Catalyst composition in prepregs

The catalyst composition in Fiberite 934 and Hercules 3501 prepregs was investigated by 19F NMR. The epoxy resin in these commercial C-fiber/TGDDM-DDS prepregs was dissolved in DMSO. 

The fluorine species observed in five different lots of Fiberite 934 were identified and tabulated in Table 5. A typical spectrum is illustrated in Fig. 6. The catalyst in 

Lots bf3(oh - NH3+C2H5 BF4NHj+C2H5 BFjiNHjCjHj Epoxide-BF3 Products 

We associate the various additional fluorine peaks observed in the NMR spectra with principally the products of epoxide-active fluorine species reactions. The total fluorine in the form of these products is relatively constant from prepreg lot to lot (28.2 to 36.3%). 

The epoxy resin of a Hercules 3501 sample was dissolved in DMSO and investigated by 19F NMR. The 19F peaks associated with BF3 NH2C2H5 were absent and the 1 1 1 1 quartet associated with BF3 NHC5H10 was found at an 19F chemical shift value of — 155.17 ppm. The fluorine distribution among species found in this sample was BF3(OH) NH2+ CjH10 (2.8%), BF4-NH2+C5H10 (9.9%), BF3 NHCSH10 (78.3%), and epoxide-fluorine products (9.0%). 

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