SINOSORB® BL 326-S (CAS 1877301-52-4) is a highly efficient, red-shifted benzotriazole light absorber derived from UV-326 with 5-position p-tolylthio modification, manufactured for optical lenses and display films providing sharp UV/HEV blue light cut-off (<390 nm) and high visible transparency. As an ISO certified supplier, we offer this low-volatility absorber for PC, PET, PMMA, and CR-39 systems.
SINOSORB® BL 326-S
(High-Performance Red-Shifted UV & HEV Blue Light Absorber)
Chemical Name:
2-(tert-Butyl)-4-methyl-6-(5-(p-tolylthio)-2H-benzo[d][1,2,3]triazol-2-yl)phenol
2-(2-Hydroxy-3-tert-butyl-5-methylphenyl)-5-(p-tolylthio)-2H-benzotriazole
CAS No.: 1877301-52-4
MF: C24H25N3OS
MW： 403.54
Molecular structure:
SINOSORB® BL 326-S is a highly efficient, red-shifted benzotriazole-type light absorber derived from the classic UV-326 skeleton, optimized via 5-position p-tolylthio conjugation modification.
Appearance | Light yellow crystalline powder |
Purity (HPLC) |
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Water Content (KF) |
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Rapid Moisture |
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Melting Point |
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Transmittance @ 390nm | 0.0% (Completely Opaque) |
Transmittance @ 430nm |
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Red-Shifted, Narrow-Band Absorption & Sharp Cut-Off
Compared to conventional benzotriazoles (λmax ~340-350 nm), Sinosorb® BL 326-S exhibits a distinct red-shift with an absorption peak at ~365 nm. The 5-position thioether modification provides an exceptionally steep absorption curve: spectral scanning demonstrates 0% transmittance at 390 nm and near 100% transmittance at 430 nm, enabling precise blocking of harmful high-energy visible (HEV) blue light (especially the 400-420 nm band).
High Visible Transparency & Low Yellowing
While delivering strong UV and blue light blocking performance, the polymer matrix maintains a total light transmittance of ≥87%. Unlike traditional red-shifted absorbers, Sinosorb® BL 326-S transitions rapidly to full transparency beyond 430 nm, introducing minimal background tinting and meeting strict optical requirements for a low Yellowing Index (Y.I.).
High Thermal Stability & Exceptionally Low Volatility
The 5% weight loss temperature (TGA) exceeds 280°C, making it perfectly suited for high-temperature melt processing (e.g., PC and PET extrusion, injection molding, film stretching). The increased molecular weight combined with the unique aromatic thioether structure effectively suppresses sublimation, significantly reducing mold plate-out, die deposit, and vacuum vent line clogging during manufacturing.
Superior Compatibility & Solubility
Optimized steric hindrance and aromatic thioether structures provide excellent solubility and compatibility with a wide range of polar and non-polar resins, including PC, PMMA, PET, and optical monomer matrices (e.g., CR-39, MR series). It prevents blooming, migration, haze increase, or surface frosting over extended use.
Outstanding Weatherability (High Light Fastness)
The robust benzotriazole skeleton enables highly efficient energy conversion via the ESIPT mechanism (Excited-State Intramolecular Proton Transfer), drastically delaying substrate yellowing, degradation, and loss of gloss under prolonged light exposure.
Sinosorb® BL 326-S is widely used in premium optical and electronic materials requiring strict protection against UV and high-energy blue light:
Optical Lenses: Anti-blue light eyeglasses, functional resin lenses (CR-39, MR-8 systems), and contact lenses. (Recommended dosage:0.1% - 0.8% )
Display Protection Films: PET screen protectors, Optical Clear Adhesives (OCA), and polarizer protective layers for smartphones and monitors. (Recommended dosage: 0.5% - 2.0%)
Functional Coatings & Window Films: High-end automotive films, architectural window films, and premium UV-curable functional coatings. (Recommended dosage: 1.0% - 3.0%)
25 kg/fiber drum or carton with a double PE inner bag
Store in a cool, dry, and well-ventilated warehouse. Keep away from direct sunlight, heat, and sources of ignition.
Keep containers tightly sealed when not in use.
Protect the product from leakage, rain, and severe insolation during transportation.
We offer a variety of options to help you find the right product for your application
Provide formulation optimization support for water-based/solvent-based systems
Full coverage of REACH, FDA, and GB standards
99.8% on-time delivery rate, 10,000-ton production capacity guarantee
≥98.5%