Amine reactivity, accelerator

Hydroxyl compoimds accelerate the rate of amine curing. A mechanism has been proposed (100) in which the hydrogen atom of the hydroxyl group partially protonates the oxygen atom on the epoxy group, rendering the methylene group more susceptible to attack by the nucleophilic amine. Reactivity is proportional to the hydroxyl acidity and fimctionality phenolics, aryl alcohols, and polyfunctional alcohols afford the best results. 

An amine accelerated, medium reactive, non-thixotropic, isophthalic resin for the manufacture of chemical ... 

An amine accelerated, low reactivity, thixotropic, flexible orthophthalic resin for the manufacture of many forms of putty and filler paste. 

An amine accelerated, high reactivity, medium viscosity orthophthalic offering bright colours for putties and fillers in the stone industry, b. 64.5% c. 810-1090... 

Reduction in the undesirably high compression set at high temperatures began to be achieved in the late 1960s. In 1968 it was found that tropolene and phenanthroline not only accelerated amine cure but were also effective with certain bisnucleophiles such as resorcinol, hydroquinone, the bisphenols A, AF and S, and their salts which were otherwise insufficiently reactive to cure the rubbers ... 

Halobutyl Cures. Halogenated butyls cure faster in sulfur-accelerator systems than butyl bromobutyl is generally faster than chlorobutyl. Zinc oxide-based cure systems result in C—C bonds formed by alkylation through dehydrohalogenation of the halobutyl to form a zinc chloride catalyst (94,95). Cure rate is increased by stearic acid, but there is a competitive reaction of substitution at the halogen site. Because of this, stearic acid can reduce the overall state of cure (number of cross-links). Water is a strong retarder because it forms complexes with the reactive intermediates. Amine cure may be represented as follows ... 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Avoid contamination with combustible materials, various inorganic and organic acids, alkalies, alcohols, amines, easily oxidizable materials such as ethers, or materials used as accelerators in polymerizations reactions Stability During Transport Extremely explosion-sensitive to shock, heat and friction. Self-reactive Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent inhibitor of Polymerization Not pertinent. 

At higher temperature, however, (> 100°C) an accelerated decomposition of hydroperoxide by the hindered amine II was very clearly seen. As Table I shows, the effect is observable in solvents with differing reactivities towards radicals. It is interesting to note that in the experiments made under nitrogen the loss of... 

C]-Cyanide is a secondary precursor, produced from 11C02, but nevertheless as a result of microwave-enhanced accelerations can be used to label a wide range of amines, acids, esters and alcohols. Such an example is illustrated in Scheme 13.12 [95-98]. Reactions with less reactive substrates can be achieved by increasing the polarity of the reaction medium through the addition of various salts. 

This new process has one unexpected benefit the rates and turnover numbers are increased substantially with the result that the amount of the toxic and expensive 0s04 is considerably reduced (usually 0.002 mole %). The rate acceleration is attributed to formation of an Os04-alkaloid complex, which is more reactive than free osmium tetroxide. Increasing the concentration of 1 or 2 beyond that of 0s04 produces only negligible increase in the enantiomeric excess of the diol. In contrast quinuclidine itself substantially retards the catalytic reaction, probably because it binds too strongly to osmium tetroxide and inhibits the initial osmylation. Other chelating tertiary amines as well as pyridine also inhibit the catalytic process. 

Silk can be readily dyed with conventional high-reactivity dyes of the dichlorotriazine, dichloroquinoxaline or difluoropyrimidine classes. Exhaust dyeing at 60-70 °C and pH 5-6 gives satisfactory results, especially if a mildly alkaline aftertreatment is given to enhance fixation. Dichlorotriazine dyes can also be applied by pad-batch dyeing with bicarbonate and a batching time of 4-6 hours. The relatively low reactivity of aminochlorotriazine dyes, however, results in moderate to poor build-up on silk. Tertiary amine catalysts such as DABCO (7.66) can be used to accelerate the dye-fibre reaction and increase the fixation substantially [116], but it is difficult to achieve satisfactory compatibility in mixture dyeings by this method (section 7.4.2). 

In HO -catalyzed hydrolysis (specific base catalyzed hydrolysis), the tetrahedral intermediate is formed by the addition of a nucleophilic HO ion (Fig. 3.1, Pathway b). This reaction is irreversible for both esters and amides, since the carboxylate ion formed is deprotonated in basic solution and, hence, is not receptive to attack by the nucleophilic alcohol, phenol, or amine. The reactivity of the carboxylic acid derivative toward a particular nucleophile depends on a) the relative electron-donating or -withdrawing power of the substituents on the carbonyl group, and b) the relative ability of the -OR or -NR R" moiety to act as a leaving group. Thus, electronegative substituents accelerate hydrolysis, and esters are more readily hydrolyzed than amides. 

Reactivity of Amine Accelerators with Anhydride-Epoxy Resin Systems ... 

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