This chapter is a discussion of the application of near-infrared (NIR) for the analysis of textiles and the fibers constituting textile materials. It discusses the use of NIR spectroscopy for the analysis of natural fibers, such as cotton and cotton blends. The topic of NIR analysis of synthetic fiber parameters is also included in the text, such as the analysis of nylon, moisture, finish-on-fiber, and heatset temperature. Polyester fiber and carpet analyses are also summarized.

Access to water sources is critical because it can affect cotton fiber growth, yields, and quality. It is of interest to determine how a water-limited field environment compares to a well-watered environment, especially when it comes to how cotton quality and surface characteristics are affected. In the current investigation, metal ion quantities were monitored using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The effect of variety and field treatments on high volume instrument (HVI) parameters were examined. the results were quite variable overall, with reflectance (Rd) and strength having the least statistically different means among the quality parameters.

Cotton fiber wax extraction yields of the contemporary accelerated solvent extraction (ASE) method were compared to the reference Soxhlet extraction method. Two Upland cotton varieties, referred to as the STV5458 B2F and the FM9180 B2F varieties grown in Lubbock, TX, USA, were examined. Effects of ASE extraction time and temperature were investigated. Characteristic environmental scanning electron microscopic (ESEM) images revealed fiber damage following both extraction methods, with the ASE method showing the least damage. A one-way ANOVA showed the two methods to be statistically different according to a 95% confidence level (p < 0.05) when combining analyses of the two cotton varieties.

Maturity and strength are two of the physical properties that determine the quality and value of cotton (Gossypium hirsutum L.). Their relationship has been poorly understood due to technical difficulties of directly measuring maturity and strength from individual fibers. The narrow maturity and strength ranges of most upland cotton fibers have also impeded cotton scientists from performing statistical approaches. Therefore, we used genetic approaches to construct 168 new upland cotton materials covering broad ranges of maturity and strength and measured maturity ratio (MR) and strength‐related properties from bundle and single fibers with reference methods. Comparisons of their properties showed that the MR values were significantly and positively correlated with single‐fiber breaking force (cN) as well as bundle fiber strength (g tex−1) and elongation values. There were also correlations between the MR values and single‐fiber strength (cN tex−1), although its r value was substantially affected by the linear density (tex) that normalized the breaking force (cN). The results showed that secondary cell wall development (maturation) is a major factor in determining bundle and single‐fiber strength. These results will help cotton scientists understand the correlations between fiber maturity and strength and develop strategic plans to improve quality and yield of cotton fibers.

The differential dyeing (DD) method has been a subjective method for visually determining immature cotton fibers. We attempted to quantitate DD results and offer an efficient means of elucidating cotton maturity, without visual discretion. Image analysis of cotton color obtained with a scanner was performed and compared to spectrophotometrically measured color. Low, Medium and High micronaire (Mic) cotton standards were dyed, and we determined that blending the cotton yielded more precise color measurement; with the mean red, green and blue (RGB) values for a low Mic sample being: 101.6 ± 23.9, 83.1 ± 22.0 and 98.3 ± 23.1, respectively; while blending yielded RGB values: 121.6 ± 9.0, 98.8 ± 8.6 and 116.0 ± 8.9, respectively. Comparing RGB values to Mic, it was found that R and B color parameters do not show a trend, but G values decrease with increasing Mic indicating a decrease in G dye uptake with an increase in maturity. The conventional L*a*b* color space values were also obtained for the dyed cottons and compared to RGB and Mic results. The %CV for a* values are higher compared to L* and b* measurements: ∼31.9%, 18.9% and 8.6% for low, medium and high Mic samples, respectively. L* and b* decrease while a* increases with Mic, indicating an increase in R dye with an increase in maturity. The DD Bath method was found to be reliable, with R showing the greatest variances. G and a* values obtained were found to be the best correlation of differences in Mic.

Upland cotton is naturally white, with its yellowness (+b) rating highly influencing its economic value. Field conditions, microorganisms, and growth problems can cause cotton to become discolored at harvest, which has historically been thought to indicate a decrease in product quality. Previous research has suggested that some reactions between amino acids and carbohydrates on the surface of cotton fibers may lead to color development after harvest during certain storage and shipping conditions. There has been a lack of research evidence to understand how initial amounts of those surface constituents present at harvest may indicate the propensity for potential future changes in +b ratings. Due to the monetary implications, it is important for those in the cotton industry to better understand exactly how detrimental the +b value is on the functionality of the cotton. This study aimed to identify potential relationships between the post-harvest surface amino acids and carbohydrates content with color rating values to gain insight using High Volume Instrument (HVI), a portable spectrophotometer, ion chromatography, and a ninhydrin test to compare amino acid and carbohydrate content of 45 upland cotton samples with their color measurements: +b, Rd, and L*a*b*. A correlational statistical analysis found a quadratic relationship between amino acid content and +b; and highly positive correlations between amino acids and +b ratings: 0.8607; and b* values: 0.820 (p<0.05).

