Natural fibers characterization by inverse gas chromatography

Vegetable fibers can be considered as naturally occurring composites, consisting mainly of cellulose, lignin and hemicellulose. Their properties are significantly affected by many factors such as variety, climate, harvesting and maturity, among others. Thus, prior to their application, the fibers should be properly characterized. In the present study, inverse gas chromatography was used to study the surface properties of several cellulosic fibers and the effect of an alkaline treatment. Dispersive surface energy ranged from 38.41 mJ/m2 for piassava to 52.39 mJ/m2 for assai. The studied fibers presented Lewis basic character with a Kb/Ka ratio between 1.27 and 4.00, corresponding to curaua and pita Mexicana, respectively. Based on the obtained linear adsorption isotherms, the surface area and monolayer capacity were higher for piassava. Pita Mexicana appeared to be the most heterogeneous one, with two energetic sites. The alkaline treatment of sisal increased the number of active sites for specific interactions, significantly increasing its basic character. It also increased its surface area, with a consequent decrease in the diffusion coefficient.