Vibration welding of radiation crosslinked polyamide 66 leads to a different relationship between process, structure, and properties. The radiation-induced altered material properties result in an impeded squeeze flow and higher temperatures in the weld. It is possible to achieve weld strengths up the value of the base material. General theories cannot completely explain the adhesion for these crosslinked polymers. A possible explanation could be an additional temperature-dependent adhesion mechanism. The high temperatures during vibration welding could affect the degree of crosslinking and lead to a post-irradiation crosslinking of the polyamide. These additional links across the joining zone may be an additional adhesion mechanism and could explain the high weld strength of crosslinked polymers. The scope of this paper is to investigate the influence on the degree of crosslinking from material and welding parameters and to correlate these results with temperatures and weld strengths generated in a vibration welding process. POLYM. ENG. SCI., 56:735-742, 2016. (c) 2016 Society of Plastics Engineers