HALS UV Stabilizer (Tinuvin 770 Type, Bis-TEMPO Sebacate)

HALS UV Stabilizer (Tinuvin 770 type) is a hindered amine light stabilizer based on bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (CAS 52829-07-9), the industry-reference HALS used in UV-resistant polyester, vinyl ester, and epoxy composite formulations. HALS compounds work through a catalytic free-radical scavenging mechanism rather than UV absorption — the piperidyl nitrogen radical (nitroxide) formed under UV exposure traps carbon-centered radicals generated by photooxidation, preventing chain scission and discoloration of the polymer matrix. The HALS nitroxide is regenerated in the process, providing long-term catalytic protection that outlasts conventional UV absorbers at equivalent loadings.

In unsaturated polyester gel coats and composites for outdoor exposure — boats, pools, outdoor furniture, construction panels — HALS stabilizers are used alongside UV absorbers in a synergistic stabilization system. The UV absorber (benzophenone or benzotriazole type) prevents UV from penetrating the matrix and initiating photooxidation, while the HALS scavenges any radicals that do form. This dual approach provides significantly better weathering durability than either additive alone.

Tinuvin 770 type HALS is a low-molecular-weight, monomeric liquid at room temperature (or low-melting solid), which provides good compatibility and solubility in UPR and VER resin systems. It is used at 0.1–0.5 phr in gelcoat formulations and at 0.2–1.0 phr in composite laminates intended for extended outdoor service. For high-temperature service applications or where extractability is a concern, consider higher-molecular-weight oligomeric HALS (polymeric HALS type) with lower volatility and migration.