Comparison of colors, microstructure, chemical composition and thermal properties of bamboo fibers and parenchyma cells with heat treatment

Jieyu Wu,Jiangjing Shi,Hong Chen,Tuhua Zhong,Benhua Fei,Wenfu Zhang

doi:10.1186/s10086-021-01988-2

Abstract

The effects of heat treatment at various temperatures on mechanically separated bamboo fibers and parenchyma cells were examined in terms of color, microstructure, chemical composition, crystallinity, and thermal properties. The heat-treated parenchyma cells and fibers were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), chemical composition analysis, and thermogravimetric analysis (TGA). The results revealed that the colors of bamboo fibers and parenchyma cells were darkened as treatment temperature increased. The microstructure of the treated fibers and parenchyma cells slightly changed, yet the shape of starch granules in parenchyma cells markedly altered at a temperature of above 160 °C. The chemical compositions varied depending on the heat treatment temperature. When treated at 220 °C, the cellulose content was almost unchanged in fibers but increased by 15% in parenchyma cells; the hemicellulose content decreased and the lignin content increased regardless of fibers and parenchyma cells. The cellulose crystal structure was nearly unaffected by heat treatment, but the cellulose crystallinity of fibers changed more pronouncedly than that of parenchyma cells. The thermal stability of parenchyma cells after heat treatment was affected more substantially compared to fibers.

Highlights

Bamboo powder has been considered as one of the most suitable fillers for plastic composite because of their impressive features, for example, renewable, cost-effective, environmentally benign, and high modulus yet low density [1]
The results indicated that the heat-treatment temperature played a critical role in influencing fibers and parenchyma cells in terms of color, microstructure, chemical composition, and thermal stability
The difference in the change between the heat-treated parenchyma cells and the treated fibers was compared: (1) The colors of fibers and parenchyma cells were darkened after heat treatment, and the extent of the darkness between parenchyma cells and fibers treated with the heat at different temperatures was similar

Summary

Introduction

Bamboo powder has been considered as one of the most suitable fillers for plastic composite because of their impressive features, for example, renewable, cost-effective, environmentally benign, and high modulus yet low density [1]. Bamboo plastic composites have been widely used for flooring, furniture and so on [2, 3]. To further reduce water absorption and improve mechanical properties, bamboo powder is usually pretreated with acid, alkali, coupling agent, carbonize, etc. Bamboo fibers and parenchyma cells have an apparent discrepancy in microstructure, chemical composition, and performance [12, 13]. Bamboo fibers had higher cellulose and lignin contents, but lower hemicellulose content when compared with parenchyma cells [14]. The cellulose crystallinity in fibers was higher than that of parenchyma cells

Methods

Results

Conclusion