Cellulose-based composites processing

In this chapter, the discussion is focused on the research on cellulose-based polymer composites conducted in some tropical countries in Southeast Asia. Southeast Asia is a subregion of Asia located in the tropical zone, where a variety of plants grow. Hence, there is a high availability of cellulose-based materials found in this area. This situation enhances the attractiveness of research on cellulose-based composites. The reported findings of researchers in Southeast Asia about the processing, properties and apphcation of composites made of commonlyused cellulose-based fibers such as sisal, flax, hemp, ramie, jute, kenaf, etc., are discussed along with many kinds of cellulose-based fibers of interest which have not been reported elsewhere. This chapter is a combination of reviews on some unique ceUulose-based polymer composites in Southeast Asia together with a report on the research conducted by the authors. 

At present, there is one main commercial application of pervaporation, the production of high purity alcohol by a hybrid process which also incorporates distillation. Such separations use cellulose-acetate-based composite-membranes, with an active layer of polyvinyl alcohol, for example. Membrane fluxes are in the range 0.45-2.2 kg/m2 h. Pervaporation... 

The aim of this paper is to present the different properties of polysaccharide composites obtained by the introduction of cellulose fibres, varying in length and content, into plasticized wheat starch. We have used LDPE-based composites as reference, because without compatibilizer, the LDPE-fibres interactions are usually considered as very poor. To highlight the interactions developed between cellulose and starch, we have compared both kinds of composites. Finally, we have evaluated the post-processing ageing of TPS compared to some other systems. 

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. 

Homogeneous asymmetric CAs and polyamides made by the phase inversion process and cross-linked TFC polyamides have been the workhorse of RO plants for more than 30 years [21], Both CA and PA membranes possess an economically viable combination of high rejection and water flux [8]. However, TFC membranes now dominate the RO/NF market with CA membranes a distant second. For example, with the exception of Toyobo CTA polymer, all new seawater RO desalination plants deploy interfacial composite membranes of the fuUy aromatic type manufactured by Dow, Hydranautics (Nitto Denko), Tri-Sep and Toray. Along with the ability to remain stable over a greater pH range than cellulose-based membranes, TFC membranes exhibit much higher intrinsic water permeabilities because of their extremely thin ( 100 nm) polyamide-selective layers [21]. A typical spectrum of TFC membranes for various applications is given in Table 1.8. 

The precursor fiber type for reinforcing the carbon matrix can be an oxidized PAN fiber (opf), or either a PAN or pitch based carbon fiber. In some instances, for special applications, such as the Shuttle, a cellulose based carbon fiber is used. The reinforcements can be unidirectional have a random chopped fiber presentation as in a felt format a woven product from continuous fiber presented in a 2D, 3D, or in a Multi-D format (Section 21.1), or a non-woven carbon fiber. The chosen fiber architecture is most important for a given application and Lei et al [4] describe how, for example, 3-D braiding can be applied to carbon-carbon composites. One of the early forms of near net shape reinforcement used for carbon-carbon aircraft brakes was based on a weft knitted 3-D fabric made by the Pressure Foot process (Figure 14.1). 

Another important aspect is the moisture content of natural fibres. These fibres are hydrophilic and absorb water. The moisture content can be as high as 20%, but in most cases it will be in the range of 5-10%. Lack of good interfacial adhesion with the polymer phase, due to the inherently poor compatibility and the ability of the hydrophilic cellulose fibres to disperse with the hydrophobic resins, makes the use of cellulose-based fibre-reinforced composites less attractive. During processing, the presence of water can create voids in the matrix and also lead to a poor adhesion of the fibres with the hydrophobic resin. The hydrophilic nature of natural fibres can be a problem in the finished composites as well. 

Chapter 5 summarizes the investigation of lignocellulosic flax fiber-based reinforcement requirements to obtain structural and complex shape polymer composites. This chapter discusses in detail the possibility of forming complex shape structural composites which are highly desirable for advanced applications. Chapter 7 focuses on the structure and properties of cellulose-based starch polymer composites, while Chapter 8 focuses on the spectroscopic analysis of rice husk and wheat gluten husk-based polymer composites using computational chemistry. Chapter 9 summarizes the processing, characterization and properties of oil palm fiber-reinforced polymer composites. In this chapter, the use of oil palm as reinforcement in different polymer matrices such as natural rubber, polypropylene, polyurethane, polyvinyl chloride, polyester, phenol formaldehyde, polystyrene, epoxy and LLDPE is discussed. Chapter 10 also focuses on... 

There are good adhesion characteristics of the cellulose fiber-cellulose ester interface. Cellulose derivatives have been overlooked as potential components in composites with lignocellulosics only a few studies have considered the use of cellulose esters as matrices in biocomposites. Cellulose esters are very well suited for use as matrix binders in natural fiber-based composites. Cellulose esters can be injection molded, extruded, blow and rotationally molded into structrual components, thermoformed from sheet, and extruded in films. Typical processing temperatrues lie between 180°... 

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