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What is the role of Calcium Zinc Stabilizer in the production and use of PVC products?

What is the role of Calcium Zinc Stabilizer in the production and use of PVC products?

Not only Calcium Zinc Stabilizer can replace toxic stabilizers, such as lead, cadmium salt and practice has proved that in PVC resin products, processing performance is good, is equivalent to the lead salt stabilizer, the thermal stability is a kind of good non-toxic stabilizers.

Its macromolecule chain in the process of PVC processing unstable chlorine atoms (such as allyl chloride) easy to take off the HCL, heated with conjugated double bonds of polyene structure formation, lead to PVC color changes are as follows: colorless or white to pale yellow to yellow orange and red orange to red brown to brown, make the physical and chemical properties of PVC. Calcium zinc stabilizer mechanism is: zinc soap as the primary stabilizer, have the function of active chlorine and absorbing HCl replacement at the same time, then the generated metal chloride is a lewis acid, can promote to take off the HCI reaction. PVC can degrade in a very short time, leading to "zinc burning". The equation is:

Zn (O2C -R)2+2PVC-- -ZnCl2 +2PVC-- O-CO-R

Therefore, zinc soap must be used with coactive stabilizer, mainly including stearic acid soap. Since calcium stearate is not toxic, zinc soap is often coupled with calcium stearate. Calcium soap only shows the effect of capturing HCI, and can not replace active chlorine. The generated metal chloride is not catalyzed by dehci reaction, but can effectively replace the chloride of zinc soap to regenerate. The equation is:

ZnCl2 + Ca (O2C - R) 2 -- -- -- -- -- -- -- -- -- Zinc (O2C - R) 2 + CaCl2

Generally speaking, the increase of calcium soap content can improve the long-term stability of the products, but it can inhibit the poor performance of the initial staining. On the contrary, the content of zinc soap is high, the initial color of the product can be improved, but the other "zinc burning", and the long-term stability of the decline. Therefore, by choosing reasonable calcium soap and zinc soap ratio in the calcium and zinc composite stabilizer, the synergistic effect can be used to achieve a better stable effect.

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