Plastic welding is very common in manufacturing and among hobbyists – but it differs greatly from metal welding. The welding of plastic is a popular joining method for bonding plastics to ensure a sufficient and permanent connection. It is mainly used to bond plastics that are famously difficult to do so, such as polypropylene and polyethylene. While the process is simple, there are several essential factors to consider – especially for beginners.
Use the Right Plastic Welder
The most suitable machine for welding plastics is a hot air fan welder; it delivers high-quality welds and is fairly inexpensive, particularly in comparison to handheld extrusion welders –commonplace in welding shops.
Also known as a hand extruder, a handheld extrusion does the job significantly faster and is thus excellent for shops and manufacturers that weld plastic daily in larger quantities – such as several hundred meters of weld seams every day, for instance. But that comes at a higher price tag of several thousand dollars.
On the other hand, hot-air fan welders typically start at a few hundred dollars, making them affordable and ideal for those who desire good results with their plastic welds but won’t necessarily pump out the same vast quantities as wedding shops.
Identify the Type of Plastic Being Welded
Different plastics have different chemical compositions, so welding differing types isn’t possible since it doesn’t allow a permanent bond. As such, only plastics of the same type can be welded together. For instance, polypropylene or polystyrene cannot be welded with polyethylene. For the same reason, the plastic welding rod must be the same type of plastic material being welded.
In contrast, it’s possible to weld polypropylene to polypropylene or polyethylene to polyethylene, for example, as is welding ABS with ABS – as well as other plastics when welding is the joining method (not bonding).
Ensure Proper Temperatures
Both the welding rod and the plastics must be heated up adequately to ensure the surfaces attain the ideal fusion level required for a secure, durable weld. Furthermore, maintaining optimum temperatures helps avoid burning or cold welds.
Polyvinyl chloride (PVC)
Welding PVC requires close monitoring of the heating time and temperature level; it burns quickly and easily, and any burned areas weaken the weld. Burning PVC also creates hydrochloric acid, which not only has a pungent smell but can be harmful to inhale. Burned PVC also reduces the appearance of the plastic, forming brown and black imperfections. For optimum PVC welding, maintain air temperatures between +482°F to +536°F (250° and +280°C).
Polypropylene (PP)
Like PVC, careful attention to the heating time and temperature is necessary when welding polypropylene because it burns quickly, with any burned material deteriorating the weld. The air temperature for PP welding ranges from +446°F to +536°F (+230° to +280°C).
Polystyrene (PS)
Polystyrene’s required air temperature for welding is between +518°F and +590°F (+270°C and +310°C).
Polyethylene (PE)
Conventional adhesives cannot bond polyethylene, so welding this plastic is the best practice. The air temperature should be between +428°F and +536°F (+220°C and +280°C) to weld PE.
Acrylonitrile-butadiene-styrene (ABS)
For best results, welding ABS plastics needs an air temperature in the range of +518°F and +590°F (+270°C and +310°C)