Structure of natural fibers

In the course of his studies of the dyeing process, he became deeply interested in the structure of natural fibers, and most of his efforts were directed toward this new field of research, with the help of able associates, among them R. Brill, M. Dunkel, G. von Susich, and E. Valkd. His investigation of various aspects of the problem utilized physical means (for example, x-ray diffraction, optical properties, and viscosity) and the purely chemical approach. A young scientist, H. Mark, who later became an authority in the field of high polymers, was appointed head of the physical chemistry laboratory. 

When reducing the fibers into microfibrils, the hierarchical structure of natural fibers is exploited and important craisequences occur. The first one is obviously an increase in the specific area of the particles, from values of approximately a few... 

The fatigue strength is in the range of glass mat reinforced PP (GMT-PP) with the same fiber mass content. A higher mechanical damping of the natural fiber/PP-composites is typical. This is caused by the structure of natural fibers being themselves composite structures. 

Climatic conditions, age, and the digestion process influence not only the structure of fibers but also the chemical composition. Mean values of components of plant fibers are shown in Table 4. With the exception of cotton, the components of natural fibers are cellulose, hemi-cellu-lose, lignin, pectin, waxes, and water-soluble substances. 

The mechanical and physical properties of natural fibers vary considerably, as it is with all natural products. These properties are determined by the chemical and structural composition, which depend on the fiber type and growth circumstances. With this cellulose, the main component of all natural fibers varies from fiber to fiber. 

The Fitting Problem. In many studies in particular of natural fibers, orientation distributions are picked from spherical arcs in scattering patterns and then fitted by Gaussians or Lorentzians. The result is the finding of an isotropic background. At least part of this background is not related to structure, but to a fundamental misunderstanding. 

Paper products (newsprint, tissue, packaging, etc.) are made from pulps that consist of natural fibers derived from vascular plants such as trees, sugar cane, bamboo, and grass. The vascular fiber walls are composed of bundles of cellulose polymeric filaments. This long, linear glucose polymer is what paper is made from. The polymer has the structure shown in Scheme 8.18. 

Fibers exist as natural, or synthetic, hydrophilic, hydrophobic, nonionic, and ionic. Natural fibers hnvc complex chemical structures with a multitude of possible points of attraction for a dyestuff and are difficult io characterize because of the structure being strongly influenced by regional, climatic variations and the species of plant or animal. Dyeing of natural fibers is therefore much more complex than dyeing synthetic fibers where structures can be characterized and the availability of points of attraction can be deliberately engineered into the fiher s molecular chain. The various types of liher arc summarized in Tahle I. The fiber type dictates the type of dye needed. 

Electrospinning of natural fibers offers unique capabilities for producing novel natural nanofibers and fabrics with controllable pore structure. Current research effort has focused in understanding the electrospinning of natural fibers in which the influence of different governing parameters are discussed. 

In 1949, a series of authoritative papers on the structure of textile fibers was published by the Textile Institute in the Proceedings section of Journal of the Textile Institute (85), Three of the papers are general and five deal with specific natural fibers. 

To appreciate fully the influence of the structural features of natural fibers on their susceptibility and resistance to enzymatic degradation, it is necessary to understand the relationship between cellulolytic microorganisms, their extracellular enzymes, and the fiber substrate itself. 

Since the cellulose and other major constituents of natural fibers are insoluble molecules and are deposited within the cell walls in an intimate physical mixture of great structural complexity, formation of this requisite physical association can be achieved only by diffusion of these enzymes to susceptible sites on the gross surfaces of the fiber or the microfibrillar and molecular surfaces within the fiber wall. Thus, any structural feature... 

X-ray diffraction techniques are the only way of determining the crystal structure of natural and synthetic polymers, although the x-ray data itself obtained from a crystalline polymeric fiber or film is not sufficient to allow complete refinement of the structure. Conformational analysis and electron diffraction represent complementary methods which will facilitate the determination of the structure. The necessary requirements for the x-ray approach are crystallinity and orientation. X-ray data cannot be Obtained from an amorphous sample which means that a noncrystalline polymeric material must be treated in order to induce or improve crystallinity. Some polymers, such as cellulose andchitin, are crystalline and oriented in the native state.(1 )... 

Biagiotti, J. Puglia, D. Kenny, Jose M. A review on natural fibre-based composites-Part I structure, processing and properties of vegetable fibres. Journal of Natural Fibers, 2004, Vol. 1 Issue 2, pp. 37-68. 

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