Effects of microwave drying on the cell wall structures of round bamboo

Abstract

Effects of microwave irradiation on bamboo cell wall structures were studied. Microwave treatment resulted in samples exhibiting smoother surfaces, deformed parenchyma cells, and increased porosity. Microwave treatment altered microfibril orientation through the formation of hydrogen bonds. The peak at 3440 cm-1, assigned to O-H stretching, decreased. Meanwhile, intermolecular and intramolecular bonds were formed, increasing the uniformity of microfibrils. Condensation reactions in surface hydroxyl groups and the formation of intramolecular hydroxyl groups in the amorphous region under microwave irradiation also improved the fiber arrangement uniformity. After treatment, the HCH and HOC bonds were reduced and the ester bonds were broken down. The methoxy and aromatic ring hydroxyl groups were oxidized, as indicated by the increase in the absorption peak at 148 ppm. The hydroxyl groups in the amorphous region near the fiber surface decreased, as did hemicellulose content, but there was an increase in secondary crystalline fibers.