Wood pulp fibres

The use of ceric ion initiation to graft polymers on to the surface of wood pulp fibres requires pre-bleaching of the fibres to remove most of the lignin (Mansour etal., 1982). The reaction requires acidic conditions, with a typical system utilizing ceric ammonium... 

We already mentioned in Section 3.5 [70] the partial oxypropylation of cellulose fibres and the interest of the ensuing composite materials in which the unmodified fibre cores represent the reinforcing elements and their thermoplastic sleeves the source of a matrix. Other interesting approaches have been recently put forward to prepare composite materials in which cellulose or one of its derivatives prepared in situ are the only component. Glasser was the first to tackle this problem through the combination of cellulose esters and fibres by two distinct approaches, viz. (i) the incorporation of lyocell fibres into a cellulose acetate matrix [92] and (ii) the partial esterification of wood pulp fibres with -hexanoic anhydride in an organic medium [93] that produced thermally deformable materials in which the thermoplastic cellulose ester constituted the matrix and the unmodified fibres the reinforcing elements. 

Mitchell AJ (1986) Composites of commercial wood pulp fibres and cement. Appita J 30 229... 

Michell AJ (1986) Composites containing wood pulp fibres. Appita 39 223-229... 

Coutts, R.S.P., Michell, A.S., 1983. Wood pulp fibre cement composites. Journal of Applied Polymer Science, Applied Polymer Symposium 37, John Wiley Sons, pp. 829-844. 

Quantitative birefringence measurements on wood-pulp fibres have indicated that lignin is randomly oriented in the wood and the wood-pulp, whereas cellulose is highly oriented, and that the hemicellulose chains lie parallel to the cellulose fibres. ... 

Various types of fibres could be used in making filter fabrics they include glass fibres, synthehc fibres, ceUulosic fibres (eg, natural wood pulp fibres, viscose fibres, and Lyo-ceU fibres), wool fibres, metal fibres, ceramic fibres, high-performance polymer fibres (eg, inherenfly fire-resistant fibres, chemical resistance fibres, high-strength, and high-modulus fibres), microfibers, and nanofibers. 

Wood pulp fibres are frequently less than 1 pm in fibre size and dominate wet-laid nonwoven filter media they are able to provide higher filtrafion efficiency and are environmentally fiiendly. Synthetic fibres (eg, polyolefin, polyester, and polycarbonate (PC) fibres) could work as electret fibres to provide additional electrostatic filtration mechanism, and also could be made binder-fitee, thermobond nonwoven fabrics if they are made Ifom thermoplastic polymers. 

Both natural wood pulp fibres and staple viscose fibres dominate wet-laid filter media, and their pulp fibres are available from various lengths ranging from 1 to 12 mm in many special geometries and shapes these cross sections include traditional round, flat and grooved, ttilobal, C-shaped and V-shaped, hollow, and cross-shaped fibres. Round fibres with a smaller diameter have less impact on the pressure drop, and they have a positive influence on strength of paper filter made from wood pulp. Tri-lobal fibres have a similar influence on paper porosity to round fibres, but have improved particle capture capacities. 

More recently, cellulose fibres have been investigated as potential precursors for self-reinforced polymer composites, as well summarised in a review by Eichhom et al. [191]. Numerous authors have reported the use of cellulose fibres from various sources, including wood pulp fibres [192, 193], filter and Kraft paper [194-197], microcrystalline cellulose fibres [198-202], sisal fibres [203, 204], ramie fibres [205], cotton fibres [206], regenerated cellulose (Lyocell) and cellulose fibres spun from an anisotropic phosphoric acid solution (Bocell) [207], and fibres from bacterial cellulose [208]. Two main technologies have been presented to produce these so-called self-reinforced cellulose or all-cellulose composites, and these are, first, the conventional impregnation of cellulose matrix into cellulose fibres and, second, a novel selective dissolution method in which the cellulose fibre surfaces are partially dissolved to form a matrix phase that bonds fibres together. 

G. G. Duffy, S. N. Kazi, X. D. Chen, Pulp fiber quality measurement from flowing wood pulp fibre suspensions. Das Papier 2002,... 

Carlsson G. Surface composition of wood pulp fibres, relevance to wettability, sorption and adhesion. PhD thesis. Royal Institute of Technology, Stockholm, Sweden 1996. 

R.S.P. Coutts, Air cured wood pulp, fibre/cement mortars . Composites. 18, 1987, 325-328. 

Use of renewable feedstocks is most likely where they can compete economically with petrochemically derived materials. This already happens in many areas, and it is sometimes forgotten that even in a world that seems to be dominated by chemicals and materials from fossil carbon and other non-renewable sources, industry already uses annually 19.8 MT of vegetable oils, 22.5 MT starch, 28.4 MT of plant fibres and 42.5 MT of wood pulp. These all compete on price and performance with synthetic alternatives. 

In 1891, British chemistry Cross and Bevan discovered that wood pulp when treated with sodium hydroxide solution and carbon disulphide, gets converted into cellulose xanthate. When cellulose xanthate is dissolved in caustic soda solution it gives a viscous solution that could be spun to form fibres called Viscose Rayon. Rayon is produced in large scale today in many countries including India. Rayon (also know as viscose) is in fact regenerated cellulose. 

Fig. 81. Electron micrograph of cellulose fibres, from purified cotton and wood pulp respectively, magnification 39,000, according to RSnby [41a].

The form of the cellulose affects its permeability to acid, and the retention of spent acid in the fibres. Schur and McMurtrie [4] report that wood pulp cellulose from coniferous trees retains the more acid, the larger the diameter of the cellulose fibres. 

Wood pulp for nitration is made exclusively from coniferous trees, since it has been found that conifers give cellulose with long fibres, and hence mechanical losses are small. 

Methoxylation of TMP samples was achieved by heating pulp fibres together with appropriate amounts of dimethyl sulphate in an equivolume solvent of water, ethanol and dimethoxyethane(74), methoxyl content of the pulp fibres being controlled by the amount of dimethyl sulphate added (Schmidt, J.A. Heitner, C. J. Wood Chem. Chem. Technol., In Press). Samples were analysed for methoxyl content by Scharwzkopf Microanalytical Laboratories, Woodside, New York. Analysis of the TMP samples for phenolic hydroxyl content was according to the method of Gellerstedt and Lindfors(76). 

Wood, J. R., and Goring, D. A. I. (1973). The distribution of lignin in fibres produced by kraft and acid sulphite pulping of spruce wood. Pulp Pap. Mag. Can. 74, T309-T313. 

Pulp and Paper Manufacture, Vol. 3 Secondary Fibres and Non-wood Pulping , TAPPI and CPPA. 

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