Preparation and properties of cellulose/silica hybrid composites

Abstract

Cellulose/silica hybrid (CSH) composites were prepared from bleached Eucalyptus globulus kraft pulp or primary treatment sludge cellulose fibers by a sol–gel method, using solely tetraethoxysilane or with the addition of trimethoxyoctylsilane as the silica precursors and heteropoly acid (H3PW12O40) as the catalyst. Silica aging was accomplished during the hot pressing of preformed CSHs plates, and the properties of the resulting materials have been evaluated. The incorporation of a silica network in cellulosic materials increased their dimensional stability significantly during soaking in water, hydrophobicity, thermal stability, and bending strength. The thermal conductivity of these hybrid materials is comparable to commercially available insulation foams. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Silica modified cellulosic aerogels

“…Goncalves et al, for example, used fluorosiloxanes as silica precursor to get superhydrophobic surfaces (Goncalves et al 2008). Other studies dedicated to hybrid silica/ cellulose xerogels and fibres evidenced the possible improvement of thermal and mechanical properties by silica modification (Amarasekara and Owereh 2009;Barud et al 2008;Goncalves et al 2008;Hou et al 2009;Kulpinski 2005;Love et al 2008;Maeda et al 2006;Pinto et al 2008;Sequeira et al 2009;Sequeira et al 2007;Tanaka and Kozuka 2004;Xie et al 2009;Yano et al 2008). Acid-catalyzed hydrolysis of tetraalkoxysilanes, in particular tetraethoxysilane, and subsequent condensation of the intermediary formed silanols is obviously the most commonly used approach for silica reinforcement (Maeda et al 2006;Sequeira et al 2007;Yano et al 1998).…”

Chapter 14. Cellulose and Protein Aerogels for Oil Spill Cleaning, Life Science and Food Engineering Applications

“…79,80 The thermal conductivities of the silica-cellulose aerogels (0.0385-0.0410 W mK À1 ) were lower than those of the silica-cellulose composites fabricated by other groups (0.15 W mK À1 ), and comparable to those of conventional insulation materials, such as polyurethane foams (0.02-0.04 W mK À1 ) and insulation boards (0.035-0.16 W mK À1 ). 81 As shown in Figure 14.10, it is clear that the thermal stability of the composite was better than that of the pure cellulose aerogel without the silica which is greater than that of the composite. This smaller weight loss from the desorbed water was due to the super-hydrophobicity of the composite.…”

Cellulosic and Polyurethane Aerogels

“…Very recently, some cellulose/silica hybrids have been prepared by a sol-gel method using pulp fibers as the cellulose source and tetraethoxysilane (TEOS) as the silica precursor, in the presence of heteropoly acids [67]. The resulting hybrid materials exhibit covalent silica/cellulose bounded together with physical interactions [68]. A similar cross-linking approach with lignin can also be found in the literature [69].…”