Effects of chromated-phosphate treatment process on the green color protection of ma bamboo (Dendrocalamus latiflorus)

Abstract

Ma bamboo (Dendrocalamus latiflorus Munro) treated with chromated phosphate (CP) exhibits an excellent green color. To understand the effects of the treatment sequence of CrO₃ and H₃PO₄ and their interactions regarding green color protection, CrO₃-H₃PO₄ and H₃PO₄-CrO₃ two-step treatments plus a H₃PO₄-CrO₃-H₃PO₄ three-step treatment were carried out in this study. Results revealed that the treatment sequence of CrO₃ and H₃PO₄ definitely affects the effectiveness of bamboo color protection. Green color protection of ma bamboo culm could not be achieved by treating it with CrO₃ or H₃PO₄ alone or with the H₃PO₄-CrO₃ two-step treatment. Only by treating it with the CrO₃-H₃PO₄ two-step treatment or the H₃PO₄-CrO₃-H₃PO₄ three-step treatment did ma bamboo exhibit an excellent green color. The results indicated that bamboo reacts first with CrO₃ and then forms an insoluble complex with H₃PO₄, which produces the green color on its epidermis. Chlorophyll analyses demonstrated that chlorophyll is not a key factor for green color protection. The green pigment was also formed when chlorophyll-free bamboo was treated with 2% CP at 60°C for 3h.