LOCATION OF THE ANTIPLASTICIZER IN CROSS-LINKED EPOXY-RESINS BY H-2, N-15, AND C-13 REDOR NMR

Carbon-13 rotational-echo double-resonance (REDOR) NMR with N-15 or H- 2 dephasing, combined with N-15 REDOR NMR with C-13 dephasing, has bee n obtained for a fully cross-linked epoxy resin prepared from a nomina lly uniform mixture of two parts of diglycidyl ether of Bisphenol A, o ne part of hexamethylenediamine, and 19% (by weight) antiplasticizer m ade from a carbonyl-C-13-labeled aromatic acetamide. The antiplasitici zer contains the hydroxypropyl ether moiety of the epoxy repeat unit. A partially cross-linked resin was formed from five parts of epoxide, one part of hexamethylenediamine, three parts of hexylamine, and 19% ( by weight) antiplasticizer. Labels were introduced into the resin by r eplacing both methyl groups of the isopropylidene moiety of Bisphenol A with CD3 groups and by using [N-15(2)]hexamethylenediamine and [N-15 ]hexylamine (and their unlabeled counterparts) in various combinations . The antiplasticizer C-13-carbonyl carbon is 4.9 +/- 0.5 Angstrom fro m an amine N-16 (With no preference for free or cross-linked sites) an d 6.7 +/- 1 Angstrom from a quaternary carbon of the isopropylidene mo iety.