fiber and fiber Consumption in
|The Educational information in this section has been graciously donated to the Apparel Search Company by Professor Kermit Duckett.|
Monika kannadaguli and Haoming Rong
fibers are the basic element of nonwovens. Manufacturers of nonwovens products can make use of almost any kind of fibers. These include traditional textile fibers, as well as recently developed hi-tech fibers. The selection of raw fibers, to considerable degree, determines the properties of the final nonwoven products. The selection of fibers also depend on customer requirement, cost, process ability, changes of properties as a result of web formation and consolidation. The fibers can be in the form of filament, staple fiber or even yarn. The following table shows the significant fibers used in the nonwovens industry all over the world.
Although there are several natural fibers available for nonwovens, wood pulp - which is far shorter in length than the conventional textile fibers - is the only natural fiber used in very large amounts because of its high water absorbancy, bulk and low cost. Cotton has excellent inherent properties for nonwovens fabrication. Viscose rayon has been widely used in the nonwovens industry in the area of disposables and sanitary products. Rayon fibers can be easily made into webs and readily bonded into nonwovens fabrics. All these cellulosics such as cotton, rayon and acetate are absorbent, act as carriers for microbial agents, and give strength combined with biodegradability(1). Among the synthetic fiber polypropylene(PP) is widely used. PP is inexpensive and has very good rheological characteristics to form fine fibers. PP fibers are hydrophobic, voluminous, and thermoplastic in nature. Polyethylene terephthalate (PET) is used where strength and mechanical properties are of prime importance. Nylon fibers are used for their excellent recovery (resilency) properties. Bicomponent fibers with different polymers in the core and sheath are widely used in thermally bonded nonwovens(2).
fiber requirements for nonwovens depend on the product being produced and the fabrication process being used. Since each process leads to a different range of fabric properties, all available fibers cannot be used equally well in all nonwoven processes. Table 2 briefly gives the relation between the various fibers and the technologies used in developing the nonwovens from them.
With nonwovens products successfully moving into more technical end-uses, the fiber requirements have also become more exacting with regard to the fiber properties. The cooperation between fiber supplier and fabric producers is now seen as an important criteria for additional advancements to come about in the nonwovens field.
Although a large number of fibers are available, commercially important nonwoven fabrics have been limited to relatively few types, The dominant fibers include polyolefins, polyester, and rayon. These three fiber types made up a substantial part of the overall nonwovens markets for fibers. The increasing importance of olefin-based fibers is well illustrated by data from major nonwovens-producing regions that show increasing shipments of PP and PE at the expense of some natural fibers, rayon and polyester(3). Much of this shift in fiber consumption can be attributed to the growing use of olefin-based nonwovens in absorbent products around the world.
Rayon was a major fiber used in the nonwovens industry until 1985 . Over the past decade, production of rayon has decreased considerably in the US and Western Europe because of the increasing cost of the fiber. The cost of PP and PET is now comparable to that of rayon, and yet they provide superior strength. There was another big drop in1989, after which the shipment of rayon staple kept declining slowly. Nonwovens made of rayon are mainly found in medical/surgical/sanitary products and wipes. The cleanliness and absorptive properties make rayon still popular in these field. Similarly, cotton is the preferred fiber in tampon and incontinence products. Its consumption is stable at 40-45 million pounds. Nylon, which is more expensive than most other fibers, is used in a lesser extent. The other "special fibers" listed in table 1 have only a limited market share, probably no more than 15 percent of the whole nonwovens market.
The North American nonwovens industry is the largest in the world and accounts for just under a 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). This is up by 17% from its 1992 value. Being the most mature nonwovens market in the world, Table 3 from the fiber Economics Bureau show that the increase in shipments of staple fiber for nonwovens is being led by olefin fibers, dominated by polyproylene, which further cemented their domination of shipments in 1998. Polyester staple fiber shipments were also up slightly from 1997 to 1998. Rayon shipments increased slightly in 1998, but their share of overall fiber consumption continued to be the same. The figures for rayon may have been affected by a rise in rayon prices while polyester and olefin prices generally fell in 1998, but historical figures show a long term pattern of decline in rayon consumption. In 1989, rayon staple shipments for nonwovens were almost 100 million lb, almost double their 1998 level(4).
Olefin Staple, which became the dominant fiber in the business in 1996, edged a little further ahead of polyester last year. In the latest figures olefin had 49% of sales while polyester=s share of the business dropped to 42%. The balance of 9% each year represented the estimated rayon staple sales. Looking back over the 10 year period covered by Table 4, the increase in olefin market share at the expense of polyester and rayon has been striking. Ten years ago, olefin=s participation in the business was a mere 35% compared with 65% for the two competitive fibers. Since then, as noted above, olefin has risen to over 49% with polyester and rayon dropping to 51%.
West European consumption
In Western Europe, the three major fibers accounted for nearly 70% of staple fiber consumption by the nonwovens industry in 1997. Total Western European nonwovens production increased 11% in 1997 to reach almost 760,000 tonnes - almost doubling the 6% growth in 1996 - according to annual figures published by the European Disposables and Nonwovens Association (EDANA). Output of the 15 European Union countries plus Norway and Switzerland is forecast to top 800,000 tonnes in 1998, and could reach as much as 820,000 tonnes. Turnover of the nonwovens industry in Western Europe was estimated by EDANA to be 3 billion ECU in 1997. Although overall use of polypropylene in nonwovens increased over 10% from 1996 to 1997, the fastest rising market has been in spun-melt applications where PP accounts for 61% of polymer granule consumption. PP staple fiber consumption in Europe increased less than 1% in 1997, and it accounted for only around 41% of staple fiber used in dry-laid nonwovens. By comparison, polyester staple consumption increased almost 5%, and rayon by 8% for dry-laid nonwovens in 1997, respectively. The use of natural fibers other than woodpulp hardly grew in 1997, and cotton in particular is not a widely used fiber in the region.
Present and Future fiber Requirements
For high performance nonwovens, fibers or polymers with exceptional properties must be either engineered to further fit the various formation, consolidation and conversion processes or the processes must be modified to fit the fiber material(5). More rapid advancements in nonwovens will come about as the fiber supplier and the fabric producer work closely together and in concert with the auxiliary resin supplier and machinery vendor on this mutually dependent challenge.