Heat stabilizers are one of the important categories of plastic processing aids. Stabilizers are synchronized with the birth and development of PVC resin and are mainly used in PVC resin processing. Therefore, heat stabilizers are closely related to PVC resin and the proportion of soft and hard products in PVC.
1. Why does PVC need to add heat stabilizer:
When PVC is at 100~150℃, Ultraviolet light, mechanical force, oxygen, ozone, hydrogen chloride and some active metal salts and metal oxides will accelerate the decomposition rate based on their own decomposition.
For the processing of PVC, thermal decomposition does not change its properties much, but mainly affects the color of the finished product. Adding heat stabilizers can inhibit the initial coloration of the product. In addition, if oxygen is present during the thermal decomposition of PVC, colloidal carbon, peroxide, carbonyl and ester compounds will be generated.
In order to solve this phenomenon, it is necessary to add heat stabilizers during the processing of PVC. This can, to a certain extent, replace unstable chlorine atoms in PVC, absorb hydrogen chloride, and interact with unsaturated parts. Addition reactions and other methods can inhibit the degradation of PVC molecules.
2. Calcium stearate/zinc stearate composite heat stabilizer:
According to supply Understanding calcium stearate and zinc stearate: Calcium stearate and zinc stearate are commonly used non-toxic heat stabilizers with low prices and are suitable for PVC products used in food packaging. Research results show that zinc soap stabilizer has high ionization potential energy and reacts with allyl chloride on PVC molecules to stabilize PVC and inhibit initial coloration.
Usually, non-toxic composite heat stabilizers are mainly composed of calcium stearate, zinc stearate and epoxy soybean oleate. It is worth noting that the new auxiliary heat stabilizers of β-diketones are used together with calcium and zinc soap stabilizers, which promotes the expansion of the use of non-toxic calcium and zinc composite stabilizers. Used in some food packaging materials such as PVC bottles and sheets.
3. Introduction to calcium stearate and zinc stearate:
Calcium stearate is White light crystalline powder. The melting point is 179~180℃, and it will decompose under high heat. Insoluble in water, cold ethanol and ether, soluble in hot benzene, toluene and turpentine, slightly soluble in hot ethanol and ether. Used as lubricant, sliding agent, heat stabilizer, release agent, accelerator, etc. in plastics, machinery, rubber, paint and ink and other industries.
Zinc stearate is a white powder that is insoluble in water. Mainly used as lubricant and release agent for styrene resin, phenolic resin and amino resin. At the same time, it also has the functions of vulcanization activator and softener in rubber. Can be used as heat stabilizer for PVC resin
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