Effect of drying temperature on the curing properties of phenolic resin-impregnated heat-treated bamboo bundles

Abstract

ABSTRACT Unreasonable drying temperatures may lead to precuring of phenolic (PF) resin-impregnated heat-treated bamboo bundles before hot-pressing, which is detrimental to the bonding performance of the bamboo scrimber during hot-pressing. In this study, PF resin-impregnated heat-treated bamboo bundles were dried at 50°C, 60°C, and 70°C for 16 h (PHB50, PHB60, and PHB70) and then prepared into bamboo scrimber (BS50, BS60, and BS70) by hot-pressing. The relationship between the curing properties of the PHBwet after drying and the water uptake of BS specimens was analyzed, which showed that the water uptake of BS was inversely proportional to the drying temperature. The curing degrees of the PHB50, PHB60, and PHB70 were 27%, 58%, and 60%, respectively. The water uptake of BS50, BS60, and BS70 after 24 h immersion in room-temperature water was 5%, 11%, and 19%, respectively, resulting in thickness swelling rates of 1%, 2%, and 4%. Compared with BS50, the cross-section of BS70 broke more easily during the cyclic treatment and showed more cracks afterward. The relative contents of C–O bonds and hydroxymethyl groups decreased, indicating that the PHB specimens underwent pre-curing at higher drying temperatures, which inhibited interfacial bonding during hot-pressing.