Modification of Kraft wood pulp fibre with silica for surface functionalisation

Abstract

A new science strategy was devised in which glass surface properties would be imparted to woodderived fibre so that the enhancements known from addition of silane reagents to glass fibre-polymer composites could be realised for modified cellulose fibre-polymer composites. A process is described whereby the internal void spaces and micropores of never-dried Kraft pulp fibre walls were impregnated with silica, without substantially affecting the fibre integrity. This was achieved by initial dehydration of never-dried fibre through azeotropic distillation to achieve substitution of fibre water with the silicon chemical over a range of concentrations. Specific chemical reaction of the prepared fibre with the novel reagent ClSi(OEt) 3 (which is more reactive than Si(OEt) 4 ) was followed by base-catalysed hydrolysis of the ester groups to form a fibre-bound silica composite. As a result of this process, Kraft fibres were stiffened and made resistant to collapse. The physico-chemical substitution of water from micropores and internal voids of never-dried fibre with property-modifying chemicals offers possibilities in the development of new fibre characteristics, including fibres which may be hardened, plasticised, and/or stabilised against moisture, biodegradation or fire. The embedded silica may also be used as sites of attachment for coupling agents to modify the hydrophilic character of the fibre or to functionalise the fibre surface.

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).…”

The effect of alkaline–silane treatment of rubberwood flour for water absorption and mechanical properties of plastic composites

“…3,17,24 When the RWF had alkaline–silane treatment at 5% silane concentration for 2 h, a peak around 1035 cm −1 was observed due to the stretching of Si–O–C and Si–O–Si bonds around 1030–1200 cm −1 . 3,18,21,25,26 This peak does not change much because it is overlapped by C–O and C–O–C stretching vibrations of cellulose. 3 However, the result reveals silane presence on the RWF surfaces.…”

Mechanical, thermal, and morphological properties of PLA biocomposites toughened with silylated bamboo cellulose nanowhiskers

“…Qu et al employed 0.5–2.0 v/v% silane coupling agent (A‐174) to modify CNW, and found the ideal effect at 1.0 v/v% content; Saini et al investigated the A‐1100 silane coupling agent in different concentrations of alcohol‐aqueous and acetone solutions, and the suitable concentration was 50 g·L −1 . Coupling agents are generally silicon compounds with functional groups that can react both with silanol surfaces on nanowhiskers and with functional groups on PLA by forming C‐O‐Si silicate ester bonds, or otherwise interact with PLA through mechanical and/or physical (e.g., van der Waal's forces) mechanisms . Although application of silane coupling reagents for improvement of wood‐cellulose‐fiber/polymer composites dates from 1983 and the effectiveness of them on improvement of surface property is proved , there is a paucity of fundamental knowledge of the reactivity of various types of coupling reagents with BCNW.…”

“…Coupling agents are generally silicon compounds with functional groups that can react both with silanol surfaces on nanowhiskers and with functional groups on PLA by forming C‐O‐Si silicate ester bonds, or otherwise interact with PLA through mechanical and/or physical (e.g., van der Waal's forces) mechanisms . Although application of silane coupling reagents for improvement of wood‐cellulose‐fiber/polymer composites dates from 1983 and the effectiveness of them on improvement of surface property is proved , there is a paucity of fundamental knowledge of the reactivity of various types of coupling reagents with BCNW. Thus, a comparative study and characterization on the improvements of commercial available silane coupling agents on the PLA composites remains a necessary investigation.…”