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 assand 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.
FAQ Section
Why is recycled PVC often used in the core layer of pipes?
Recycled PVC is often used in the core layer of multi-layer pipes because this inner section carries significantly less structural load than the outer and inner skins, making it a suitable place for material that might have slightly lower properties due to recycling.
How can contaminants in recycled PVC affect pipe quality?
Contaminants like sand or rubber in recycled PVC can act as stress risers or foreign particles. If not adequately controlled or micronized, they can negatively impact mechanical properties such as burst pressure or impact resistance, especially in pipes with thinner walls.
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Humberto Goldoni
