Spunbond materials are a subset of what's termed non-woven fabrics. That is, they are webs of material without the interlacing of threads produced by weaving on a loom. That means the fibers are randomly oriented and not interlocked, so a bonding process or medium is needed to fix them in place.
Non-woven fabrics are everywhere. Disposable wipes, diapers and pillow covers are just a few of the many uses around the home, but they're also used in agriculture, civil engineering and automobile interiors.
Why So Popular?
Non-woven fabrics compete with wovens in two ways. First, they can be engineered to have practically any combination of properties needed. Tensile strength, absorption, and density are just of few of the characteristics polymer chemists are able to manipulate. In contrast, woven fabrics derive their properties mainly from the characteristics of the yarns employed.
Second, non-woven production processes are much faster than weaving. While a loom might turn out three to seven meters of woven material per hour, many non-woven processes could produce several hundred meters per hour. Naturally, this has an impact on cost.
Non-woven Production Processes
Non-woven materials may be produced either from short lengths of fiber, (known as staple fibers,) or from continuous filament. Fibers can come from many sources, both natural and man-made, but filament is generally produced from polymers such as polypropylene, polyester and nylon.
A variety of methods are used to randomly orient fibers into a web before bond them together. One issue is that staple fibers must go through some kind of chopping process first. In contrast, spunbond materials, while lacking the randomness of fiber, are made directly from the polymer.
The Spunbond Process
Polymer is melted and extruded through very fine holes, typically measuring 15 to 35 microns diameter. These thin continuous strands are made to spin as they solidify before landing on a moving conveyor or web of supporting material. The spinning randomizes the orientation of the strand as it lands and the conveyor motion ensures it forms a mat or web of material.
A bonding process, mechanical, chemical or thermal, joins the overlapping filament coils together, creating an engineered fabric. From polymer pellets to fabric web, it's an integrated process, and so highly cost-competitive.
Types of Spunbond Materials
- Polypropylene. This offers low density, good chemical and water resistance, and is readily formed as a breathable material. It works well in protective bags, sheets, pockets or pouches, is a good filter medium and absorbs oil well thanks to a porous structure. Spunbond polypropylene is also used for single-use gowns in the medical field.
- Polyester. More expensive than polypropylene, this has higher tensile strength and better heat stability. It can be dyed or printed with conventional textile industry methods. Applications include fabric softener dryer sheets, automotive carpet backing and geotextiles.
- Nylon. Has good tensile strength and tear resistance. Can absorb water but resists attack by alkalies and weak acids. Has good heat resistance and is air permeable. It's widely used as carpet underpad reinforcement, as quilt backing, and in automotive interiors.
- Polyethylene. Similar to polypropylene, although with generally inferior properties, this is chemical and water resistant, and has good electrical insulation characteristics. A porous structure makes it a good oil absorber.
- Polyurethane. This is an emerging material in spunbond form. Somewhat elastic, uses are anticipated in masks, diapers, medical tape, and also disposable clothing, thanks to textile-like properties.
- Rayon. This creates non-wovens with textile-like properties like good drape and soft feel.
- Bicomponent fibers. These consist of one polymer molded around a second, different, polymer. This enables a combination of properties such as the ability to take a dye combined with high strength.
Development of spunbond manufacturing processes is continuing, with new forms of material entering the market and new applications being found. Spunbond foam offers superior handling characteristics with lower weight and increased softness. Today, we are able to laminate adhesive to spunbond materials to film, foam, and other materials as well as die cut, water jet cut, slit, and kiss cut this material in a number of application settings. The cost-effective spunbond process facilitates engineering of specific performance characteristics such as strength, water and chemical resistance, and feel. New spunbond materials are emerging constantly, and improved manufacturing methods are enabling yet more applications. Already spunbond polypropylene is seen as an alternative to polyurethane foam, and other applications are sure to follow. If you are interested in learning more about Spunbond Fabrics, give us a call and we would be happy to help you learn more.