Boron trifluoride-ethylamine complex

BORON TRIFLUORIDE/ETHYLAMINE COMPLEX (0.4%) Fig. 2. Chemical constituents of Fiberite 934 epoxy resin... 

On another side, the synthesis of the diphosphirenium salt (4d) by treatment of amino-substituted 1,3-diphosphapropene with boron trifluoride-ethylamine complex at room temperature was reported (Equation (11)) <9iJA8i60, 94JA6149). Its structure has been established by x-ray diffraction study and shows a substantial participation of resonance structures and the ionic character of the salt. 

Catalytic curing agents require a temperature of 200°F (93°C) or higher to react. These epoxy formulations exhibit a longer working life than the aliphatic amine cured epoxies. The exothermic reaction may be critically affected by the mass of the resin mixture. Typical materials used include piperidine, boron trifluoride ethylamine complex, and benzyl dimethyl-amine (BDMA). 

In practice the epoxide-amine cure is often accelerated by the addition of catalysts such as boron trifluoride complexes, and the boron trifluoride-ethylamine adduct (BFE) is widely used for this purpose. In addition to catalysing the epoxide-amine reactions, BFE can initiate homopolymerisation of epoxide. The accelerating effect of BFE is illustrated by DSC scans for the TGDDM/DDS/BFE system in Figure 12. The multiple-peaked exotherm associated with the BFE-catalysed TGDDM/DDS cure indicates that the kinetics of this system are more complex than those for the cure with amine alone. For this system the overall heat of reaction was found to decrease with increasing BFE concentration 89). For DDS alone Q0 was about 110 kJ per mole epoxide while the value for BFE alone was 75 kJ/mole, and the DDS/BFE values were between these limits. It appears that the proportion of epoxide homo-polymerisation relative to amine or hydroxyl addition increases with increasing BFE concentration. 

---