Flame-retarding materials, 3 - Tailor-made thermal stability epoxy curing agents containing difunctional phosphoric amide groups

Four different phosphoric amides, p-phenyl-, phosphonic diamide (2-NH2-PH), phenylphosphonic-, bis(N-butylamide) (2-BU-PH), phenylphosphorobis(N- buty lamide) (2-BU-PHO) and phenylphosphonicbis(N-benzylamide) (2-BZ-PH), have b een successfully synthe- sized by low temperature condensation and characte rized, by FT-IR, H-1 NMR and P-31 NMR. These phosphoric, amides have been u sed to cure commercially available unmodified, liquid epoxy resins. The cur ing behaviors and thermal stability of the cured films have been studied. C omparing the curing temperatures (initial (T-i), peak (T-p), and final (T-f )) and the degree of curing, it has been,, observed that using the curing a gent containing bulks, groups i.e., more sterically hindered structure, res ults in higher curing temperatures but a lower degree of curing, When compa ring 2-BU-PHO, which contains a phenoxy group, with 2-BU-PH containing a ph enyl group in the, back bone, it is interesting to note that the phosphorus content in 2-BU-PHO is lower (4.81%) than that of 2-BU-PH (4.93%), but the residual weight percent at 800 degreesC (R-800) and also the temperature n eeded to obtain 10% weight loss (T-0.1) is significantly higher for 2-BU-PH O cured epoxies. Also the results from 2-BZ-PH, which unlike 2-BU-PH contai ns aromatic benzyl groups, indicate, that the aromaticity of the curing age nt does not affect the thermal stability of the cured polymer film.