Cellulose-based composites properties

Influence of Polysaccharide Composition on the Structure and Properties of Cellulose-based Composites... 

Keywords Cellulose-based composites Composite properties cellulose Nanofibrillated cellulose Production methods... 

Fiber alignment in short fiber composites (SFCs) is very difficult to achieve, however the results obtained with anisotropic aU-cellulosic based composites point out for a simple and new way of producing fiber aligned SFCs with enhanced mechanical properties, as discussed later on. 

In the cross-linked films, the difference between the roughness parameters of the two surfaces is smaller than that observed in the case of the uncross-linked ones, as shown also in Fig. 15.5. This means that the effect of fiber settling at the bottom surfaces is less pronounced for the cross-linked films, suggesting a better distribution of the fibers over the cross section. This influences the mechanical properties of isotropic all-cellulosic based composites, as discussed later. Also, the asymmetry between top and bottom surfaces will have an impact in gas barrier properties of these composites. 

Mechanical properties of anisotropic all-cellulosic based composites are presented in Table 15.3. 

For comparison. Table 15.4 presents the mechanical properties of anisotropic and uncross-linked isotropic all-cellulosic based composites. 

Table 15.4 clearly shows that anisotropic composite films present better mechanical properties. It is worth noting that anisotropic composites also have higher Young s modulus, yield stress and ultimate tensile strength than cross-linked isotropic homo-logues [13]. This, along with results presented in Table 15.4, seems to indicate that the mechanical properties of these all-cellulosic based composites depend on matrix anisotropy and fiber orientation rather than on cross-linking. 

Table 15.3 Mechanical properties of anisotropic all-cellulosic based composite films, measured in the shear direction (0°) and perpendicular to it (90°)...

Table 15.4 Comparison of the mechanical properties of uncross-linked isotropic (I) and anisotropic (A) all-cellulosic based composite films...

From the mechanical properties of all-cellulosic based composites, an order parameter, Se, was calculated using (15.3) [20] ... 

In this section the mechanical properties (Young s modulus) and the strength of the fiber-matrix interface (quality of the interface) of isotropic all-cellulosic based composites will be analyzed using theoretical models existing in literature. For the anisotropic composites such an approach was not performed. The anisotropy in these composites arises mainly from the liquid crystalline character of the matrix. 

Gas barrier properties were evaluated to access the potential of isotropic all-cellulosic based composites for packaging applications. The mechanical properties, fiexibility and biocompatibility of these materials can be useful, in particular, for food packaging. Due to the nature of the envisaged application insoluble materials are required. This requisite is only fulfilled by cross-linked composites and, therefore, we have decided to subject only cross-Unked films for gas permeation measurements. 

All-cellulosic based composite films can be prepared from either isotropic or anisotropic cellulosic derivatives solutions. However, these composites cannot compete with mechanical properties of cellulose nanofiber reinforced composites. Pioneering studies reported by Favier et al. [35, 36], showed that small amounts of cellulose tunicate whiskers resulted in dramatic improvements in modulus above the glass transititMi temperature of an amorphous polymer matrix, due to the percolation of the cellulose nanofibers. Also recently, a completely new route to cellulose-based composites was proposed by Nishino and Arimoto [37], Soy-keabkaew et al. [38—40], They focused on approaches following self-reinforcing polymer concepts [41, 42] to create composites that often outperform traditional nanofiber reinforced composites [38,40],... 

The use of cellulosic nanofibers in the productiOTi of all-cellulosic based composites can greatly improve the mechanical performance of these composites. With these nanofibers and a cellulosic anisotropic matrix a synergy between the percolation of the nanofibers and its matrix-induced orientation can lead to composites with enhanced mechanical properties. 

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. 

Chemical modification with suitable chemicals and innovative technology provides a noble and facile route for the development of intrinsic negative properties of cellulose-based composites materials. Although, the chemical treatments sometimes improved the certain properties composites, however, negative effect also observed. Alkali treatment improved adhesion and compatibility considerably among all conventional... 

Liquid crystalline properties of cellulose and its derivatives can be exploited to produce biomimetic materials or all-cellulosic-based composites with enhanced mechanical properties. These materials will be the focus of this chapter. 

Fiber alignment in short-fiber composites is very difficult to achieve. However, the results obtained by these authors, with anisotropic all-cellulosic-based composites, point out a simple way of producing this type of composite with enhanced mechanical properties. 

Richardson, M.J., Johnston, J.H., Borrmann, T., 2006. Electronic properties of intrinsically conducting polymer-cellulose based composites. Current Applied Physics 6, 462—465. 

Dall Acqua et al.45 reported the development of conductive fibres made by cellulose-based fibres embedded with polypyrrole. Several efforts with cotton, viscose, cupro and lyonell have followed. The conductivity is directly related to the amount of polypyrrole, oxidant ratio and fibre structure with significant differences between viscose and lyonell. Polymerisation occurs uniformly inside the fibre bulk, by producing a coherent composite polypyrrole/cellulose. The mechanical and physical properties of cellulose fibres were not significantly modified as they are the best available45. 

WO 99/14245 03/1999 Leupin et al.l Procter Gamble Laundry detergent compositions containing cellulosic-based polymers to improve fabric appearance and integrity Laundering of fabric/textiles with the additive leads to overall improvements in fabric appearance, pill/fuzz reduction, antifading properties, improved abrasion resistance, and enhanced softening... 

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. 

S. Kalia, "Development of polymer matrix based composites using grafted Flax cellulose as reinforcing agent and evaluation of some mechanical and chemical properties" Ph.D. Thesis, Punjab Technical University, Jalandhar, Punjab, 2008. 

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