THERMODYNAMICS OF MOISTURE SORPTION BY THE GIANT-TIMBER BAMBOO

The thermodynamic interaction of water with giant-limber bamboo (Phyll ostachys bambusoides Sieb. & Zucc.) was investigated. Thermodynamic pr operties were evaluated based on isosteric calculations from sorption isotherms at 20, 30, 40 and 50 degrees C. The results show that, compa red to wood, giant-timber bamboo exhibits less hygroscopicity and grea ter hysteresis. The differential heat of sorption, Q(5), was found to be an exponential function of fractional moisture content, m, and decr eased somewhat with increasing temperature. The relation Q(s) = (Q(s)) (0) exp(-B(1)m) was considered to be reasonably adequate, but a better fit was provided by the equation Q(s) = A(2) + B(2)m + C-2 exp (-D(2) m) so that it was used in the calculation of the heat of wetting, W, a nd the integral heat of sorption, (W-0 - W). The differential heat of sorption at ovendry condition fell within the range observed for wood and other lignocellulosic materials. The free energy, G(s), and the en tropy, S-s, of sorbed water were in close agreement with those observe d for wood, reconfirming the theory that definite enthalpy, free energ y, and entropy changes accompany the sorption of water by lignocellulo sic materials.