Plastic products are widely used in all walks of life in my country's industry. The plastic industry is the second largest user of titanium dioxide. It plays an irreplaceable role in many industries such as electronics, information networks, and biomedicine. China's plastic production ranks first in the world and is also the world's largest plastic market. According to industry data, the total output of plastic products in China will be 74.885 million tons in 2023, a year-on-year increase of 3.0%.

Polypropylene, PVC, polystyrene, etc. are used in plastics with titanium dioxide. In most thermosetting and thermoplastic plastic products, the colorant is mainly titanium dioxide, and its content is usually between 0.5% and 10%. Some special plastics use more titanium dioxide, and its proportion in masterbatch is 40%-70%.

The application of titanium dioxide in plastic products, in addition to its high hiding power, chroma and good performance when mixed with other pigments, can also improve the heat resistance, light resistance and weather resistance of plastic products, protect plastic products from ultraviolet rays, and improve the mechanical strength and electrical properties of plastic products. It is suitable for almost all thermosetting and thermoplastic plastics, polyolefins (mainly low-density polyethylene), polystyrene, ABS (acrylonitrile-butadiene-styrene copolymer), polyvinyl chloride, etc. It can be mixed with resin powder and dried, or mixed with liquid containing plasticizer. Some titanium dioxide is first made into masterbatch through the factory intermediate before use.

Therefore, the performance of titanium dioxide used for plastics is mainly fine particle size and uniform particle size distribution to enhance the reflection ability of short wavelengths and make better plastic products. In addition, titanium dioxide pigments must have good heat resistance and high dispersibility. Therefore, titanium dioxide for plastics is generally divided into inorganic coating and organic coating treatment. Like the coating system, rutile type should be used for outdoor plastic titanium dioxide, and other anatase types can also be used.

Requirements of titanium dioxide for plastic products
Hiding power: titanium dioxide with good hiding power can produce lighter and thinner plastic products
Whiteness: determines the appearance of light-colored or white plastic products
Dispersibility: affects the production cost of plastic products. Poorly dispersed titanium dioxide in plastic products will affect the smoothness and brightness of the products
Weather resistance: plastic products used outdoors and plastic doors and windows must ensure the weather resistance of titanium dioxide.

Most titanium dioxide particles for plastics are fine. Usually, the particle size of titanium dioxide for coatings is 0.2~0.4μm, while the particle size of titanium dioxide for plastics is 0.15~0.3μm. In this way, a blue base phase can be obtained, which has a shielding effect on most yellow-phase resins or resins that are prone to yellowing. However, titanium dioxide for plastics cannot be used in coatings because of its small particle size and poor durability.

Ordinary titanium dioxide for plastics generally does not undergo inorganic surface treatment, but generally undergoes organic surface treatment (polyol, silane or siloxane). This is because, for example, titanium dioxide coated with inorganic substances such as hydrated alumina is used in plastics. When the relative humidity is 60%, its adsorption equilibrium water is about 1%. When the plastic is extruded at high temperature, the evaporation of water will cause pores on the smooth plastic surface. In addition, titanium dioxide for plastics is generally mixed in low-polarity resins through shear force processing. Titanium dioxide with organic surface treatment can be dispersed relatively well under appropriate mechanical shear force.

Since plastic products are much thicker than paint and ink coatings, they do not require too high a pigment volume concentration. In addition, it has high hiding power and strong tinting power, and the general dosage is only 3%~5%. It is used in almost all thermosetting and thermoplastic plastics. It can be mixed with resin dry powder or liquid containing plasticizer. Some titanium dioxide is processed into masterbatch before use.

With the expansion of the application scope of plastic products, many plastic products for external use, such as plastic doors and windows, building materials and other plastic products, have high requirements for outdoor weather resistance. In addition to the use of rutile titanium dioxide, surface treatment is also required. Surface treatment generally does not add zinc, but only silicon, aluminum, zirconium, etc. Silicon has a hydrophilic dehumidification effect, which can prevent the formation of pores in plastics due to high-temperature evaporation of water during extrusion, but the amount of these surface treatment agents is generally not too much.