1. Melt characteristics

Although UHMWPE is a thermoplastic, because its molecular weight is too high, its properties when melted are completely different from those of general thermoplastics, so it cannot be processed by conventional processing methods.

① UHMWPE melt is a rubbery high elastic state, with very high viscosity and poor processing fluidity.

② UHMWPE has a lower critical shear rate, and at a lower shear rate, a slip flow or jet flow phenomenon will occur; the jet flow is prone to cause the product to appear porous or delaminated during injection molding.

③ The friction factor is small, it is easy to slip in the feeding section during the feeding process, and it cannot be pushed forward.

2. Forming method

Due to the characteristics of UHMWPE, the promotion and application of UHMWPE is largely limited. However, in recent years, the processing technology of UHMWPE has developed rapidly, from the initial compression molding to extrusion, blow molding and injection molding and other special methods of multi-branch molding methods.

① Molding

The oldest plastic molding method is characterized by: low cost, simple equipment, low investment, and no restriction on the molecular weight of the plastic to be processed; disadvantages are: low production efficiency, high labor intensity, prone to oxidation and degradation, unstable product quality, etc. . According to the specific process difference, it is divided into: pressing-sintering-pressing method, sintering-pressing method, simultaneous pressing and sintering method, and rapid heating pressing method.

② Extrusion

Extrusion molding equipment mainly includes plunger extruder, single-screw extruder and twin-screw extruder. Among them, the co-rotating twin-screw extruder is preferred.

a. Plunger extrusion

Plunger extrusion can be viewed as a pressing-sintering method. This method has long plasticization time, low production efficiency, and limited product width.

b. Single screw extruder

At present, single-screw extruder molding only accounts for 2% of the total UHMWPE processing, but from the perspective of economy and practicability, single-screw extrusion technology is the most valuable

c. Twin screw extruder

The twin-screw extruder overcomes the problem of UHMWPE powder slipping on the screw and greatly improves the feeding capacity. The co-rotating twin-screw extruder minimizes the shearing action of the material and minimizes the overheating degradation of the material during the extrusion process.

③ Injection molding

The essence of the UHMWPE single screw injection molding process is to disperse the material evenly and fill the cavity through high-speed shearing. The general plastic injection is molten fluid.

④ Blow molding

Blow molding of UHMWPE is mainly used for large hollow products, such as automobile fuel tanks, cylinders, etc.

⑤ Other molding methods

Other special molding methods of UHMWPE include: jelly spinning, stamping molding, rolling molding, forging molding, welding molding, etc.

3. Recycling method of UHMWPE products

Due to the ultra-high mechanical properties and difficult processability of UHMWPE, the recycling and reuse of UHMWPE products has also become an important problem. Some scrap sites even refuse to recycle this product outright.

The most common recycling methods are:

① Grinding method

After crushing the UHMWPE products, they are made into powder by a granulator or other equipment, and then reused.
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② Shear and tear method

For some fiber products, the fibers can be sheared, and can be directly applied after being chopped.

4. Application of UHMWPE

① UHMWPE is widely used in the lining of drag buckets, silos, and chutes for powdered documents such as coal, lime, cement, mineral powder, salt, grain, etc.;

② In terms of national defense military equipment, it is widely used as protective clothing, helmets, and bulletproof materials;

③ In aerospace engineering, the decelerating parachute that can be used for the landing of the space shuttle and the rope for suspending heavy objects on the plane have replaced the traditional steel cable and synthetic fiber rope, and its development speed is extremely rapid;

④ In the civilian field, the ropes, cables, sails and fishing gear made are suitable for marine engineering;

⑤ In industrial applications, it can be used as pressure-resistant container, conveyor belt, filter material, automobile buffer board, etc.; in construction, it can be used as wall, partition structure, etc.;

⑥ It has been made into helmets, snowboards, sailboards, fishing rods, rackets, bicycles, gliders, ultra-lightweight aircraft parts, etc. on sporting goods;

⑦ In medicine, it is used in the fields of dental tray materials, medical implants and plastic sutures. It has good biocompatibility and durability, and has high stability and does not cause allergies.