n layer a few 100 ??m thick and is converted into heat, which leads to melting in the contact zone and finally to bonding of the two components of the join by means of a weld. [0008] Partially crystalline thermoplastics such as polyamides, for example polyamide 6 (PA 6) and polyamide 66 (PA 66), or polyesters, for example polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), are l