The purpose of the research was to study the influence of H2O2 on the properties of fluid phenolic (PF) resin, the curing process, the cured resin structure, and the properties of the particleboards produced with its use. The influence of added H2O2 on resin usability at 20degreesC, on the gel time of the modified PF resin in the temperature range 110-140degreesC, and on the activation energy of the curing process were studied. Also, the structure of the cured resin was examined by Fourier transform infrared spectroscopy. Finally, the properties of the obtained particleboards were determined. The results indicate that the H2O2 modification leads to greater reactivity of the phenolic resin and increases the mechanical properties of particleboards. In contrast, there is no significant influence of H2O2 on the water resistance of the particleboards. (C) 2003 Wiley Periodicals, Inc.