The thickness of cotton fiber cell walls is an important property that partially determines the economic value of cotton. To better understand the physical and chemical manifestations of the genetic variations that regulate the degree of fiber wall thickness, we used a comprehensive set of methods to compare fiber properties of the immature fiber (im) mutant, called immature because it produces thin-walled fibers, and its isogenic wild type Texas Marker-1 (TM-1) that is a standard upland cotton variety producing normal fibers with thick walls. Comprehensive structural analyses showed that im and TM-1 fibers shared a common developmental process of cell wall thickening, contrary to the previous report that the phase in the im fiber development might be retarded. No significant differences were found in cellulose content, crystallinity index, crystal size, matrix polymer composition, or in ribbon width between the isogenic fibers. In contrast, significant differences were detected in their linear density, cross-section micrographs of fibers from opened bolls, and in the lateral order between their cellulose microfibrils (CMFs). The cellulose mass in a given fiber length was lower and the CMFs were less organized in the im fibers compared with the TM-1 fibers. The presented results imply that the disruption of CMF organization or assembly in the cell walls may be associated with the immature phenotype of the im fibers.

The extra-long length of ramie fibers and the high variation in fiber length has a negative impact on the spinning processes. In order to better study the feature of ramie fiber length, in this research, the probability density function of the mixture model applied in the characterization of cotton fiber length was used to fit the ramie fiber length distribution tested by the Y131 wool fiber comb stapling sorter. Furthermore, the generation of ramie fiber length distribution with the commonly used ramie fiber length parameters was also studied, and it was concluded that ramie fiber length distribution could be generated by the corresponding tested fiber length parameters.

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.

In this study, a Fourier transform infrared (FTIR) microscope equipped with a focal plane array detector (FPA) was used for the identification of common cotton contaminants. The detector provided highly-sensitive and spatially-resolved spectra that allows sampling of microscopic samples (e.g., single fibers and small specks), and the chemical imaging of samples. Seven cases of contaminant identification were studied; in each case, examination with a FTIR spectrometer and a reflection accessory provided inconclusive determinations. Spectra of contaminants were easily obtained with the FTIR microscope. While small deviations were observed, comparison to reference spectra allowed easy contaminant identification. This proof-of-concept study indicates that the FTIR-FPA microscope was particularly useful for identifying minute contaminants. Spatial resolution of the system also allowed for the chemical imaging of samples.

Specific levels of the carbohydrates melezitose and trehalulose deposited on the surface of cotton fibers are indicators of whitefly or aphid contamination. These deposits could cause stickiness problems during cotton ginning and textile processing. Cotton stickiness is highly complex, but surface carbohydrates may play the largest role in manifesting an issue. We utilized ion chromatography (IC) to identify and quantify nine sugars of interest present in the water extracts of 25 cotton samples to create sugar profiles for each sample: inositol, trehalose, glucose, fructose, trehalulose, sucrose, melezitose, raffinose and maltose. We compared the sugar profiles to the respective Minicard ratings of either NONE, LIGHT, MODERATE or HEAVY to draw correlations between the IC data and the rating. Trehalulose and melezitose in water extracts highly and positively correlate to Minicard ratings, confirming past researchers' attribution of cotton stickiness to insect sugars. Trehalose and maltose also highly correlated, possibly due to their marker content in honeydew. Glucose and fructose moderately correlated to the ratings. IC studies of the collected Minicard sticky spot material found trehalulose and melezitose were the most prevalent sugars in HEAVY rated samples. Glucose and fructose were present in larger amounts in the MODERATE versus HEAVY rated samples. This result may indicate that the Benedict Test, which attributes these reducing sugars to stickiness, may not be sufficient for conjecturing a stickiness issue. When comparing the averages of the nine sugars present in water extracts versus those sugars contained in Minicard sticky spots, the overall distributions were very similar.

