Effects of alkali pretreatment on surface properties and green color conservation of moso bamboo (Phyllostachys pubescens Mazel)

Standing bamboo culms have an attractive greenish skin. Once harvested, however, they turn yellow and the color starts to decay. These adverse properties limit their applications and degrade their performance. Chromated copper arsenate (CCA) based preservatives have been reported to be good protectors for preserving the green color of bamboo culms. An alkali pretreatment was required before applying CCA. However, the mechanism of alkali pretreatment on color conservation is not fully understood. In this study, morphology, wettability, chemical and pigment changes of moso bamboo (Phyllostachys pubescens Mazel) were studied after treating with four alkali reagents. The results showed that 2% KOH effectively removed the waxes and capes of silica cells on moso bamboo surface and also increased the surface wettability much better than treatments with 4% K2CO3, 10% K2CO3, 4% Na2CO3, or 4% NaHCO3. The KOH pretreatment also results in a better penetration and reaction with the green color protector (5 % Boliden K-33, type-B CCA), and subsequently preserved the green color appearance of moso bamboo.