PVC lubricants are divided into internal lubricants and external lubricants. However, the internal and external lubricants are relatively different, and there is no strict classification standard. The main distinction is based on the compatibility of lubricants and resins. Internal lubrication has great affinity with resin, its function is to reduce intermolecular force and improve the dispersion of raw material components; The external lubricant has little affinity with resin, and its function is to reduce the friction between resin and metal surface. Due to the different polarity of resin, the effect of internal and external lubricants may change. Generally, extremely polar lubricants such as stearic alcohol, stearic amide, butyl stearate and monoglyceride stearate are listed as internal lubricants, and lubricants with poor polarity such as Paraffin Wax and Pe Wax are listed as external lubricants. This is for PVC and PA resins with strong polarity, while for non-polar resins such as PE and PP, the results are just the opposite. For example, PARAFFIN WAX, PE WAX , etc. are non-polar substances with good compatibility with PE and PP resins, Therefore, it is a typical internal lubricant. The compatibility of lubricant and resin is not invariable, but varies with the change of processing temperature. For example, Stearic Acid and stearic alcohol are used in the initial stage of PVC extrusion molding. Due to the low melt temperature and poor compatibility with PVC Resin, they mainly play the role of external lubrication; When the temperature rises, the compatibility with PVC increases, and the small molecular lubricant is easier to enter between the molecular chains, which becomes the role of internal lubricant. The change of lubricant properties is also related to the amount of lubricant added. When the amount of lubricant added is less than its compatibility, there is no external and internal lubrication of PVC secondary particles washed out. When the amount of lubricant added is greater than its compatibility, some of them are excluded from PVC macro particles and secondary particles and show external lubrication. Stearic acid is a widely used lubricant next to metal soap. It is a typical external lubricant in soft products, which can effectively reduce the heat generated by friction between resin and processing equipment, and can also effectively prevent the adhesion of molten resin to metal surface. However, in PVC-U, when the amount is small, it plays an internal lubrication role, can significantly promote plasticization and reduce melt viscosity; When the dosage is large, it can obviously delay the plasticizing speed and play the role of external lubrication. In view of the fact that the compatibility of lubricants, especially metal soap lubricants, with PVC RESIN changes under certain temperature, pressure and shear heat. In fact, few lubricants are purely internal or external. To say whether a certain lubricant is internal or external, it means whether the internal or external lubricity is dominant according to the conventional addition under certain circumstances. The reason why alkoxy waxes are generally used as external sliders is that they have little polarity and have little compatibility with highly polar resins. Before plasticizing, it is evenly coated on the surface of PVC particles, making particles slide each other, preventing the expansion, adhesion and delayed plasticizing of particle chains; After plasticization, it is excluded from the outer surface of the melt and forms a liquid lubricating film, which reduces the adhesion and friction between the PVC melt and the metal surface of the processing equipment, thus reducing local overheating, and improving the thermal stability and fluidity of the Pvc Resin.
We have done chemical products for over 30years. Our main products include PVC RESIN, CPE , TIO2 , Stabilizer, PE WAX, PARAFFIN WAX ETC.
