Fibers colorants

Strand of glass fiber colored differently from the remainder of the roving package. It allows a means of determining whether equipment used to chop and spray glass fibers is functioning properly and provides a check on quality and thickness control. 

Following massive crush injury, myoglobin released from damaged muscle fibers colors the urine dark red. Myoglobin can be detected in plasma following a myocardial infarction, but assay of serum enzymes (see Chapter 7) provides a more sensitive index of myocardial injury. 

Changes in reflectance due to changes in fiber might be due to fiber color, fineness, maturity or other similar aspect. We will assume, however, that the changes in reflectance due to these factors are negligible. Thus the reflectance will depend only on dust and trash. 

Natural fiber color is gold. Dyeable to dark shades with basic dyes following caustic treatment. 

Madder dyes belong to the group of mordant dyes. They are dyed on wool or silk that has been previously mordanted with aluminum or iron salts. The madder dyes react with these salts to form on the fiber color lakes that are water-insoluble and do not bleed even when treated with dilute ammonia. For the identification of madder dyes with the aid of TLC, however, we require a dye solution that can be applied to the thin-layer plate. At acid pH (pH 3 or lower), the dyes are liberated from the lake, a process during which the color visibly changes, and the organic constituents can be extracted. 

Vinyl bromide (VBr) as a comonomer does not improve the solubility to the same extent. Evidently, the smaller molecular volume of CH2=CHBr is responsible. The molecular order of PAN is less perturbed by this comonomer. As a consequence, more severe conditions are required to get a copolymer AN (96%)/VBr(4%) in solution. However, since color formation is evidently not a problem in the case of carbon fibers (color formation actually signals the onset of the stabilization reactions aimed at, cf. Sect. 3), dissolution of AN/VBr copolymers can be achieved at high temperature (110-120 °C). 

Ramie fibers consist of a very high proportion of pure cellulose. Therefore, treatment with iodine and sulfuric acid turns the fiber pure blue, but treating it with aniline sulfate gives no color. Treatment with zinc chlor-iodide reagent gives the fiber a blue color, while the fiber color is rose red when treated with calcium chlor-iodide [108]. 

More recently, Wang and Postle [182] found that increasing the concentrations of sodium hydroxide and sodium sulphite in the alkaline boiling process, X, Y, Z, and WIE (whiteness) of the hemp fiber increase linearly. The alkali boil facilitates further improvements in the fiber color during bleaching. Peroxide bleaching of the fiber can greatly improve its color in terms of X, Y, Z, and whiteness. 

Uses Azo dye intermediate photographic developing agent intermediate in mfg. of antioxidants, accelerators for rubber, synthetic fibers colorant for hair dyes, fur laboratory reagent... 

Major Applications Wool dyeing, tints for polyester fibers, coloring metal oxide Safety/Toxicity No data available... 

Unit or Fiber Color Unit or Fiber Color... 

DyStar Textilfarben GmbH Co. Deutschland KG, Tngeo Fiber Coloration Pack . 

Choosing carbon black as a filler for fibers has many implications. Figure 19.18 shows the effect of carbon black loading on viscosity in PET. Viscosity depends on the type of carbon black. A reduction of 50% viscosity can be attained at the same carbon black concentration simply by change to another grade of carbon black. Moisture absorption, which affects the drying time, can be substantially reduced (by about 50%) by the selection of the appropriate carbon black. Fiber color and tone are affected by the carbon black type and by the method of its dispersion. 

Fabrics and fibers colored with these macromolecular dyes showed good resistance to solvent wash. 

Several characteristics of fibers are targeted by forensic analysis. As shown in Figure 14.8, the chemical composition of the fiber is just one of many important characteristics. The diameter and cross section are useful for determining how a fiber is used. For example, carpet fibers are relatively thick and often have hollowed-out cross sections compared with those of fibers used in clothing. Cotton fibers have a characteristic flat ribbon geometry. Fiber color and how it... 

Next to PLM, IR spectroscopy (principally, micro-IR) makes up the most important family of techniques in fiber analysis. As with PLM, IR spectroscopy is minimally destructive or nondestruchve and is useful on even the smallest fiber fragments. Microspectrophotometry (MSP) probes the chemical identification of the synthetic fiber, colorants, and other treatments. MSP is indispensable in the comparative analysis of questioned and known fibers, the central task of most forensic fiber analysis cases. The caveat is that such comparisons require knowledge of typical inter- and intrasample variation. Consider, for example, a pair of blue jeans typically, fibers from along the seams and hems are worn compared with fibers to other portions of the garment. Also, the source from which a sample is obtained will clearly affect any visible spectra and color analysis. Along a single fiber, characteristics of a dye or colorant will vary as well. Such inherent variations must be factored into any conclusions drawn from a comparative analysis, be it of dye or chemical composition. 

Figure 14.17 shows the elliptical regions of uncertainty for the fibers shown in Figure 14.18. The fiber here is a round polyamide type treated with different dispersive dyes. Figure 14.19 shows an example of an error or uncertainty ellipse in more detail. When a fiber is treated with a single colorant, the centr axis of the uncertainty ellipse generally points toward the coordinates of the undyed fiber. This observation is attributed to the depth of penetratiim of tiie dye varying from fiber to fiber. In other words, the fiber "starts" at the undyed position on the chromaticity diagram. The more of a single dye that is accepted by tile fiber, the deeper the color is and the farther the chromaticity coordinates shift away from e undyed fiber color. Taken to the extreme, this line would extend to coordinates of the pure dye. Because different individual fibers have different dye uptake characteristics, some fibers will take on more dye and some less, even when made of the same polymer in the same batch.

Tuinman, A. A., et al. "Trace Fiber Color Discrimination by Electrospray Ionization Mass Spectrometry A Tool for the Analysis of Dyes Extracted from Submillimeter Nylon Fibers." Analytical Chemistry 75 (2003), 2753-2760. 

Material form and name 1. Natural or modified fibers Colored cotton thread or rayon thread Colored synthetic fiber thread or colored plastic sheet... 

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