that the Cottonscope is an efficient instrument for cotton breeders to monitor fiber maturity and fineness of developing and mature cotton fibers.

The accurate and precise measurement of cotton maturity and fineness is often difficult, laborious, and/or expensive to perform. The Cottonscope® rapidly, accurately, and precisely measures fiber maturity and fineness with small quantities of sample (approximately 50 mg). Interest has been expressed in the use of different sample weights of fiber, especially lower sample weights by geneticists. A program was implemented to establish the capabilities of the Cottonscope to rapidly and accurately measure maturity (maturity ratio (MR), original polarized light microscopy maturity ratio (MRBF)), fineness, and ribbon width with different sample weights of fiber. The change in sample weight significantly impacted the Cottonscope results for MR, fineness, and ribbon width. Fineness was most impacted by varied sample weight. The impacts of sample weights on the cotton results were removed by re-calibrating the instrument at each sample weight. Decreasing the sample weight below 50 mg increased sample measurement times, especially at 10 mg sample weight. These results demonstrated that the Cottonscope can accurately and precisely measure the fiber’s maturity, fineness, and ribbon width with cotton fiber samples as small as 10 mg.

In the U.S.A., cotton is classed (primary quality parameters) by the Uster ^® High Volume Instrument (HVI), which must be maintained under tightly controlled laboratory environmental conditions. Improved and fast response quality measurement systems and tools are needed to rapidly assess the quality of cotton. One key area of emphasis and need is the development and implementation of new fast-response quality measurements that can be used not only in the laboratory but which also can be adapted to field and at-line quality measurements. A program was implemented to determine the ability of portable near-infrared (NIR) instrumentation to monitor critical fiber properties of cotton samples in the laboratory, at-line, and in the field, with initial emphasis on the laboratory measurement of cotton fiber micronaire. Micronaire is a key cotton property, and it is an indicator of the fiber’s maturity and fineness. Distinct NIR spectral differences between samples with varying micronaire were observed. A comparative evaluation was performed to determine optimum instrumental conditions for laboratory cotton micronaire measurements. The comparative evaluation established that the optimum instrumental conditions for laboratory measurements of micronaire was obtained with the use of a glass-covered sampling port and increased instrumental gain, with high R² values, low residuals, and with ≤ 12% outliers. For a NIR measurement with potential for multiple simultaneous analyses and non-laboratory measurements, the micronaire measurement was fast (< 3 min per sample) and easy to perform. The rapid and accurate laboratory measurement of cotton fiber micronaire with portable NIR instrumentation was demonstrated.