Magnesium carbonate (MgCO₃) is often used in PVC (polyvinyl chloride) plastics as an inorganic filler, especially in improving its thermal stability. PVC is prone to decomposition at high temperatures, releasing hydrogen chloride gas, resulting in yellowing, decreasing intensity and the generation of decomposition products. The addition of magnesium carbonate can effectively improve this situation, with the specific impact as follows:
1. Improve thermal stability: Magnesium carbonate is a substance with good thermal stability. It can form a stable magnesium oxide (MgO) layer during heating, reducing the thermal degradation of PVC. It can “absorb” hydrogen chloride gas, thereby delaying the decomposition process of PVC.
2. Hygroscopicity: Magnesium carbonate has a certain hygroscopicity and can play a stable role in an environment with high humidity to avoid degradation of PVC due to moisture during processing.
3. Inhibit the release of hydrogen chloride: When PVC thermally degrades, the release of hydrogen chloride (HCl) is one of the main problems. Magnesium carbonate can effectively neutralize hydrogen chloride and produce magnesium chloride (MgCl₂) and water, thereby slowing down the degradation rate of PVC.
4. Improve physical properties: Magnesium carbonate is added to PVC as a filler, which usually improves its hardness and mechanical strength and improves its wear resistance, but may affect flexibility and transparency.
5. Improve processing performance: The addition of magnesium carbonate may also improve the processability of PVC, making it more stable when processed at high temperatures, and reducing the viscosity and inhomogeneity that occur during the melting process.
However, excessive use of magnesium carbonate can also lead to some negative effects, such as affecting the transparency and liquidity of PVC, so it is necessary to control its added amount according to actual needs.
In short, magnesium carbonate has a significant effect on the thermal stability of PVC, especially under high temperature conditions, by slowing down the decomposition reaction, inhibiting the release of harmful gases, and improving the heat resistance and service life of the product.