Thermal bonding is a technique for bonding a web of fibers using a pressurized or non-pressurized heat or ultrasonic process to activate a heat-sensitive material. The material can be in the form of homophilic fibers, bicomponent fibers, and fusible powders as part of the web. Bonding can be applied all over (e.g. through-line or area bonding) or can be limited to predefined, discrete areas (e.g. spot bonding).

There are different types of thermal bonding systems that can be used:

Calendar bonding thermally bonds a web of loose fibers by passing it through the nip of a pair of calender rollers, one or both of which are heated.

Air-through bonding (or air-through bonding) is a bonding system that uses high-temperature air to fuse web fibers. There are two basic systems: blowing hot air through the web in a conveyor oven, or passing heated air through the web on a rotating drum.

Ultrasonic bonding is the use of high-frequency sound to generate localized heat through vibration and cause the thermoplastic fibers to bond together.

Thermal bonded nonwovens can be thin – which goes into the core of feminine care products – or high loft materials that are several inches thick.