How to Weld Plastic

14 Aug

Worker preparing for plastic welding inside a large cylindrical structure.

Cleaning

Immediately following the removal of the oxidation layer, clean the welding zone with a minimum 70% isopropyl alcohol solution to remove any final contaminants. Never touch the prepared weld zone once scraped and cleaned.

Scrape between welds - If you are layering welds, make sure you also scrape between each pass to remove any new oxidation layer.

Close-up of a handheld welding tool performing plastic welding on a black plastic component.

Practice

If you are new to plastic welding, practice on test pieces to get the feel of the process. Make sure you apply good pressure to the weld zone, and that the base material is appropriately preheated (melted) to accept the welding rod. This might take several attempts to get right.

K Type Thermometer with various probes, cables, and a battery for temperature measurements.

Hot Air Welding

Hot Air Welding uses heated air generated by a hot air gun to melt the base material and weld rod. Special welding gun tips are used to create the pressure necessary at the weld zone to perform a successful fusion weld.

Close-up of an extrusion welder in use, with a worker's hand guiding the tool along a plastic surface.

Restrain Materials Before Welding

It is critical that the materials you are welding together are properly restrained during the welding process. Two common methods are clamping (using a range of clamping devices) and tacking (using a hot air gun tacking tip attachment.)

It is important that materials do not move during the welding process or cooling period, as movement can significantly reduce the resulting weld strength.

Close-up of a hand holding a small white alarm clock showing the time at 3 o'clock.

Preparation

Before commencing any plastic welding, the oxidation layer must be removed from the base material immediately prior to welding to ensure molecular bonds of base material can join. This can be done using a hand/paint scraper or die grinder. Do not use grinding wheels, flapper discs, or sand paper as these can leave residues that contaminate the weld.

Plasson XL Welding Wipes container, high-performance impregnated wipes for electrofusion jointing.

Use the Right Material

It is critical that you select the right weld rod product for the job. Only use the same family of plastic. For example, only use polyethylene weld rod with polyethylene sheet; or polypropylene weld rod with polypropylene sheet. It’s like trying to weld steel with aluminium. See the FAQ section, or Contact your stockist or SuperFUSION for more information on what product to use.

Worker performing plastic welding on a black plastic component using a handheld welding tool.

Weld at the Correct Temperature

Each thermoplastic has its own unique melt temperature. Too hot and the material burns causing irreparable damage to the weld zone, and too cool results in the polymer bonds not being sufficiently broken to form a proper molecular fusing of material.

Worker using a hot air welding tool to join two pieces of plastic secured with a clamp.

Extrusion Welding

Extrusion Welding uses a sophisticated electronic hand tool that:

a) melts the weld rod in an extrusion chamber.

b) heats and melts the base material using hot air.

c) expels the melted weld rod material through a Teflon shoe that creates specific shapes and the pressure required to perform a successful fusion weld.

Whilst extrusion welding undoubtedly creates the strongest and most effective welds, not everyone can afford the investment to purchase an extrusion welder.

Close-up of a Plastic Welding Clamp with a screw mechanism and ridged jaws.

Allow sufficient cooling time

Like all fusion welding, cooling time is a critical element to successful welding. The weld zone should be cool to the touch before being put under any stress. WARNING: Do not accelerate the cooling of the weld zone. Preferably, cover the weld area because slower cooling creates stronger welds.

Luke Woolard