NOR-HALS

NOR HALS Reduced co-additive interactions acidic polymer applications flame retardancy... 

Other noteworthy developments are carrier materials, such as Stamypor (DSM) and Accurel (AKZO), for production of concentrates with liquid or low-melting additives and reactants (see Section 1.2.1). The biggest growth area for additive carriers is coming from liquid peroxides and silanes, due to related health and safety issues for shopfloor staff. The NOR HALS stabiliser Tinuvin 123-S (a non-interacting, low-MW liquid) for TPO, PP and some blends is delivered in a solid carrier (Accurel). 

Although, for the photolytically degrading halogenated flame-retardants combinations of absorbers and HALS might give sufficient stability [108], in combination with a flame-retardant several other UV stabilizer types can outperform HALS. The development of less basic NOR HALS types can change this situation. These types are less deactivated, causing that in combination with flame-retardants they can outperform all other stabilizers [103,108]. 

Roofing membrane with NOR-HALS. [Data from Capocci, G Hubbard, M., J. Vinyl Additive TechnoL, 11, 3, 91-94, 2005.]... 

A HALS molecule s active amine group is typically hydrogen (NH), alkyl (NR), or alkoxy (NOR) based. Traditional HALS are basic (nonacidic), and their effectiveness is reduced by addic environments thus less-basic, NOR-group HALS molecules have been developed as the latest generation of radical scavengers. Especially when used in combination with UVAs, for example, Ciba s Tinuvin XT 850 stabilizer is a NOR HALS that reportedly resists degradation... 

Painted TPO Add paint-curing systems used in automotive can Interact with conventional, basic HALS. Ciba s less-basic Tlnuvln XT 850 NOR HALS is said to allow good paint adhesion in acid-cured systems, allowing partially... 

An obvious strategy for avoiding the acid/base reactions between acidic FR decomposition products and basic HALS is to choose a nonhalogen, nonacidic FR. However, researchers at Ciba Specialty Chemicals followed the reverse path, developing an NOR HALS light stabilizer that is nonbasic and provides some flame retardance as weU to PP fiber. 

There is a particular caution the researchers note however UV stability with the H-FR/NOR HALS PP cannot reach the level of a non-FR/HALS PP (even when it contains less HALS). This illustrates the power H-FR decomposition products have over HALS. 

Interestingly, the NOR HALS by itself m PP with no FR has been shown to provide minimal flame retardance m a PP fiber, even passing the automotive Industry s FMVSS 302 burn test at only 0.5% loading. Also, 1% NOR reportedly allowed a 200-pm PP fitm to pass D1N4102 B2 burn testing. 

It was thought earlier that the non-interactive nature of NOR HALS with the halogens present in FR additives positively influenced the performance. It was found that NORs alone provide flame retardancy in their own right. 

NOR HALS (alkoxyamine hindered amine stabilisers) are the latest products for stabilising agricultmal films. They have very low basicity, with low pKa values of aroimd 4.6 compared with the 7 to 10 typical of many more basic HALS. This makes them much less likely to lose efficiency by reacting with the acidic derivatives of agrochemicals. 

NOR HALS also improve the outdoor weathering of flexible PVC and are used as light stabilisers in PVC products like patio furniture, window and door trim, fencing and pond liners. Ciba has compared the performance of NOR HALS in PVC favourably with benzophenone and cyanoacrylate stabilisers, as well as with a benzotriazole and a conventional HALS. 

NOR HALS have excellent resistance to pesticide interaction. NOR-1 is a sohd, high molecular weight NOR HALS. In one greenhouse trial in Italy, a low dose (0.4%) of NOR-1 outperformed 0.8% of the best conventional HALS in the test. 

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. 

NOR HALS alkoxyamine hindered amine light stabilisers... 

NOR-HALS (Alkoxyamine Hindered Light Stabilizers) represent a new generation of sterically hindered amines. Thanks to their low basicity and high chemical resistance, they disrupt radically initiated processes faster than standard HALS stabilizers [527]. 

Although superior to Neoprene and Hypalon , NBR/PVC blends do not have as great resistance to UV light as pure PVC. Thus, nonblack compounds should be protected with titanium dioxide and UV light absorbers. The latter have been commonly chosen from the benzotriazole class. New hindered amine stabilizers have been introduced (e.g., NOR HALS 833 from Ciba), that are resistant to hydrogen chloride. These should be considered for NBR/PVC compounds (except if tin mercaptide stabilizers are used). All NBR/PVC compounds should contain antioxidants of broad compatibility (e.g., Irganox 1076). 

Non-interacting, nonbasic NOR-HALS in free-flowing solid form, for molding applications... 

Zah, M. Kohler, J. NOR HALS Technology for Agricultural Films-The Evolution Continuous, SPE Polyolefins RETEC, Houston, 2010. 

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