Answers to the most common questions about plastic welding — identifying plastics, choosing the right welding rod, and selecting the tools and kits for your job. Can’t find your answer? Contact our team and we’ll help.
Which plastics can be welded?
Only thermoplastics can be plastic-welded — they soften when heated and re-fuse on cooling. The common weldable plastics are PP (polypropylene), PE-HD and PE-MD (high- and medium-density polyethylene), PVC, ABS, and PP/EPDM blends. Thermoset plastics (e.g. epoxy, polyurethane, Bakelite) cannot be welded because they char rather than melt.
How do I know which plastic I'm welding?
Start with the recycling code moulded into the part (e.g. >PP<, >PE-HD<, >ABS<). If there's no marking, a float test (PP and PE float in water; PVC, ABS and most others sink) and a small burn test (flame colour, smell and whether it drips) will narrow it down. Matching the plastic correctly is the single most important step before welding.
What welding rod should I use?
The rod must be made of the same plastic as the parts you’re joining. Welding PP with a PE rod, or HDPE with a PEMD rod, produces a weak joint that fails under stress. Match PP to PP, HDPE to PEHD, bumpers (usually PEMD) to PEMD, and so on. When unsure, identify the base plastic first.
What's the difference between hot-air and extrusion welding?
Hot-air (hot-gas) welding uses a stream of hot air to soften the rod and base material, and is ideal for thinner sections, repairs and detail work. Extrusion welding feeds and plasticises a larger volume of filler for thick-section fabrication (roughly above 6-8 mm), laying down a much larger weld bead in a single pass — the right choice for HDPE tanks, pipe and heavy fabrication.
Can I repair a cracked car bumper?
Yes. Most modern bumpers are PE-MD, which welds well with a hot-air tool and a matched PEMD rod. A proper plastic weld restores structural strength at a fraction of replacement cost. An automotive welding kit includes the welder, PEMD/PP rods and the nozzles needed for bumper and interior-trim repairs.
What temperature should I weld at?
It depends on the plastic: PVC welds cooler than PP, and HDPE hotter again. Digitally-controlled welders let you set and hold the correct temperature for the material, which is why a digital tool produces more consistent welds than a fixed-temperature one. As a rule, start at the lower end of the material’s range and increase until the rod flows and bonds without scorching.
Hand welding or an automatic welder — which do I need?
Hand (hot-air) welding suits repairs, fabrication and short or detailed seams where the operator controls heat and speed by feel. Automatic welders run at a calibrated temperature, speed and pressure along a seam, producing consistent, repeatable welds — the right choice for long production seams in roofing membrane, pond and landfill liners, and industrial tarpaulins.
What's included in a plastic welding kit?
A kit gives you a complete, calibrated system in one purchase: a hot-air welder, a selection of welding rods matched to common plastics, the welding shoes (speed nozzles) for the application, and supporting accessories such as pressure rollers, brushes and a carry case. Kits are configured by application — automotive, fabrication, flooring, roofing, tarps and ACM panels.
How strong is a plastic weld?
A correctly executed plastic weld — right rod, right temperature, clean and properly prepared surfaces — can approach the strength of the parent material, which is why welding is used for structural fabrication of tanks, liners and roofing membranes. Weld strength depends heavily on surface preparation and matching the rod to the base plastic.
Do you provide support choosing the right tool?
Yes. If you’re unsure which welder, rod or kit suits your job, contact our team with the details of what you’re welding and we’ll point you to the right setup. Our How to Weld Plastics guide and application videos also walk through surface preparation, tacking, pendulum welding, speed welding and extrusion welding.