How much polyolefin wax is added to PVC? Polyethylene waxes are not only suitable for PVC films, but also for rigid PVC, such as PVC profiles. Polyethylene wax can be used as an internal and external lubricant in PVC film. It has the characteristics of high melting strength and low volatility, and can play a good role in internal and external lubrication.
1. Increase the melt index: Due to the limitation of the thermal stability of the material and other factors, the processing temperature cannot be increased indefinitely. At this time, adding an appropriate amount of internal lubricant can change the rheological behavior of the resin melt, effectively Increase the melt index to achieve the purpose of reducing melt viscosity and improving melt fluidity.
2. Reduce internal heat generation: The adverse consequences of internal heat generation will lead to local overheating of the polymer melt and reduce its thermal stability. Adding an internal lubricant can effectively reduce the viscosity of the melt and effectively reduce internal heat generation.
3. Mold release effect: In the later stage of polymer processing, when the product is formed, a lubricant with a release effect can be added. Lubricants for mold release are generally external lubricants, mostly polar compounds. They have limited compatibility with resins and can migrate from the melt to the surface. Polar groups have a certain affinity with the metal surface sex. This forms a relatively stable, mutually isolated molecular layer between the melt and the metal surface, thereby inhibiting the adhesion between the polymer melt and the surface of the processing machine.
4. Delayed plasticization: In PVC processing, PVC resin is melted under shear deformation and mixed evenly with various additives. In specific cases, the requirements for resin melting are not consistent. The resin is mixed with a lubricant with low compatibility, which can migrate to the surface of the resin particle or melt at the processing temperature, thereby forming a lubricating layer between the surface of the resin particle or melt and the metal surface of the processing machine, so that It produces good sliding, weakens the effect of shear deformation, and achieves the purpose of delaying the plasticization of the resin.
5. Prevention of melt fracture: High viscosity at high shear rates can lead to a surface phenomenon called melt fracture, because the extruded material undergoes a regular stick/slip transition in the flow channel.
6. Change the self-lubricating property of the product: Many plastic products require good surface lubrication, such as wheels. Lubricants with external lubrication can often form a self-lubricating layer by migrating or exuding to the surface of the product. Produces long-lasting lubrication.
7. Slippery and anti-adhesion effects: For plastic products with large specific surface area, surface adhesion often brings many difficulties to its production or application. Surface migration is relatively large, and a uniformly distributed thin coating can be formed after cooling. Since the two interfaces are inserted into the isolation layer, it not only endows the surface of the product with sliding properties, but also does not cause surface roughness. This function helps The agent is called a slip agent.
Due to the poor thermal stability of PVC, it is necessary to add corresponding stabilizers to repair the defects of the PVC chain, and at the same time absorb the HCL produced by the dechlorination of PVC in time. At the same time, due to the processing characteristics of PVC with high viscosity and high shear, it is necessary to add corresponding lubricants such as polyvinyl wax when adding stabilizers.
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