Browsing by Author "Ferreira, P. J."
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Item Surface Energy and Lewis Acid-base Characteristics of Lignocellulosic Fibers upon Modification by Chemical Vapor Deposition of Trichloromethylsilane: An Inverse Gas Chromatography Study: An Inverse Gas Chromatography Study(2018-05-04) Gamelas, J. A. F.; Azpeitia, M.; Ferreira, P. J.; Tejado, A.; VALORIZACIÓN DE RESIDUOS; BIOECONOMÍA Y CO2The surface of a thermomechanical pulp (TMP), containing 26 wt% of lignin, was modified by silanization with trichloromethylsilane (TCMS) via chemical vapor deposition, and thoroughly analyzed for its physicochemical properties by inverse gas chromatography (attenuated total reflection-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy being used as complementary tools). For a 2-min TCMS-treated TMP, a decrease of the dispersive component of the surface energy from 38 to 14 mJ m−2 (at 40°C), and, at the same time, an increase of the Lewis acidic and Lewis basic characters were found. The surface of this sample, modified in a high extent, was similar to that of a bleached kraft pulp (<0.1 wt% of lignin) subjected to the same silanization process, which is suggested as being due, in both cases, to the formation of a methyl-silica coating on the fiber’s surface. The new silanized fibers obtained from cheap TMP can be used for the production of a new generation of biocomposites with a variety of matrices.Item Unique combination of surface energy and lewis acid-base characteristics of superhydrophobic cellulose fibers(2017-01-31) Gamelas, J. A.F.; Salvador, A.; Hidalgo, J.; Ferreira, P. J.; Tejado, A.; Tecnalia Research & Innovation; BIOECONOMÍA Y CO2Cellulose fibers were first functionalized on their surface by silanization with trichloromethylsilane in an optimized gas-solid reaction, and the occurrence of the reaction was assessed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Then, the changes in the physicochemical surface properties of the material were thoroughly assessed using inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy as surface specific tools. A very surprising combination of results was obtained: (i) the dispersive component of the surface energy was found to decrease from 42 to 14 mJ m-2 (at 40°C), the latter figure representing one of the lowest values ever reported (by IGC) for cellulose-based materials, and (ii) both Lewis acidic and Lewis basic characters of the fiber surface, as measured by the injection into the IGC columns of 15 different vapor probes, significantly increased with silanization. Moreover, those remarkable changes in the surface properties of the material were obtained at a low degree of silanization (as shown by ATR-FTIR). The present results may have a great impact in what concerns the application of the described type of superhydrophobic cellulose fibers for the production of new biocomposites: an unusual enhanced compatibility both with low-surface energy polymeric matrices, such as polyolefins, as well as with other types of matrices through Lewis acid-base interactions, can be predicted. (Graph Presented).