Natural fibers reaction mechanisms

Within the area of natural fibers, wool has the highest inherent nonflammability. It exhibits a relatively high LOI of about 25 vol % and low flame temperature of about 680°C.25 The inherent FR activity of the fiber can be associated with char-forming reactions which may be enhanced by a number of flame retardants. Based on their fundamental work to enhance char formation, Horrocks and Davies offer intumescent formulations based on MP to flame-retarded wool.61 From TGA and SEM characterization, they proposed a comprehensive model on the mechanism of protection via an intumescent process, which involves the formation of cross-linked char by P-N and P-0 bonds resistant to oxidation. More recently, they used spirocyclic pentaerythritol phosphoryl chloride (SPDPC) phosphorylated wool to achieve intumescent wool which exhibits large char expansion and good flame retardancy.62... 

Figure 1.6 Schematic representation of (a) the diffusion-precipitation mechanism of carbon filament growth from the gas phase [32], and (b) the carbon-fiber growth mechanism proposed by OberUn et al. [33]. Important details regarding the effects of metal particle size and shape on the chemical reactions occurring at the metal-carbon interface, and thus on the nature and size of the filaments or nanotubes produced, have yet to be sorted out.

Recently, natural fiber has also been treated with benzene diazonium salt to improve its physical, mechanical and thermal properties. Benzene diazonium salt reacted with cellulose in wood and produced 2, 6-diazocellulose by a coupling reaction, as confirmed... 

Cellulose-based natural fiber can be oxidized using oxidizing agent with acidic catalyst. Oxidation reactions applied to cellulose in fiber for chemical modifications [43]. Oxidation reactions occur on cellulose selectively at particular position. The reaction of sodium metaperiodate with cellulose in wood fiber in the presence of sulfuric acid catalyst at 120°C and 85 KPa pressure yielded the oxidized product. Sodium metaperiodate reacts with hydroxyl groups of cellulose and produce 2,3-dialdehyde cellulose which improved the physical and mechanical properties of polymer composites [44]. 

FIGURE 14 J The reaction mechanism of silane and natural fiber [66]. 

Kinetic Degradation and Reaction Mechanisms in the Solid State of Natural Fibers... 

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. 

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