With the rapid development of industrial production, plastics are widely used in various fields of the national economy and people's lives, because of their advantages of light weight, high strength, corrosion resistance, and easy processing. However, due to processing technology and other reasons, many products with complex structures cannot be processed at one time, and multiple parts need to be seamlessly connected together. There are generally two methods: bonding and welding.
Generally speaking, the production efficiency of the bonding process is low and the adhesive has a certain degree of toxicity, which is easy to cause environmental pollution and harmful consequences to the health of production personnel. Therefore, plastic welding technology has been more and more widely used.
In the actual production process, not all plastic materials can be welded. Plastics that can be welded by laser are all thermoplastics. Only thermoplastics with the same or similar molecular structure can be welded. On the welding surface, there is intermolecular chemistry combination, so the closer the parent material, the better the welding effect.
We also need to consider the factors that affect welding quality to get a better welding effect. While welding, pressure, time and heat absorption (melting amount) are the three elements to ensure welding quality.
1. Stress
Appropriate pressure is applied to the welding surface, the welding material will transition from elasticity to plasticity, and it can also promote the mutual diffusion of molecules and squeeze out the residual air in the welding seam, thereby increasing the sealing performance of the welding surface.
2. Time
There must be proper melting time and sufficient cooling time. The heating power is constant, if time is not enough, it will cause a false welding, if too long time will cause the weldment to deform and the slag will overflow. And sometimes there will be hot spots (discoloration) in the non-welded positions. It is necessary to ensure that the welding surface absorbs enough heat to achieve a fully molten state 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.
3. Heat absorption
Heat absorption, you can also understand as the amount of melting. Only by coordinated adjustment of the melting time and heating power can the most appropriate melting volume be achieved, sufficient intermolecular fusion can be ensured, and the phenomenon of virtual welding can be eliminated.
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