Fibre separation

World pulp production statistics are summarised in Table 13.1. There are three main categories, mechanical, semichemical and chemical pulp. The elassification is based upon the process used for fibre separation. The major industrial operations are mechanical and chemical pulps, with most of the latter being manufaetured by the kraft process. 

Schnabel, S. Moulin, P. Nguyen, T. Roizard, D. Aptel, P. Removal of volatile organic components (VOC) from water by pervaporation with dense silicone hollow fibres. Separation improvement by Dean vortices. J. Membr. Sci. 

Jin J-M, Zhang Y-J, Yang C-R (2004) Four New Steroid Constituents from the Waste Residue of Fibre Separation from Agave americana Leaves. Chem Pharm Bull 52 654... 

Fibre stress a, Is evaluated vrith the shear lag theory, (a) The mean fibre separation is labelled 2R. (b) The composite in the vicinity of the fibre is modelled as a cylinder of matrix with radius R surrounding the fibre, embedded in a block which deforms as the composite as a whole, (c) Within the cylinder of matrix, a shear stress r acts at radius r. 

In one case, the swelling of cellulose fibres in water, some more light has been thrown on the optical behaviour of the system by investigationsof the present author and his collaborators which we shall now briefly describe. It has already been mentioned in Section 6b. 7 (p. 575) that the change in refractive power of isotropic cellulose upon swelling in water follows the simple rule of additivity of the refractions (n — 7)/d of the components. It was established that, up to a water content of about 20 per cent, the same rule may be applied to the principal refractive indices of anisotropic fibres separately. This implies that the double refraction // — of the fibre is simply inversely proportional to the degree of swelling p ... 

As indicated earlier, the materials may be either in the form of compounds or resins and fibres separately. Sheet moulding compound (SMC), dough moulding compound (DMC) and bulk moulding compound (BMC) use polyester resin plus filler, catalyst, pigment, low profile additive, etc. 

The production or extraction of the primary bast fibres has traditionally been a very labour-intensive process, but recently an alternative fibre separation process has been developed using technologies such as ultrasound and steam explosion, which are much less labour intensive. Once separated, the bast fibres are ready for spinning and weaving into textiles, or for pulping into high-quality pulp. 

Standard screening and air separation techniques can then be used to separate the two different materials. Commercially, kenaf bast fibre separated this way can be purchased 98% pith-free. 

Hojo, H., Kim, E. G., Yaguchi, H. and Onodera, T. (1988), Simulation of compression moulding with matrix-fibre separation and fiber orientation for long fibre-reinforced thermoplastics . International Polymer Processing, 3,54-61. 

With dew or field retting, plant stems are cut or puUed up and left in the field for 4—5 weeks to allow dew and rainfall to affect the process under suitable climate conditions including air, humidity and ambient temperature. The process is monitored to avoid underretting or overretting to ensure that the bast fibres separate firom the inner core without much deterioration in quafity. The dew retting process is weather dependent and time-consuming, so it is usually replaced by other methods. 

After retting is completed, the stalks are left to dry in the field, which is termed gassing . At this point, the retted harvest is dried to less than 10% moisture and baled to bring to a central location for processing. The fibre separation process is done either manually or in industrial machines. 

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