Structural, thermal and rheological behavior of a bio-based phenolic resin in relation to a commercial resol resin

A commercial phenolic resin and a bio-based phenolic resin formulated partially substituting phenol by a methylolated softwood ammonium lignosufonate were studied to characterize their structural, thermal and rheological properties. The structures of the resins and the modified and non-modified lignosulfonates were studied by FTIR, showing a similar structure for both resins and higher reactivity for the modified lignosulfonate than for the non-modified. The curing heats of both resins were obtained by DSC, showing a reduced reactivity of the lignin-resol due to the incorporation of lignosulfonates. The thermal stability of lignin-phenolic resin studied by TGA was enhanced with respect to that of the commercial resin due to the high thermal stability of lignosulfonate used in its formulation. The addition of lignosulfonates modified the rheological behavior of resol resin changing its flow behavior from Newtonian to pseudoplastic. Rheological behavior of both resins were modeled by applying the experimental data to several models. (C) 2012 Elsevier B.V. All rights reserved.