How to use calcium stearate in plastic processing?

Calcium stearate serves as a heat stabilizer for PVC and a lubricant and release agent for various plastic processing. When used as a PVC lubricant, it is generally considered an internal lubricant. Calcium stearate is a stearate of medium to strong alkaline calcium with strong polarity. The chemical active points of PVC resin particles can form a relatively stable complex system with calcium stearate. The two long chain alkyl groups of calcium stearate have less compatibility with polar resins such as PVC, forming a local microscopic two-phase interface within the PVC resin, known as a lubricating film. 

The microscopic essence of calcium stearate 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 applications, calcium stearate, as a PVC lubricant, does not only play an internal lubrication role, but its lubrication effect is relatively complex. In other cases where the proportion of internal lubrication is relatively high, it will reflect the role of external lubrication. Moreover, it has synergistic effects with many lubricants.

In hard products, the gel speed can be improved by combining with basic lead salt and lead soap. It is also used for food packaging, medical equipment, and other non-toxic soft films and appliances. It can be used as a halogen absorber for PE and PP to eliminate the adverse effects of residual catalysts on color and stability. 

As a plasticizer in rubber processing, it can soften natural rubber and synthetic rubber, with almost no effect on vulcanization. It is also used as a lubricant for polyolefin fibers and molded plastics, a thickener for lubricating grease, a waterproof agent for textiles, a leveling agent for paints, a plasticizer for making plastic records, a lubricant and release agent for thermosetting plastics such as phenolic and amino acids, a lubricant for pencil leads, and a food grade calcium stearate as an anti bonding agent.

The use of calcium stearate alone in the formula can accelerate plasticization, increase melt viscosity, increase torque, and have a certain demolding effect. However, the use of paraffin alone shows delayed plasticization, reduced torque, and no demolding effect. When calcium stearate and paraffin (polyethylene wax) are mixed in a certain proportion, good results are shown, and the material torque value can be significantly reduced. This is because paraffin penetrates between calcium stearate molecules, strengthening lubrication and showing a strong synergistic effect, changing the dispersion of the lubricant.

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