AATCC TM 20 Test Method for Fiber Analysis: Qualitative

The standard “AATCC TM 20 Test method for fiber analysis: qualitative,” published by the American Association of Textile Chemists and Colorists (AATCC), describes physical, chemical, and microscopic techniques for identifying textile fibers commercially used in the United States. These methods can be used to examine fibers in raw fiber form or to extract them from yarn or fabric.

These test methods can be used to identify general fiber types as defined in the Textile Fiber Product Identification Act and other legal regulations and in the standard “ISO 2076 Textiles - Man-made fibers - Generic names”. Quantitative methods for determining percentages in fiber blends are covered by the standard “AATCC Test method 20A Fiber analysis: quantitative”. The test methods are valid for fibers grouped according to general classifications and shown in the standard.

This test method involves a series of procedures that must be used together to identify a fiber type: microscopic examination, solubility in solvents, melting point, refractive index, and micro-Fourier transform infrared spectroscopy. It is known that some procedures are more effective than others for identifying certain fibers. For example, microscopic examination is particularly useful in characterizing natural fibers. It should be used with caution in man-made fibers, as they are frequently manufactured with a series of modifications that alter their longitudinal or cross-sectional appearance. In addition, man-made fibers may contain some or no matting or other additive particles. Filaments within a given type may vary in size or cross-sectional shape. Individual filaments may have two or more component sections of the same or different general types.

Even natural fibers exhibit a wide variety of typical cross-sections. No particular sample will ever look exactly like the published images. A sufficient number of fibers should be examined to cover the range of appearance in any given sample.

Successful identification of fibers depends on experience and familiarity with the fibers. Identification of an unknown fiber is best accomplished by comparison with suitably identified fibers used as reference standards. It is therefore desirable to have at least one representative fiber sample from each general fiber class available for comparative identification.

This test method provides the means to determine the general classification of common fiber types. In special cases, such as when dealing with fibers not defined by this method or when trying to distinguish products from different suppliers of the same general type, reference should be made to standard texts on fiber identification or technical bulletins published by manmade fiber suppliers.

• The main equipment used in these tests includes:
• Compound microscope with matching objectives and eyepieces to achieve magnifications of 100-500× and equipped with a polarizer and analyzer.
• Glass slides and cover glasses.
• Dissecting needles.
• Small scissors and fine tweezers.
• A sectioning device such as one of the following:
  • Stainless steel sheet (dimensions 2,54 × 7,62 × 0,0254 cm and punched with 0,09 cm diameter holes) and 0,016 cm diameter soft copper magnet wire.
  • Microtome (hand).
• Razor (sharp, thin, single-edged or double-edged, with holder).
• Density gradient tube (approximately 2,5 cm in diameter and 45 cm long, sealed at the bottom and with a glass stopper at the top with a 24/40 standard conical union to prevent moisture uptake or evaporation of solvents).
• Melting point apparatus consisting of a heated block, a temperature measuring device such as a thermometer, and means for controlling the heating rate and viewing the sample at low magnification (this apparatus should have a range of 100–300 degrees or more and an accuracy of plus/minus 1 degree over the entire range).
• Micro-FTIR instrument.
• Differential scanning calorimeter.

To obtain a representative sample for identification, it is necessary to consider:

• If the sample is loose fiber or yarn, it may contain only one fiber or may be a tight blend of two or more fibers.
• A yarn sample may be a solid or wrapped core blend of two or more yarns. These yarns may be the same or different in sequence and may themselves contain a blend of fibers.
• Woven or knitted fabrics can be made from yarns of a single fiber type or more than one fiber type. Additionally, fabrics can be made with yarns having different individual fiber types or more than one fiber type in the length or width directions of the fabric structure, which may require separate analysis.
• Different types of fibers can be dyed the same color. Conversely, the same type of fiber can appear in different colors in the finished product by mixing stock-dyed or yarn-dyed materials or by using fibers with modified dyeing properties.
• It is essential that the samples selected are representative of the entire sample of raw fiber, yarn or fabric being examined.

In many cases, the identity of an unknown fiber can be determined without pretreatment. When the presence of starch, wax, oil, or other coatings obscures the appearance of the fiber, heating in warm to hot distilled water may be necessary to remove the impurities. If this does not work, remove the impurities with organic solvents, 0,5 percent hydrochloric acid, or 0,5 percent sodium hydroxide. Some fibers, such as nylon, are damaged by acid treatment, and others, such as silk and wool, are damaged by caustic treatment.

Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also test services in accordance with the "AATCC TM 20 Test method for fiber analysis: qualitative" standard.