Inhibiting round bamboo cracking under high-temperature by cell level modification with polyethylene glycol

Moisture content within round bamboo would rapidly convert into steam due to the rapid heat transfer by the thin wall under high temperature; however, its evaporation is restricted by the densified outer skin, causing bamboo cavities to crack. Additionally, due to the longitudinal and radial heterogeneity of round bamboo, rapid changes in moisture content can cause uneven cellular contraction, leading to wall cracking. In this study, the multi-pore structure of round bamboo was permeated with polyethylene glycol (PEG) to interrupt heat transfer and moisture evaporation using ethanol as a rapid transmission medium. The cracking behavior of round bamboo under high temperatures was investigated in sub-model featuring varying heights and node types. After modification with a PEG-ethanol solution and drying at 120 °C, the bamboo culm exhibited excellent dimensional stability without cracking, the bamboo wall showed almost no shrinkage from saturated moisture content to absolute dry moisture content, while the shrinkage rate of the control bamboo was 7.16 %. PEG modification slowed down the temperature increase in the bamboo cavity during the pre-drying period and reached the maximum at 2 h. Scanning electron microscopy showed that cellular shrinkage and deformation were inhibited by PEG filling. PEG only underwent physical permeation. Fourier transform infrared spectroscopy revealed no chemical reaction between PEG and bamboo. Notably, round bamboo samples of varying heights and node types all exhibited 100 % high-temperature crack resistance after modification with the PEG-ethanol solution. Since PEG is inexpensive, chemically stable, and environmentally friendly, this study provides a practical technical solution for processing round bamboo and its application in green buildings and furniture. • Modified bamboo of different heights and node types with 100 % high-temperature crack resistance. • The wall of modified bamboo showed almost no shrinkage from saturated moisture content to absolute dry. • The variation of relative humidity and temperature in the bamboo cavity was tracked. • The PEG in this study physically thickened the cell wall and inhibited drying shrinkage. • The permeability of PEG in round bamboo was enhanced by ethanol at atmospheric pressure.