HAS hindered amine

HAS hindered amine stabilizer PBSA poly(polybutylene succinate-co-... 

GMI geometric modeling system HAS hindered amine stabilizer... 

Besides providing effective protection of polymers against photo-degradation, some high molecular weight and oligomeric HALS (e.g. HALS-3) have been shown to act as effective long term heat stabilizers. For this reason, in some relevant literature, it is possible to find the abbreviation HATS (Hindered Amine Thermal Stabilizers) or HAS (Hindered Amine Stabilizers). A detailed overview of the various mechanisms proposed for HALS action can be found in [1]. 

HAS Hindered amine stabiliser LETS Long-term thermal stabiliser... 

A polymer-bound hindered amine light stabilizer [P-HALS] has been synthesized by terminating the living anionic polymerization of isoprene with 4(2,3-epoxy pro-poxy)-1,2,2,6,6-pentamethylpiperidine followed by hydrogenation of the resulting polymer to E-P copolymer using Zeigler type catalyst [40] ... 

Other examples of esterification with trialkyloxonium salts have been reported.7,8 The present procedure offers the advantages that the reactive carboxylate ion is generated in sitv and that a low-boiling, nonaqueous solvent is employed, whereby the experimental procedure is considerably simplified. A related method has been reported which utilizes a hindered amine wdth dimethyl sulfate [Sulfuric acid, dimethyl csterj as the alkylating agent.9 The present procedure is carried out under somewhat milder conditions and avoids the use of highly toxic reagents. 

However, modification of the allyl fragment by substitution of one of the terminus positions has provided more active complexes by enabling a more facile activation step [159], This allows the coupling of highly hindered amines with hindered aryl chlorides at room temperature and with low catalyst loadings [160] (Scheme 6.48). 

The reductive alkylation of DAP with acetone led to high conversions and selectivity to the dialkylated product over Al, Bl, and BS2 catalysts. The ASl catalyst, which typically has lower activity than the Al or Pt-based catalysts showed greater formation of heterocycles. These results indicate that a more active catalyst, a shorter reaction time, a higher operating temperature, or sterically hindered amines/ketones will help minimize the formation of the heterocycles. Similar high selectivities were obtained with DAP-MIBK reaction over BSl and BS2 catalysts with no heterocycles being formed. However, over Al, the undesired heterocyclic compound was over 15%. This indicates that the reaction between diamines and ketones has a significant potential to form heterocyclic compounds unless the interaction between these is kept to a minimum by the use of a continuous flow reactor as proposed by Speranza et al. (16) or by other methods. 

Sc(03SCF3)3 in the presence of a BINOL ligand.113 Optimized conditions involved use of 5-20 mol % of the catalyst along with a hindered amine such as cis-1,2,6-trimethylpiperidine. A hexacoordinate TS in which the amine is hydrogen bonded to the BINOL has been proposed. 

The driving force for replacement of BHT (MW 220) for hindered phenolics such as Irganox 1010 and/or Anox 20 (MW 1178) as well as of the low-MW hindered amine Lowilite 77 (MW 481) for polymeric HALS such as Uvasil 299 (MW 1800) has been the greater permanence in the polymer matrix. 

SFC-FID is widely used for the analysis of (nonvolatile) textile finish components. An application of SFC in fuel product analysis is the determination of lubricating oil additives, which consist of complex mixtures of compounds such as zinc dialkylthiophosphates, organic sulfur compounds (e.g. nonylphenyl sulfides), hindered phenols (e.g. 2,6-di-f-butyl-4-methylphenol), hindered amines (e.g. dioctyldiphenylamines) and surfactants (sulfonic acid salts). Classical TLC, SEC and LC analysis are not satisfactory here because of the complexity of such mixtures of compounds, while their lability precludes GC determination. Both cSFC and pSFC enable analysis of most of these chemical classes [305]. Rather few examples have been reported of thermally unstable compounds analysed by SFC an example of thermally labile polymer additives are fire retardants [360]. pSFC has been used for the separation of a mixture of methylvinylsilicones and peroxides (thermally labile analytes) [361]. 

NMR spectroscopy is most effective in qualitative analysis when the samples examinated are substantially pure compounds and has been used to confirm the theoretically predicted low-energy conformations of the Af-acylated hindered amine light stabiliser Tinuvin 440 [210]. Trace amounts of PDMS (quantification limit 0.1 ppm) in plastic additives, dyes and pigments were determined by 111 NMR after Soxhlet extraction [211]. ll NMR was also used for the detection of octadecanol, an impurity in Irganox PS 802 (3,3 -dioctadecyl thiodipropionate). NMR has identified the nature of a supposedly UV stabiliser of empirical formula C17H18N3CIO [44] (Scheme 5.2). 

Figure 3.22) [22]. Another typical example of a new, evolutionary high-MW hindered amine stabiliser (HMW HAS), with new levels of light stability and reduced interaction with pigments, is Chimassorb 2020 (Fig. 3.25e). 

Three factors determine the effectiveness of antioxidants in polymers, namely (i) intrinsic molar activity (ii) substantivity in the polymer and (iii) solubility in the polymer. Multifunctional AOs combine multiple functions in one molecule. Sterically hindered amine stabilisers (HAS), such as Chimassorb 944, Tinuvin 622 and Tinuvin 783 are prime examples. 

Atmospheric ozone has also been reported as causing fading of certain dyes in some countries [425,426] diallyl phthalate (10.182) used as a carrier in the dyeing of cellulose triacetate fibres, is said to be an effective ozone inhibitor [427]. Nylon, especially when dyed with certain amino-substituted anthraquinone blue acid dyes, can also be susceptible to ozone fading [428,429]. Selection of ozone-resistant dyes is obviously the best counteractive measure, although hindered phenols (10.161) and hindered amines (10.162) are said to provide some protection. 

An aspect of particular interest is the performance of hindered amines in protective coatings such as lacquers. Weathering tests in our application laboratories have shown that a tetramethylpiperidine derivative (HALS 1) has in fact a very good protective effect. 

A further effect of sterically hindered amines that could contribute to polymer stabilization has been described by Allan / McKellar31i-lft-41. They reported a conversion of a,3 to 3,Y unsaturated ketones in polyolefins and assumed that this played a role in the photooxidation of the polymers. The conversion... 

Similar to phenols, they can cause staining and are often used in conjunction with carbon black filled elastomers (e.g., tyres) — although carbon black itself has antioxidant capacity. For non-staining applications, e.g., polypropylene carpets, a stoically hindered amine is used, e.g.,... 

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