Introduction to Hot Air Gun Plastic Welding

Plastic Welding Background

Hot air gun welding is a processing method for thermoplastic plastics. This plastic welding process was invented in the mid-20th century. It uses heated hot air to heat and melt thermoplastic base materials and thermoplastic welding rods. The base material and welding rod form a weld seam.

In order to form a weld seam, we need to apply appropriate temperature and pressure to the welding rod, while using the correct welding speed and welding gun angle. Because plastic welding is a purely manual technique, the quality of the welding depends entirely on the welding skills of the welder. Typical applications of plastic welding include chemical storage containers, ventilation ducts, and repair of plastic molded parts (such as car bumpers).

Plastic Welding Materials

Plastics are divided into two types: thermoplastics and thermosets. Hot air gun plastic welding technology is only applicable to thermoplastics, which can be repeatedly heated and melted.

Although there are many thermoplastics that can be welded using this plastic welding process, only PP, PE, PVC and some fluoroplastics, such as PVDF, FEP and PFA, are frequently used with this technology.

Extruded plastic welding rods and plastic plates are the most commonly used raw materials in plastic welding processing. When plastic welding, it is important that the welding rod and plastic plate are of the same material and composition. For example, although we can weld polypropylene homopolymer and polypropylene copolymer together by plastic welding, the welding strength will be greatly reduced. In addition, because bubbles may be generated in the welding rod during production, we should also check the quality of the welding rod before welding. Because these bubbles will cause poor welds in plastic welding.

Plastic Welding Parameters

In the hot air gun plastic welding process, there are four main welding parameters, including: temperature, pressure, welding speed and welding gun angle. Because plastic welding is purely manual, the welder's correct understanding and control of the four parameters during the welding process is very important.

Temperature is the most important of the four parameters in plastic welding. The temperature between the welding rod and the base material is not only controlled by the welding gun's set temperature, but also affected by the welding gun's travel speed and the position between the welding gun and the base material. Generally speaking, the welding gun's set temperature is 80-100°C higher than the melting point of the welded material, and the welding gun's travel speed is 0.1-0.3 meters/minute. However, the parameters of different materials in plastic welding are also different.

The welding pressure in hot air gun plastic welding is formed by firmly holding the welding gun and pressing down, so that the nozzle foot presses the welding rod. The pressure generally applied to the welding rod is 15-30N.

Plastic Welding Quality

As a manual process, the quality of plastic welding depends on the welding technique. At present, there is no officially recognized non-destructive testing method that can detect welding defects that lead to welding failure. Therefore, the skilled technique of the welder is particularly important in plastic welding.