PVC pipes and fittings require stabilizers to address the material’s inherent thermal instability during processing and its susceptibility to degradation under heat, light, and mechanical stress.
Key requirements include:
1.Thermal Stability: Prevents decomposition during high-temperature extrusion/molding (160–200°C).
2.Long-term Durability: Resists UV, oxidation, and environmental factors for outdoor applications.
3.Processability: Ensures smooth flow and uniform product quality during manufacturing.
4.Compatibility: Must not negatively interact with other additives (e.g., lubricants, fillers).
5.Regulatory Compliance: Must meet safety/environmental standards (e.g., lead-free for potable water pipes).
Common PVC Stabilizers for Manufacturers:
●Lead-based Stabilizers (e.g., tribasic lead sulfate):
Pros: Cost-effective, excellent stability.
●Calcium-Zinc (Ca-Zn) Stabilizers:
Pros: Non-toxic, widely used in food/water-contact applications.
●Organotin Stabilizers (e.g., methyltin from China, octyltin):
Pros: High efficiency, good clarity (suitable for transparent pipes).
●Antimony-based Stabilizers( Antimony mercaptide from China）
Pros:Same stability as tin stabilizer, good brightness and low cost
Example PVC Pipe Formulations:
1. General-Purpose PVC Pipe (Non-Pressure Applications)
| Component | Function | Weight Parts |
|---|---|---|
| PVC resin (SG-5) | Base polymer | 100 |
| Calcium-Zinc stabilizer | Thermal stabilization | 2–4 |
| Paraffin wax | External lubricant | 0.5–1.0 |
| Calcium stearate | Internal lubricant | 0.5–1.0 |
| Calcium carbonate | Filler (cost reduction) | 5–15 |
| Titanium dioxide (TiO₂) | UV stabilizer/pigment | 1–2 |
| Processing aid (ACR) | Improve melt flow | 1–2 |
Processing: Extrusion at 170–190°C.
2. High-Pressure PVC Water Pipe
| Component | Function | Weight Parts |
|---|---|---|
| PVC resin (SG-7) | High molecular weight for strength | 100 |
| Organotin stabilizer | High thermal stability | 1.5–3.0 |
| Oxidized polyethylene | External lubricant | 0.8–1.2 |
| Glycerol monostearate | Internal lubricant | 0.5–1.0 |
| Impact modifier (CPE) | Enhance toughness | 4–8 |
| Antioxidant (e.g., BHT) | Prevent oxidative degradation | 0.2–0.5 |
Processing: Twin-screw extrusion at 180–200°C.
3. Eco-Friendly PVC Pipe (Lead-Free)
| Component | Function | Weight Parts |
|---|---|---|
| PVC resin (SG-5) | Base polymer | 100 |
| Rare earth stabilizer | Non-toxic stabilization | 3–5 |
| Ester-based lubricant | Reduce friction | 1.0–1.5 |
| Nano CaCO₃ | Reinforcing filler | 10–20 |
| Epoxidized soybean oil | Co-stabilizer/plasticizer | 2–4 |
| UV absorber (Tinuvin) | Protect against sunlight | 0.5–1.0 |
Processing: Controlled cooling to minimize thermal stress.
Key Notes on Formulation Design:
- Cost vs. Performance: Higher filler (CaCO₃) reduces cost but may lower impact strength.
- Transparency: Avoid fillers and use organotin/Ca-Zn stabilizers for clear pipes.
- Regulatory Limits: Ensure stabilizers comply with regional regulations (e.g., EU REACH).
