Fibre structure cotton

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. 

Metallisation of fibres is not only a physical process determined by absorption capacity of the fibres for the metal and diffusion capacity of the metal in the fibre structure, but also depends on chemical parameters such as chemical structure of the fibres, presence of functional groups, reactivity of the fibre and the metal, oxidation state of the metal and the presence, necessity and reactivity of supporting chemicals (e.g. reducing agent). Therefore, it was necessary first to study metallisation at different types of fibres in order to investigate which structure is most useful for further research. In this respect, viscose, cotton, natural silk and polyacrylonitrile fibres were investigated because of their different structure and properties and their availability in the New Independent States of the former Soviet Union (Uzbekistan, Kazakhstan, Kyrgyzstan). 

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 fully developed cotton fibre consists of a waxy cuticle that envelopes it, a cell wall that is differentiated into primary (outer) and secondary (inner) layers and residual protoplasm called the lumen. Although this concept of the fibre structure persists, more recent ideas do not differentiate between the cuticle and the primary wall, which is less than half a micrometer thick and consists of around 50% cellulose, with pectin, waxes and proteins making up the remainder. The secondary wall, which differs considerably in chemical composition and structure from the primary wall, consists of up to 95% cellulose. ... 

Ansell, M.P., and Mwaikambo, L.Y., The Stmcture of Cotton and Other Plant Fibres , in Handbook of Textile Fibre Structure, Volume II Natural, Regenerated, Inorganic and Specialist Fibres, editors Eichhoiu, S.J., Hearle, J.W.S., Jafie, M., and Kikutani, T, Woodhead Pubhshing Limited, 2009. 

McKelvey etal. (1959) investigated the reaction of epoxides with cellulose in alkaline conditions, reporting that alkaline cellulose reacted readily once the concentration of sodium hydroxide was sufficiently high. However, no evidence was found of reaction between cotton yarn and cellulose with a range of epoxides under a variety of reaction conditions. It was concluded that the apparent reactivity of cellulose with epoxides was primarily due to alkaline swelling of the cellulose, self-polymerization of the epoxide monomers then occurring within the interior structure of the fibres. It was also noted that the reactivity with phenol OH groups was very low (e.g. only 1 % conversion of ethylene oxide with various phenols). 

Much of our technology has been developed by observing and imitating the natural world. Synthetic polymers, such as those you just encountered, were developed by imitating natural polymers. For example, the natural polymer cellulose provides most of the structure of plants. Wood, paper, cotton, and flax, are all composed of cellulose fibres. Figure 2.15 shows part of a cellulose polymer. 

Cellulose is reputedly the most abundant organic material on Earth, being the main constituent in plant cell walls. It is composed of glucopyranose units linked pi 4 in a linear chain. Alternate residues are rotated in the structure, allowing hydrogen bonding between adjacent molecules, and construction of the strong fibres characteristic of cellulose, as for example in cotton. 

An alternative way of classifying dyestuffs is by their application areas, but as there is large overlap between product structural classes and their uses, it is less satisfactory. However, from a commercial standpoint it is the application method that determines the potential of a dyestuff and the reason for its industrial manufacture and sales. In this section the different application methods will be described mainly in relation to the end use, e.g. the dyeing or printing of cotton and other fibres, the coloration of paper or leather, the use in food and cosmetics etc. 

Warwicker, J. O. Jeffries, R. Colbran, R. L. Robinson, R. N. A Review of the Literature on the Effect of Caustic Soda and Other Swelling Agents on the Fine Structure of Cotton, Shirley Institute Pamphlet No. 93, The Cotton Silk and Man-Made Fibres Research Association, Manchester, England, 1966. 

It is worth noting that the mercerisation process, bom in the 19th century, produces a cellulose II structure too, but without dissolution of the fibres and therefore with no reshaping. Cotton fibres are soaked in a concentrated (19%) NaOH solution then washed. Mercerised cotton shows a softer touch and more brilliance than natural cotton. 

Arthur et al.54 have shown that cotton modified by AN grafting retains the structure and appearance of the initial fibre (particularly the transverse cross-section shape) much better if the grafted polymer is located in the surface layer. To this end, they suggest graft polymerization to cotton pre-irradiated in an inert atmosphere and the use of solvents causing no swelling of the fibre. 

Cotton is single cell fibre and develops from the epidermis of the seed [4]. An elongation period continues for 17-25 days after flowering. Cotton consists of cellulosic and non-cellulosic material. A morphological structure of the cotton fibre is given in Fig. 1-1. The outer most layer of the cotton fibre is the cuticle, covered by waxes and pectins, and this surrounds a primary wall, built of cellu-... 

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