How to choose absorbent during plastic laser welding?

In order to meet the requirements of plastic laser welding, some laser absorbing media are added to the plastic surface or in the production process of plastic products so that the plastic can be laser welded. Laser absorbing media commonly used are laser absorbing resin, absorbing coating, and carbon black. So how to absorb the absorbent in plastic laser welding? Let's take a look.

How to choose absorbent in plastic laser welding process?

Laser absorption coating is a material with solvent as carrier. It can evaporate quickly, and the absorbent material adheres to the plastic surface, effectively absorbing the laser heat energy, meeting the process requirements of plastic laser welding.

The absorbent resin is determined by factors such as polymer compatibility and color requirements, and additives are added to the resin. The additive ensures that the resin still has a transparent appearance, but it will add a little color, which can be corrected. Laser absorbent resin is very suitable for transparent and light-colored opaque plastic welding, as well as smaller parts but with large welding areas.

Carbon black is a common substance in our lives, economical and cheap, but it cannot be used in applications with high requirements for appearance color, especially equipment in the medical industry.

How to choose absorbent in plastic laser welding process?

In traditional plastic laser welding technology, the upper transparent plastic material and the lower substrate should convert laser energy into heat, and carbon black or other media can be added to the lower substrate to provide designers with more color choices and design flexibility.

In transparent plastic laser welding technology, the above method is not used, but the laser wavelength is changed to meet the plastic laser welding requirements. According to a large number of experiments, natural colorless plastics easily absorb infrared wavelengths from 1.6um to more than 5um, and the beam energy is deposited on the top of all plastics (including semi-crystalline and amorphous) for several millimeters. Using this feature, plastic plates with a thickness of no more than a few millimeters can be welded without additives.

Conclusion: The three laser-added media have their own advantages and disadvantages. Carbon black is economical and effective, but it affects the appearance of the product; the absorption coating can weld transparent parts, but it needs to increase the coating process; the laser absorption resin does not need to increase the process and gives the product a rich color, but it is not economical for products with large parts but small welding area. Each method has its advantages and disadvantages (see the table below).