Effect of Hydrothermal Treatment Temperature Thermal Modifications on Physical, Mechanical and Chemical Properties of Bambusa tulda

Abstract

Hydrothermal treatment is an effective modification technique for improving bamboo performance; however, treatment temperature critically influences structural integrity and material properties. This study investigated the effects of high-temperature hydrothermal treatment on the physical, mechanical, and chemical characteristics of Bambusa tulda culms, considering variations among the base, middle, and top sections. Bamboo specimens were treated at 120°C, 140°C, 160°C, and 170°C for 60 minutes under hydrothermal conditions. The mass loss percentages were 5.98%, 5.45%, and 3.5% for the bottom, middle, and top sections, respectively, in the control; 4.2%, 3.4%, and 2.34%, respectively, at 120°C; and 10.67%, 6.68%, and 5.5%, respectively, at 170°C, with the basal section exhibiting the greatest mass loss. Density exhibited a temperature-dependent response, increasing in the basal section after treatment at 120°C (Bottom: 5.22 g/cm3, Middle: 4.13 g/cm3, Top: 2.34 g/cm3) but decreasing markedly at 170°C (Bottom: 2.84 g/cm3, Middle: 2.67 g/cm3, Top: 0.17 g/cm3) due to thermal degradation, especially in the top portion of the bamboo. Mechanical evaluation showed that treatment at 120°C markedly improved the modulus of elasticity (MOE) (Bottom: 27199.9 MPa, Middle: 13025.07 MPa, Top: 9961.41 MPa) and modulus of rupture (MOR) (Bottom: 231.66 MPa, Middle: 105.70 MPa, Top: 93.38 MPa) in the basal section, whereas treatment at 170°C resulted in marked deterioration of MOE (Bottom: 2950.42 MPa, Middle: 5215.37 MPa, Top: 4516.79 MPa) and MOR (Bottom: 37.30 MPa, Middle: 57.02 MPa, Top: 72.31 MPa). Near-infrared (NIR) spectroscopy confirmed molecular modifications through changes in O–H and C–H absorption bands, indicating moisture redistribution and structural alterations within the cell wall. Chemical analysis showed an increase in Klason lignin content and a corresponding decrease in holocellulose content with increasing treatment temperature, reflecting preferential degradation of carbohydrate components. Overall, hydrothermal treatment at 120°C provided the most favourable balance between property enhancement and structural preservation, whereas higher temperatures led to progressive degradation. These findings highlight the importance of optimising hydrothermal treatment conditions according to bamboo culm position and intended application, providing valuable insights for the sustainable utilisation of Bambusa tulda in structural and value-added products.