Amines thermal oxidation

Figure 1 Thermal oxidative breakdown of polyethylene (temperature 200°C P02 = 350 Tor stabilizer concentration 0.5 mass percent). 1-without stabilizer 2-CaO-6 3-polydii-minodiphenylmethane disulfide 4-polydiiminodiphenylsul-fon disulfide 5-polyparaoxydiphenylamine disulfide 6-po-lydimethylaniline disulfide 7-polyaniline disulfide 8-polydiiminodiphenyloxide disulfide 9-polythiosemicarbaz-ide disulfide 10-polyamine disulfide 11-polycarbamide disulfide 12-poly thiocarbamide disulfide 13-polyethylenedi-amine disulfide.

The beneficial effects of amine A-oxide promoters are well documented in the example given in Equation (1). While the aromatized product 12 instead of the PKR product was obtained from the reaction of diethylacetylene 10 and compound 11 under thermal conditions, the desired PKR product 13 was formed only by the aid of amine A-oxide. 

Attempts have also been undertaken to improve the processability of PMR imide resins through molecular weight adjustments and exchange of the monomers employed. LARC 160 as an example here Jeffamine AP22, a eutectic blend of MDA type amines, was used as a polyamine instead of the crystalline MDA. This modification provided a quasi melt processable PMR resin (15). Other modifications were studied with the aim of improving the thermal oxidative stability by using hexafluoroisopropylidene dipthalic anhydride as a monomer (16). 

C capability. A resin coded AFR 700, based on a NE/HFDE/PPDA backbone with a stoichiometry imbalance, providing a prepolymer with a mixture of NE and amine/or anhydride endcaps, as is shown idealistically in Fig. 39. The thermal oxidative stability improvements vis a vis PMR-15 are presumably achieved because of a reduced aliphatic (NE) endgroup concentration. Unfortunately, no publication has appeared in the open literature on the mechanical performance of AFR-700 composition. 

A solventless PMR resin became known under the designation LARC 160 (15), which could be processed as a hot melt. An exchange of MDA in PMR-15 with a liquid isomeric mixture of di- and trifunctional amines (Jeffamine 22) provided a mixture of monomeric reactants which was tacky at room temperature. In the presence of 3% methanol the resin could be processed via a hot melt process. Unfortunately, the cured resin was inferior with respect to thermal oxidative stability in comparison to PMR-15. 

Furthermore, the chemical structure of networks are changed by thermal oxidation reactions 17,23,24F These are rather important for epoxy networks with aliphatic amines since they usually take place in the presence of air at T 130 °C. In aromatic amine-based polymers this kind of reaction becomes important at T > 220° 240 °C 17-23>. The only exception are polymers with a large excess of epoxy groups in the initial mixture. For example, the polymer with P = 0.4 23) starts loosing its weight at 160 °C17 23,24). All polymers considered in this paper are prepared from mixtures with 0.6 P 1.6. Cure and post-cure treatment temperatures are below 190 °C. This means we may not consider thermal oxidation processes in our structural analysis of the networks. 

The method has also been applied to the synthesis of alkyl-substituted quinoxalin-2-amines. Thermal rearrangement of l-(2-aminophenyl)-4,5-dihydro-5-morpholino-l,2,3-triazoles 15 affords unstable 2-alkyl-l,2,3,4-tetrahydroquinoxalin-3-amines, which undergo deamination and consequent oxidation to afford 2-alkylquinoxalines 16. ... 

Commercially available antioxidants include phenols and amine derivatives the latter, though generally more effective, have the drawback of alteriiig the coloration of dyed products. These additives are necessary to prevent, to some extent, the process of thermal oxidation of rubbers, though it has to be borne in mind that the stability of rubbers is primarily determined by the chemical nature of the chains as well as by the cross-links that define network structure. 

Cope elimination Thermal syn elimination of 3° amine N-oxides to form alkenes. 96... 

Interaction Between the HALS Compound and the Antioxidant Present in the Polymer System. Thermal oxidation of the films containing different amounts of IRGANOX and TINUVIN 770 as a function of TINUVIN 770 concentration is shown in Figure 4. As expected, the induction period of the oxygen absorption increases with the antioxidant content, but also with the increase of the TINUVIN 770 concentration. That means that the hindered amine can operate during the radical process of the thermal oxidation as a radical scavenger. 

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