Advanced Characterization and Testing of Textiles

Patricia I. Dolez, Olivier Vermeersch, Valério Izquierdo

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN:
  9780081004531
• eBook ISBN:
  9780081004548
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

Advanced Characterization and Testing of Textiles explores developments in physical and chemical testing and specific high-performance tests relating to textiles. The book introduces the principles of advanced characterization and testing, including the importance of performance-based specifications in the textiles industry. Chapters are organized by textile properties, providing in-depth coverage of each characteristic. Tests for specific applications are addressed, with the main focus on high-performance and technical textiles. - Focuses on advanced testing methods for technical and high-performance textiles, covering state-of-the-art technology in its field - Details specific textile properties and associated testing for each characteristic

Part One

Principles of textile characterization and testing

1

Introduction to advanced characterization and testing of textiles

P.I. Dolez; O. Vermeersch CTT Group, Saint-Hyacinthe, QC, Canada

Abstract

The earliest evidence of textile processes may be dated to 35,000–15,000 BC. Then, the ability to better control the quality and performance of what was produced came thanks to the evolution of raw materials available for textile manufacturing—from natural fibers with very high inherent variability to synthetic fibers produced with commodity polymers to high performance fibers—, and the gain in precision of production techniques and equipment. This gave rise to large efforts to develop test methods that could characterize the performance of textile properties at the different stages of production, i.e., from the raw material to the finished product; these include physical, mechanical, chemical, barrier, and thermal properties as well as comfort, flammability, and durability.

Keywords

Textile manufacturing; Textile testing; Textile applications; Quality control; Certification; Third-party testing; Properties vs performance; Standardization; Laboratory accreditation

1.1 Introduction

The earliest evidence of textile processes may be dated to 35,000–15,000 BC with dyed flax fibers discovered in a cave in the Caucasus and sewing needles found in France (Hearle, 2002; Jenkins, 2003). The first manufactured textiles were most probably felt, produced with wool. Some articles demonstrating a high level of development of the felt-making technology have been found in Siberia in a tomb dated from the 5th century BC. Weaving may have been known since the Paleolithic era as indicated by cloth burnt remnants and imprints in clay found in the Czech Republic and dated around 25,000 BC. Around 5000–3500 BC, textile manufacturing was well implanted in many parts of the world with hemp in the Middle East, cotton and wool in South America, linen in Egypt, cotton in India, and silk in China, for example. Production techniques further improved over the centuries. Then, in the period of 1750–1850, textile manufacturing transitioned from crafting to industrialization with the mechanization of the equipment. More recently, new high performance fibers/materials were developed, leading to the emergence of a high value-added technical textiles market. This market is projected to reach 42.2 million metric tons by 2020, at a compound annual growth rate (CAGR) of 4.68% between 2015 and 2020 (M&M, 2015a). As a whole, the global textile sector is currently valued at USD 439.1 billion (EHER, 2017).

Textile manufacturing involves the transformation of fibers into fabrics. The four main textile structures are wovens, knits, braids, and nonwovens. In the case of weaving, knitting, and braiding, fibers are first made into yarns, which are then used to produce the textile structure. Nonwovens are manufactured directly from fibers. Woven textiles are produced by interlacing warp and weft yarns according to a regular pattern. They are generally stronger but less stretchable than the other textile structures. Knitted textiles are manufactured by interlacing symmetrically disposed loops together. They offer a very large extensibility and display directional mechanical performance. Braids are formed by interlacing three or more yarns to yield a long and narrow product. Finally, nonwovens are produced by disposing fibers in a more or less random manner to form a three-dimensional structure. The web is further consolidated using mechanical, thermal, and/or chemical means. The advantages of the nonwoven process include a high manufacturing rate, low cost, capacity to handle a wide variety of fibers, lower level of requirements in terms of fiber properties, and a wide range of functions. Textile structures may then receive a finishing treatment, for instance, to provide them with flame-resistance properties; they may be dyed; and/or they may be coated with a polymer, for example, to make them water-tight. More information about textile manufacturing techniques is available in Horrocks and Anand (2000). The wide variety of technologies available for each type of textile structure, with the additional possibility of combining them into hybrid structures, gives rise to a myriad of products with different characteristics. These engineered materials have found countless applications in a whole range of different markets.

