Applications of Nonwovens in Technical Textiles

R Chapman

• Publisher: Woodhead Publishing
• Year: 2010
• Print ISBN: 9781845694371
• eBook ISBN: 9781845699741
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Nonwovens have been one of the fastest growing and most exciting sectors of the textiles market. Such fabrics have a broad spectrum of end uses, ranging from medical products to interior textiles. This book focuses on the variety of technical nonwoven applications available.Opening chapters in part one briefly discuss the fundamental principles of nonwoven fabrics, topics such as the formation of nonwovens and the influence of fibre and fabric properties on nonwoven performance are covered. Part two provides valuable examples of how nonwoven materials can be used in a variety of textile products for apparel, filtration and personal hygiene.With a collection of international contributors, this book is an important reference for professionals involved in the production, technology and use of nonwoven materials, extending from industries such as the medical textile industry to the apparel sector. It will also be suitable for researchers in academia with an interest in nonwoven fabrics. - Focuses on the variety of technical nonwoven applications available and provides a comprehensive overview of current developments and likely future trends - Reviews the formulation of various types of nonwovens and examines the influence of fibre and fabric properties on nonwoven performance - Provides a broad overview of nonwoven applications in a variety of different areas from apparel to automotive interiors

Part I

Fundamental principles of nonwovens

1

The formation of dry, wet, spunlaid and other types of nonwovens

A. Wilson, Nonwovens Report International, UK

Abstract:

The term ‘nonwoven’ arises from at least half a century ago when these materials were often regarded as low-price substitutes for traditional textiles and were generally made from carded, ‘dry’ fibres on converted textile processing machinery. The nonwovens industry, however, has drawn on the practices and know-how of many other fields of materials manufacturing, with a piratical disregard and an eye to the most diverse range of end-use products. Today, it would be reluctant to be associated with the conventional textile industry and its commodity associations. The nonwoven technologies originating from the textile industry manipulate fibres in the dry state. Paper-based nonwoven fabrics, meanwhile, are manufactured with machinery designed to manipulate short fibres suspended in fluid and referred to as ‘wetlaid’. ‘Spunlaid’ nonwovens – spunbond, meltblown, apertured films and the many layered combinations of these products – are manufactured with machinery developed from polymer extrusion, with the fibre structures simultaneously formed from molten filaments and manipulated like plastics. This chapter examines the various bonding processes for producing nonwovens.

Key words

drylaid

wetlaid

spunlaid

carding

plastics

paper

extrusion

airlaid

meltblown

nanofibres

1.1 Introduction

The term ‘nonwovens’ arises from at least half a century ago, when the materials were often regarded as low-price substitutes for traditional textiles and generally made from carded, staple fibres on converted textile processing machinery. The yarn spinning stage is omitted in the nonwoven processing of staple fibres, with bonding of the web by various methods – chemical, mechanical or thermal – replacing the weaving or knitting together of the yarns in traditional textiles. In dividing today’s nonwoven products into three major areas – drylaid, wetlaid, airlaid or spun – it can generally be said that drylaid materials have their origins in textiles, wetlaid materials in papermaking, and spunlaid products in polymer extrusion and plastics.

However, in defining what a nonwoven is, there is always at least one exception that breaks the rule. The process of stitchbonding – which originated in Eastern Europe in the 1950s and is still used for some industrial applications – employs both layered and consolidating yarns, just to prove this point. This is perhaps fitting, since while being now recognised in its own right, the nonwovens industry has drawn on the practices and know-how of many other fields of materials manufacturing with a piratical disregard and an eye to the most diverse range of end-use products.

For this reason, it is possible for companies with almost nothing in common – with vastly different structures, raw materials and technologies, areas of research and development and, finally, customers – to be grouped together under the nonwovens ‘umbrella’. Many would define themselves by the customers they serve, as being in the consumer products, medical, automotive or civil engineering industries, for example. And now, certainly, the nonwovens industry would be reluctant to be associated with the conventional textile industry and its commodity associations. But nor would it want its products to be called nonpapers or nonplastics.

The term ‘nonwoven’, then – describing something that a product is not, as opposed to what it actually is – has never accurately represented its industry, but any attempts to replace it over the years have floundered. The illusion created by this misnomer has certainly been of some kind of bulk commodities, when the opposite is often true. The nonwovens industry is highly profitable and very sophisticated, with healthy annual growth rates – often in double digits in certain sectors and parts of the world. It is perhaps one of the most intensive in investing in new technology, and also in research and development.

In nonwoven manufacturing systems, the fibre material or extruded thermoplastic is deposited or laid on a forming or conveying surface, and the physical environment at this phase can be dry, quenched in air, wet or molten – drylaid, wetlaid or spun.

The web formation phase of nonwoven manufacturing processes transforms previously prepared/formed fibres, filaments or thermoplastic resins or films into layers of loosely arranged networks – webs, batts, mats or sheets. Mechanical and fluid means are employed to achieve the preferred fibre or plastic orientation in the web, through the use of machinery adapted from the textile, paper or extrusion industries. Other critical fabric parameters established at the web formation stage are the unfinished product weight and the manufactured width. Each web-forming system is used for specific fibres or products, although the exception here is with highloft nonwoven production, which employs both cards and crosslappers and air-forming systems.

A key trend observed over the past twenty years has been a tremendous shift – especially for the hygiene and medical markets – away from drylaid techniques to the spunlaid route, to the extent that the latter now account for well over 40% of nonwovens manufactured worldwide. Another trend currently having a significant impact is that of incorporating nanofibre nonwoven layers into products – most notably, to date, in the area of filtration fabrics. The next major change is likely to be a shift away from petrochemical-based polymers and fibres towards biobased alternatives such as polylactic acid (PLA), for some, if not all, technologies. At the time of writing it is difficult to predict how significant this will be, since it is dependent on a number of factors outside the control of the industry. It could even be driven by legislation as the drive towards less reliance on petrochemicals increasingly becomes a political tool. It can safely be said that it has the industry’s attention, and is currently the subject of expansive rese...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Textiles
• Preface
• Part I: Fundamental principles of nonwovens
• Part II: Nonwoven applications
• Index