Lignocellulose-based fibers, chemical

Chemical modification reactions continue to play a dominant role in improving the overall utilization of lignocellulosic materials [1,2]. The nature of modification may vary from mild pretreatment of wood with alkali or sulfite as used in the production of mechanical pulp fibers [3] to a variety of etherification, esterification, or copolymerization processes applied in the preparation of wood- [4], cellulose- [5] or lignin- [6] based materials. Since the modification of wood polymers is generally conducted in a heterogeneous system, the apparent reactivity would be influenced by both the chemical and the physical nature of the substrate as well as of the reactant molecules involved. 

In cellulosic ethanol production processes, a pretreatment procedure is needed to disrupt the recalcitrant structure of the lignocellulosic materials so that the cellulose can be more efficiently hydrolyzed by cellulase enzymes [2], These pretreatments include physical, biological, and chemical ways, such as uncatalyzed steam explosion, liquid hot water, dilute acid, flow-through acid pretreatment, lime, ammonium fiber/freeze explosion, and ammonium recycle percolation [3, 4], Most of these methods involve a high temperature requirement, which is usually achieved through convection- or conduction-based heating. 

In all plant materials, the major component will be the cellular lignocellulosic material. Several possible uses for this material exist. Some of the more attractive are cattle feed fiber for pulp, paper, and board chemical feedstock or energy (8,1 1,22). Detailed evaluation of the cellular portion should provide bases for suggesting their most appropriate uses. 

In this chapter we have reviewed some of the most important characteristics of cellulose and cellulose based blends, composites and nanocomposites. The intrinsic properties of cellulose such as its remarkable mechanical properties have promoted its use as a reinforcement material for different composites. It has been showed that cellulose is a material with a defined hierarchy that tends to form fibrillar elements such as elementary fibrils, micro fibrils, and macro fibers. Physical and chemical processes allow us to obtain different scale cellulose reinforcements. Macro fibers, such as lignocellulosic fibers of sisal, jute, cabuya, etc. are used for the production of composites, whereas nano-sized fibers, such as whiskers or bacterial cellulose fibers are used to produce nanocomposites. Given that cellulose can be used to obtain macro- and nano-reinforcements, it can be used as raw material for the production of several composites and nanocomposites with many different applications. The understanding of the characteristics and properties of cellulose is important for the development of novel composites and nanocomposites with new applications. 

Ashori et al. [58] used recycled PP and HDPE as matrices for lignocellulosic fiber composite using MAPP as coupling agent. This composite has been used for board preparation. Ardanuy et al. [59] prepared recycled polypropylene-based green foams reinforced with untreated and chemically treated cellulose fibers obtained from agricultural residue. Their results showed that these foams may find potential... 

Plant based natural fibers are lignocellulosic, consisting of cellulose micro fibrils in an amorphous matrix of lignin and hemicellulose. To improve the incorporation of natural fibers into polymers and to have higher fiber/matrix interfacial adhesion, natural fibers can be altered by different physical and chemical treatments. 

Liqnefaction is an effective way to convert lignocellulosic materials into bio-based chemicals. Liqnefaction is a process in which solid biomass is liquefied in organic solvents with or withont catalysts, resnlting in a liquid containing smaller solvent-soluble chemicals that can be nsed directly or from which other products can be derived. Liquefied materials have been made into reactive adhesives, foams, moldings, fibers, carbon fibers, and so on. 

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