In order to overcome the shortcomings of the conventional extrusion technologies and to prepare polyethylene(PE) pipes with higher performances

our research group designed and manufactured a novel rotation extrusion processing system.The effect of mandrel and die opposite rotation extrusion on PE pipe's microstructure and resistance to slow crack growth was studied.The experimental results showed that when the mandrel and die rotated in the opposite directions during the extrusion process of PE pipes

apart from the axial stress

the pipes were also subjected to the hoop stress

both of which could set up a tangential stress relative to the axial direction

so as to induce the shish-kebab crystal direction deviate from the axial direction.When a double cooling mode of both inner and outer walls was introduced into rotation extrusion

the relaxation of the oriented molecule could be slowed down and the shish-kebab structure in the PE pipe could be fixed.As a result

the PE pipe with better resistance to slow crack growth was prepared.Compared to the PE pipe produced by the conventional extrusion

the crack initiation time of the PE pipe manufactured by the novel method increased by 204% from 27 h to 82 h.