Thermal bonding has become a popular method for creating high-quality nonwoven fabrics. In general, thermally bonded fabrics are created utilizing the required amount of heat to effectively melt fibers like polypropylene, polyester or different types of thermoplastic powders. As most of the thermal bonded nonwoven materials are produced using fibers, here you will get to know more about them.
There are different ways to apply heat to various fibers. Well, at the point where multiple fibers combine or intersect, those fibers can be heated and melted to combine them all. When you cool them, they will be bonded, and that will affect the durability and strength of the final fabric. If you compare, you will find that these fabrics are very lightweight and thin, and sometimes, they can be very thick and heavy. You can use them for different applications based on your requirements. For example, nonwoven fibers made using a thermal bonding process can be used for hygiene products, such as feminine pads or diapers, cushioning like furniture and mattresses, insulation material and other useful products.
Different Materials for Different Methods
Well, in general, the thermal bonding process will begin by using different fibers. You can use thermoplastic fibers or can also combine that with different non-thermoplastic fibers. Then you need to convert them into a durable fiber batt utilizing air-laying machines or carding methods. During this point, the fibers webs can be properly heated utilizing different methods. Some of the common methods are:
Calendaring is a process where you need to move the web between a heated roll and, using a high level of pressure; the roll will properly squeeze the web. During the process, the fibers will get melted between the roll. The pressure produced by the rolls will then flatten the fibers web, creating a thin and flat fabric.
The rolls used in this process can come with different patterns or can be solid. If you use a solid roll for thermal bonding, then you will attain a proper melting process of thermoplastic fiber, which, in turn, creates stiff and solid fabric. Sometimes, different patterns can be engraved on the roll. In such a case, the parts that are not engraved will be higher than compared in the engraved areas. The process of boding will occur when there is an intersection of multiple fibers. This will create soft, flat and flexible fabrics.
Under this process, a device that generates heat utilizing ultrasonic energy will be used in the place of the top drum and can be used to create the same type of fabric that you generally produce through the calendaring process. In the process of ultrasonic bonding, the pattern can be found on the lower roll.
Both types of fabric, i.e., ultrasonic and calendared, are limited in fabric weight as if you make the web very thick, heat will not properly transfer to the middle of the web, and you may not get a well-developed bond between the webs.
The Through-Air Bonding Process
Under this process, webs are produced and then run through a large oven that is heated on one side. On the other hand, negative pressure will move hot air through the web to melt as well as different bond fibers. This method ensures even heat throughout the web. Lofty and thick fabrics can be created using this method. If the material web is perfectly sandwiched between the belts, then you can get thin fabrics.
Cotton- The Best Material For Thermal Bonding Process
Cotton fibers can be utilized to create quality nonwoven fabrics through thermal bonding. All you need to do is combine it with a quality thermoplastic fiber. Cotton can be used along with different types of thermoplastic fibers, like polyethene, polyester, polypropylene, and more.
Blend around 80 percent cotton can be used to create fabric. Well, as the strength of nonwovens created by thermal bonding comes from the process of the thermoplastic fibers melting to each other at the fiber intersections, when you add more cotton to it, the fabric will lose its strength.
Wondering why? Well, where cotton material intersects, the bonding is not possible. However, where the cotton fibers and thermoplastic combines, the thermoplastic will perfectly bond to the cotton.