Fluorescent Brightener Suitable for Polymer Whitening and Brightening

In recent years, China's production and research of fluorescent brightener for polymers have developed rapidly. Currently, eight major varieties are in commercial production. These brighteners mainly fall into three structural categories :

• Bisbenzoxazoles (e.g., C.I. Fluorescent Brighteners 135, 184, 185, 367, 368, 393)
• Distyrylbenzenes (e.g., C.I. Fluorescent Brightener 199)
• Distyrylbiphenyls (e.g., C.I. Fluorescent Brightener 378)

Below are the most widely used fluorescent brighteners for polymer whitening and brightening applications :

1. C .I. Fluorescent Brightener 393 (CAS 1533-45-5)

Trade Name: Optical brightener OB-1 / Eastobrite OB-1

C.I. Fluorescent Brightener 393 is one of the most heat-resistant brighteners , withstanding processing temperatures up to 375°C . It offers excellent whiteness and good compatibility with other polymer additives, making it ideal for high-melting-point engineering plastics such as polysulfone , polyester , nylon , ABS , EVA , rigid PVC , and polycarbonate .

It is widely used for polyester fiber whitening and food-contact plastics , owing to its low toxicity and compliance with safety regulations.

• Appearance: Bright yellowish green powder
• Melting point: 360°C
• Absorption wavelength: 370 nm
• Fluorescence emission: 427 nm
• Dosage: 25-300 mg/kg

2. C.I. Fluorescent Brightener 184 (CAS 7128-64-5)

Trade Name: OB / Uvitex OB / Tinopal OB

A general-purpose brightener suitable for a broad range of plastics including PVC, PS, ABS, PE, PP, PC, PET , as well as varnishes , inks , and synthetic fibers . It produces a pure blue fluorescence and offers high whiteness , excellent fastness , and very low toxicity , making it ideal for children's products and food packaging applications.

• Appearance: Pale yellow to white crystalline powder
• Melting point: 198-203°C
• Absorption wavelength: 375 nm
• Fluorescence emission: 435 nm
• Dosage: 10-50 mg/kg

3. C.I. Fluorescent Brightener 378 (CAS 40470-68-6)

Trade Name: Optical brightener FP-127 / Uvitex FP / Hostalux KVC

C.I. Fluorescent Brightener 378 delivers high whitening performance and excellent heat stability across multiple plastics, including PVC, polyamide, polystyrene, polyurethane , and thermoplastic rubber . It exhibits superior lightfastness in nylon fibers and high migration resistance in soft PVC.

It is also effective for transparent plastics , where it counteracts yellow tones at very low dosages.

• Appearance: Yellow-white powder
• Melting point: 216-222°C
• Absorption wavelength: 364 nm
• Dosage: 0.0005-0.001% for transparent products
• 50-500 mg/kg for colored plastics

4. C.I. Fluorescent Brightener 367 (CAS 5089-22-5)

Trade Name: Optical brightener KCB / Hostalux KCB

C.I. Fluorescent Brightener 367 is a versatile optical brightener suitable for films, injection molding, extrusion materials , EVA foam , rubber , paints , and lacquers . It features excellent migration resistance and good lightfastness across different substrates.

• Appearance: Yellow-green crystalline powder
• Melting point: 210-212°C
• Absorption wavelength: 373 nm
• Fluorescent hue: Blue
• Dosage: 0.01-0.05%

5. C.I. Fluorescent Brightener 368 (CAS 5242-49-9)

Trade Name: Optical brightener KSN

C.I. Fluorescent Brightener 368 provides exceptional whitening power even at low dosages and performs well under high temperatures and outdoor exposure . It is widely used in polyester resins , polyamides , polyacrylonitrile , and other plastics for film extrusion , injection molding , and polymerization whitening .

It offers excellent compatibility , UV resistance , and weather durability .

• Appearance: Yellow powder
• Melting point: 260-310°C
• Dosage: 2-30 g per 100 kg of substrate (general use)
• 0.5-2 g per 100 kg for transparent plastics
• 10-20 g per 100 kg for polyester resins

Conclusion

Fluorescent brighteners play a vital role in enhancing the whiteness, brilliance, and visual appeal of polymer products. Selecting the right brightener - based on thermal stability, substrate compatibility, and safety - is key to achieving optimal whitening performance.