Incorporation of carboxyl groups into xylan for improved absorbency

Abstract

The objective of this research was to investigate green, renewable reaction systems for xylan that introduce crosslinking and carbonyl group for improved performance in water absorption applications. Xylan was modified separately with three different reaction agents, citric acid, succinic anhydride and sodium monochloracetate (SMCA). The xylan was reacted with citric acid in the presence or absence of sodium hypophosphite (SHP) as a catalyst, both in a solution form and in a semi-dry form in an oven. Acidbase titrations, FTIR, TGA, and DSC were used to confirm the composition of the reactant products. Reacted xylan had significantly increased carboxyl content, degree of esterification and degree of substitution with citric acid, succinic anhydride, and sodium monochloracetate. Effective reaction conditions were determined for high yield products. For the xylan reacted with citric acid, the catalyst (SHP) and the use of a semi-dry reaction condition increased the yield significantly. Succinic anhydride and SMCA had high yields. The reaction trends observed were consistent with similar results for starch. Increases in water absorption, saline solution absorption, and decreases in water contact angle for the xylan citrate relative to the xylan indicate that high carboxyl content materials can be generated with xylan and that the resulting materials have enhanced water affinity.

Fluorine-based surface decorated cellulose nanocrystals as potential hydrophobic and oleophobic materials

“…5. Weight loss below 100°C was due to water evaporation; however, the weight loss above 100°C was caused by the thermal decomposition of the cellulose nanocrystals and fluorinated cellulose nanocrystals (Salam et al 2011). Cellulose nanocrystals have a single weight loss peak at 329.96°C, whereas polyfluorinated cellulose nanocrystals have a significant decrease in maximum weight loss temperature (286.38°C) and a significantly higher residual mass (18.5 %) after heating to 600°C.…”

Enhanced Absorbent Products Incorporating Cellulose and Its Derivatives: A Review

“…Their work with measurement of ion diffusion rates, in addition to freeze-fracturing of hydrogels, led to the conclusion that the bulk-like water within hydrogels tended to be confined to isolated "lakes" within the pore structure. This finding suggests that various reported porous hydrogels or "foams" might be expected to contain substantial bulk-like water in addition to chemically bound water (Kabra et al 1998;Omidian et al 2005;Lu et al 2007;Chang et al 2009a,b;Sehaqui et al 2010;Salam et al 2011a). Joshi et al (2008) proposed that the relatively sharp gelation transition that takes place upon heating of methylcellulose solutions can be attributed to a thermal breakdown of the water structure, allowing coalescence of the polymer chains.…”

“…A second factor that contributes to the hydrophilic nature of hemicelluloses is the content of carboxyl groups, which can dissociate to the carboxylate form at intermediate to high conditions of pH (Lindström and Carlsson 1982). Indeed, Salam et al (2011a) showed that hemicellulose could be rendered even more hydrophilic by derivatizing it to further increase the content of carboxyl groups.…”

“…The importance of hemicellulose was also shown by Laine and Stenius (1997), who demonstrated a positive relationship between fiber ionic charge and swelling with water. Recently several researchers have attempted to take advantage of the hydrophilic nature of hemicelluloses by using them as a key component of highly absorbent hydrogels (Gabrielli and Gatenholm 1998;Gabrielli et al 2000;Meena et al 2011;Peng et al 2011;Pohjanlehto et al 2011;Salam et al 2011a;Yang et al 2011;Karaaslan et al 2010Karaaslan et al , 2011Karaaslan et al , 2012.…”

“…Thus, the goal of this review is to highlight published literature regarding enhanced absorbent materials and products that incorporate various forms of cellulose or its derivatives. Main sections are shown in the following table of contents: (Yoshinobu et al 1992;Kabra et al 1998;Omidian et al 2005;Lu et al 2007;Chang et al 2009a;Zamani et al 2010;Salam et al 2011a). However, even without employing SAP technologies (see later), it has been shown that substantial absorbency can be achieved by suitable preparation of highly porous cellulose or its chemical derivatives.…”