Botanical and field cotton trash comingled with Upland cotton lint can greatly reduce the marketability and quality of cotton. Trash found comingled with cotton lint during harvesting, ginning, and processing is of interest to the textile community. In the current study attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic imaging was employed as an analytical technique to analyze cotton trash. Some benefits of this technique were its non-destructive nature and lack of required sample preparation. The technique used in this study, specifically ATR-FTIR spectroscopic chemical imaging, allows for three-dimensional spectral and spatial data to be obtained. In the current study, cotton in mixtures with botanical and field trash types have been identified spectrally and spatially using ATR-FTIR imaging. Botanical trash types (trash derived from the cotton plant) were evaluated and identified independently from cotton, even though both contained cellulose. The field trash types were easily identified from cotton due to their differences in chemical composition. This study can complement current cotton qualitative studies by adding spectral and spatial information to sample analysis.

Micronaire is an important fiber quality parameter in the cotton and textile industry. Micronaire is a function of maturity (the degree of the fiber secondary wall development) and fineness (linear density). In prior research, bench-top near infrared (NIR) spectroscopy demonstrated the ability to measure micronaire, maturity, and fineness in and out of the laboratory. Small, portable handheld NIR instruments have been introduced and a program was established to measure micronaire in and outside the laboratory on seed cotton fiber and cotton lint, and consequently to measure maturity and fineness in the fiber. Adding new data to the original commercial lint-only samples, including data from different environments (laboratory and greenhouse) and fiber type conditions (laboratory ginned lint and seed cotton) made the calibration more robust, increasing the accuracy of the two NIR instruments (MicroNIR 2200 and Luminar5030) used in this experiment. Each instrument has its individual strengths. It is advisable to use the instrument that best fits the laboratory research objectives.

The moisture content of cotton fiber is an important fiber property, but is often measured by a laborious, time-consuming, laboratory oven-drying method. The ability of a laboratory microwave moisture measurement instrument to perform rapid, precise, and accurate fiber moisture measurements was studied. The microwave instrument was calibrated versus two significantly different oven-drying methods. The agreement between the two oven-drying methods was very good, with low residuals observed. The precision of the microwave moisture content measurements was very high, approaching 0.1% moisture. The impact of sample fiber weight was minor, and instrument stability and long-term repeatability were excellent. Microwave cotton fiber moisture content measurement was shown to be viable and applicable for quality control use.

Certain levels of the carbohydrates melezitose and trehalulose deposited on cotton surfaces are indicative of either whitefly or aphid contamination, which may cause problems during cotton processing. Raffinose and sucrose are isomers of melezitose and trehalulose, respectively, making it difficult to fully separate them via ion chromatography (IC), especially when analysis time is shortened. We have successfully developed an IC method to separate the retention peaks of melezitose from raffinose and trehalulose from sucrose, with baseline resolution and improved quantitation of these sugars. This improved separation may elucidate useful information about constituent sugars on cotton, aiding in the identification of carbohydrates possibly contributing to stickiness.

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 micro-spectrometer 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 (<1min 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.

Market demands for cotton varieties with improved fiber properties also call for the development of fast, reliable analytical methods for monitoring fiber development and measuring their properties. Currently, cotton breeders rely on instrumentation that can require significant amounts of sample, which complicates fiber development studies. Herein, we explored the use of high-resolution, Fourier-transform infrared (FT-IR) microscopy to examine cotton fiber secondary cell wall development in single fibers. Notably, there was a marked intensity increase for the C-O bending region near 1015 cm–1 and the C-H stretch at 2900 cm–1. These changes agree with those observed with macroscopic FT-IR tests. Chemical distribution maps and principal component analysis plots visually depict these spectral changes. Our results suggest the FT-IR microscopy can potentially be utilized as a tool to monitor and assess important fiber properties, such as cotton maturity, during fiber development.

Gossypium raimondii Ulbrich, a wild diploid species of cotton, was sequenced due to its small genome size and similarity with the cultivated allotetraploid Upland cotton. The D-genome of G. raimondii has become the reference sequence used extensively in cotton genomic and genetic studies. However, phenotypic information is limited because photoperiodicity prevents flowering outside its native environment and its fiber quality cannot be measured by conventional methods. Fiber and seed properties of G. raimondii were measured and compared with those of Upland cotton cultivars. Fiber length, fineness, cellulose content, and seed lint percentage were all significantly reduced in G. raimondii compared to Upland cotton, whereas fiber maturities were comparable. Spectophotometric properties of G. raimondii fibers were similar to green Upland cotton fibers but differed from white and brown Upland fibers. Seed kernels of G. raimondii were smaller but their chemical compositions were similar to those of Upland cotton. Quantitative traits of G. raimondii will aid in interpreting its genome and accelerating comparative genomics approaches for identifying potential genes regulating fiber and kernel properties among Gossypium species.