PVC Extrusion vs. PO Extrusion

Plastic pipes offer distinct advantages over traditional materials because of their weight, corrosion resistance, flexibility, and ease of connection. This article focuses on extruding pipes from high-volume commodity polymers: UPVC (Unplasticized Polyvinyl Chloride) and Polyolefins (PO), specifically HDPE and PP. These are further referred to as PVC, PE, and PP.

Processing Differences

The main processing difference lies in the extruder type and material form. PVC extrusions are typically processed in dry blend form using a double-screw extruder. In contrast, PO resin pipe grades are processed in granular form on single-screw extruders.

Double screw extruders are well-suited for PVC extrusion because the material exhibits more wall slip than PO. Single screw extruders are commonly used for polyolefin pipe extrusion because it needs substantial heat input (approximately 3 times more than PVC) and isn't as prone to degradation.

The extrusion process differs accordingly: intermeshing double screws transport material through cavities independent of barrel friction, offering higher pump efficiency. Dry blend is optimally processed on double screw extruders; using it on single screw extruders with a smooth intake is too dependent on friction for consistent output. You can extrude granulated PVC on grooved single screws, but double screws avoid the granulation step and are self-wiping, offering cost advantages.

PO pipe extrusion involves processing a real melt that crystallizes upon cooling. Under extrusion conditions, PVC behaves more like a rubber-like solid, forming a structure of tie molecules and crystallites in the pipe wall.

Modern high-grade plastic extrusion technologies for PO, using pipe extrusion machines, now share similarities with PVC pipe extrusion processes. They rely on forced transport, grooved intake, and short residence time at low shear in the die head to form an optimal structure.

This type of extrusion system and its benefits are also seen in extruded PVC tubing for specialized applications, where material consistency and dimensional stability are key.

T-Rex Extruder

Our T-Rex extruder is a perfect example of modern extrusion technology used in both PVC and PO extrusion systems. It reflects ongoing innovation in plastic extrusion process design.

Material Property Differences

Material properties differ significantly between PVC and PO. Generally, PVC is 2–3 times stronger and stiffer than PO, though it has lower impact resistance. PO has higher creep, which matters for buried pipe applications.

PVC has lower diffusion through the pipe wall, which matters for drinking water pipe extrusion in contaminated soil (brownfields). PVC pipe also has less risk of biofilm and is not vulnerable to chlorinated water, unlike PE pipe. PO materials allow oxygen diffusion, so they require barrier layers for hot/cold water applications.

In both materials, control over the extrusion machine and the overall plastic equipment setup plays a vital role in achieving optimal pipe performance.

Technical Specifications

FAQ Section