Effect of Recycled PVC on Pipe Quality

Integrating Recycled Material into PVC Pipes

The integration of recycled PVC, particularly post-consumer material, into pipe production can impact final pipe quality depending on the application and how the material is used. The source specifically discusses the use of recycled PVC in the core layer of multi-layer pipes like foam core pipe.

Quality Considerations in Sandwich Structures

In structured wall pipes such as foam core pipe, the pipe wall is designed with layers. The core layer, where recycled material is often placed, carries significantly less load than the inner and outer skins. This makes the core a "safe place" for a lower-grade material like recycled PVC.

However, using recycled material requires careful control to maintain overall pipe quality. Potential issues can arise from the presence of contaminants such as sand or rubber particles in the recycled stream. These foreign particles can act like large fillers and, if not properly managed, can negatively impact pipe performance in tests such as burst pressure or impact resistance, similar to how other large foreign particles can cause failure. For smaller pipes, this is a greater concern as thinner skins mean contaminants can more easily protrude.

Ensuring Quality with Recycled Content

To mitigate potential negative effects on quality when using recycled PVC, several measures are necessary:

• Reliable Suppliers: Sourcing from consistent, clean streams.
• Homogenization: Blending materials from different sources in a mixing silo to ensure consistency.
• Contaminant Control: Ideally, incoming material is checked for sand amount, K-value, and other properties. Micronizing the material to a specific particle size is also critical, with finer sizes (e.g., 500 micron) potentially reducing the impact of contaminants, though at a higher cost.
• Formulation Adjustments: Adding CaCO₃ to the core can help maintain stiffness.
• Processing Equipment: Using extruders and dies designed to handle recycled material, especially K67 pipe grade PVC, is essential for achieving consistent quality.

When these measures are followed, recycled material can be successfully integrated. The formulation-extruder-die combination must be balanced, particularly for challenging processes like foaming recycled K67 PVC for foam core pipes.

Technical Specifications/Considerations:

• Application: Primarily in the core layer of non-pressure, multi-layer pipes.
• Potential Contaminants: Sand, rubber.
• Particle Size: Finer micronizing can improve contaminant dispersion.
• Mitigation: Supplier control, homogenization, contaminant checks, specific equipment.

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