Cotton fibres mechanical properties

The mechanical properties of plastics materials may often be considerably enhanced by embedding fibrous materials in the polymer matrix. Whilst such techniques have been applied to thermoplastics the greatest developents have taken place with the thermosetting plastics. The most common reinforcing materials are glass and cotton fibres but many other materials ranging from paper to carbon fibre are used. The fibres normally have moduli of elasticity substantially greater than shown by the resin so that under tensile stress much of the load is borne by the fibre. The modulus of the composite is intermediate to that of the fibre and that of the resin. 

The common elements in the cited examples are the mechanical characteristics and the insulation properties. These advantages come, not only from macroscopic configuration of these materials (the hollow cylindrical structure of stubble for instance), but, mainly, from their microscopic structure. Most the vegetal fibres can be described by two models wood fibres and cotton fibres, which will be presented later. In order to better understand the mechanical properties of these fibres, let us first consider their molecular constitution, then their hierarchical structure. 

The first high-strength carbon fibres were produced in the 1950s (see Donnet and Bansal, 1984). The early carbonized products were rayon-based, but it was soon found that the mechanical properties and the carbon yield could be improved by the use of polyacrylonitrile (PAN) as the precursor. Also, less expensive fibres of somewhat lower strength and modulus could be made from various other precursors including petroleum pitch and lignin. However, cotton and other forms of natural cellulose fibres possess discontinuous filaments and the resulting mechanical properties were consequently found to be inferior to those of the rayon-based fibres. 

Hearle, J.W.S, and Morton, W.E. (1993) Physical Properties of Textile Fibres. Textile Institute, Manchester. Hearle, J.W.S, and Sparrow, J.T. (1979a) Mechanics of the exten.sion of cotton fibres, I, Experimental studies of the effect of convolutions. J. Appl. Polym. Sd.. 24 1465-1477. 

As mentioned before, agro-based lignocellulosics suitable for composites stem from two main sources. Tbe first is agricultural residues, which have unknown mechanical properties and the second source is those lignocellulosics grown specifically for their fibre. Examples of the second source are cotton, jute, flax, sisal and many others. 

XPS analysis is an adequate technique to characterize the siuface ehemical composition of cotton fibres. The present study clearly shows that the raw fibers, whatever their origin and maturity, are totally covered by waxes and other non-eellulosic materials and exhibit surface properties eloser to those of polyolefin polymers (or high molecular weight alkanes) than those of eellulose. It appears also that a standard treatment of extraction by means of hot ethanol for 6 hrs is not able to remove all the waxes initially present on the fiber surfaces. These results are in good agreement with previous ones concerning the mechanisms of adsorption of gas probe molecules onto such raw and extracted fiber siufaces... 

Recently, some papers were published showing the need for conducting LCA of nanoproducts. A group of Brazilian researchers studied the LCA of cellulose nanowhiskers. Vegetal fibres are an important source of cellulose for the extraction of nanowhiskers, which can be used to enhance the mechanical properties of different polymers. The study contributes to the environmental performance of cellulose nanowhisker production processes in the development stage. Environmental aspects and related impacts of two cellulose nanowhiskers product systems are evaluated nanowhiskers extracted from unripe coconut fibres (EUC system) and from white cotton fibres (EC system). The comparison between the two systems showed that nanowhiskers produced in the EC system required less energy and water, emitted fewer pollutants, and contributed less to climate change, human toxicity and eutrophication than those produced in the EUC system. 

The mechanical properties of PETP fibres are dictated by the amount of cold drawing of the amorphous fibre—the longer the draw the higher the crystallinity and tensile strength developed. PETP fibres are dyed almost exclusively using dispersed dyes (see section 2.4.2.4). For permanent press polyester/cotton apparel, the press is obtained by treating the material with UF resin (i.e. only the cotton fibre is modified). 

C5 ras VP, Manfredi LB, Ton-That M-T, Vazquez A (2008) Physical and mechanical properties of thermoplastic starch/montmorillonite nanocomposite films. Carbohydr Polym 73 55-63 de Morals Teixeira E, Correa A, Manzoli A, de Lima Leite F, de Oliveira C, Mattoso L (2010) Cellulose nanofibers from white and naturally colored cotton fibers. Cellulose 17 595-606 de Moura MR, Aouada FA, Avena-Bustillos RJ, McHugh TH, Krochta JM, Mattoso LHC (2009) Improved barrier and mechanical properties of novel hydrox5q)ropyl methylcellulose edible films with chitosan/tripolyphosphate nanoparticles. J Food Eng 92 448—453 Dean K, Yu L, Wu DY (2007) Preparation and characterization of melt-extruded thermoplastic starch/clay nanocomposites. Compos Sci Technol 67 413 21 Duanmu J, Gamstedt EK, Rosling A (2007) Hygromechanical properties of composites of crosslinked allylglycidyl-ether modified starch reinforced by wood fibres. Compos Sci Technol 67 3090-3097... 

Zeroruan, S. H., Bertoruere, N. R., Alger, K. W., Xin, Q. (1990), The effect of cross-linking with DMDHEU on the mechanical properties of liquid-ammonia-treated cotton fibres. Journal of Textile Institute, 81(3), 310-18. 

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. 

For Runge, all elements in an experiment come to expression. He notes that the fibre that is to be dyed is not just a mechanical vehicle to which the colour simply adheres. It is rather an essential component, and that is why cotton, linen, silk and wool react so differently to dyestuffs.18 In an analysis of the properties of gold in Basic Lessons in Chemistry for Everyone Runge notes that gold is the most ductile metal, for a single grain can be drawn out to a 50-foot strand of wire. 

Cotton and Linen Cloth, etc.— The two most important sources of cellulose for the manufacture of thread and cloth and similar articles are the holl of the cotton plant and the stalk of the flax plant. The former is the source of all goods known as cotton while the materials made from the latter are termed linen. Another important fibre plant is hemp, the leaves or stalk of which yields fibres which are principally used in making twine, rope and canvas. Several varieties of hemp are used such as manila hemp, sisal, etc. The stalk of ihtjute plant is the source of materials out of which sacking or burlap and carpets are made.. In the manufacture of these products the fibre of the plant is mechanically separated and then spun into thread or twisted into yarn or rope. The thread or yarn are then woven into fabrics. The products possess properties characteristic of the particular fibre used. As in the manufacture of all of these important materials the cellulose undergoes no chemical change but is simply mechanically treated no further details of the processes will be given. 

---