Polymeric films used in greenhouse and mulch film applications have been a subject of great interest to additive manufacturers, film processors, and researchers for over 25 years [29-34].
In the 1960s and 1970s antioxidants and UV absorbers provided basic levels of protection against thermal and UV degradation. During the 1980s, hindered amine light stabilizers (HALS) extended the service lifetime of a range of polyolefin-based applications. Even during the past 10 years development has continued in the area of new structures of HALS, their performance, controlling the negative effects of agro-chemical (particularly acidic pesticides) on the performance of HALS. There are three classes of UV stabilizers generally used by the agri-film processors. These UV-stabilizers include the following :
1. UV absorbers: benzophenones and benzotriazoles
2. Ni quenchers: first compounds used for greenhouse stabilization in combination with UV absorbers
3. Polymeric HALS: have superior UV stability; have disadvantage of possibility of deactivation with acidic pesticides
Ciba has currently produced two new Tinuvin products: Tinuvin 492 and Tin-uvin 494. These structures have lower basicity as compared to original hindered amines [31, 35]. Great Lakes Chemicals has added two new HALS, UVASIL 816 and UVASIL 299 (HALS2). These are tertiary HALS that provide higher performance in greenhouse films and greater resistance to pesticide spraying. Tinuvin 123 is particularly designed to give sulfur resistance in rose greenhouses.
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