What are the differences in mold release requirements during production of PVC versus polypropylene?

The production of PVC (polyvinyl chloride) and polypropylene involves distinct mold release requirements due to their differing material properties and processing behaviors.

1. Material Properties:

- PVC is more prone to sticking due to its higher viscosity and chlorine content, requiring stronger mold release agents.

- Polypropylene has lower adhesion and often needs less aggressive release agents, though additives may influence requirements.

2. Processing Temperatures:

- PVC typically processes at lower temperatures (160–210°C), reducing thermal stress on molds but necessitating specialized release coatings.

- Polypropylene operates at higher temperatures (200–300°C), demanding heat-resistant release agents to prevent degradation.

3. Mold Surface Interaction:

- PVC’s clinginess may require frequent mold cleaning or non-stick coatings like PTFE.

- Polypropylene’s semi-crystalline structure allows easier release but may need tailored agents to avoid surface defects.

4. Additives and Lubricants:

- PVC formulations often include internal lubricants (e.g., stearates) to aid release.

- Polypropylene relies more on external mold sprays or silicone-based agents.

Understanding these differences ensures optimal mold performance and product quality in plastic manufacturing.