What are the advantages and disadvantages of adding hydrotalcite to calcium zinc stabilizers?

Hydrotalc is an indispensable raw material for calcium zinc stabilizers. Hydrotalc has a special structure and properties, and its most basic properties are alkalinity and multi porosity, with unique and excellent performance and efficacy. It can effectively absorb the hydrogen chloride released during the degradation of PVC, slow down the self catalytic effect of hydrogen chloride on PVC resin, and act as an acid absorbent, which is also known as thermal stability. It is commonly used as a thermal stabilizer.
Hydrotalc also has the advantages of good transparency, insulation, weather resistance, and processability. It is not contaminated by sulfides, non-toxic, and can synergistically work with heat stabilizers such as zinc soap and organic tin. It is a highly promising type of non-toxic auxiliary heat stabilizer.
The structure of hydrotalcite is layered with a large interlayer spacing of 0.76-0.79nm, and it has a large specific surface area, which allows its surface hydroxyl groups to fully react with hydrogen chloride and has a good effect on stabilizers.
The disadvantages of hydrotalcite are:
1. In terms of initial whiteness, hydrotalcite has no effect on the improvement of PVC's initial coloring either alone or in synergy with the calcium zinc system. After aging in a 180 ℃ hot oven, the sample color tends to red.
2. On the stability of Congo red heat, the single action of hydrotalcite can improve the thermal stability time of PVC, and with the increase of addition amount, the thermal stability time of PVC shows an increasing trend, but the increase is not significant.
3. When the combination of hydrotalcite and calcium zinc system is used as a thermal stabilizer, the thermal stability time of PVC is significantly improved, and the trend of increasing thermal stability time with increasing addition amount is also satisfied. Therefore, dihydroxy metal hydroxides should be classified as long-term auxiliary thermal stabilizers, which can effectively extend the long-term thermal stability time of PVC. So, when compounding calcium zinc stabilizers, hydrotalcite is one of the important raw materials.