Synthetic resins, plastics and synthetic fibers are important components of modern industry and are widely used in packaging, construction, automobiles, electronics, electrical appliances and daily necessities. With the rapid development of these industries, the demand for colorants continues to grow. Due to the differences in the process and performance requirements of different coloring objects, colorants (especially organic pigments) need to continuously improve their quality level. The performance of colorants not only directly affects the appearance of the product, but also affects the application properties of plastics, resins and synthetic fibers, such as weather resistance and strength.

1. Performance requirements of colorants in plastics and resins Colorants (including organic pigments, inorganic pigments, dyes, etc.) used for coloring plastics and synthetic resins must meet the following key performance indicators:

1.1 Color expression High color strength, vividness and color purity Appropriate transparency or hiding power, selected according to application requirements

1.2 Thermal stability Plastic processing temperatures are usually high (160–300°C), and colorants must have good heat resistance to prevent color change, decomposition or changes in crystal structure. Especially in high-temperature thermoplastic resins such as polyester and polycarbonate, the thermal stability of colorants is a key indicator.

1.3 Migration resistance High migration resistance helps prevent colorants from precipitating from the plastic matrix or migrating to the surface, avoiding phenomena such as "blooming". Migration is closely related to the size, polarity, solubility, etc. of the pigment molecule, and is usually tested by contacting with white plastic at 80°C and 0.98MPa for 24 hours.

1.4 Dispersibility and compatibility Pigments should have good dispersibility, be evenly distributed in the resin, not agglomerate, not settle, and not react adversely with the resin or additives. The particle size should generally be controlled within 2-3μm to avoid affecting the performance of the product.

1.5 Weather resistance and light resistance Pigments used for outdoor products must have good light resistance and weather resistance. Although inorganic pigments have strong weather resistance and high stability, their colors are not bright enough. Organic pigments have bright colors and strong tinting power, and are widely used on the basis of improving weather resistance.