What is Nonwoven Fabric?
Nonwoven fabrics are made directly from fibers, without turning them into yarn first. One of the key steps in this process is web formation, where loose fibers are arranged into a thin sheet or layer called a web. This web is the base of the nonwoven fabric and is later bonded to give it strength and structure.
Nonwoven fabrics are usually produced as sheet materials from fibers or filaments in two stages. Firstly, a web of fibers is formed (web formation), which is then treated to consolidate and increase its strength (bonding). In this article, I will explore various web formation techniques for nonwovens.
In traditional fabric production, the process looks like this:
Fiber → Yarn → Fabric (by knitting or weaving)
But for nonwoven fabrics, it’s simpler and faster:
Fiber → Fabric
Since nonwoven fabrics skip the spinning stage, they don’t gain the strength and cohesion that yarns get during spinning. Instead, the fibers are arranged into a web and held together using heat, chemicals, or mechanical methods. While this makes production quicker and cheaper, the resulting fabric is not as strong or durable. That’s why nonwoven fabrics are generally used for short-term purposes.
To produce half a million meters of woven sheeting using fifty looms will require two months of yarn preparation, three months of weaving, and one month for finishing and inspection. Alternatively, the same quantity of a non-woven will take two months total. Breaking that number down further, non-woven production is approximately one hundred meters per minute whereas knitting can produce two meters per minute and weaving can produce one meter per minute. Knitting and weaving are more labor-intensive practices, and they use high amounts of energy as compared to the non-woven industry, which uses a mainly automated production plant.
A wide variety of fibers are used for non-woven fabrics, including polypropylene, polyester, viscose, polyamide, polyethylene and some natural fibers such as wool. Nonwovens make up approximately 7% of the fabric construction market.
Nonwoven fabrics are made using two processes; web formation and bonding.
Web Formation Techniques for Nonwovens
The fibers, which can be staple, continuous filament or portions of a polymer, are used to form a web, which is the basic element of non-woven materials. There are two types of web formation techniques for nonwovens: Staple fiber webs and Filament fiber webs.
A. Staple Fiber Webs
There are four main ways that the webs from staple fibers can be produced:
- Dry-laid
- Spunmelt
- Wet-laid
- Electrostatic
1. Dry-Laid:
Drylaid webs are usually formed from either staple fibers of 20–150 mm in length or short cut and pulp fibers of 1–10 mm in length. These materials may be of natural or synthetic polymer composition and can be processed alone or in blends. Dry laid used for wet wipes, medical textiles, interlinings.
These can be produced by carding or air laying:
a) Carding – staple fibers are carded to make the fibers parallel, which offers strength in the length of the web. The webs tend to be thin, so they may require more than one layer during the fabric production. The webs themselves can be formed by laying the fibers in parallel webs in horizontal and vertical layers.
The webs can also be cross-laid, which entails the fibers passing through the carding machine. The fiber web is concertinaed backwards and forward on top so that layers stack on top of each other. Carded webs have high tensile strength, low elongation and low tear strength.
b) Air-laid—also called random-laid, entails blowing the fibers onto a conveyor belt or a rotating drum with an internal vacuum that holds the fibers onto the drum so that they stick together. These two methods offer greater choice in fibers and blends that can be used. These webs offer lower density and greater softness than carded webs, and they make up 75% of the non-woven market.
2. Spunmelt Webs:
Spunmelt webs are formed from continuous filaments that are produced by extrusion processes derived from melt spinning. Commercially, most spunmelt nonwoven production is based on spunbond and meltblown technologies. It is widely used in hygiene, medical, and filtration products due to its excellent balance of strength, softness, and barrier properties.
Spun-Melt or High-Velocity Webs are used on thermoplastic fibers that are sprayed onto a belt to form a random web. Heat is applied to hold the fibers together. These processes can be carried out as either spun-laid or melt-blown procedures.
a) Spun-melt procedures use melted polymer chips that are extruded through the spinneret as continuous filament. The polymer is then cooled and blasted onto a conveyor belt. In this method, the elasticity of the fiber is more controlled and has better strength than other non-woven materials. Often, other chemicals are extruded to provide other properties and bonding choices.
b) Melt-blown procedures use low-viscosity polymers that are extruded into a high-velocity air stream. The air stream distributes the very fine fibers, solidifies them, and breaks them apart at the same time to form the web.
3. Wetlaid Webs:
Wetlaid webs are produced using technology that originated from the papermaking process, in that fibers are first suspended in water. Wetlaid used for tea bags, filters, and medical gauze. There are four steps in this type of manufacturing process:
- The fibers are dispersed in water to form a fiber suspension.
- The fiber suspension is collected on a continuous screen to form a uniform web.
- The web is drained and filtered to remove the water.
- The web is heated to dry and bonded to form a sheet of wetlaid nonwovens (or paper).
Fig: Wetlaid web formation technique
Wet-Laid nonwovens are produced like paper: a pulp of water and fibers are put onto a moving wire screen or revolving drum and that forms the web. It is then pressed between rollers to remove the excess water, dried and bonded. Acrylic fibers use a salt solution, and when the water evaporates, the salt binds the fibers chemically to make a strong, waterproof fabric.
4. Electrospinning or Electrostatic Webs:
The fine fibers are given an electrostatic charge, which causes fibrillation of the fibers. The fibers then fall randomly onto the conveyor belt. This method uses electrostatic forces to draw and deposit fibers onto a collector, forming a web. It is primarily used for producing very fine and uniform fibers, often in the submicron or nanometer range.
Process flow of electrostatic webs formation:
Polymer Liquid → Electric Field → Jet Formation → Fiber Solidification → Web Collection
Normally used manufacturing in medical masks and filters, battery separators, wound dressings and nanofiber membranes etc.
B. Filament Fiber Webs
Webs using filament fibers are much stronger than those from staple fibers because the continuous flow of filaments can curl and spiral once dropped onto the conveyor belt. The fibers used are thermoplastic, so they adhere once they are solidified to produce strong fabrics. Sometimes, the filaments may be textured before the web is formed which offers more end uses or the conveyor belt may have patterns outlined by pins that create a lace-type fabric. Another method of producing lace-like fabrics is to shoot a jet of water up through the web, which will create the holes in the lace structure. This fabric is pliable, resistant to damage during laundering, quick drying, lightweight, warm and soft. It is often used for curtains and tablecloths. Filament fiber webs are used in medical textiles, hygiene products, industrial filters, geotextiles, cleaning wipes, packaging, apparel interlinings, and automotive components due to their strength, uniformity, and versatility.
Conclusion
Making the initial web is the crucial first step in creating nonwoven fabrics. Web formation techniques—dry laid, wet laid, and polymer laid—are core to producing nonwovens fabrics with a wide range of properties tailored for different applications in hygiene, medical, industrial, and consumer products. Each web formation technique has its own advantages and is chosen based on the type of fiber used and the final application of the fabric. Understanding these methods helps us see how different nonwoven products—from face masks to baby wipes—are made quickly and efficiently.
References
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[3] Sinclair, R. (2014). Textiles and fashion: Materials, Design and Technology. Woodhead Pub Limited.
[4] Albrecht, W., Fuchs, H., & Kittelmann, W. (2006). Nonwoven fabrics: Raw Materials, Manufacture, Applications, Characteristics, Testing Processes. John Wiley & Sons.
[5] Elise, R. (2020). Nonwoven fabric: Manufacturing and Applications. Nova Science Publishers.
