Stabilization Mechanism Of PVC Compound Stabilizer Introduction
Thermal decomposition of PVC compound stabilizers are sensitive to heat from the partial release HCL, formed double bond in PVC structure, due to the high activity of allyl chloride, the reaction constant, continue to form a conjugated, polyene structure, causing product coloring.
When the calcium-zinc composite stabilizer is, first of all, SOAP in replacing the allylic Bing chloride of zinc at the same time, accompanied by the double bond transfer. Polyene structures destroyed, inhibiting the discoloration. In PVC, however zinc chloride precipitation, on the removal of HCL has a catalytic role, PVC instability caused bridge and even black. Calcium SOAP by double decomposition of zinc SOAP with stability after exposure to chlorine in the PVC production of zinc chloride and zinc SOAP, which on the one hand-activated zinc SOAP, which activated zinc SOAP on the one hand, and inhibits the damaging effects of zinc chloride. A large number of organic compounds can greatly improve the initial coloring, so often used in stabilizer to compensate for inadequate calcium zinc stabilizer of coloring in the early.
Polyol class is also used in PVC stabilizers. Polyols is the role of chloride by chelating metals to prevent deterioration, and polyols can also metal salt catalyst replacement propyl-Ene, calcium zinc stabilizer to improve initial hue and has a good effect, but severe pressure on the application effect of polyols and insulated in PVC products that require application of polyol is limited.
Acid absorbent can be used as secondary stabilizers for PVC. People speculated that their degradation forms complexes and reaction activity decreased as well as capture the catalytic activity of HCL to avoid reactions of HCL removal continues. Epoxides, calcium zinc stabilizer and, up to a certain synergy
In short, compound heat stabilizer to the scale of production, for the development of lead salt heat stabilizer provides new directions. Lead salt composite stabilizer lead content is an important indicator, current production of lead salt composite stabilizer 20%-60% by weight of lead; in the production of PVC plastic profile 3. 5-6