Analysis of Discoloring of PVC Heat Stabilizers after Being Heated
Ideal heat stabilizers is thought that it should have functions including absorption of HCL, elimination of active part, addition with conjugated polyene chain, damage to cation carbonate salt and prevention from automatic oxidization, but without outcome which has catalytic action to Polyvinyl Chloride (PVC). Specific PVC heat stabilizers is characterized by different heat stability due to different functions, thus being approximately divided into initial type, long-term type, intermediate type and all-around type.
1. Initial type--Cd and Zinc Soap Stabilizer
This type of PVC Stabilizer can absorb HCL quickly and replace unstable chlorine atom in PVC chain with carboxylate radical under the catalytic action of Cd and Zn, thus effectively prohibiting initial decomposition and coloring of Polyvinyl Chloride (PVC). However, because they are consumed quickly and converted products are CdCl2 and ZnCl2, which is high-efficiency catalytic action for effluent of HCl from Polyvinyl Chloride (PVC). It will cause severe decomposition of Polyvinyl Chloride (PVC) and make PVC products turn blackish.
2. Long-term type--Barium and Calcium Soap Stabilizer
This type of PVC Stabilizer has the only function to absorb HCl, thus not prohibiting coloring of PVC products well. But the converted materials--BaCl2 and CaCl2 don’t have catalytic activity. It won’t make PVC products turn blackish suddenly and has good long-term stability.
3. Intermediate Type--Fatty-acid Organo-tin
This type of PVC Stabilizer can absorb HCl and replace unstable chlorine atom in PVC chain with carboxylate radical. Their converted materials don’t have catalytic activity.
This type of PVC Stabilizer has all-around properties and can stabilize Polyvinyl Chloride (PVC) in different ways. Their converted materials also don’t have catalytic activity, thus acquiring excellent initial and long-term heat stability.