ACIDITY AND SOLUBILITY OF RUBBERWOOD AND THEIR IMPACTS ON THE CURING BEHAVIOUR OF UREA– FORMALDEHYDE RESIN

Abstract

In this study, effects of rubberwood acidity and catalyst content on curing behaviour of urea–formaldehyde (UF) resin were investigated. Various types of rubberwood raw materials, namely, wood without bark, wood with bark, bark and pressure-refined fibres were measured for pH and buffer capacity. Their solubility extractives were also determined. There were significant differences between raw materials. Bark had the highest pH and buffer capacity. Bark also had the highest extractive content. Hot water solubility, cold water solubility, 1% NaOH solubility, alcohol–benzene solubility and ash content were significantly correlated with buffer capacity, while only ash content was correlated with pH. Addition of catalyst decreased peak temperature but increased the reaction enthalpy of UF resin. This influence was not evident in higher level of added catalyst because further increase had little effects.