Natural fibres lignin

Hemicelluloses are constituted of different hexoses and pentoses glucose, mannose, xylose, etc. Since these heteropolysaccharides are often branched polymers, they cannot constitute crystalline structures. However, their function in the constitution of natural fibres is crucial. Together with lignin, they constitute the bonding matrix of the cellulose microfibres. 

Natural fibres incorporated in synthetic polymeric matrices (mainly polypropylene) had a real industrial success natural additives like lignin were also used. 

Development of ARBOFORM started in the late 1990s, the material being composed only of the components lignin, reinforcing natural fibres and some natural additives. The material... 

Figure 5.15 HPH-lignin and test material samples composed of HPH-lignin, natural fibres and natural additives obtained by injection moulding. ( Fraunhofer ICT, 2013.)...

The lignin based bio-composite ARBOFORM reinforced by natural fibres exhibits a series of... 

Coir fibre is obtained from the hard internal shell and the outer coat of coconuts. The individual fibre cells are narrow and hollow and the thick walls are made of cellulose. It is thick, strong and has high abrasion resistance. Mature brown coir fibre contains more lignin and less cellulose than fibres such as flax and cotton and is therefore stronger but less flexible. Coir fibre is relatively waterproof and is one of the few natural fibres resistant to be damaged by salt water. 

The two main sources of natural fibres are plants and animals. The main component of animal based fibres is various proteins examples include mohair, wool, silk, alpaca, angora, etc. The components of plant fibres are cellulose microfibrils dispersed in an amorphous matrix of lignin and hemi-cellulose examples include cotton, jute, flax, ramie, sisal, hemp, etc. 

ATR-FTIR, solid state C-NMR and XRD results showed the composition of the fibre surface and the relationship of its characteristic with thermal resistance. The crystalline content of the natural fibre remarkably increased after chemical treatment, which was confirmed by XRD and solid-state C-NMR. HCIO4 is the most efficient chemical in terms of wax and fatty acid residue removal in our work. Hence, the dynamic mechanical properties of the natural fibre after HCIO4 treatment were improved. It was reported that the acidolysis lignins were isolated from sugar cane bagasse and curaua fibres by adding a mixture of dioxane and 0.1 N aqueous HCl (8.5 1.5, v/v) at 100 °C for 2 h under N2. ATR-FTIR and TGA of the oxidized lignins revealed a decrease in... 

The chemical composition as well as the morphological microstmcture of vegetable fibres is extremely complex due to the hierarchical organisation of the different compounds present at various compositions. Depending on the type of fibre, the chemical composition of natural fibres varies. Primarily, fibres contain cellulose, hemicellulose and lignin. The property of each constituent contributes to the overall properties of the fibre. 

Natural fibres are classified into three main groups, namely, bast (or stem), leaf and seed (or fruit). Bast fibres such as jute, hemp, kenaf and flax are fibrous bundles found in the inner bark of the plant stem. The fibre bundles consist of filaments of fibre cells made up of mainly cellulose and hemicelluloses. The cementing material between the fibre bundles is lignin while the filaments are held together by pectins. These fibres are separated from the woody matter through a process of natural... 

Pineapple leaf fibre (PALF), which is rich in cellulose, relatively inexpensive and abundantly available has the potential for polymer-reinforced composite. PALF at present is a waste product of pineapple cultivation. Hence, without any additional cost input, pineapple fibres can be obtained for industrial purposes. Among various natural fibres, PALFs exhibit excellent mechanical properties. These fibres are multicellular and lignocellulosic. They are extracted from the leaves of the plant Ananus cosomus belonging to the Bromeliaceae family by retting. The main chemical constituents of pineapple fibres are cellulose (70-82%), lignin (5-12%) and ash (1.1%). The superior mechanical properties of PALFs are associated with their high cellulose content. 

Guigo N, Vincent L, Mija A et al (2009) Iimovative green nanocomposites based on silieate clays/lignin/natural fibres. Compos Sei Teehnol 69 1979-1984... 

With the exception of cotton, the components of natural fibres are cellulose, hemi-cellulose, lignin, pectin, waxes and water soluble substances, with cellulose, hemi-cellulose and lignin as the basic components with regard to the physical properties of the fibres. The concentration of cellulose achieved is 82.7% in cotton and 64.4% in jute. In contrast hemi-cellulose concentration is 5.7% in cotton and 16.7% in flax. Pectin levels are 5.7% in cotton and 0.2% in jute. In contrast lignin levels are 11.8% in jute and 2.0% in flax and do not exist in cotton. The water content is 10% for cotton, jute, flax and sisal [11]. 

Jute is a long, soft, shiny fibre that can be spun into coarse, strong threads. It is one of the cheapest natural fibres. Jute fibres are composed primarily of the plant materials cellulose, lignin and pectin. Both the fibre and the plant from which it comes are called jute. It belongs to the family Tiliaceae, which belongs to the genus Corchorus. 

The biopolymers covered in this book chapter are Starch polymers, polyhydroxyalkanoates (PHA), polylactides (PLA), lignin-epoxy resins, epoxidised linseed oil and composites reinforced with natural fibres such as flax, hemp, and china reed (miscanthus). The first three materials are biodegradable while this is not the case for the remaining studied materials. 

The physical and chemical properties depend on the chemical constituents of the natural fibres. The proportion of each of these components varies for different fibres. Generally, the fibre contains 60—75% cellulose, 4—20% lignin and up to 20% moisture. The chemical compositions of commonly used natural fibres are given in Table 4.3. 

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