Isocyanate curing of novolac-type ligno-phenol-formaldehyde resins

This work proposes the use of a diisocyanate as curing agent for novolac-type lignin-phenol-formaldehyde (LPF) resins, instead of typical hexamethylene-tetraamine (HMTA), with the aim of overcoming the loss of reactivity of lignophenolic resins resulting from the introduction of lignin. Curing LPF resins with methylene-diisocyanate (MDI) and HMTA has been investigated through Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and rheological analysis. The analysis of experimental results shows that the proposed curing reaction with MDI gives similar results to those for HMTA-cured systems. However, MDI curing is faster than HMTA one and proceeds easier at lower temperatures. (c) 2007 Elsevier B.V. All rights reserved.