Stabilizers are main components added to PVC powder (dry blend) during pipe production. They are essential to prevent the rapid degradation of PVC at the high temperatures encountered during extrusion.
Historically, Lead (Pb) was used as a stabilizer for PVC. However, due to environmental concerns, Lead formulations have been phased out in Europe, similar to its removal from car fuels.
Tin (Sn) stabilizers are widely used, for example, in the USA. Unlike most other stabilizers supplied as powder or flakes, Tin stabilizers are typically in liquid form. They are effective heat stabilizers, contributing to the processability and stability of the PVC melt.
Calcium Zinc (CaZn) and Organic Based Stabilizers (OBS), based on Uracil and per-chlorates, are modern alternatives that are increasingly substituting traditional Lead formulations. These newer systems provide the necessary heat stabilization for processing PVC dry blend on double screw extruders. PVC itself is polar and does not suffer from stabilizer wash-out issues seen in non-polar polyolefins, contributing to its long lifetime stability.
|
Stabilizer Type |
Status / Regional Use |
Form Supplied (Examples) |
Processing Impact |
|
Lead (Pb) |
Phased out (e.g., in Europe) |
Not specified |
Historically used |
|
Tin (Sn) |
Widespread (e.g., in USA) |
Liquid form |
Protects against heat degradation during extrusion |
|
Calcium Zinc (CaZn) & OBS |
Increasing substitution for Lead |
Powder/flakes |
Protects against heat degradation during extrusion |
|
General Stabilizers in PVC |
Prevents rapid degradation |
Varied |
Crucial for melt quality and long-term pipe properties |