THE CHEMORHEOLOGY OF PHENOL-FORMALDEHYDE THERMOSET RESIN AND MIXTURESOF THE RESIN WITH LIGNIN FILLERS

The chemorheology of phenol-formaldehyde (PF) resin, PF mixed with amm onium salt lignosulfonate (ALS) filler, and PF mixed with methylolated ALS (MALS) filler was studied in order to characterize their isotherm al cure behaviours. The results show that both ALS and MALS have a low er reactivity than PF and act as diluents in the resin. The cure rate of the resin decreases when increasing the ALS or MALS content in the PF. In addition the cure rate constant increases when PF is mixed with ALS and decreases when PF is mixed with MALS. These results are in ag reement with those obtained from differential scanning calorimetry (d. s.c.) studies. The viscosity can also be expressed as a function of th e cure degree, which is calculated from the kinetic parameters of the d.s.c. measurements by using the Williams-Landel-Ferry (WLF) equation. This expression gives a better calculated profile than does the dual Arrhenius model, in particular for PF mixed with filler, above the gel point.