C-13-NMR study on cure-accelerated phenol-formaldehyde resins with carbonates

Both liquid- and solid-state carbon-13-nuclear magnetic resonance (C-13-NMR ) spectroscopies mere used to investigate the cure acceleration effects of three carbonates (propylene carbonate, sodium carbonate, and potassium carb onate) on liquid and cured phenol-formaldehyde (PF) resins. The liquid-phas e C-13-NMR spectra showed that the cure acceleration mechanism in the propy lene carbonate-added PF resin seemed to be involved in increasing reactivit y of the phenol rings, whereas the addition of both sodium carbonate and po tassium carbonate into PF resin apparently resulted in the presence of orth o-ortho methylene linkages. Proton spin-lattice rotating frame relaxation t ime (T-1 rho H) measured by solid-state C-13 cross polarization/magic-angle spinning NMR spectroscopy was smaller for the cure-accelerated PF resins t han that of the control PF resin. The result indicated that the cure-accele rated PF resins are less rigid than the control PF resin. (C) 2000 John Wil ey & Sons, Inc.