What Is Plastic Welding?

Plastic welding refers to the method of melting the contact surfaces of two plastic parts at the same time by heating, so that they are combined into a whole. Only for thermoplastic connections. Welding electrodes can be used or not. When using welding electrodes, the end surface of the welded end needs to be made into a joint with a fixed shape (such as U-shaped, X-shaped, etc.). The welding surface is heated and melted, and then vertical pressure is applied to the surface to be welded until tightly fused into one body.

First, before work

1. Workers must wear work clothes when entering the workplace, and those with long hair must wear work hats.

2. check

Plastic welding,

When welding, pressure, time, and heat absorption (melting amount) are the three elements to ensure the quality of welding.

Plastic welding pressure

By applying appropriate pressure on the welding surface, the welding material will transition from elastic to plastic, and it can also promote the mutual diffusion of molecules and squeeze out the residual air in the weld, thereby increasing the sealing performance of the welding surface.

Plastic welding time

Have proper hot melt time and sufficient cooling time. When the thermal power is constant, insufficient welding will occur when the time is not enough. If the time is too long, the weldment will be deformed, the slag will overflow, and sometimes hot spots (discoloration) will appear in the non-welded parts. It must be ensured that the welding surface absorbs enough heat to reach a fully melted state, in order to ensure sufficient diffusion and fusion between molecules, and at the same time, sufficient cooling time must be ensured to achieve sufficient strength of the weld.

Plastic welding melting amount

Coordinated adjustment of hot-melt time and thermal power will get the most appropriate melting amount, ensure sufficient intermolecular fusion, and eliminate the phenomenon of false soldering. In addition to the welding equipment and the skill level of the operator, various factors that come from the inside or outside of the plastic have a certain impact on the welding quality and should be paid attention to.

Other factors for plastic welding

Hygroscopicity of plastic

If a wet plastic product is welded, the moisture contained in it will turn into steam after heating and air bubbles will appear on the welding surface, which will weaken the sealing performance of the welding surface. The more hygroscopic materials are PA, ABS, PMMA, etc. Products made from these materials must be dried before welding.

Fillers in plastic

Such as glass fiber, talc, mica, etc., they have changed the physical characteristics of the material. The content of filler in plastic has a great relationship with the weldability and welding quality of plastic. Plastics with a filler content of less than 20% can be normally welded without special treatment. When the content of the filler exceeds 30%, due to insufficient surface plastic ratio, insufficient intermolecular fusion will reduce sealing performance.

Cleaning of the welding surface

The welding surface must be clean and free of impurities to ensure sufficient welding strength and air tightness.

In addition to selecting the correct welding materials and eliminating the disadvantageous factors that affect the welding results, it is necessary to take appropriate welding methods according to the shape of the product and the cost of the product ^[1] .