Tiangang® HS-791

What it is

Tiangang® HS-791 is a hindered amine light stabilizer (HALS). HALS trap the radicals formed when a polymer photo-oxidises and regenerate in the process, so the protection window is longer than that of a UV absorber, which is consumed as it works.

Technical data

Chemical name	Tiangang® HS-944:  Poly-{[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4- piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}, and Tiangang® HS-770:  Bis(2,2,6,6-tetramethyl-4-piperidyl)-sebaceate
CAS number	Preparation: 71878-19-8/70624-18-9 (US) and 52829-07-9
Structure
Description	Tiangang® HS-791 is a synergistic mixture of Tiangang® HS-944 and Tiangang® HS-770. It is a highly effective radical scavenger belonging to the Hindered Amine Light Stabilizers (HALS) family of stabilizers. It is a UV stabilizer for the following thick applications of PP, PP/EPDM and PP/PE/EPDM blends (TPOs), such as automotive bumpers, garden furniture, tapes and woven sacks.

Where it is used, and at what loading

Suitable for polyolefins (PP, PE), polyurethane, polyamide, polyacetal and polyester. Thin and thick parts call for different grades: thin sections suffer from volatilisation and migration, thick sections from surface bloom.

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 HS-791: molecular weight and volatility, basicity, and compatibility with the other components in the system. Pre-blends 944 with 770 to cover fast onset and long retention in one product, removing two weighing steps at the line.

Frequently asked questions

Is this grade meant for thin or thick parts?

It depends on molecular weight and migration tendency. Low-MW grades diffuse quickly and act early but volatilise and migrate over time; high-MW grades (HS-950, HS-362, BW-10LD) suit long-service outdoor parts. Tiangang offers both, so the choice follows wall thickness and design life.

Is it worth combining with a UV absorber?

Yes, they cover different stages. The UV absorber shields incoming UV energy; the HALS scavenges radicals that have already formed. Agricultural film, automotive exterior and PV backsheet usually need both to reach their design life.

What happens if the loading is too high?

Beyond the compatibility limit the additive blooms to the surface, which wastes material and harms appearance and print adhesion. Protection also stops scaling linearly. Our practice is a loading ladder on the actual system, then fix the cost-performance knee.

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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