Introduction to Nonwovens

Monika kannadaguli

An average person is unlikely to be familiar with the term nonwoven and a few decades back there were no experts in this field. When the consumer hears the term nonwovens it makes him think of something which is not like traditional woven fabrics, something >modern=, >advanced=, >hygienic=, but he is not aware of any specific types of materials among those which carry the same name. But now the precise meaning of the term is somewhat clearer to the experts. According to the experts, nonwovens is a class of textiles/sheet products, unique in industry, which is defined in the negative; that is, they are defined in what they are not. Nonwoven fabrics are different than the conventional textile fabrics and paper. Nonwovens are not based on yarns and (with frequent exceptions) do not contain yarns. They are based on webs of individual Fibers. Nonwovens are different than paper in that nonwovens usually consist entirely or at least contain a sizeable proportion of long Fibers and/or they are bonded intermittently along the length of the Fibers. Although paper consists of fiber webs, the Fibers are bonded to each other so completely that the entire sheet comprises one unit. In nonwovens we have webs of Fibers where Fibers are not as rigidly bonded and to a large degree act as individuals [ 1 ].

The definitions of the nonwovens most commonly used nowadays are those by the Association of the Nonwovens fabrics Industry (INDA) and the European Disposables and Nonwoven Association (EDANA).

The various methods for bonding are:

a) Adding an adhesive

b) Thermally fusing the Fibers or filaments to each other or to the other meltable Fibers or powders.

c) Fusing Fibers by first dissolving, and then resolidifying their surfaces.

d) Creating physical tangles or tuft among the Fibers.

e) Stitching the Fibers or filaments in place.

Nonwovens find numerous applications ranging from baby diapers to industrial high performance textiles. Some of the important areas where nonwovens are treated as primary alternative for traditional textiles as geotextiles, materials for building, thermal and sound insulating materials, hygienic and health care textiles and automotive industries. Nonwovens are also used in cover stocks, agriculture, aerospace, home furnishings etc. Although it is not possible to list all the applications of nonwovens, some of the important applications are listed in Table 1 [2 ] .

Table 1

The nonwoven industry is one of the fastest growing industries in the world. It is rapidly developing a sophisticated and diverse market. It has been exhibiting an average growth of about 10% over the past twenty years and should continue this rate of growth in the next ten years. The technology in nonwoven industry has been improved significantly in nearly all available major manufacturing processes, including those of spunbond, meltblown, needle punched, spunlaced, wet laid and dry laid fabrication.

The most important point in rapid development and commercial acceptance of nonwovens is the ability to produce materials of special properties in less time and at reasonable prices. The relative production speeds of various textile technologies are compared in Table 2 [3,4 ].

A large number of Fibers are available n the market, but the nonwoven market is mainly dominated by three Fibers, namely polyolefins, polyester, and rayon. These three fiber types make up a substantial part of the overall nonwoven markets for Fibers [5 ].

The North American nonwoven industry is the largest in the world and accounts for almost one third of the worldwide sales of roll goods - around $2.8 billion - in 1997, according to estimates from the Association of the Nonwoven fabrics Industry (INDA). A major portion of the polyolefin and polyester fiber in the U.S. market is consumed by the nonwovens industry. Last year (1998), 57% of the polyolefin share was consumed by the nonwoven industry (Table 3) and only 43% was consumed by all the other industries, in spite of the fact that polyolefins are the major raw products for the packaging industry. Even in the case of polyesters, the share has increased to 14%. The major share of polyester fiber goes to high loft industry.

Table 3 U.S. shipments of olefin staple: Nonwovens Vs Other Markets, 1989-1998

Source : fiber Economics Bureau and Trade Estimates

CAGR- Compound annual growth rate.

Figure 1

The production of nonwovens amounts to approximately 20% of the total production of textiles and this percentage grows year by year. The total world production is shown in Table 5 [ 6]. The growth rates of nonwoven production are extremely high, when compared with the conventional textiles industry.

Table 5

The leading producers of nonwovens are given in Table 6 [7 ].

Table 6

With the nonwovens successfully moving into more technical end-uses, the fiber requirements have also become more important with regard to the fiber properties. The cooperation between fiber supplier and fabric producers is now seen as an important criteria for more advancements to come about in the nonwovens field.

1. Arthur Drelich, ANonwoven classification: A simple system@, Nonwovens Industry,54-55, Oct.1998
2. The Nonwoven fabrics Handbook, Association of the Nonwoven fabrics Industry, Cary,NC
3. J.Lunenscholss,J., Albrecht,W., Vliesstoffe,Georg Thieme Verlag, Stuttgart, NY (1982)
4. Princlples of Nonwovens, INDA, Cary,NC(1993)
5. R.W.Mason,
6. Najoul,J., ANonwovens in a Global Market@, Nonwovens Industry,26,#9,39-48 (19
7. Nonwovens Industry, 26, #9,39 (1005)

Why the Definition Matters

Starting from webs of individual fibers rather than yarns changes everything downstream. A woven fabric's properties are set first at the yarn stage and then by the weave; a nonwoven's properties are set by fiber selection, by how the web is formed and oriented, and by how it is bonded. That is why the articles in this collection are organized around fibers, web formation and bonding: those three decisions are the nonwoven equivalent of yarn, loom and finish. It also explains the industry's breadth — the same basic approach produces disposable medical and hygiene products, durable geotextiles, filters, wipes and interlinings.

The introduction also places nonwovens between two older technologies. From textiles they borrow fibers, cards and finishing equipment; from papermaking they borrow wet forming and the idea of a continuous sheet made at high speed. Holding those two inheritances together is what makes the field its own discipline, with its own association (the Association of the Nonwoven Fabrics Industry, INDA), its own handbooks, and its own course literature, several of which appear in this article's references.