Nickel quencher

Figure III.6 Product sheet of the nickel quencher 2,2 -thio-bis-(4-tert-octylphenolato)-n-butylamine nickel(ll). After Gijs-man [1]. Reproduced by permission of P. Gijsman...

Comparison Different UV Stabilizers The addition of UV stabilizers leads to a tremendous increase of the stability of LLDPE during outdoor weathering (Florida). The addition of a combination of a Nickel Quencher (Ni-1) and a UVA (UVA-BP-1) lead to a six times larger lifetime. The additions of a HMW-HALS (HMW-HALS-2) leads even to alarger (> 10 times) increase in the lifetime (Fig. 17.8). In another comparison between different UV stabilizers (see Table 17.6) it is also shown that HALS is by far the best performing UV stabilizer. In this table it is also shown that UVA-BP-1 is the most effective UVA. 

Among the numerous commercial light stabilizers only a few are suitable for low density polyethylene (LDPE). This is mainly due to the fact that most light stabilizers are not sufficiently compatible at levels of concentration necessary for the required protection and so they bloom more or less rapidly. Initially, UV absorbers of the benzophenone and benzotriazole types were used to protect LDPE materials. With the development of nickel-quenchers, significant improvement in the light stability of LDPE films has been achieved. For reasons of economy, however, combinations of nickel-quenchers with UV absorbers are mainly used. The service life of LDPE films may be increased by raising the concentrations of light... 

One way that has been explored toward improving the use and efficiency of nickel quenchers is to include it with other... 

The combination of HALS with a UV absorber is used in fihns of polypropylene and polyethylene as well as in thick sections. In films of LDPE, nickel quenchers were commonly used with a UV absorber, except in a very thin film, in which a higher concentration of nickel stabilizer is superior to the combination. The low-molecular-weight HALS are not sufficiently compatible with LDPE at the concentrations necessary, possibly as high as 2%, for the required protection. Incompatibility of HALS with LDPE has been overcome with the development of polymeric HALS. It is considerably better than either the UV absorber or nickel quencher or combinations of the two. For thicker films (100-200 ftm), the combination of a benzophenone-type UV absorber with polymeric HALS is significantly superior to an equivalent amount of polymeric HALS. The type of stabilizers used for linear low-density polyethylene (LLDPE) and ethyl vinyl acetate (EVA) copolymer are similar to those for LDPE. Since LLDPE has superior mechanical properties (elongation at break and tensile strength), thinner films can be used for most applications, and the loss of UV stabihty with reduction in thickness has to be compensated for by improving the stabilization system. 

Name CAS Chemical name Chemical category Structural formula Mixture Product contents Lowilite NDB 021 14516-71-3 1843-05-6 (butylamine)[[2,2 -thiobis[4-(1,1,3,3-tetramethylbutyl)phenolato]](2-)-0,0, S] nickel octabenzone 1 nickel quencher H ... 

The NOR-HALS varieties mentioned above have very low basicity, and are technically effective, but a conventional UV absorber combined with a nickel quencher can be more economical. Cabot Corp. offers masterbatches containing nickel quenchers combined with benzophenone. Clariant and Ampacet also offer nickel quencher systems. 

Tinuvin 111 from Ciba Specialty Chemicals is used in greenhouse films. It is a synergistic blend of two tertiary HALS compounds and is said to offer better pesticide resistance than conventional HALS such as Chimassorb 944 and Tinuvin 622. It is also claimed to deliver better thermal stability than nickel quenchers. 

Nickel quenchers suffer from needing high melt temperatures, but Great Lakes has produced one called Lowilite NDB Q21 that melts at temperatures as low as 55 to 60 C. It can be used in conjimction with a HALS to provide better thermal stabihty where the film is in contact with greenhouse frameworks and heat is transferred by conduction. The company claims that film protected with Lowilite NDB Q21 will last four summers, which is considerably more than can normally be expected of either the benzophenones or the benzotriazole stabilisers. 

Demand for nickel quenchers in agricultural film could be increased by the growing practice of using sulphur compoimds in agriculture. 

Nickel quenchers—American Cyanamid Co., Ciba-Giegy Corp., DuPont Ferro Corp., Hoechst Celanese Corp. 

Schulmann has introduced a new HALS UV stabilizer with good resistance to pesticides. For greenhouse and agricultural films, a HALS offering excellent clarity and outstanding UV resistance and an alternative nickel quencher have been introduced by Colortech for applications where conventional stabilizers may be exposed to chemical deactivation (as when exposed to halogenated or sulphur-based pesticides or fumigants). 

The new additive masterbatches are products that are free of nickel quenchers, improving the stability of polyethylene films and developed specifically for horticultural films likely fo be contaminated by pesticides. They will provide protection for up to four years, even in high-radiation areas such as the Mediterranean. 

Nickel quencher Diphenyl acrylates Benzophenones Cinnamic esters... 

Nickel quenchers such as nickel dibutyldithiocarbamate [13927-77-0] and 2,2 -thiobis-(4-octylphenolato)-n-butylamine nickel (II) [14516-71-3] deactivate excited chromophores which act as sensitizers for the photolysis of hydroperoxides (24). Once widely used in pp fibers, they have been replaced almost entirely by HALS. Because of their high resistance to pesticides used in greenhouses, these products are widely used in PE agrofilm applications. Their usage is gradually declining, however, because of concerns over the toxicity of nickel. Cytec remains the leading producer of nickel quenchers. 

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