Browsing by Author "Gouveia, C."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Investigation of surface properties of physico-chemically modified natural fibres using inverse gas chromatographyPublication . Cordeiro, N.; Gouveia, C.; John, M. JacobInverse gas chromatography (IGC) is a suitable method to determine surface energy of natural fibres when compared to wetting techniques. In the present study, the surface properties of raw and modified lignocellulosic fibres have been investigated by IGC. The fibres chosen for the study were flax, hemp, kenaf, agave, agave hybrid, sisal and pineapple. The treatments used were 4% NaOH and 2% zein. The uniqueness of zein treatment is that it is bio-based and therefore maintains the biodegradable character of the natural fibres. Fourier transform infrared spectroscopy (FTIR) and environmental scanning electron microscope (ESEM) were also performed to characterize the surface changes in fibres. The surface properties of fibres are influenced by the chemical composition, crystallinity and morphology of the fibres. Bast fibres exhibited higher surface dispersive energy than leaf fibres. The raw fibres have a predominant basic character, whereas the alkaline treatment makes the fibres more acidic. Both alkaline and zein treatments decrease the dispersive surface energy and the specific free energy of adsorption.
- Natural fibers characterization by inverse gas chromatographyPublication . Cordeiro, N.; Gouveia, C.; Moraes, A.G.O.; Amico, S.C.Vegetable fibers can be considered as naturally occurring composites, consistingmainly 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.