Calcium stearate is a white powder, insoluble in water, cold ethanol and ether, soluble in hot benzene, benzene, Turpentine and other organic solvents, slightly soluble in hot ethanol and ether. When heated to 400, it slowly decomposes and is flammable. When exposed to strong acids, it decomposes into stearic acid and corresponding calcium salts, which are hygroscopic.

Application of Calcium stearate in PVC formulation

Calcium stearate is used as heat stabilizer of PVC and lubricant and release agent for various plastics processing. When used as a PVC lubricant, it is generally considered an internal lubricant. Calcium stearate is a stearate of moderately strong calcium base, with strong polarity. The chemical active point of PVC resin particles can form a more stable complex system with Calcium stearate. However, the two long-chain alkyl groups of Calcium stearate are less compatible with polar resins such as PVC, and form a local micro two-phase interface in the PVC resin, that is, a lubricating film. 

The microscopic essence of its lubrication effect is that the local lubrication interface formed by non polar long chain alkyl groups and the force between polar resin segments is less than the force between resin segments. Additionally, due to the many small pores between resin segments, when the resin segment is displaced, the alkyl groups that can be arbitrarily deformed are squeezed into other adjacent pores, thereby reducing the resistance during resin segment displacement and providing internal lubrication.

In practical application, Calcium stearate, as a PVC lubricant, does not only play an internal lubrication role, but also has a complex lubrication role. In other cases where the proportion of internal lubrication is high, it will play an external lubrication role. Moreover, it has synergistic effects with many lubricants.

The use of Calcium stearate alone in the formula can accelerate the plasticization, improve the melt viscosity, increase the torque, and have a certain demoulding effect. The use of paraffin alone shows delayed plasticization, reduced torque, and no demoulding effect. When Calcium stearate and paraffin/PE wax are mixed in a certain proportion, the effect is good, and the material torque value can be reduced a lot. This is because paraffin penetrates into Calcium stearate molecules, strengthening the lubrication, showing a strong synergistic effect, and changing the dispersion of lubricants.

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