PA, PES and PP fibers for Non-Woven applications
Detailed information on non-woven
What is a non-woven?
Non woven fabrics are flat, flexible, porous sheet structures that are produced by interlocking layers or networks of fibers, filaments, or film-like filamentary structures. They generally fall into two categories depending on end use: disposable or durable-and provide the basis for a wide variety of consumer, industrial, and healthcare products used around the world.
Disposable end uses of non-wovens account for around 60% of total non-woven fabric consumption in the US and Japan (around 50% in Europe), and durable the remainder. Disposable uses include all those in which the non-woven product is disposed of after limited use, such as diaper fabric, medical fabric, wet wipes and face masks. Durable uses are, as the name implies, those in which the fabric has a longer lifespan, such as roofing textiles, automotive fabrics and clothing interlinings.
The non-wovens industry has its roots in wartime Europe, where rudimentary non-woven technologies such as needle punching, stitch bonding and wet laying were used to manufacture apparel, medical supplies and blankets cheaply and quickly. In the 1970s, the introduction of polypropylene and polyester fibers to the non-woven industry allowed producers to manufacture fabric without the need for expensive chemical binders and to find major new markets for such dry laid, thermally-bonded non-wovens.
Definition of a non-woven
Non-wovens markets and applications
The technical criteria for disposable non-wovens includes sufficient strength and extensibility to withstand high-speed converting processes; a balance of softness and rigidity to accommodate both packaging and the intended use; fluid transport; absorption, containment, or repellency; porosity; and density.
Types of disposable non-woven converted products include:
• Baby diapers
Durable (extended- and limited-use) non-wovens generally are used in roll form by other processing or fabrication industries. They are manufactured to fairly rigid engineering specifications, and they compete on an intensive cost-performance basis with industrial woven and knitted textile fabrics, technical papers, and specialty films.
Types of durable non-woven converted products include:
• Filtration media
Non-wovens manufacturing processes
Processes for manufacturing non-woven fabrics can be grouped into four general categories:
Textiles. Textile technologies include garneting, carding, and aerodynamic forming of fibers into selectively oriented webs. Fabrics produced by these systems are referred to as dry laid non-wovens, and they carry terms such as garneted, carded, and air laid fabrics. Textile-based non-woven fabrics, or fiber-network structures, are manufactured with machinery designed to manipulate textile fibers in the dry state. Also included in this category are structures formed with filament bundles or tow, and fabrics composed of staple fibers and stitching threads.
In general, textile-technology based processes provide maximum product versatility, since most textile fibers and bonding systems can be utilized and conventional textile-fiber processing equipment readily can be adapted with minimal capitalization.
Paper. Paper-based technologies include dry laid pulp and wetland (modified paper) systems designed to accommodate short synthetic fibers, as well as wood pulp fibers. Fabrics produced by these systems are referred to as dry laid pulp and wet laid non-wovens. Paper-based non-woven fabrics are manufactured with machinery designed to manipulate short fibers suspended in fluid.
Paper-technology based non-woven processes provide the least product versatility and require extensive capitalization, but they yield outstanding uniformity in products at exceptional speeds.
Extrusions. Extrusions include spun bond, melt blown, and porous film systems. Fabrics produced by these systems are referred to individually as spun bonded, melt blown, and textured or apertured film non-wovens, or generically as polymer-laid non-wovens. Extrusion-based non-wovens are manufactured with machinery associated with polymer extrusion. In polymer-laid systems, fiber structures simultaneously are formed and manipulated.
Extrusion-technology based processes provide somewhat less versatility in product properties, but they yield fabric structures with exceptional strength-to-weight ratios (spun bonds), high surface-area-to-weight characteristics (melt blown), or high property uniformities per unit weight (textured films) at substantial to modest capitalization levels.
Hybrids. Hybrids include fabric/sheet combining systems, combination systems, and composite systems. Combining systems employs lamination technology or at least one basic non-woven web formation or consolidation technology to join two or more fabric substrates. Combination systems utilize at least one basic non-woven web formation element to enhance at least one fabric substrate. Composite systems integrate two or more basic non-woven web formation technologies to produce web structures. Hybrid processes combine technology advantages for specific applications.
Non-woven web forming
The web formation phase of non-woven manufacturing processes transforms previously prepared/formed fibers, filaments, (or films), into preferentially arranged layers of lofty and loosely held fiber networks called webs, batts, mats, or sheets. Mechanical and fluid means are employed to achieve the preferred fiber orientation in the web through the use of machinery adapted from the textile, paper, or extrusion industries. Other critical fabric parameters established at web formation are unfinished product weight and manufactured width. In all non-woven manufacturing systems, the fiber material is deposited or laid on a forming or conveying surface, and the physical environment at this phase may be dry, wet, quenched, or molten; hence the terms dry laid, wetland, and fluid polymer laid.
The future trend in web formation is in improved quality, increased speeds, and process monitoring by using electronic information as a feedback mechanism to control the process and quality of the web. Important factors to consider in web formation are economy, versatility, speed, and quality of the web. A cost comparison when dealing in web formation is difficult to compile since each web-forming system is used for specific fibers or products, although an exception is with high loft products where both cards/cross lappers and air-forming systems are used. The current preference is toward air forming. However, this is beneficial when a modest range of product characteristics are desired. The most versatile web-forming system for high loft is carding and cross lapping. The most streamlined system is the use of air formers.
Fibers for non-wovens
Fibers are the basic units of a non-woven structure. Consequently, much of the utility, properties, aesthetics, and performance of a non-woven is due to the constituent fibers. A fiber has been defined as any substance, natural, or manmade, with a high length-to-width ratio and with suitable characteristics for being processed into a fabric.
A wide range of fiber types, both synthetic and natural, have been employed in the production of non-woven products. It is very likely that every fiber known to mankind has been used in a non-woven structure at one time or another. However, commercially important non-woven fabrics have been limited to relatively few fiber types, in view of the large number that are available.
The dominant fibers include polypropylene, polyester, and rayon, and between them, these three fiber types made up a substantial part of the overall non-woven markets for fibers. In Western Europe, for example, the three accounted for nearly 70% of staple fiber consumption by the non-wovens industry in 1997.
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