Optical brighteners are functional additives used in plastics processing and fiber manufacturing to improve visual whiteness and gloss. They work by converting ultraviolet light into visible blue-violet fluorescence, offsetting the yellow cast that can make materials appear dull. The effect is optical rather than a change in the material’s physical or chemical properties.

How optical brighteners work

The mechanism is based on optical compensation. The additive absorbs invisible ultraviolet light and re-emits it as visible blue-violet fluorescence. This fluorescence complements yellow light generated by aging or process residues, producing a visual increase in whiteness. The effect does not alter the material’s physicochemical attributes, but it can significantly improve the product’s visual appearance.

Technical characteristics and performance

High-purity optical brighteners are typically pale yellow or gray-white powders. In industrial use, their primary value lies in high thermal stability and processing adaptability.

• Thermal stability: The additives can withstand processing temperatures above 280°C, meeting the extrusion, injection molding and blown-film requirements of most engineering plastics, including PET, PC and ABS.
• Weather resistance and migration resistance: Under long-term outdoor exposure or intense light, these additives show strong stability and are not prone to degradation or migration, helping products maintain whiteness over time.
• Addition efficiency: Because of their high optical activity, typical recommended dosages range from 0.01% to 0.1%, offering cost efficiency alongside the desired visual effect.

These properties make optical brighteners suitable for applications where both processing durability and appearance are important, including engineering plastics, fibers and masterbatch systems.

Selection and application guidance

In production, the timing of addition is critical. Optical brighteners can be added directly to monomers or prepolymers, or mixed in before molding through a masterbatch. Different substrates, such as PP, PE, PET and PC, require compatible grades to ensure proper dispersion and performance.

For plastics that must retain high transparency, low dosage levels and a grade with a matching refractive index can help improve brightness without compromising transparency or mechanical properties.

Storage and safety

Products should be stored in a cool, dry warehouse, away from moisture and direct sunlight. Under standard packaging of 25 kg drums or 20 kg bags, the shelf life is generally 24 months. Small-sample testing is recommended before full-scale production to determine the optimal ratio.