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Studies on the reaction pathways involved in the curing of novolac resins with hexamethylenetetramine (HMTA) have been further extended by a 13 C n.m.r. examination of the thermal decomposition of tris(2-hydroxy-3,5-dimethylbenzyl)amine and its reactions with 2,4- and 2,6-xylenol. Both the thermal decomposition and reactions with the xylenols lead to methylene-bridged phenolic structures (for...
The reactions of 2,4-xylenol and 2,6-xylenol, with bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines derived from the reaction of 2,6-xylenol with hexamethylenetetramine (HMTA) were studied as models for the curing of novolac resins. The structural changes during the process were examined by 13 C and 15 N n.m.r. spectroscopy. The results indicate that reactions between bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines...
As part of our study on the curing reactions between novolac resins and hexamethylenetetramine (HMTA), a model benzoxazine, 3-(3,5-dimethyl-2-hydroxybenzyl)-6,8-dimethyl-3,4-dihydro-(2H)-1,3-benzoxazine, was heated under carefully controlled conditions, and the structural changes were studied by 13C and 15N n.m.r. spectroscopy. The benzoxazine structure is relatively stable, and detectable decomposition...
The reaction between 3-(,5-dimethyl-2-hydroxybenzyl)-6,8-dimethyl-3,4-dihydro-(2H)-1,3-benzoxazine and either 2,4-xylenol or 2,6-xylenol was studied by 13C n.m.r. techniques, to model the reactions between benzoxazine intermediates and free ortho- and para-phenolic sites in the curing of novolac resins with hexamethylenetetramine (HMTA). The results indicate that 2,4-xylenol can directly react with...
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