Plant Fibre: Molecular Structure and Biomechanical Properties, of a Complex Living Material, Influencing Its Deconstruction towards a Biobased Composite

Abstract

Plant cell walls form an organic complex composite material that fulfils various functions. The hierarchical structure of this material is generated from the integration of its elementary components. This review provides an overview of wood as a composite material followed by its deconstruction into fibres that can then be incorporated into biobased composites. Firstly, the fibres are defined, and their various origins are discussed. Then, the organisation of cell walls and their components are described. The emphasis is on the molecular interactions of the cellulose microfibrils, lignin and hemicelluloses in planta. Hemicelluloses of diverse species and cell walls are described. Details of their organisation in the primary cell wall are provided, as understanding of the role of hemicellulose has recently evolved and is likely to affect our perception and future study of their secondary cell wall homologs. The importance of the presence of water on wood mechanical properties is also discussed. These sections provide the basis for understanding the molecular arrangements and interactions of the components and how they influence changes in fibre properties once isolated. A range of pulping processes can be used to individualise wood fibres, but these can cause damage to the fibres. Therefore, issues relating to fibre production are discussed along with the dispersion of wood fibres during extrusion. The final section explores various ways to improve fibres obtained from wood.

The Important In Terms of Health of Flax (Linum usitatissimum L.)

“…Fibers are not affected much by bleaches such as cold chlorine and hypochlorite, boiling water, sun and detergent [12,13,19] Flax fiber cannot be spun due to its fiber structure. Therefore, it can be used by mixing with fibers such as cotton, silk and wool [20,21]. Compared to hemp fibers, it is relatively thin and soft and has low elasticity.…”

“…[26], noise-resistant materials in construction and automotive industry, insulation material, biocomposites, bioplastics, pulp [21,27].…”

Wide Angle X-Ray Scattering to Study the Atomic Structure of Polymeric Fibers

“…There are different crystalline polymorphs of cellulose [36], but the most known are cellulose I (with the two allomorphs, triclinic Iα and monoclinic Iβ [37,38], which corresponds to native cellulose) and cellulose II, obtained by chemical regeneration or mercerization of natural cellulose [38]. The term fiber usually refers to a bundle of cells adhering to each other [39]. The cellulose Iβ is thermodynamically more stable.…”

“…Cellulose chains are linked together to form microfibrils. Various hypotheses have been proposed regarding the cross-sectional arrangement of microfibrils [39]. In particular, a microfibril of 18−24 chains should be 2−3 nm wide, leading to main X-Ray scattering signals in the SAXS regime.…”

“…These partially ordered structures lead to scattering signals in the WAXS regime, from which information about the degree of crystallinity of the fibers can be extracted. Amorphous cellulose is the result of mechanical/chemical damage of crystalline cellulose, rather than being a native state [39]. Thus, the WAXS patterns contain specific features of the fibrous samples and of its state of integrity and conservation.…”