Effects of Colored Materials on Plastic Laser Welding

The color of plastics is usually obtained in two ways: toner or dye. Toners are generally of organic or inorganic structure and are insoluble in plastics. Organic toners have a stronger coloring power than inorganic toners, but are not transparent. Dyes are organic molecules that are soluble in plastics. After adding dyes, no particles are visible and the transparency of the material remains unchanged.

The characteristics of toners and dyes belong to the table below.

1. Features Inorganic toner Organic toner/dye;

2. Particle size 0.5-1.0um0.01-0.1um;

3. Coloring ability medium low high;

4. Transparency Opaque Transparent;

5. Heat resistance High to High;

6. Color fastness to light Generally better than Excellent;

7. Excellent Color fastness to weather Very Poor;

In plastic laser welding, the upper layer material requires the laser to be penetrable, and the lower layer material requires the laser to be absorbable. For the lower layer material, if the color of the plastic has poor absorption performance for the wavelength laser, a light absorber can be added. For the upper layer material, adding color will affect laser penetration. In general colored plastics, due to the application requirements of opacity, the color powder added to the plastic is inorganic color powder. As can be seen from the above table, the particles of inorganic color powder are relatively large, and like the crystalline particles of semi-crystalline materials, they will refract and reflect laser penetration, affecting the laser penetration rate and thus affecting the welding performance. For laser welding of colored plastics, the ideal solution is to add organic dyes or organic color powder to the plastic. These organic molecules are very small and can be completely dissolved in plastic without affecting the laser penetration of the plastic. However, the opacity of organic molecular toner or dye is too poor, and inorganic toner or additives are generally required for color matching.

Laser welding of colored plastics requires special color matching of the upper plastic. Currently, there are only a few professional suppliers, and the price of masterbatches or materials after color matching is much more expensive than ordinary materials. Therefore, in practical applications, laser welding with colored plastics should be avoided as much as possible.