Because the viscosity of ultra-high molecular weight polyethylene (UHMW-PE) in molten state is as high as 108Pa*s, the fluidity is extremely poor, and its melt index is almost zero, it is difficult to be processed by general machining methods. Ultrahigh molecular weight polyethylene (UHMW-PE) processing technology has been rapidly developed, through the transformation of ordinary processing equipment, has made ultrahigh molecular weight polyethylene (UHMW-PE) from the initial pressing – sintering molding development to extrusion, blow molding and injection molding and other special methods of molding.
General method
1. Pressing and sintering
(1) Pressing and sintering is the most original processing method of ultra-high molecular weight polyethylene (UHMW-PE). The production efficiency of this method is quite low, and oxidation and degradation are easy to occur. In order to improve production efficiency, direct electric heating can be used
(2) Ultra-high speed fusion processing method, using blade type mixer, the maximum speed of blade rotation can reach 150m/s, so that the material can rise to the processing temperature in only a few seconds.
2. Extrusion molding
Extrusion molding equipment mainly includes plunger extruder, single screw extruder and twin screw extruder. Twin-screw extruder is mostly used in the same direction rotating twin-screw extruder.
In the 1960s, most of the plunger extruder was used. In the middle of the 1970s, Japan, the United States and West Germany successively developed the single screw extrusion process. Mitsui Petrochemical Company of Japan first achieved the success of round rod extrusion technology in 1974. At the end of 1994, φ45 type ultra-high molecular weight polyethylene (UHMW-PE) special single screw extruder was developed, and the success of φ65 type single screw extruder pipe industrial production line was achieved in 1997.
(3) Injection molding
Mitsui Petrochemicals developed the injection molding process in 1974 and commercialized it in 1976, followed by reciprocating screw injection molding. In 1985, Hoechst also realized the screw injection molding process of UHMW-PE. In 1983, the domestic XS-ZY-125A injection machine was modified. The ultra-high molecular weight polyethylene (UHMW-PE) supporting wheel and the axle sleeve for water pump for beer caning production line were injected successfully. In 1985, the artificial joint for medical use was also injected successfully.
(4) blow molding
Ultra-high molecular weight polyethylene (UHMW-PE) processing, when the material extrusion from the mouth die, due to elastic recovery and a certain shrinkage, and almost no sagging phenomenon, so hollow containers, especially large containers, such as oil tank, drum blow molding to create favorable conditions. Ultrahigh molecular weight polyethylene (UHMW-PE) blow molding can also lead to a high performance film with balanced strength in the vertical and horizontal direction, which solves the problem that the strength of HDPE film is not consistent in the vertical and horizontal direction for a long time and is easy to cause longitudinal damage.