Fluorescent brighteners (optical brighteners) play a crucial role in improving the whiteness and brightness of polymer-based products such as plastics and synthetic fibers. These additives work by converting invisible ultraviolet (UV) light into visible blue light, offsetting yellow tones and enhancing visual brightness.
To perform effectively in high-temperature and chemically active polymer environments, fluorescent brighteners must meet strict performance and compatibility requirements.
Key Performance Requirements
1. Heat Resistance of the fluorescent brighteners
Polymers such as polystyrene, ABS, and polycarbonate are processed at temperatures up to 300°C. Therefore, fluorescent brighteners used in these systems must possess excellent thermal stability, maintaining their fluorescence and color integrity without decomposition or discoloration during high-temperature extrusion, injection molding, or spinning.
2. Resistance to Sunlight and Weathering
Many plastic and synthetic fiber products are used outdoors and exposed to sunlight for long periods.
Fluorescent brighteners for these materials must therefore exhibit high lightfastness and weather resistance, similar to high-performance organic pigments, to ensure long-term brightness and color retention even under harsh UV exposure.
3. Migration Resistance
During processing, some fluorescent brighteners can partially dissolve in the polymer melt, which can cause migration—movement to the surface or into adjacent layers.
High-quality optical brighteners must have low migration tendencies, maintaining their position within the polymer matrix to ensure consistent whitening and prevent surface blooming, color changes, or performance loss over time.
4. Chemical Inertness and Compatibility with Additives
Polymers typically contain various processing additives such as titanium dioxide, plasticizers, pigments, and fillers.
An effective fluorescent brightener must be chemically stable and compatible with these materials:
- It should not react with other additives.
- It should maintain performance even in the presence of UV absorbers or light stabilizers, such as hindered amine stabilizers.
- When used with titanium dioxide, the absorption overlap in the UV region must be carefully managed to avoid reduced brightness.
5. High Purity of the fluorescent brighteners
The fluorescence efficiency of an optical brightener depends heavily on its purity.
Even trace levels of impurities or residual solvents can reduce brightness and fluorescence strength. Therefore, high-purity grades are preferred for polymer applications, ensuring maximum optical performance and consistent product appearance.
6. Non-Toxicity and Environmental Safety
Polymer materials are often used in consumer products, including food packaging, toys, and textiles that come into direct contact with the skin.
Therefore, fluorescent brighteners must be non-toxic and comply with international safety and environmental regulations, such as:
- U.S. FDA standards
- Japan MITI certification
- EU REACH and food-contact safety regulations
Additionally, modern OBAs should be environmentally friendly, not releasing harmful residues during use or disposal.
Application Considerations
Fluorescent brighteners for polymers can be incorporated:
- Before or during polymerization, by adding to the monomer stage.
- Before molding or spinning, by blending into the polymer resin.
In both cases, the product must remain thermally stable, non-reactive, and well-dispersed within the polymer matrix to achieve uniform and durable whitening.
Conclusion
Selecting the right fluorescent brightener for polymers requires balancing thermal stability, migration resistance, compatibility, purity, and safety.
By meeting these key performance requirements, brighteners can deliver superior whiteness, lasting brilliance, and color consistency in plastics and synthetic fibers — ensuring products remain visually appealing and high-performing throughout their lifecycle.
✉️ About Shandong Grand Chemical Co., Ltd.
Shandong Grand Chemical Co., Ltd. is a leading manufacturer and exporter of fluorescent whitening agents and optical brighteners in China.
Our polymer-grade OBAs feature high thermal stability, excellent migration resistance, and outstanding compatibility for use in plastics, coatings, fibers, and films.
📧 Email: sales@obachemical.com
🌐 Website: www.obachemical.com