There are thermoplastic materials, elastomers, and thermoset resins: Thermoplastic materials are plastics that are processed by heat and are well suited for ultrasonic welding. Elastomers are plastics that are processed by means of cross-linking; they do not react to ultrasonics. The same applies for thermoset resins that are processed by curing and cannot be welded by means of ultrasonics. Plastic welding is defined as molecular material bonding of thermoplastic materials. As a general rule: only identical thermoplastic materials can be welded homogeneously. All thermoplastic materials (except PTFE) can be welded. PC, PMMA, and ABS can be welded to one another under certain conditions. By means of staking, embedding, and swaging it is also possible to bond other types of materials to thermoplastic materials. Equally, it is possible to bond thin materials, such as PET films or membranes, with rigid plastic parts.