Micronaire is a key cotton fiber quality assessment property, and changes in fiber micronaire can impact fiber processing and dyeing consistency. Micronaire is a function of two fiber components—maturity and fineness. Historically, micronaire is measured in a laboratory under tightly controlled environmental conditions. There is increased interest by the cotton and textile industry to measure key fiber properties both in the laboratory and in-field (non-controlled conditions), using small portable near infrared (NIR) spectroscopy instruments. A program was implemented to determine the feasibility of using portable NIR instruments to monitor fiber micronaire, maturity, and fineness. Prior to outside the laboratory measurements (field, warehouse, etc.), laboratory feasibility was performed to assess the NIR instruments’ capabilities. Comparative evaluations for fiber micronaire, maturity, and fineness were performed on three portable NIR instruments. Instrumental, sampling, and operational procedures and protocols for each instrument were established. Although representing different measurement technologies, very good spectral agreement was observed between the portable NIR instruments and a bench-top NIR unit used as a comparison. Rapid (less than 3 minutes per sample), easy to use, and accurate measurements of fiber micronaire and maturity were achieved, with regressions ( R values) greater than 0.85, low residuals, and a low number of outliers observed for each NIR instrument. Improvements are required for the accurate measurement of fiber fineness by portable NIR instruments. Thus, for well-defined cotton fiber samples, the universal nature of the NIR measurement of cotton fiber micronaire and maturity by portable NIR instruments was validated.

A key quality and processing parameter for cotton fiber is micronaire, which is a function of the fiber's maturity and fineness. Near-infrared (NIR) spectroscopy has previously shown the ability to measure micronaire, primarily in the laboratory and using large, research-grade laboratory NIR instrumentation. International interest has been expressed by the industry in the measurement of fiber micronaire using small, portable NIR spectroscopy instruments for both laboratory and outside the laboratory (e.g., field or greenhouse) locations. New, very small NIR micro-spectrometers have been commercialized that offer the potential advantages of smaller size and lower weight, lower cost, and increased portability over current portable units. A program was implemented to determine the feasibility of a small NIR microspectrometer to measure fiber micronaire both in the laboratory and outside the laboratory, with initial emphasis on laboratory measurements prior to moving to field evaluations. In the laboratory, distinct spectral differences with increasing micronaire were observed. Optimal sampling and instrumental procedures and protocols for two units (different spectral wavelength capabilities) were established. Comparative evaluations established very good method micronaire agreement between the micro-spectrometer and a standard portable spectrometer, with high Regression (R) value, low residuals, and few outliers (less than 20%). The NIR micro-spectrometer measurements were fast (<1 min per sample), required no sample preparation, and were easy to perform. All end-state criteria were exceeded. The rapid and accurate laboratory measurement of fiber micronaire with a NIR micro-spectrometer was demonstrated.

A key cotton fiber property is micronaire. Micronaire can impact the fiber’s quality, textile processing efficiency, and fabric dye consistency. Fiber micronaire is normally measured in a laboratory under tight standard temperature and relative humidity (RH) environmental conditions (21 ± 1℃, 65 ± 2% RH). Near infrared (NIR) measurements have been performed both inside and outside of the laboratory, but measurements outside the laboratory have at times demonstrated reduced predictive capability, possibly due to the lack of standard environmental conditions. A program was implemented to determine the impact of non-standard conditions of temperature T and relative humidity RH on NIR micronaire results for bench-top and portable NIR instruments. Non-standard T and RH resulted in varying fiber moisture, which impacted the NIR spectral response. The NIR micronaire results were impacted by the non-standard conditioning for all instruments, with the lower wavelength region (∼910–1680 nm) portable instrument impacted the most. The impacts and deviations were greater at high temperature/RH compared to low temperature/RH conditioning. These results provide a rationale for the deviations observed previously in NIR micronaire results for outside the laboratory micronaire measurements with portable NIR units.