Chemistry of Novolac/Furfuryl Alcohol Resins Cured with Hexamethylenetetramine: A Solid-State NMR Study
1998; American Chemical Society; Volume: 10; Issue: 7 Linguagem: Inglês
10.1021/cm9800175
ISSN1520-5002
AutoresXiaoqing Zhang, David H. Solomon,
Tópico(s)Epoxy Resin Curing Processes
ResumoThe chemical processes involved in the reactions between novolac resins, furfuryl alcohol (FA), and hexamethylenetetramine (HMTA) have been studied by solid-state NMR spectroscopy. A highly cross-linked homogeneous network which incorporates both novolac and furan entities is formed. The initial reaction below 90 °C is between the novolac and HMTA and produces mainly benzoxazine and benzylamine intermediates. When the temperature is increased to 90−120 °C, FA reacts with these initially formed intermediates to generate methylene-linked novolac/furan structures as the major products. Minor amounts of nitrogen-containing structures are also formed. In the absence of HMTA, only a minor amount of cross-reactions occur between novolac and FA, and cross-linked structures are not formed. The curing reactivity and chemical structures of the finally cured materials can be controlled through variation of the HMTA ratio, FA content, and curing conditions.
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