How does chemical magnesium hydroxide improve the thermal stability of PVC film?
Publish Time: 2025-08-04
Polyvinyl chloride (PVC), a widely used plastic material, is employed in various industries due to its excellent mechanical properties and low cost. However, PVC is prone to decomposition at high temperatures, producing hydrogen chloride gas. This not only reduces the material's service life but can also pose environmental and health risks. To address this issue, chemical magnesium hydroxide has been introduced as a thermal stabilizer, significantly improving the thermal stability of PVC film through various mechanisms.1. Inhibiting PVC DegradationPVC is prone to dehydrochlorination at high temperatures, leading to molecular chain breakage and, in turn, discoloration and embrittlement. Chemical magnesium hydroxide, as an alkaline substance, neutralizes the hydrogen chloride gas produced in the early stages of PVC degradation, preventing further degradation. This neutralization effectively reduces the release of harmful gases and slows the thermal decomposition of PVC, thereby improving the material's overall thermal stability. Specifically, when the temperature of PVC rises during processing or use, magnesium hydroxide rapidly reacts with the generated hydrogen chloride to form stable compounds such as magnesium chloride and water. This process not only eliminates the structural damage caused by hydrogen chloride but also absorbs some heat, lowering the local temperature and further slowing degradation.2. Providing a Thermal Buffering EffectIn addition to directly neutralizing hydrogen chloride, chemical magnesium hydroxide also has a significant thermal buffering effect. It undergoes an endothermic decomposition reaction at high temperatures, producing magnesium oxide and water vapor. This process absorbs a significant amount of heat, effectively lowering the ambient temperature and providing an additional protective barrier for the PVC. In this way, chemical magnesium hydroxide can mitigate the rapid rise in internal temperature of the PVC, preventing rapid degradation caused by overheating. Furthermore, the resulting magnesium oxide is inert and does not negatively impact the physical properties of the PVC. On the contrary, it can be incorporated into the PVC matrix, enhancing the mechanical strength of the material and further improving the overall performance of the PVC film.3. Optimizing Processing ConditionsIn actual production, the addition of chemical magnesium hydroxide can optimize the processing conditions of PVC film. The presence of magnesium hydroxide allows operations such as extrusion and film blowing to be performed at higher temperatures without worrying about excessive material degradation. This makes the production process more flexible and efficient while ensuring consistent and stable product quality.4. Extended Service LifeThrough the mechanisms described above, chemical magnesium hydroxide significantly extends the service life of PVC film. This advantage is particularly evident in outdoor applications or those exposed to long-term high-temperature environments, such as building coverings and agricultural greenhouse films. The modified PVC film exhibits improved weathering and aging resistance, maintaining excellent physical properties and appearance even in extreme climates.5. Synergistic Benefits with Other AdditivesNotably, chemical magnesium hydroxide often exhibits a stronger synergistic effect when used in combination with other stabilizers (such as organotin stabilizers and metal soaps). These agents complement each other, forming a multi-layered protective system that comprehensively enhances the thermal stability of PVC film.In summary, chemical magnesium hydroxide significantly improves the thermal stability of PVC film through multiple mechanisms, including inhibiting PVC degradation reactions, providing a thermal buffering effect, optimizing processing conditions, and extending service life. Its unique advantages make it an ideal thermal stabilizer, particularly in harsh environments such as high temperature and high humidity.
