HC Plastics News: "Amazing plastic" - ultra high molecular weight polyethylene (UHMWPE). This is a linear structure of thermoplastic engineering plastics with excellent comprehensive properties. It has a molecular weight of more than 1.5 million. It has unmatched wear resistance, impact resistance, corrosion resistance, low temperature resistance, self-lubrication, impact energy absorption and hygiene. Non-toxic and other comprehensive properties.
1, melt characteristics
Although UHMWPE is a thermoplastic, its molecular properties are too high, and the properties exhibited during melting are quite different from those of ordinary thermoplastics, so that it cannot be processed by conventional processing methods.
The 1UHMWPE melt is in a rubbery state with high elasticity, very high viscosity and poor processing fluidity.
2UHMWPE has a lower critical shear rate, and at lower shear rates, slip or jet flow occurs; the injection is prone to jetting to cause porosity or delamination of the product.
3The friction coefficient is small, and it is easy to slip in the feeding section during the feeding process, and it cannot advance forward.
2, molding method
Due to the characteristics of UHMWPE, the promotion and application of UHMWPE is largely restricted. However, in recent years, UHMWPE's processing technology has developed rapidly, from initial molding to multi-branched molding methods for extrusion, blow molding and injection molding, as well as other special methods.
"Amazing plastic" started the battle for plastic recycling
1 compression molding
The oldest plastic molding method is characterized by low cost, simple equipment, low investment, and no limitation on the molecular weight of the processed plastics. The disadvantages are: low production efficiency, high labor intensity, easy oxidation and degradation, unstable product quality, etc. . According to the specific process differences, it is further divided into: pressing-sintering-pressing method, sintering-pressing method, pressing and sintering simultaneous method, and rapid heating pressing method.
2 extrusion molding
Extrusion molding equipment mainly includes a plunger extruder, a single screw extruder and a twin screw extruder. Among them, a co-rotating twin-screw extruder is preferred.
Plunger extrusion
Plunger extrusion can be considered as a compression-sintering process. This method has a long plasticizing time, low production efficiency, and limited product width.
b. Single screw extruder
At present, single-screw extruder molding accounts for only 2% of UHMWPE processing, but from the perspective of economy and practicality, single-screw extrusion technology is the most valuable.
c. Twin screw extruder
The twin-screw extruder overcomes the screw slip problem of UHMWPE powder and greatly improves the feeding ability. The co-rotating twin-screw extruder minimizes shearing of the material and minimizes thermal degradation of the material during extrusion.
3 injection molding
The essence of UHMWPE single-screw injection molding is mainly to make the material evenly dispersed by high-speed shearing, and to fill the cavity. The general plastic injection is a molten fluid.
4 blow molding
Blow molding of UHMWPE is mainly used for large hollow products, such as automobile fuel tanks and cylinders.
5 other molding methods
Other special molding methods of UHMWPE include: jelly spinning, stamping, roll forming, forging, and welding.
3. Recycling method of UHMWPE products
Due to the ultra-high mechanical properties and ease of processing of UHMWPE, the recycling and reuse of UHMWPE products has become an important problem. Even some waste stations refused to recycle the product directly.
Currently commonly used recycling methods are:
1 grinding method
The UHMWPE product is crushed and then made into a powder by a granulator or other equipment and reused.
"Amazing plastic" started the battle for plastic recycling
2 shear tear method
For some fiber products, the fibers can be sheared and cut directly for application.
4. Application of UHMWPE
1Ultra high molecular weight polyethylene is widely used in the lining of buckets, silos and chutes for powder files such as coal, lime, cement, mineral powder, salt, grain, etc.;
2 In the defense military equipment, a large number of used as protective clothing, helmets, bulletproof materials;
3 In aerospace engineering, it can be used as a deceleration parachute for space shuttle landings and as a rope for hanging heavy objects on the aircraft, replacing traditional steel cables and synthetic fiber ropes, and its development speed is extremely rapid;
4 In the civilian sector, ropes, cables, sails and fishing gear are made for marine engineering;
5 In industrial applications, it can be used as pressure vessel, conveyor belt, filter material, automobile buffer board, etc.; construction can be used as wall, partition structure, etc.;
6 has made helmets, skis, sail boards, fishing rods, rackets and bicycles, gliders, ultra-lightweight aircraft parts, etc. on sporting goods;
7 In the medical field, it is used in the fields of tray materials, medical implants and plastic sutures. It has good biocompatibility and durability, high stability, no allergies, and has been used clinically. 
Editor in charge: Wang Ning 12
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