Identification of Textile Fibers

M M Houck

• Publisher: Woodhead Publishing
• Year: 2009
• ISBN:
  9781845695651
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

The identification of fibers is important to the textile industry, forensic science, fashion designers and historians among others. Identifying fibers involves observing the physical and chemical properties of the fiber for which there are a wide diversity of instruments available. This book provides a comprehensive review of fiber structure, the diversity of instruments available to identify fibers and applicications for a range of industries.The first part of the book examines the main fibers, their structure and characteristics. Part two focuses on methods of fiber identification, ranging from microscopic to DNA analysis. Specific applications, including how textiles are identified in forensic investigations.Identification of textile fibers is an important text for forensic scientists, police and lawyers who may be involved with the use of textile fibers to provide evidence in criminal cases. It will also be relevant for textile designers, technologists and inspectors wishing to assess fiber quality and understand fiber damage.

• Provides a comprehensive review of the main types of fibre together with their structure, characteristics and identification
• Assesses methods of fibre identification from optical microscopy to DNA analysis as well as instruments available to identify fibres

Part I

Textile fiber structure and characteristics

1

Introduction to textile fiber identification

M.M. Houck West Virginia University, USA

Abstract

The identification of fibers is critical to a number of industries, including textiles, forensic science, fashion, and design. The actual identification, however, varies with industry and method. Changes in textile technology create a constant need to improve identification methodology. The old methods – despite the increased pace of new technology – are often the best. Microscopy still dominates the field for analytical methods and provides a range of analysis barely possible with any other method. Combined with spectroscopy, microscopy is the quintessential fiber identification tool.

Key words

fiber identification

microscopy

methodology

spectroscopy

Manufacturers use set methods to ensure a quality product fit for purpose. This implies a market-based taxonomy with a company-product orientation, a supply chain of raw and processed materials, and explicit rules on categories. For example, the American Association of Textile Chemists and Colorists (AATCC) lists the following specified methods:

• colorfastness to commercial laundering and to domestic washing

• flammability of clothing textiles

• smoothness of seams in fabrics after repeated home laundering

• electrostatic propensity of carpets

• wrinkle recovery of fabrics: appearance method

• dimensional changes in textiles other than wool.

The titles to these methods indicate what is important to define in their products. AATCC lists microscopy as a method to identify fibers but notes that it should be used with caution since manufactured fibers are frequently produced in a number of modifications which alter their appearance.¹ The Association also lists ‘reaction to flame’ (Table III) as a test method with the following diagnostics: melts near flame, shrinks from flame, burns in flame, etc.

By contrast, ASTM International lists the following in their methods:

• flame resistant materials used in camping tentage

• pile retention of corduroy fabrics

• elastic properties of textile fibers

• performance specifications for underwear fabrics, woven, men’s and boys’

• commercial moisture regains for textile fibers.

While the view is similar to that of AATCC, ASTM International lists infrared spectroscopy as the preferred method for fiber identification: ‘additional physical properties of the fibers such as density, melting point, regain, refractive indices, and birefringence… are useful for confirming the identification’ (Volume 7.01, D276). Both organizations treat the samples as bulk for purposes of the possible identifying tests; after all, if you make them, sample size should not be a problem.

By comparison, the forensic sciences treat microscopy as the primary method for fiber identification:

Microscopic examination provides the quickest, most accurate, and least destructive means of determining the microscopic characteristics and polymer type of textile fibers. Additionally, a point-by-point, side-by-side microscopic comparison provides the most discriminating method of determining if two or more fibers are consistent with originating from the same source.²

Forensic fiber examiners use microscopy first and then other methods, such as infrared spectroscopy, as confirmatory techniques. Why not start with infrared spectroscopy, as do the manufacturers? A company that spins fibers knows what products it makes; therefore, the universe of possible answers is sufficiently limited. For a forensic scientist, however, fibers found at a crime scene could conceivably be from nearly any source and you can’t make assumptions. A rayon fiber and a cotton fiber will both show up as ‘cellulose’ on an infrared spectrum; a microscope easily distinguishes between them. Two nylon 6,6 fibers may be chemically identical but have different diameters, cross-sections, or birefringences.

The orientation of the analysis is different (comparison), although the goal is partially the same (identification). Forensic fiber analysis routinely has minimal samples with which to work and this structures what tests can be used. Forensic fiber analysis is also interested in traits of which the manufacturers may not be aware. For example, delustrants, typically titanium dioxide, are added to deluster or dull otherwise bright fibers. The manufacturers add the delustrants during the fiber spinning process at a certain rate to achieve the desired end goals with little regard for the distribution of the granules within the fiber. For ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Dedication
• Contributor contact details
• Woodhead Publishing in Textiles
• Part I: Textile fiber structure and characteristics
• Part II: Methods of fiber identification
• Part III: Applications
• Index