Bonded Fabrics are non-woven fabrics where the fibers get together with the help of adhesive rather than woven or knitted technique. These fabrics are typically stiff and inelastic. The term bonded also refers to a fabric made from two layers of the same fabric or a piece of fabric and lining fabric attached either by a chemical process or an adhesive.
The Process Of Thermal Bonding
Thermal bonding is the widely used method for bonding in textiles specially used for nonwovens manufacture. The Thermal Bonding Non Woven is followed widely due to its higher production rate because it is associated with high speed over heated rolls or ovens. Thermal bonding is the process that is successfully used with several thermoplastic fibers. These bonded fabrics are used in products like belts, where a neat finishing is needed on both sides. Bonded fabrics are manufactured for specific uses like water-repellency, resilience, and flame-retardancy.
The initial process of Thermal Bonding Non Woven starts by taking the thermoplastic fibers alone with non-thermoplastic fibers, for example, cotton. It further forms into a fiber batt using the air-laying machines. After this, the webs are heated using various methods.
Hot Calendering Process
Calendaring is how the web between heat rolls is confined under pressure. It ultimately squeezes it together. The fibers get melted between the rolls. The pressure between the rolls is flattened, forming a flat and thin fabric.
It can be both solid or can have patterns. The usage of solid rolls results in melting all the thermoplastic fiber, which produces a solid fabric. Patterns are engraved on the top roll, which results in a roll where the parts are not engraved. The bonding occurs between the fiber intersection in the areas between the raised parts of the top and the bottom roll.
This process produces a flat, flexible, and soft fabric. In the Thermal Bonding Non Woven, the calendar bonding is highly applicable for light and medium-weight webs. The thick web insulates heat from the interior structure leading to a temperature gradient. The web is pre-heated before calendar bonding using the infra-red heaters to propel the efficiency.
Ultrasonic bonding is the rapid application of compressive forces to localize the web’s fiber areas. Stress is generated through the process, which converts into thermal energy. It also softens the fabric. After the source through which the ultrasonic vibration is produced is removed, the soft fabrics get cool and solidify the bonding points. This process is used for spot or patterned bonding of mechanically bonded materials.
A device that produces heat replaces the top drum and further produces the same kind of fabrics as in the above process. Both calendered and ultrasonic fabrics are limited in weight for effective heat transfer to the middle of the web. In case the fabric remains heavy, the heat doesn’t transfer, and it will not be bonded.
Through Air Bonding Process
The webs are produced and run through the oven heated on another side. The negative pressure pulls up the hot air through the web for the melting and bonding of fibers, allowing heat transfer throughout the web. Through this method, thick fabrics are produced. If the web is bonded tightly between the belts while heating, then it may result in thin fabrics.
The application of hot air to the surface of the nonwoven fabric is the major principle followed by the through-air thermal bonding process. The hot air travels through the holes in a plenum above the nonwoven. But the air is not pushed through the non-woven, like in common hot air ovens. It results in a negative pressure or suction generation that pulls the air through the open apron that supports the nonwoven when it gets passed through the oven.
Advantages Of Thermal Bonding Of Non Woven
Thermal bonding is accepted due to its huge advantageous factors. The finished products are relatively soft and textile-like, depending on blend composition and bonding area. Thermal Bonding Non Woven provides sound economic efficiency compared to other chemical bonding it further meets the lower thermal energy requirements.
It does not require expensive machinery. Through this bonding process, high bulk products are bonded uniformly throughout the entire web cross-section. The fiber components can be recycled up to 100 %. The process is considered environmentally friendly because no latex binders are required.