Hemicelluloses, due to their hydrophilic nature, may tend to be overlooked as a component in water-resistant product applications. However, their domains of use can be greatly expanded by chemical derivatization. Research in which hydrophobic derivatives of hemicelluloses or combinations of hemicelluloses with hydrophobic materials are used with to prepare films and composites is considered herein. Isolation methods that have been used to separate hemicellulose from biomass are also reviewed. Finally, the most useful pathways to change the hydrophilic character of hemicelluloses to hydrophobic are reviewed. In this way, the water resistance can be increased and applications of targeted water-resistant hemicellulose developed. Several applications of these materials are discussed.

No abstract

Hemicellulose material is an abundant and relatively under-utilized polymeric material present in lignocellulosic materials. In this research, an alkaline treatment was applied to pinewood (PW), switchgrass (SG), and coastal bermuda grass (CBG) in order to extract hemicelluloses to subsequently produce a novel biosorbent. Alkaline extraction at 75 °C recovered 23% of the biomass as a predominantly hemicellulose material with a number average degree of polymerization of ∼450. These hemicelluloses were grafted with penetic acid (diethylene triamine pentaacetic acid, DTPA) and were then cross-linked to chitosan. The effects of hemicellulose−DTPA concentration, reaction time, and temperature of reaction with chitosan on the resulting salt (sodium chloride, NaCl) uptake and weight loss in saline solutions were determined. A maximum salt uptake for the materials was ∼0.30 g/g of foam biosorbent. The foam biosorbent was characterized by FT-IR spectra, porosity, and dynamic mechanical analysis. Batch adsorption equilibrium results suggest that the adsorption process for salt follows a second-order kinetic model. The hemicellulose-DTPA-chitosan foam biosorbent had uptakes of 2.90, 0.95, and 1.37 mg/g of Pb 2+ , Cu 2+ , and Ni 2+ ions, respectively, from aqueous medium at initial concentrations of 5000 PPB at pH 5. The cross-linked hemicellulose−DTPA− chitosan material has good potential for environmental engineering applications.

Cellulose and some cellulose derivatives can play vital roles in the enhancement of the performance of absorbent products. Cellulose itself, in the form of cellulosic fibers or nano-fibers, can provide structure, bulk, water-holding capacity, and channeling of fluids over a wide dimensional range. Likewise, cellulose derivatives such as carboxymethylcellulose (CMC) have been widely studied as components in superabsorbent polymer (SAP) formulations. The present review focuses on strategies and mechanisms in which inclusion of cellulose -in its various formscan enhance either the capacity or the rate of aqueous fluid absorption in various potential applications.

For commercial success, bioplastics have to possess adequate physical properties. But the same properties of biopolymers — such as starch — that make them environmentally attractive feedstocks can affect their performance as materials. Despite the attractive properties of plant-based plastics, there have been few commercial applications due to their property drawbacks (e.g., high cost, brittleness, and lower impact resistance). Many biopolymers, such as starch, are often hydrophilic and some are even soluble in hot water. These properties have to be managed and controlled through the development of adequate formulations and processing. The primary challenge is to develop fast reactions that can be transformed into viable processes and integrated into existing process lines with economically viable formulations that are friendly to the environment. Cross-linking of starches is the most common method used in polysaccharide chemistry. This article briefly reviews some of the most promising chemistries available for the cross-linking of biodegradable starch materials and their applications.