Effects of microwave-assisted softening treatment on dynamic mechanical properties and chemical composition of bamboo

In response to the global plastic pollution crisis, a sustainable manufacturing strategy for replacing plastic with bamboo is proposed. Bamboo softening treatment is important for bamboo processing. In this study, the effects of microwave-assisted alkali/boiling treatment on the microstructure, chemical composition, glass transition temperature, compression ratio, and surface wettability of the bamboo species Phyllostachys edulis and Dendrocalamus sinicus were studied. Microwave-assisted alkali (0.1 % NaOH)/boiling (2 h) treatment increased the flexibility and processability of both species. Dynamic mechanical analysis showed that the storage modulus of P. edulis slices was reduced from 6429 MPa to 5128 MPa, loss modulus was reduced from 134.1 MPa to 100.6 MPa, and glass transition temperature was reduced from 204.25 degrees C to 100.39 degrees C indicating that bamboo stiffness was reduced and elasticity was enhanced. With the temperature increase, the alkali solution destroyed the dense fiber structure and broke the bonds between lignin, cellulose, and hemicellulose. The glass transition temperature decreased in P.edulis by 103.86 degrees C, which was 1.14-times higher than that of D. sinicus, and the compression ratio increased form 10.52-37.58 %, which indicated better thermoplasticity compared with D.sinicus. The vascular bundles and thin-walled cells of the specimens showed different degrees of shrinkage and deformation, and the hydrophobicity of bamboo increased resulting in improved thermal stability and optimal process conditions, providing an effective solution for the realization of replacing plastic with bamboo. This lays the theoretical foundation for subsequent furniture-bending components and molded products.