“Noble in Plastics” – Ultra High Molecular Weight Polyethylene (UHMWPE). This is a linear structure with excellent overall performance of the thermoplastic engineering plastics, the general molecular weight of more than 1.5 million, with other plastic unmatched wear, impact resistance, corrosion resistance, low temperature, self-lubricating, absorbing impact energy, health Non-toxic and other comprehensive performance.
1, melt characteristics
Although UHMWPE is a thermoplastic, but because of its molecular weight is too high, when the performance of the melt and the general thermoplastics are different, it can not be processed by conventional processing methods.
① UMWMWPE melt for the rubber state of high elasticity, viscosity is very large, poor processing fluidity.
②UMWMWPE has a lower critical shear rate, at a lower shear rate, it will produce slip flow or jet phenomenon; injection prone to jet products to produce porous or delamination phenomenon.
③ friction factor is small, the feeding process in the feeding section easy to slip, can not move forward.
2, forming methods
Due to the characteristics of UHMWPE, UHMWPE is widely used to limit the application. However, in recent years, UHMWPE processing technology has been the rapid development of the initial molding from the development of extrusion, blow molding and injection molding and other special methods of multi-branch molding method.
① molding: the oldest plastic molding methods, characterized by: low cost, simple equipment, less investment, not subject to the processing of plastic molecular weight constraints; drawbacks are: low production efficiency, labor intensity, prone to oxidation and degradation, product Quality instability and so on. According to the specific process differences are divided into: pressing – sintering – pressing method, sintering – pressing method, pressing sintering at the same time, rapid heating method.
② Extrusion molding: Extrusion molding equipment are mainly plunger extruder, single screw extruder and twin screw extruder. Which with the same twin screw extruder is better.
③ injection molding: UHMWPE single screw injection molding process is mainly through the high-speed shear material dispersion evenly, and full of cavity. While the general plastic injection is molten fluid.
④ blow molding: UHMWPE blow molding is mainly used for large hollow products, such as car fuel tanks, tubes and so on.
⑤ other molding methods: UHMWPE other special molding methods are: jelly spinning, stamping, rolling molding, forging forming, welding and so on.
3, UHMWPE products recycling methods
As a result of UHMWPE ultra-high mechanical properties and ease of processing, UHMWPE products recycling has also become an important problem. And even some waste stations directly refuse to recover this product.
① grinding method: the UHMWPE products broken through the granulator or other equipment made of powder, and then use.
② shear tear method: for some fiber products, the fiber can be cut, cut directly after the application.
Post time: Sep-13-2017