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Foamcore PVC Pipes – Structure and Benefits

Picture of Patrick van Bezouw Patrick van Bezouw Jun 10, 2025 12:18:36 PM

Structured and Specialized PVC Types Multi-Layer Technology
Foamcore PVC Pipes – Structure and Benefits
Foamcore PVC Pipes – Structure and Benefits
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Foamcore pipe is a type of Structured Wall pipe used for pressure-less applications. It resembles a standard solid wall pipe but incorporates a low-density core. Essentially, it is a sandwich pipe where foam replaces structures like the honeycomb often used in rigid plates.

Structure and Formulation

Foamcore pipe typically consists of an inner and outer solid skin made of PVC, with a foamed PVC core in between. This design allows for weight saving. Production is demanding, requiring a highly uniform melt temperature for even gas expansion in the core. The combination of formulation, extruder, and die must be carefully balanced.

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Foamcore formulations for PVC often include additives like CaCO3 (Calcium Carbonate), sometimes up to 15-20 phr (parts per hundred resin), to compensate for the lower stiffness of the foam33. This allows the total wall thickness to remain similar to, or even thinner than, a solid wall equivalent while meeting stiffness requirements. Higher filler levels can also permit adding more blowing agent without creating blisters, leading to even higher cost savings per pipe length. Amorphous polymers like PVC are generally easier to foam than crystalline polymers. ABS scrap/rework, compatible with PVC, can be added in micronized form to enhance melt elasticity and achieve a fine foam structure.

Standards and Benefits

Standards exclusively for foam core pipe exist, including ASTM F891, JIS 9798, and SANS 160119. ASTM includes a requirement for closed cells to prevent axial leakage through the foam.

Benefits of foamcore pipes include:

  • Light weight: As a structured wall pipe, it significantly reduces material weight compared to solid wall pipes of equivalent stiffness.
  • Cost savings: Replacing polymer with foam (gas) and filler like CaCO3 significantly reduces the amount of raw material per pipe length. Using recycled PVC, especially in the core where loads are lower, further enhances cost savings and sustainability.
  • Sustainability: Replacing fossil fuel-based polymer with air, filler, and recycled material contributes considerably to reducing the carbon footprint over the pipe's long lifespan. The core is a safe place for lower grade recycled material as it carries less loa.
  • Process Improvement: Mastering the advanced foamcore production process can lead to improvements across other production lines, such as achieving more homogeneous melt temperatures without needing excessive heat stabilizer.

Risks

Low density cores in foamcore pipes carry risks, including skins acting independently if the core lacks shear resistance, difficulty complying with rubber ring chamber tolerances, and potential axial leakage if cells are not closed.

 

FAQ Section

Can recycled PVC be used in foamcore pipes?

Yes, recycled PVC material, especially post-consumer recycled pipe grade PVC (K67), is successfully used in the core of foamcore pipes39.... The core is a suitable location for recycled material as it carries a smaller portion of the structural load compared to the skins40.

 

How does adding CaCO3 benefit foamcore pipe production?

Adding CaCO3 (filler) increases the stiffness of the formulation, helping to compensate for the lower stiffness of the foamed core33.... This allows for achieving the required pipe stiffness with the same or even thinner total wall thickness, contributing to weight and cost savings33.... Higher filler levels can also facilitate the use of more blowing agent for increased weight saving35.