The Performance Difference Between PE Wax And Stearic Acid

The performance difference between PE wax and stearic acid. PVC lubricants are divided into two categories: internal lubricants and external lubricants. However, the distinction between internal and external lubrication is only relative and there is no strict classification standard. The main distinction is based on lubrication. The compatibility between the agent and the resin.
The compatibility of lubricants and resins is not static and changes with processing temperature. For example, when PE wax is used in the early stage of PVC extrusion molding, due to its low melt temperature and poor compatibility with PVC resin, it mainly plays an external lubrication role; when the temperature rises, its compatibility with PVC increases, and small molecule lubricants are more effective. It easily enters between the molecular chains and acts as an internal lubricant.

The change of lubricant properties is also related to its addition amount. When the added amount of lubricant is less than its compatibility, the PVC secondary particles are not washed out to show external internal lubrication. When the added amount of lubricant is greater than its compatibility, part of it is excluded from the PVC macro The external lubrication effect is shown outside the particles and secondary particles. It is a typical external lubricant in soft products. It can well reduce the friction and heat between resin and processing equipment, and can also well prevent the adhesion of molten resin to metal surfaces. However, in PVC-U, when the dosage is small, it acts as internal lubrication, which can significantly promote plasticization and reduce the melt viscosity; when used in large quantities, it can significantly slow down the plasticization speed and acts as external lubrication.

The reason why waxes are generally used as external slip agents is that they have little polarity and have little compatibility with highly polar resins. Before plasticization, it evenly coats the surface of PVC particles, causing the particles to slide with each other, preventing the particle segment chains from expanding and adhering to each other, and delaying plasticization; after plasticization, it is repelled on the surface of the melt, and The formation of a liquid lubricating film reduces the adhesion and friction between the PVC melt and the metal surface of the processing equipment, thereby reducing local overheating and improving the thermal stability and fluidity of the PVC resin.