How plastic welding works, the methods we use, which thermoplastics can be welded, and the standards that make a weld engineer-grade.
Plastic welding joins two thermoplastic parts by heating them to fusion temperature so the polymer chains intermix and, on cooling, form a single continuous material. Done correctly, the weld is as strong and as chemically resistant as the parent sheet, which is what makes welded thermoplastics suitable for tanks, pipework and process equipment that must stay leak-tight for decades. Industrial Plastics has welded HDPE, polypropylene, PVC and PVDF in our Brisbane workshop since 1971.
Brisbane workshop, since 1971. ISO 9001:2015 certified by SGS. Every weld is made by welders qualified to DVS 2207, the German thermoplastic welding standard that sets procedure and welder-qualification requirements above the AS/NZS minimums.
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What is plastic welding?
Plastic welding is the process of fusing thermoplastics with heat, and sometimes a filler rod of the same material, into a homogeneous joint. Only thermoplastics can be welded, because they soften and re-melt when heated: HDPE, polypropylene, PVC, PVDF, ABS and similar. Thermoset plastics and composites such as FRP and GRP cannot be welded, and acrylic is normally solvent-cemented rather than heat-welded. A correctly made weld restores the full strength and chemical resistance of the base material, unlike a glued or mechanically fastened joint.
The main plastic welding methods
We select the method to suit the material, the joint and the duty:
| Method | How it works | Best for |
|---|---|---|
| Butt (hot-plate) fusion | Faces are heated against a hot plate, then pressed together to fuse | Pipe joints and sheet; the strongest production weld |
| Extrusion welding | Molten filler rod is extruded into a prepared joint and fused with hot air | Tanks, liners and heavy fabrications |
| Hot-gas (hot-air) welding | Hot air softens the joint and a hand-fed rod while pressure is applied | Detail work, repairs, ducting, smaller fabrications |
| Electrofusion | An embedded heating coil in the fitting melts and fuses the joint | PE pipe fittings and tie-ins |
For a deeper look at the two we use most, see our guides to butt welding and extrusion welding.
Which plastics can be welded?
- HDPE, the workhorse for tanks, pipe and liners; butt-fused and extrusion-welded.
- Polypropylene (PP), for warm-acid and corrosive duty; extrusion and hot-gas welded.
- PVC / uPVC, for ambient acid service and ducting.
- PVDF, the premium fluoropolymer for hot and aggressive chemistry.
Dissimilar plastics generally cannot be welded to each other (for example, HDPE will not weld to polypropylene), so a fabrication is built from a single compatible material family.
What makes a weld engineer-grade
Standards we weld to
- DVS 2207, weld procedures and welder qualification for PE, PP, PVC and PVDF.
- DVS 2205, thermoplastic tank and vessel design.
- ISO 9001:2015, quality management, certified by SGS.
- AS/NZS 4130 for PE pressure pipe, butt-fused and electrofused to the matching install standards.
- Documented weld records, coupon testing and a QA pack supplied with the fabrication.
Weld testing and quality
A weld is only as good as its verification. Depending on the job we apply:
- Visual inspection of every seam against DVS acceptance criteria.
- Tensile and bend testing of weld coupons cut from trial welds.
- Hydrostatic or pressure testing of tanks and pipework before dispatch.
- A documented inspection and test plan handed over with the fabrication.
Where we use plastic welding
Chemical and water tanks · pressure and gravity pipework · wet scrubbers and process equipment · geomembrane liners · ducting, hoppers, bunds and custom fabrications.
Plastic welding FAQs
Can all plastics be welded?
No. Only thermoplastics such as HDPE, polypropylene, PVC and PVDF can be heat-welded. Thermoset plastics and FRP or GRP composites cannot, and acrylic is normally solvent-cemented.
What is the strongest plastic welding method?
Butt fusion produces the strongest, most repeatable joint and is the standard for pipe and sheet. Extrusion welding is preferred for tanks and liners where a filler weld suits the joint geometry.
Can you weld HDPE to polypropylene?
No. Different polymer families do not fuse to each other, so a fabrication is built from a single material such as all-HDPE or all-PP.
What is DVS 2207?
DVS 2207 is the German standard for welding thermoplastics. It defines weld procedures and welder qualification and is more stringent than the AS/NZS minimums. Our welders are qualified to it.
Is a welded plastic joint as strong as the material itself?
A correctly made fusion weld develops close to the full strength of the parent material, which is why welded thermoplastic tanks and pipe are specified for long-term pressure and chemical service.
Related guides
- Butt welding: the complete guide
- Plastic extrusion welding explained
- DVS 2207 welding standard
- DVS 2205 tank design standard
Get an engineer-grade quote
Send drawings, specifications or a written brief and our technical team will respond within one business day. Or call 1300 465 888, Monday to Friday.
Materials we weld
HDPE · Polypropylene · PVDF · PVC / uPVC
