| The principle of internal lubrication and external lubrication |
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| Internal and external lubrication is an important index in the processing of plastics (PVC, PE, PP, etc.). Internal and external lubrication have an important impact on the processing quality of plastic products, such as forming and finishing. Internal and external lubricants are sometimes referred to as PVC lubricants, with a wide range of lubrication, high melting strength, and can improve the flow. There are not many additives for internal and external lubrication. Lubrication principle of internal lubricants: Internal lubricants are generally small molecule organic compounds with polar groups. Therefore, it can be well compatible with PVC macromolecules. These small molecules can be evenly distributed among the structural units of PVC macromolecules, which makes the movement of PVC macromolecules easier, improves the fluidity of PVC materials, reduces the heat generated by friction and shear, and eliminates the fluctuation of melt temperature. There are also some substances that have the function of internal lubricants and external lubricants. It is generally a derivative of higher fatty acids containing polar groups and relatively large molecular weights. Euroceras oxidized polyethylene wax, C22 C32 wax acid, wax alcohol and fat, resin and asphalt. It can combine with paraffin wax, stearic acid, beeswax, rosin, and wax to synthesize stable compounds and improve melting point. It has good stability to acid and other chemical solvents, high gloss, strong wet resistance, low conductivity, high mechanical strength and solubility in a variety of organic solvents. Lubrication principle of external lubricants: External lubricants are usually organic compounds with low polarity or low polarity. The melting point is 60 -95 C. Its characteristics are long hydrocarbon chain and poor compatibility with PVC. The external lubricant melts and precipitates on the surface of the melt under certain temperature and pressure, and forms a boundary film between the melt and the metal, which can reduce the adhesion of the molten material to the basic equipment and mold. 719 oxidized polyethylene wax is suitable for PVC profile. Because of the complex section of PVC profiles, long plasticizing time in the barrel, screw torque is very large, it will easily cause burning materials and then produce black lines on the products. The addition of 719 OPE wax has better external lubrication effect than PE wax, and keeps the material from decomposition during plasticization. |
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