Curing Lewis acids/bases

Thermal cationic cures of epoxy resins can be achieved using Lewis acids based on amine-BF3 complexes. 

Catalytic curing agents initiate resin homopolymerization, either cationic or anionic, as a consequence of using a Lewis acid or base in the curing process. The Lewis acid catalysts frequently employed are complexes of boron trifluoride with amines or ethers. 

Catalytic cracking unit, 24 258-259 Catalytic curing agents, 10 388, 411-415 Lewis acids, 10 413 Lewis bases, 10 411-413 photoinitiated, 10 414-415 Catalytic cycle(s), 5 201... 

Curing of epoxy resins can also be achieved by ring-opening polymerization of epoxide groups using either Lewis acids (including those generated photochemically) or Lewis bases (Sec. 7-2). 

The catalytic curing agents commonly used include tertiary amines, Lewis acids and bases, and dicyandiamide. Since their function is truly catalytic, the catalyst is added at relatively low concentrations (0 to 5% by weight) to the epoxy formulation. Homopolymerization generally requires both the presence of catalysts and elevated temperatures for the reaction to proceed. Like the polyaddition reaction, the homopolymerization reaction is accelerated by hydroxyl groups or tertiary amines. 

One very interesting new application of Lewis acids in curing epoxy adhesives has appeared within the last 25 years. The Lewis acid initiator for the cationic polymerization is formed by the heat or ultraviolet light-induced decomposition of Lewis acid Lewis base salts. Several patents by Crivello and coworkers43 47 describe compounds containing... 

The mechanism for organometallics and Lewis acids in phenolic or anhydride cured epoxy molding compounds are still not fully understood. Lewis bases such as imidazoles can be reacted with organic acids to form salts in order to improve latency. Imidazoles are, so far, the most widely accepted as a compatible catalyst family for encapsulating microelectronics. 

Catalytic-curing agents (Lewis bases and Lewis acids)... 

Both Lewis bases and Lewis acids in catalytic quantities (2-4 phr) cure epoxy resins rapidly without requiring heat. Lewis bases are compounds that have a free pair of... 

Once the Lewis base or Lewis acid is released from the complex, the polymerization reactions involved are similar to those for curing an epoxy resin with a tertiary amine (Figure 3.5). 

Features Multifunctional epo) groups cure with Lewis acids or anhydrides compat. with other epo) resins hydrophobic resist, to aq. acid and bases adhesion to variety of substrates exc. water resist. Properties M.w. 1350 sp.gr. 1.01 (23 C) vise. 7000 mPa s max. (30 C) hyd. no. 1.7 EEW 460 0.05% water Polybd 605E [Sartomer]... 

Catalytic-curing agents (Lewis bases and Lewis acids). Both Lewis bases and Lewis acids in catalytic quantities (2-4 phr) cure epoxy resins rapidly without requiring heat. Lewis bases are compounds that have a free pair of electrons such as tertiary amines while Lewis acids are compounds that can accept a pair of electrons suchasboron trifluoride. Lewis acids such as boron trifluoride are so reactive that, in addition to their being highly... 

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