Tiangang® UV-329

What it is

Tiangang® UV-329 is a UV absorber (UVA). A UV absorber takes in 280–400 nm radiation and dissipates it as heat, acting as a filter layer at the surface. It does not scavenge radicals itself. Product identifiers: melting point 103 ~ 105.

Technical data

Chemical name	2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol
CAS number	3147-75-9
Structure
Molecular Weight	323 g/mol
Description	Tiangang® UV-329 is a highly efficient UV absorber for a variety of plastics and other organic substrates, including polyolefins, and most engineering plastics, as well as PVC, PMMA, PU, PET, POM, polyesters, and various elastomers, and adhesives. Tiangang® UV-329 features strong UV absorption, low initial color, broad compatibility, and moderately low volatility. When added to the substrates, it protects the substrate from UV degradation, preserving the original appearance and physical integrity of molded articles, films, sheets, and fibers during outdoor use.   Dosage level of Tiangang® UV-329 is between 0.10 and 1.0%, depending on substrate and performance requirements. When used in combination with Tiangang® series of Hindered Amine Light Stabilizers (HALS), synergistic performance is often observed.

Melting point 103 ~ 105 °C — the processing window needs to reach above it for uniform dispersion.

Where it is used, and at what loading

The difference from HALS is where it works: a UV absorber depends on its own absorption cross-section, so it is most visible in transparent film, coatings and sheet with a long optical path. In carbon-black or opaque systems its contribution is limited.

Figures above are typical industry ranges, not guaranteed values. The actual loading depends on wall thickness, design life and the other additives in the system, and should be established by a loading ladder on the real formulation.

Choosing between similar grades

Three things decide the choice for UV-329: molecular weight and volatility, basicity, and compatibility with the other components in the system. The lower-MW benzotriazole: fast dispersion and early onset for thin parts and coatings; pair with HALS for long outdoor life.

Frequently asked questions

Benzotriazole or benzophenone?

Benzophenones such as UV-531 are cost-effective and compatible but absorb at shorter wavelengths and migrate over time. Benzotriazoles (UV-326, 327, 328) absorb more strongly and resist migration, which is why engineering plastics mostly use them. Triazines (UV-570, UV-630) give the highest heat and weathering resistance for high-temperature processing and demanding outdoor parts.

Why pick a high-temperature grade for engineering plastics?

Engineering plastics are processed at 250–300 °C. A standard UV absorber volatilises or decomposes in that window, losing active content and contaminating the tool. High-temperature grades have a higher decomposition temperature and survive the process.

What should be watched when combining with HALS?

Acid-base interaction. Some UV absorbers and highly basic HALS interfere with each other in the same system and lose synergy. Our T-series packs are formulated with both sides of that balance in mind.

The figures and guidance above follow Tiangang's published technical material and common industry practice. For a specific formulation, refer to the batch COA and the technical agreement between the parties.

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