In the world of PVC processing and formulation, stabilizers play a crucial role in enhancing the performance and durability of the material. One popular type of stabilizer used in PVC applications is calcium zinc stabilizer. In this blog, we will delve into the properties and advantages of calcium zinc stabilizer, shedding light on why it is a preferred choice for many industries.
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Calcium zinc stabilizers exhibit excellent thermal stability, allowing them to withstand high processing temperatures without significant degradation. This property ensures consistent performance during PVC processing, resulting in products with enhanced heat resistance. The heat stability contributes to the improved long-term performance of PVC products, even under high-temperature conditions. This makes them suitable for applications where heat resistance is essential, such as outdoor construction materials and automotive components.
Calcium zinc stabilizers provide excellent weather resistance to PVC products, protecting them from degradation caused by exposure to UV radiation, moisture, and other environmental factors. This property is particularly beneficial for outdoor applications, where durability and colour retention are essential.
Calcium zinc stabilizers from the best Calcium zinc stabilizer manufacturer are considered environmentally friendly alternatives to traditional lead-based stabilizers. They do not contain heavy metals like lead or cadmium, making them safer for both human health and the environment.
These stabilizers offer a cost-effective solution for PVC processing and formulation. Compared to other stabilizer systems, they provide competitive pricing while delivering excellent performance and durability.
Highly versatile, this kind of stabilizer can be used in a wide range of PVC applications, including pipes, profiles, cables, and films. Their compatibility with various PVC formulations makes them suitable for different industries and product types.
In conclusion, calcium zinc stabilizers offer a range of advantageous properties that make them a popular choice for stabilizing PVC formulations. If you’re looking for high-grade calcium zinc stabilizers for your business, look no further. Platinum is among the top manufacturers of high-quality stabilizers, including organic based stabilizer in the market. To know more, visit https://platinumindustriesltd.com/
Introduction:
PVC contains 56.8% chlorine, out of which 1-3% chlorine is allylic chlorine and tertiary chlorine. These allylic and tertiary chlorines are labile (reactive) and are the root cause for degradation (dehydrochlorination) of PVC.
Primary thermal stabilizer is a substance which, when employed as a sole stabilizer in PVC, imparts an acceptable degree of heat stability.
Such stabilizers are usually metal compounds having two parts – A metallic part (M) and a non metallic part known as Ligand (L) covalently joint together.
The action of primary stabilizer is basically a chemical reaction wherein –
1. The ligand part of primary stabilizer molecule (L) replaces the labile chlorine atom in PVC resin to make it thermally more stable,
2. The metal part of the primary stabilizer (M) reacts with chlorine to form metal chloride.
It is essential that the metal chloride formed be neutral and incapable of causing direct degradation of PVC molecules e.g. Lead chloride (PbCl2).
What is a mixed metal stabilizer?
Certain metal chlorides like ZnCl2 or CdCl2 are not neutral. They are known as “Lewis acids”.
If not arrested, they accelerate degradation in presence of HCl, Oxygen and Higher processing temperature.
This acceleration activity for various metal chlorides is as follows -
ZnCl2 > CdCl2 > PbCl2 > PVC without additive > BaCl2 > Oc2SnCl2
To mitigate this accelerated dehydrochlorination reaction, Zn and Cd compounds (primary stabilizers) are blended with alkali or alkaline earth (like Ca and Ba) compounds (secondary stabilizers), resulting in a mixed metal stabilizers system.
Examples of such mixed metal stabilizers are Cd - Ba or Ca - Zn stabilizer systems. These stabilizers are mostly Zn and Ca soaps of fatty acids (metal carboxylates).
However, since Zn compound is a primary stabilizer, it should be aptly called Zn – Ca stabilizer and not Ca-Zn stabilizer.
How do mixed metal stabilizers work?
Barium or calcium compounds (secondary stabilizers) do not react with the labile chlorine atoms present in PVC, as directly as zinc compounds do.
The Calcium chloride or zinc chloride formed is a potent Lewis acid, capable of catalyzing catastrophic dehydrochlorination of PVC. It has to be eliminated instantaneously.
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As soon as Zinc chloride is formed, it undergoes a double displacement reaction with Ca soaps (Laurate, Myristate, Palmitate, and Stearate), regenerating the Cadmium or Zinc soap and forms Barium or Calcium chloride, which is not a Lewis acid and is relatively inert. Thus,
ZnCl2 + CaSt --> ZnSt + CaCl2 (in case of Zn – Ca stabilizers)
Cd Cl2 + BaSt --> CdSt + BaCl2 (in case of Cd – Ba stabilizer)
Thus, as soon as ZnCl2 is formed, Ca Stearate reacts with the Zinc chloride, regenerating the Zinc soap and forming Ca chloride, which is not a Lewis acid and is relatively inert.
Due to regeneration of primary stabilizer - Zn stabilizer level is kept low in Zn-Ca system.
In Cd-Ba or Zn-Ca system -
1. High barium / calcium content leads to long failure time,
2. While high cadmium / zinc content leads to best color retention and high clarity and sparkle.
Since Ca & Ba stearates get consumed, zinc or cadmium is backed up by calcium or barium in the stabilizer system at higher level than zinc.
What are metallic soaps and how do they work synergistically?
Metallic soap is a reaction product of fatty acid with strong alkali.
These metallic soaps belong to two categories in terms of their effectiveness to retard discolouration of PVC due to degradation, as a function of time at an elevated temperature.
The metal soaps of fatty acids belonging to “type A” are the alkali (Lithium, Sodium, Potassium) or alkaline earth (Beryllium, Magnesium, Calcium, Strontium, Barium etc.) metal soaps, e.g. Calcium soaps of Lauric (C12), Myristic (C14), Palmitic (C16), Stearic (C18) fatty acids.
“Type A” metal soaps correspond to soaps of metals with ionic character.
On the other hand, the metal soaps of fatty acid belonging to “Type B” are heavy metal soaps like Pb, Cd, Zn e.g. Zinc stearate.
“Type B” metal soaps correspond to soaps of metals with covalent character.
However, it is established that combination of type A and type B metal soaps results in combination of characteristics of type A and type B stabilizers.
If we assume that for every specific application, the maximum permissible degradation level is “X”, then, this level of degradation can best be prevented with a mixture of type A and type B soap in optimum ratio. (Synergistic effect)
Mixed metal stabilizers commonly used are:
1. General purpose – Cadmium – Barium compounds [solid, liquid, paste], or
2. FDA grade – Calcium - Zinc compounds [powder, paste, liquids].
To improve its effectiveness and efficiency, many ingredients such as - Salts, soaps, bases, ESBO, antioxidants, polyols, chelators, β diketones, plasticizers, solvents, diluents, hydrotalcites and zeolites are added to the formulation.
Mixed metal stabilizers are more versatile, proprietary & available in many grades.
Formulations of mixed metal stabilizer are usually custom made.
Where environmental concerns are predominant, various combinations like, Cd-Ba, Cd-Ba-Zn and Ba-Zn are avoided.
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