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Bumetrizole is an ultraviolet light absorber belonging to the hydroxyphenyl benzotriazole class, commonly used as a chemical stabilizer to protect plastics, polymers, and organic products from UV degradation.
Bumetrizole is distinct from bemotrizinol (a popular broad-spectrum sunscreen active), though both absorb light energy.
Chemical Identity & Properties
CAS number: 3896-11-5
Molar mass: 315.80 g· mol −1
State of matter :fixed
Formula: C₁₇H₁₈ClN₃O
Alternative Names: Tinuvin 326, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(tert-butyl)-4-methylphenol
Melting Point: 144--147--°C
Synonyms : 2-(5-Chloro-2H-benzotriazol-2-yl)-4-methyl-6-di-tert-butylphenol, 2-(2-Hydroxy-3-tert-butyl-5-methylphenyl)-5-chloro-2H-benzotriazole, UV-326, Tinuvin 326, BUMETRIZOLE (INCI)
Bumetrizole is a chemical compound from the group of 2-(2-hydroxyphenyl)-2H - benzotriazoles that acts as a UV absorber .
Bumetrizole is mainly used as an additive for plastics to increase their light resistance .
Bumetrizole is an ultraviolet light absorber (UVA) of the hydroxyphenyl benzotriazole class, which imparts outstanding light stability to plastics and other organic substrates.
Bumetrizole is also approved by the FDA as a stabilizer in polymers used in producing, manufacturing, packaging, processing, and transporting food.
Bumetrizole has a wide range of indirect food approvals in polyolefins.
Bumetrizole has a low volatility at high temperatures and high resistance to thermal degradation and can, therefore, be used without significant loss or decomposition in the polyolefin compounding and molding processes.
Properties
Molecular Formula: C17H18ClN3O
Molar Mass: 315.8
Density: 1.26±0.1 g/cm3 (Predicted)
Melting Point: 144-147°C (lit.)
Boiling Point: 460.4±55.0 °C (Predicted)
Water Solubility: 4μg/L at 20℃
Solubility: Chloroform (Slightly)
Ethyl Acetate (Slightly), Methanol (Slightly), Vapor Pressure: 0Pa at 20℃
Appearance: Solid, Color: Pale Yellow to Light Yellow
pKa: 9.31±0.48 (Predicted)
Storage Condition: Sealed in dry, Room Temperature
Physical and Chemical Properties: Light yellow powder
Uses & Regulation
Industrial Applications: Added to plastics, films, and coatings to prevent yellowing and breakdown caused by sunlight.
Regulatory Status: Evaluated under international chemical safety regulations (such as REACH frameworks) due to persistent bioaccumulative properties in certain environmental assessments.
Use
Bumetrizole is particularly suitable for polyolefins and cold-cured polyesters .
The material exhibits strong absorption in the 300–400 nm range and minimal absorption in the visible range (> 400 nm) of the spectrum.
The recommended levels for normal polyester resins are between 0.2 % and 0.5 %.
In many countries Bumetrizole is approved for use in food contact applications.
Use
Ultraviolet absorber UV326 is a kind of benzotriazole ultraviolet absorber with excellent performance, which is widely used as an additive in plastics, coatings, synthetic rubber, synthetic fibers, photosensitive materials, food packaging materials, etc.
Applications
Bumetrizole is used as a light stabilizer and UV absorber in polymer and plastic formulations.
Bumetrizole can be incorporated into materials where protection against sunlight and other sources of ultraviolet radiation is required.
Typical applications include plastics, coatings, polymers and other materials in which improved resistance to weathering, discoloration and UV degradation is desired.
Material Protection
UV exposure can cause polymers to undergo photochemical degradation, resulting in yellowing, cracking, embrittlement, surface deterioration and loss of mechanical performance.
Bumetrizole helps reduce these effects by absorbing harmful UV radiation before Bumetrizole can cause significant damage to the polymer matrix.
Regulatory Status
Bumetrizole (UV-326) was added to the European Union REACH Candidate List of Substances of Very High Concern (SVHC) on 23 January 2024. ECHA identified it as a very persistent and very bioaccumulative (vPvB) substance under Article 57(e) of REACH.
As of February 2026, ECHA's draft 13th recommendation proposes Bumetrizole (UV-326) for inclusion in Annex XIV of REACH based on its vPvB properties.
Trade Names
ECHA lists several trade names associated with Bumetrizole, including Tinuvin 326, UV-326, LOWILITE® 26, Milestab 326, RIASORB UV-326, EVERSTAB 326, Eversorb 73, TK 11048 and TU 1104.
Environmental Considerations
The main regulatory concern associated with Bumetrizole is its very persistent and very bioaccumulative (vPvB) character.
Its inclusion on the REACH Candidate List reflects concern about its persistence and potential to accumulate in organisms and the environment.
Overall, Bumetrizole (UV-326) is an effective benzotriazole UV absorber historically used to improve the weathering and UV stability of plastics, polymers and coatings.
Its environmental persistence and bioaccumulation characteristics have resulted in significant regulatory attention within the European Union.
