13C CP/MAS NMR study of a wood/phenol–formaldehyde resin bondline

The dynamics and interactions of a wood powder/phenol–formaldehyde (PF) resin composite are evaluated by solid-state 13C NMR. A 13C labeled and perdeuterated PF resin, with low molecular weight distribution, is synthesized and cured in the neat state and also in combination with yellow-poplar wood powder. The 13C NMR spectral features and cross-polarization dynamics of the PF hydroxymethyl and methylene nuclei are compared in the neat resin and in the wood powder composite. In the composite, a downfield shift of the PF hydroxyl bearing carbons suggests secondary interactions between the PF resin and wood. In addition, the PF resin methylene and hydroxymethyl carbons exhibit slower CP dynamics compared to the neat resin. Lower resin CP rates in the composite indicate lower molecular rigidity of the resin in presence of wood compared to the neat cured PF resin.