Frequently Asked Questions
The two main plastics that are commonly welded using extrusion welding are PP (polypropylene) and HDPE (high density polyethylene). Certain types of welding machine can also weld PVDF (polyvinylidene fluoride) and PVC (polyvinylchloride). PVDF is a very rigid, hard plastic that welds at a high temperature, therefore the extruder needs to be capable of melting this material. PVC on the other hand, has such a narrow temperature 'window' before degradation, that it is recommended that the extruder is purged between runs using either PP or HDPE, to clear the barrel of unwanted PVC polymer.
The welding parameters used should always follow the material manufacturers' recommendations.
Specialist extrusion welding machines are manufactured for the Geomembrane industry to weld the lining material that is used in landfill sites, lagoons and tank bunds etc. The materials used for these applications are PE(polyethylene) and PP. These machines are typically a lot heavier than those used for general plastics fabrications, with PTFE (polytetrafluoroethylene) shoes designed specifically for this purpose.
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