Achieving precise and visually appealing colors in plastic products requires careful selection of pigments, understanding their optical properties, and optimizing dispersion techniques. For matching a bright white product, the first choice should be blue-tone titanium dioxide produced via the chloride process. This manufacturing method yields titanium dioxide with fine particle size and a uniform molecular weight distribution, which scatters light more effectively and imparts a crisp, fresh, and vibrant white appearance. White color formulated with a blue-tone base delivers a clean and aesthetically pleasing finish. In contrast, if titanium dioxide with larger particle size and a yellowish undertone is selected, no amount of color adjustment can achieve a bright, pure white result, as the inherent yellow tint will persist and compromise the final appearance.
When the whiteness achieved with titanium dioxide alone is insufficient, additional whitening agents are commonly incorporated during the coloring process. A very small amount of blue or violet pigments can be added to neutralize residual yellow tones, a method known as optical whitening. One of the simplest and most widely used approaches is the addition of blue pigment masterbatches, which produce an effect often referred to as "magnetic white" due to its clean, bright appearance. Fluorescent whitening agents provide the most effective whitening results by absorbing ultraviolet light and re-emitting it as visible blue light, creating an exceptionally bright and luminous effect; however, this method carries the highest cost among whitening options.
2. How to Prepare Special Black Plastic Products
When formulating special black plastic products using carbon black, careful attention must be paid to the phenomenon of carbon black undertone. Under incident light, carbon black with smaller particle size typically exhibits a bluer undertone compared to larger-particle carbon blacks, but in transmitted light (for transparent coloring applications), it may appear brownish or gray. To achieve a deep, jet-black and glossy plastic product, it is essential to select low-structure carbon black with small particle size. This is because the blackness of carbon black is primarily determined by light absorption: the smaller the particle size, the higher the degree of light absorption, the weaker the light reflection, and consequently the greater the perceived blackness. Once the appropriate carbon black variety has been selected, achieving a satisfactory coloring effect demands particular attention to carbon black dispersibility. Only by fully resolving dispersibility issues can the maximum tinting strength of carbon black be realized.
Surface oxidation of carbon black introduces polar functional groups such as hydroxyl (-OH) and carboxyl (-COOH), which significantly enhance its dispersibility within polymer matrices. This characteristic is reflected in the volatile content index found in carbon black technical specifications—the higher the volatile content value, the greater the degree of oxidation and, correspondingly, the better the dispersibility.
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