Vibration welding of crosslinked polyethylene

The suitability of vibration welding for joining crosslinked polyethylene (PE-X) was investigated within the framework of a publicly funded research project. For this purpose, linear vibration welding tests were carried out on PE-Xc plates with degrees of crosslinking of 30 and 60% as well as circular welding tests on PE-Xa pipes with a degree of crosslinking of 80% and on PE-Xc pipes with a degree of crosslinking of 60%. The resulting joints were subjected to shorttime tensile tests and tensile creep tests as well as to optical and analytical investigations. Nearly all the welded joints exhibit short-time welding factors above 0.9. For the degrees of crosslinking of 60 and 80% the creep rupture times of the welds subjected to tensile loads and a wetting agent at a temperature of 85°C were below 60 h in almost all cases. For the degree of crosslinking of 30% creep rupture times above 60 h were found in several cases. Analytical investigations of the welds reveal a complex stress state frozen in the PE-X which is firstly heated during the welding process and then cooled under pressure. This presumably reduces the creep rupture time of the welded PE-X joints.