Decrosslinking of peroxide-crosslinked high density polyethylene (XHDPE) and low density polyethylene (XLDPE) by means of an ultrasonic single- and twin-screw extruders are investigated. Barrel pressure and ultrasonic power consumption during extrusion are recorded. Swelling test, rheological test, thermal analysis and tensile test are used to elucidate the structure-property relationship of decrosslinked PE. It was found that a more intensive rupture of the crosslinked network occurs at higher degree of crosslinking. Analysis based on the Horikx function shows that the type of preferential bond breakage during decrosslinking is not determined by the bond energy alone but also influenced by structural characteristics of the crosslinked network. The activation energy of viscous flow of sols extracted from various decrosslinked XPE supports the analysis based on the Horikx function. The dynamic, thermal and tensile properties of the decrosslinked XPE are greatly affected by the type of preferential bond breakage. A significant improvement in the processibility and mechanical properties of decrosslinked XPE is achieved due to the occurrence of a highly preferential breakage of crosslinks during ultrasonic decrosslinking.
