Calcium stearateis a very widely used additive and PVC stabilizer. As an additive, it plays a great role in many industries. It is applied in various fields. Used as heat stabilizer for polyvinyl chloride and lubricant for various plastic processing, release agent, etc. In hard products, the gelation speed can be increased by combining with basic lead salt and lead soap. It is also used in soft films and appliances that require nontoxicity, such as food packaging and medical equipment. It can also be used as a halogen absorber for polyethylene and polypropylene to eliminate the negative effects of residual catalyst on color and stability. Used as a plasticizer in rubber processing, it can soften natural rubber and synthetic rubber and has almost no effect on vulcanization. It is also used as a lubricant for polyolefin fibers and molding compounds, a thickening agent for grease, a waterproofing agent for textiles, a flattening agent for paints, and a plasticizer in the manufacture of plastic records. It is also used in pencil lead production and the pharmaceutical and spice industries.
The following is the main introduction to the supply of calcium stearate and stearin The role of calcium acid in PVC:
As a PVC lubricant When used, it is generally considered an internal lubricant. Calcium stearate is the stearate of medium-strong alkali calcium and has strong polarity. The chemical active points of PVC resin particles can form a more stable complex system with calcium stearate. The two long-chain alkyl groups of calcium stearate have less compatibility with polar resins such as PVC, and form a local microscopic two-phase interface inside the PVC resin, that is, a lubricating film.
The microscopic nature of its lubrication effect is caused by non-polar long-chain alkyl groups. The force between the formed local lubricating interface and the polar resin segment is smaller than the force between the resin segments, and because there are many small pores between the resin segments, when the resin segment is displaced, the alkyl group can be deformed arbitrarily. It is squeezed into other adjacent pores, thereby reducing the resistance when the resin chain segments are displaced and acting as internal lubrication.
Using calcium stearate alone in the formula can accelerate plasticization and improve The melt viscosity increases the torque and has a certain demoulding effect, while the use of paraffin wax alone shows delayed plasticization, reduced torque and no demoulding 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 reduced a lot. This is because the paraffin penetrates into the calcium stearate molecules and strengthens the lubrication effect. , showing a strong synergistic effect and improving the dispersion of lubricants.
Precautions when adding calcium stearate: strong>
1. When manufacturing PVC transparent products, the calcium stearate The added amount cannot be greater than 0.5 parts, otherwise the transparency of the PVC material will be affected;
2 When calcium stearate is added to the lead salt composite stabilizer, excessive plasticization will occur, which will affect the lubrication system and lead to a decrease in the strength of the mechanical product;
3. In the calcium-zinc composite heat stabilizer system, the proportion of calcium stearate is too low, which will lead to insufficient initial heat stabilization performance. Well, if the ratio is too high, it will cause the PVC products to turn yellow and have poor weather resistance;
4. Calcium stearate will affect the decomposition temperature of the foaming agent, so the amount of stabilizer can be appropriately increased when using it. </span
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