Required material properties and degree of plasticization. Of course, it should be noted that calcium and zinc stabilizers use more lubricants than lead salts.
The reason why stearic acid is also brought over is to give us a better understanding of the influence of the ingredients in calcium and zinc stabilizers on lubricity.
As mentioned before, maintaining the uniformity of the plasticization of PVC resin requires a combination of internal and external lubrication to transmit external energy to the PVC resin more uniformly, and stearic acid plays a role in internal lubrication. Look at the picture below. The small circle represents the polar carboxylic acid end of stearic acid. It is the function of this head that allows stearic acid to be adsorbed on the PVC resin particles, which can churn on the surface of the particles during processing. The role of internal lubrication.
Calcium stearate, zinc stearate, and stearic acid have similar structures, with more charged calcium ions and zinc ions. How to understand charged ions? To put it bluntly, polarity is actually the attraction of electric charges. The charge of calcium and zinc ions greatly enhances its polarity. It is necessary to know that calcium stearate, zinc, etc., have the strongest polarity among the lubricants commonly used in PVC. This gives it a stronger affinity with the PVC resin, thereby weakening or eliminating the attraction of the ionic bonds of the inner layers of the PVC resin particles, and promoting the intertwined segments of the PVC to easily diffuse, and the sliding layer formed has a high viscosity and generates heat by friction. Large, high transmission efficiency of mechanical force, accelerates the temperature rise of the material and initiates the over-plasticization of the resin. The lead salt itself has no such effect.
That is to say, in addition to its stabilizing effect, calcium and zinc stabilizers also shorten the plasticization time and can promote plasticization. If the original lead salt stabilizer is used, use calcium and zinc stabilizer. Under the premise of using the same lubricant (including the stabilizer), the lead salt can produce qualified products, and the use of calcium and zinc will promote the advancement of materials Plasticization may cause no discharge.
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