Study on Photo Aging Differential among Inner, Outer, and Middle Layers of Moso Bamboo (Phyllostachys pubescens Mazel)

Abstract

Abstract To better understand the photo weathering characteristics of different parts of bamboo culms, Moso bamboo (Phyllostachys pubescens Mazel) was divided into three layers from the outmost side to the inside along the radial direction and then radiated by ultraviolet (UV) light for 56 days. The lignin content on top surface was accurately measured by the acetyl bromide method and degree of crystallinity was analyzed by X-ray Photoelectron Spectroscopy (XPS) before and after UV aging. Results showed that after UV radiation, the surface color of the outer layer changed the most and turned to dark brown, however, the inner layer and middle layer became more yellowish; the lignin content of each layer all decreased, and the crystalline region increased. The lignin content of the outer layer decreased the least because of its relative high density and less light penetration. The degree of crystallinity of the outer layer bamboo increased the most, and the inner layer was the least. The photo oxidation reaction may occur only in the amorphous region, and it was very difficult for light to break the crystalline region. The crystal lattice structure kept unchanged.