Tertiary amine accelerator

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Epoxy (Anhydride-Cured) Epoxy resins may be crosslinked with various anhydrides by using a tertiary amine accelerator and heat. These cured polymers generally have good chemical resistance especially to acids. 

Tertiary amine accelerated polymercaptan/ epoxy systems, 10 410 Tertiary amine-carbonate technology,... 

On the other hand, addition of tertiary amines accelerated hydrogenation of some compounds over Raney nickel [6I. In hydrogenation of halogen derivatives over palladium [62] or Raney nickel [63] the presence of at least one equivalent of sodium or potassium hydroxide was found necessary. 

Anhydrides generally provide pot lives of days or months and cure usually at 100-180°C with very little exotherm. Tertiary amines accelerate the time for gelation but still require the elevated temperature cure to obtain optimum properties. Anhydrides usually give brittle products but the addition of polyether flexibilizing groups yields more elastomeric products [44]. 

A tertiary amine is often used as an accelerator in primary amine systems to correct for these problems and to adjust the rate of cure. Ortho-(dimethylaminomethyl) phenol, DMP-30, and tris-(dimethylaminomethyl) phenol, DMP-10, are common commercial tertiary amine accelerators. 

EMI cured epoxy adhesive formulations are claimed to have outstanding adhesion to metals, and for this reason it is added as a co-curing agent in many compositions. It is an excellent anhydride accelerator providing higher thermal resistance than typical tertiary amine accelerators. 

When formulated into one-component adhesive systems, the product is stable when stored for 6 months to 1 year at room temperature. It will then cure when exposed to 145 to 160°C for about 30 to 60 min. Since the reaction rate is relatively slow at lower temperatures, the addition of 0.2 to 1 percent benzyldimethylamine (BDM A) or other tertiary amine accelerators is common to reduce cure times or cure temperatures. Other common accelerators are imidazoles, substituted urea, and modified aromatic amine. 

Many initiator-accelerator systems that contain accelerators other than amine have been suggested for vinyl pol3rmerization, but only a few have been employed in dental resins. Substitution of p-toluenesulfinic acid, alpha-substituted sulfones and low concentrations of halide and cupric ions for tertiary amine accelerators, yields colorless products (43-48). Most of these compounds have poor shelf-life. They readily oxidize in air to sulfonic acids which do not activate polymerization. Lauroyl peroxide, in conjunction with a metal mercaptide (such as zinc hexadecyl mercaptide) and a trace of copper, has been used to cure monomer-pol3rmer slurries containing methacrylic acid (49-50). Addition of Na salts of saccharine to monomer containing an N,N-dialkylarylamine speeds up pol)rmerization (51). 

For example, an anhydride hardener (with tertiary amine accelerator) will produce a polyester -type structure with low polarity, whereas an amine hardener will form a P-hydroxyl amine network with high polarity. Hydrogen bonding of water molecules at these sites enhances the concentration of moisture which can be absorbed. However, with catalytic curing agents, polyether stmctures of relatively low polarity will form. Since it is quite common to use mixed curing agents for composite matrices, the cured... 

For an elevated temperature cure, benzoyl peroxide (BP) is used with a tertiary amine accelerator, such as dimethylamine (DMA), promoting a more rapid cure once the reaction has started. Post curing will be required. 

In almost all commercial epoxy resin/anhydride formulations, some form of accelerator is used. Tertiary amines are more conventionally used accelerators. These may be benzyldimethylamine (BDMA) and tris (dimethylaminomethyl)-phenol (DMP-30). Optimum amounts of tertiary amine accelerators in terms of cured properties fall iu the 1 to 5 phr rauge. 

Phenol/formaldehyde novolac resins react with epoxy groups at elevated temperatures to give highly cross-linked systems, with a high service temperature >150°C and excellent chemical resistance. The typical epoxy/ novolac ratio is 0.9 to stoichiometric a tertiary amine accelerator is necessary for complete cure. 

The tertiary amine accelerators are commonly used with anhydride systems to speed up their curing reactions. They are used in concentrations of 0-5 to 5 phr and typical examples are... 

In the industrial production of this PC, interfacial polycondensation is used. The bisphenol A is first dissolved in the aqueous phase as sodium salt, and the phosgene in the organic phase, which is not miscible with water, e.g. dichloromethane. The reaction occurs at the interface of the two phases to produce oligomers, which enter the organic phase. The hydrolysis product NaCl enters the aqueous phase. The addition of catalysts (tertiary amines) accelerates the polycondensation process. The chlorine leaves the process as sodium chloride, see Fig. 96. 

The model adhesive used was Dow Chemical epoxy resin D.E.R. 331 mixed with an M-5 silica filler, a dicyandiamide ( DICY ) curing agent, a tertiary amine accelerator (PDMU), and various amounts of rubber toughener (Kelpoxy G272-100), details of which have been listed elsewhere [33], The final products, according to the rubber concentration level, were designated as adhesives A (0% rubber), B (4.1 %), C (8.1 %), and E (15%). Adherends were cut from 25-mm-wide 6061-T6 aluminum alloy bar stock. 

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