In the present study the reaction of heterogeneous acetylation was applied to sugar cane bagasse. The product of heterogeneous acetylation was characterized using: (a) Fourier transformed infrared (FT-IR) spectroscopy based on the presence of the C=O stretch band of the carbonyl group (around 1740 cm(-1)), (b) wide angle X-ray scattering (WAXS) based on the presence of a maximum in the region of 2 theta between 5 and 10 degrees, and (c) differential scanning calorimetry (DSC) based on the presence of an endothermic peak at approximately 300 degrees C. The acetate produced was cast into films and the water flux was measured by the cup technique of Payne. The water flux through films of 50 mu m was (9.10+/-0.06) x 10(-7) g s(-1) cm(-2).