I. Chemical Properties & Whitening Principle
 
1. How does molecular structure affect whitening performance?
 
KCB has a symmetric structure (naphthalene ring linked to two benzoxazole groups), enabling it to strongly absorb UV light at 370nm. Its conjugated system efficiently converts this energy into blue-white fluorescence to neutralize yellow light. Additionally, it binds tightly to material molecules for stable whitening.
 
2. Core principle of emitting blue-white fluorescence?
 
After absorbing UV photons, electrons jump to an excited state. When returning to the ground state, they release blue-white visible light. This light complements the yellow tint of the treated material, creating a visually whiter and brighter effect.
 
II. Practical Application Issues
 
1. KCB dosage requirements for different plastics?
 
- PE/PP: 0.005% - 0.03% (0.01% - 0.02% for films; max. 0.03% for injection molding)
- PVC: 0.02% - 0.05% for flexible PVC; 0.01% - 0.03% for rigid PVC
- EVA foam: Fixed at 0.01% - 0.03% (compatible with foaming process)
 
2. How to integrate KCB with synthetic fiber (e.g., polyester) production?
 
Blend KCB with polyester chips before spinning (temperature: 210 - 290℃, above KCB’s melting point but below the fiber processing limit). Optimize screw speed and temperature to ensure uniform dispersion, then proceed with spinning.
 
3. How to avoid uneven whitening/precipitation in coatings?
 
First, dissolve KCB in solvents like toluene (1.02g per 100ml toluene) to make a concentrated solution. Add it to the coating while stirring at 100 - 300 rpm for 15 - 30 minutes. Use polymer dispersants and bentonite anti-settling agents.
 
III. Performance & Quality Identification
 
1. Light/weather resistance and service life extension?
 
- Light resistance: Grade 7; Weather resistance: Grade 5 - 6.
- For outdoor use: Pair with benzophenone-based UV absorbers + hindered phenol antioxidants. Ensure uniform KCB dispersion.
 
2. How to distinguish high-quality vs. low-quality KCB?
 
- Appearance: High-quality KCB is uniform yellowish-green crystalline powder, no impurities.
- Melting point: Measured via capillary method, should be 210 - 212℃.
- Purity: Tested by HPLC, high-quality KCB ≥ 99.0% (compliant with HG/T 5097-2016).
- Combustion: High-quality KCB melts evenly, with little smoke, no pungent odor, and minimal residue.