A LIGNIN-PHENOL-FORMALDEHYDE BINDER FOR PARTICLEBOARD .1. THERMAL-CHARACTERISTICS

The thermochemical behaviour of lignin-phenol-formaldehyde blends have been investigated through Differential Scanning Calorimetry. The lignin is a residue from furfural extraction of bagasse. Simple mechanical blends, mixed in water and freeze-dried, were used. Phenol-formaldehyde was replaced at a level up to 40%. The formulation of the PF resin was adjusted to take into account and compensate for the rise in viscosity due to the added lignin. The kinetics of the cure reaction can be characterized by the energy of activation and the overall energy produced by the cure as the enthalpy of polymerization. The lignin does not change much the energy of activation.Thus, the polymerization proceeds at the same rate with up to 40% lignin in the blend. However, the enthalpy of polymerization is lower with increasing lignin content, and at the 40% replacement level, is half that of the pure phenol-formaldehyde. The enthalpy of polymerization, rather than the energy of activation, seems to correlate better with the mechanical properties of the particleboard made with such resins.