Boron trifluoride hardeners

Boron trifluoride hardeners Boron trifluoride monoethylam-ine melts at 95 °C and is used in one-part adhesives. 

The most popular catalysts for epoxy resins are tertiary amines, tertiary amine salts, boron trifluoride complexes, imidazoles, and dicyandiamide. Many of these catalysts provide very long pot lives (months) at room temperatures and require elevated temperatures for reaction with the epoxy groups. These catalysts are often referred to as latent hardeners. 

Thicker epoxy-based coatings, highly flexibllized with amine-reactive nitrile liquid polymer, have been described by Mendelsohn (50) in which the flexibilizing hardener is comprised of an admixture of ATBN, fatty polyamide and boron trifluoride/amine complex. This coating ages well at 100°C and has excellent toughness/ flex with good abrasion and vibration absorption properties. 

Low-molar-mass poly(butadiene) oils with 80%-97% cw-1,4 contents are produced with other Ziegler catalysts (for example, cobalt compounds with alkyl aluminum chlorides or nickel compounds with trialkyl aluminum and boron trifluoride-etherate). The products have few cross-links and dry as fast as wood oil and faster than linseed oil. Conversion of the poly (butadiene) oils with 20% maleic anhydride gives air-drying (air-hardening) alkyd resins. Modified poly (butadiene) oils stabilize erosion-endangered soils. Because of its low viscosity, the aqueous emulsion penetrates the surface soil layers. The surface crust is reinforced by an oxidative bonding process. Since no skin is formed on the soil crust, the aqueous absorption characteristics of the soil are retained. 

Smooth oxidative fission of epoxides to give a-ketols by DMSO is also noted (130). A catalytic amount of boron trifluoride facilitates the transformation by complexing the epoxy oxygen atom, thereby hardening the C termini of the epoxide. 

Tsotra and co-workers [33] showed that when blends of epoxy resin and PANI are doped with dodecylbenzene snlfonic acid and cnred with various acidic and alkaline hardeners such as amine, imidazole, anhydride and boron trifluoride a relationship is developed between the shonlder at the 1,585 cm band in the spectral region 1,575-1,560 cm with the degree of volume resistivity developed. 

For the one-part systems diglycidyl ethers of bisphenol and diglycidyl ethers of resorcinol have been utilised with hardeners such as dicyan-diamide, aromatic substituted ureas and boron trifluoride amine complexes. For further information on component mounting with epoxides the reader is referred to an excellent review by Marshall. ... 

It has been shown that some latent hardeners of the epoxy resins may corrode the aluminium wires or bonding pads. This corrosivity has been demonstrated for the complex of boron trifluoride and monoethylamine. In the specification NSA 77-25A, small dots of adhesive are applied to the aluminized side of a Mylar polyester film and allowed to stand in the room ambient without cure. After 48 h the dots are removed from the film by washing with acetone and the requirement is that there are no changes in the light transmission of the film. 

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