Textiles are produced using natural and/or man-made fibers. Natural fibers include plant-based fibers such as cotton, hemp, flax, and jute; protein-based fibers such as silk and wool; and mineral fibers. Man-made fibers include cellulose-based or regenerated fibers, e.g., rayon, acetate, and triacetate fibers; organic fibers, e.g., polyethylene, polypropylene, acrylic, nylon, polyester, spandex, modacrylic, para-aramid (e.g. Kevlar® and Twaron®), and meta-aramid (e.g., Nomex®); and inorganic fibers, e.g., glass, carbon, and basalt. Depending on the fibers, a wide range of properties may be observed: for instance, low density and biodegradability for plant-based fibers; very high strength for para-aramid, ultra-high molecular weight polyethylene (Dyneema® and Spectra®), and carbon fibers; and flame resistance for para- and meta-aramids. More information about the characteristics and properties of natural and man-made fibers may be found in Kozłowski (2012), Eichhorn, Hearle, Jaffe, and Kikutani (2009), McIntyre (2004), and Hearle (2001).

Raw materials available for textile manufacturing evolved from natural fibers with very high inherent variability to synthetic fibers produced with commodity polymers to high performance fibers. Simultaneously, production techniques and equipment gained in precision. The resulting ability to better control the quality and performance of what was produced gave rise to large efforts to develop test methods that could characterize textile properties and performance at the different stages of production, i.e., from the raw material to the finished product. These properties include physical, mechanical, chemical, barrier, and thermal properties as well as comfort, flammability, and durability.

1.2 Importance of textile testing

The primary objective of textile testing is to assess the product properties and predict its performance during use. The information obtained may be used for the following (Anonymous, 2014):

● Research and development

● Selection of raw materials/inputs

● Process development

● Process control

● Quality control

● Product testing

● Product failure analysis

● Comparative testing and benchmarking

● Conformity with government regulations and specifications

1.2.1 Manufacturers' perspective

For a manufacturer, the two main purposes of testing are to check the quality of his inputs and his outputs. Depending on his position in the value chain, his input materials might be fibers, yarns, or fabrics. The properties of his inputs will affect both his ability to process them smoothly and in an efficient manner, and the quality and properties of the product obtained. For instance, a yarn with a low strength will have a larger probability of failure during weaving, increasing the machine down time; the woven fabric produced will also display a lower strength and eventually not meet the requirements.

The control of the manufacturer's outputs is also critical to ensure the viability of his processes: manufacturing parameters are optimized to allow a high production rate while limiting machine down time and achieving the level of quality and performance expected. Process control strategies include the use of statistical process control (SPC) methods, multistage process surveillance, and fault diagnosis (Majumdar, Das, Alagirusamy, & Kothari, 2012). Statistical quality control makes use of variability measurement, differences between means, significance of variables, control charts, and hypothesis testing, for instance.

Originally, the requirements products had to meet mostly dealt with the material properties, for instance, the yarn or the fabric tensile strength. Increasingly, more complex aspects related to the performance in service have been included; flammability and breathability are examples. Some of these properties may also be exclusive features that are part of the manufacturer's strategy to protect his share of the market with a monopoly based on particular functions only offered by his product.

Testing of outputs is also a key element for the manufacturer to ensure that he is in the desired bracket of performance/cost ratio. Indeed, it is critical for him to maximize his margin of profits by avoiding exceeding the required quality levels. Quality control over outputs is also part of the toolbox in case of disputes with clients.

1.2.2 Specifiers' perspective

The specifier is generally the one setting up the requirements. It may be the buyer, who is generally not the end-user in the case of finished products, or organisms representing consumers and end-users. Examples of these organisms include the International Organization for Standardization (ISO), ASTM International, the National Fire Protection Association (NFPA), and SAE International. If specifications were originally drafted by manufacturers independently of the product application, considerations related to end-users gradually gained importance: nowadays, requirements in terms of performance take into account criteria associated with the area of application of the product and its conditions of use.

For specifiers, testing allows parametrizing the exchange of money for goods using precise sets of requirements. The product selected has to meet the prescribed requirements while generally being the least expensive. With standard test methods, it is possible to compare different products and identify those meeting the requirements. For specifiers, testing is also a powerful driver of technical innovation because it sets new targets for performance. In addition, it can promote sociopolitical changes; examples include “green” products, local content, and fair trade.

1.2.3 End-users' perspective

For the end-user, testing ensures that his expectations in terms of quality, properties, and performance are met by the product. The characteristics he will be looking for may be related to safety, ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• About the editors
• Part One: Principles of textile characterization and testing
• Part Two: Testing by properties
• Part Three: Testing by applications
• Index