What are non-woven fabrics?
Nonwoven fabrics are flat fabrics made from short-staple fibers and long filament fibers, which are felted or bonded together by a mechanical, thermal or chemical process. The fibers may be oriented in one direction or spread randomly into webs, mats or sheets. It may consist of one layer or multiple layers.
The production process of non-woven fabrics does not involve spinning or weaving as they are made directly from separate fibers, molten or dissolved fiber forming substances like plastic. It is said to be the easiest method to create fabric from fibers. Polyester, and viscose (rayon) are the most commonly used fibers. Other fibers are nylon, microfiber, acrylic cotton, and bamboo fiber.
The main types of nonwoven fabrics that we regularly use are interfacing, fusible web, felt, fake leather, fleece, and batting. Dryer sheets and wet wipes are made of a nonwoven material. Suede and Synthetic suede are non-woven. Vinyl, vinyl and resin-coated fabrics, rubberized fabrics, and plastic laminates are other non-woven fabrics. Boiled wool is a fabric made with the non-woven method.
Another non-woven fabric is the Polypropylene material that disposable hospital gowns, bed covers, etc are made of – other than this, these materials are used to make bag lining, shopping bags, shoe bags, disposable diaper covers.
Wool nonwovens are used for filteration purposes. They are also used for making thermal blankets. They are also used to make bathroom mats.
Characteristics of non-woven fabrics
- Nonwovens are usually flat and flexible.
- They can be of any thickness.
- Do not ravel or fray at the cut edges
- Most non-wovens are easy to care for – machine washable as well as dry cleanable, sometimes either
- Can shrink in the wash, depending on fiber
- Most non-wovens are porous
- Web-like nonwovens made from natural fibers are absorbent, stretchable, and biodegradable.
- Maynot have the drape of woven and knitted fabrics
How are they made?
Fibers are bonded by various processes to form the non-woven fabric.
In the chemical process, an adhesive is used to bond the fibers together. In the mechanical process, bonding or interlocking is done by needling or fluid jet entanglement or stitching. In the thermal process, a binder in the form of powder, paste, or polymer melt is added and the binder is melted onto the web by increasing temperature.
Different types of non-woven fabrics.
Depending on the process with which they are made, there are different types of nonwoven fabrics.
Wet-laid nonwovens are made by a mechanical process called wet laying. It is similar to a paper-making technique with different raw materials. Fibers are formed into a slurry which is transported to a mesh forming mechanism to lay in a wet state to form a cloth. It is normally followed by adhesive bonding. Felt and felted fabrics are made this way.
Spun laid nonwovens
Spun laid nonwovens are also called spunbond nonwovens. Fibers or polymer slices are spun by spinnerets into endless filaments. These filaments are cooled and stretched by air and are deposited as random web on a moving sieve belt. This conveyor belt carries the web to the bonding zone to bond by a thermal, mechanical, or chemical process. Interfacing material is a spun bonded nonwoven.
Stitch bond nonwovens
A stitch bond non woven is made on a weaving machine. The web is held in place on a weaving machine and is bonded with chain-stitch seams. The fabric will have clear stitching patterns on one side or both sides. The stitch bonding process gives a flatter and softer texture to the web. Scrim in batting is stitch bonded
Solvent bond nonwovens
A web made of acrylic fibers and polyester fibers is treated with a controlled amount of solvent. It softens the fiber surfaces and thus causes bonding.
Thermal bond nonwovens
Thermal bond nonwovens are made of thermoplastic fibers or thermostatic powders like polyester, polypropylene, nylon, etc.
There are four kinds of thermal bonding. Air bonding where heated air is applied to the web placed on a conveyor belt. Impingement bonding, where the web is placed in an oven and hot air impinges to the web surface from nozzles. The calendar bonding, where the web is passed between heated rollers and ultrasonic bonding, where a device in which ultrasonic frequency produces a vibrational motion and the bonding takes place by means of energy conversion.
Chemical bond nonwovens
Chemical bond nonwovens are made by applying a binder (resin or latex) to the surface of the web. Resin bonded batting is an example.
There are four types of chemical bonding. Print bonding, spray bonding, saturation, and foam bonding. Print bonding is done by gravure roll printing and screen printing. In spray bonding latex is sprayed on the web placed on a conveyor belt. In saturation, the web is directly dipped in a latex tank and later dried in a drier. Foam bonding gives resiliency and a softer feel to the fabric.
Hydro entangled nonwovens
Hydraulic nonwovens are made by the impact force of high-pressure water jets onto the web surface on a fast-moving conveyor belt. The amount of pressure applied on the web decides the bonding quality.
This is a charactization of non woven material based on how the fibers are laid when the material is made. A carding machine is used to comb the fibers into a web and the fibers are aligned in the machine direction. This creates a very strong non woven material. The other process is air-laid. Non-woven Web materials are made in both these ways.
Nonwoven composite fabrics
Multilayer nonwovens (Multiple fibre composite nonwovens) are nonwoven fabrics with multiple layers of different types of fibers with varying functionalities. ie. Each layer of the fabric will provide the fabric with specific qualities like water repellency, fire retardancy, etc.
Reference : Sciencedirect.com
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