31 HALS UV stabilizers.

Hindered amine light stabilizers (HALS) can be considered the most important development in light stabilization for many polymers. "In a field where customer acceptance often requires several years of exposure testing, major new developments don't come too often," PLASTICS TECHNOLOGY wrote in July 1976. "This year, however, marks the commercialization of a unique class of uv stabilizer, one not apparently affected by substrate thickness." That article reported the arrival of Tinuvin 770, the first of a new family of sterically hindered amine light stabilizers (HALS) developed by Ciba-Geigy Corp.

HALS were remarkable in their effectiveness at much lower use levels than previous uv stabilizers, their broad range of applicability (including polyolefins, PS, ABS, and urethanes), and favorable performance in fibers and films as well as molded and extruded shapes having thick cross sections.

The second in this series, Tinuvin 144, arrived in 1978. It imparted a high degree of light stability and also guarded against thermal oxidation during processing and service life. Aimed at polyolefins, its lower volatility gave it an edge over Tinuvin 770 where higher processing temperatures were required, and it had better moisture resistance for use in humid environments.

In the early 1980s, virtually all other uv-stabilizer producers focused their attention on developing HALS products. Ciba's Tinuvin 622 became the first HALS approved for food contact in 1982. Other milestones were polymeric HALS with reduced leachability from Hoechst A.G. in 1983; Ciba's Tinuvin FR (2001), which is both a light stabilizer and flame retardant for PP; and Great Lakes' Lowlite 19 (2004), a monomeric HALS that has low interaction with pigments in polyolefins.