Vegetable fibres extraction

These may be either unicellular or multicellular. Cotton is the only unicellular vegetable fibre which, as the classification implies, consists of a single cell. The multicellular fibres are usually extracted from the stems of herbaceous plants. The better known members of this group are flax, ramie, jute, and hemp. 

Seeds are one source of vegetable fibres, oils, and protein. Oil-bearing seeds are mechanically squeezed in a seed expeller or the oil is extracted with a solvent leaving behind the pulp and fibre syn. seed cake, oil cake, or meal. Seed cake retains some oils as does the seed expeller. Common seed cakes include cottonseed, peanut, linseed, maize, palm, rape seed, rice bran, soy beans, and sunflower. 

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. 

Vauquelin, partly in collaboration with Fourcroy, discovered several important organic compounds. They distinguished a number of proximate constituents Yourcroy %principes immediats) in vegetables, such as acids, oils, camphor, gum, resin, tannin, starch, fibre, cork, caoutchouc, and extractive (a product of extraction with cold water and evaporation). Several definite compounds which had previously been obtained but the existence of which was in doubt were confirmed. Among these was malic acid and its salts. Sodium malate (with other salts of organic acids) was obtained by Donald Monro in 1767 and the acid from apples by Scheele in 1785 (see p. 232). The acid and its salts were studied by Fourcroy and Vauquelin. Vauquelin showed that the sorbic acid isolated from mountain-ash berries by Donovan is malic acid (the modern sorbic acid is a different substance) Vauquelin s elementary analysis of malic acid was inaccurate. 

The twin-screw extruder has proved to be a versatile tool for continuous treatment of vegetable matter, either for food or non-food applications. Trials for the direct alkaline extraction of xylans from wheat bran in a twin-screw extruder were unsuccessful. Bran impregnation with sodium hydroxide in the twin-screw extruder was very efficient, but it was necessaiy to make the separation between the hemicellulosic gel and the lignocellulosic matrix in another apparatus and remained difficult without a dilution to a L/S ratio of 50. Bran and straw co-extrusion was therefore investigated to be able to reduce the L/S ratio. Straw fibres form a dynamic plug in the restrictive elements of the screw profile just after the filtration zone. The pressure induced in the extruder sheath by the cellulosic fibres enabled the liquid/solid separation. 

Of the natural fibres, vegetable or plant fibres are the only ones that have suitable properties to meet technical requirements cost effectively for use as natural geotextiles. Plant fibres can be further classified according to the part of the plant as principal sources from which they are extracted bast fibres, leaf fibres and fruit or seed fibres. Fig. 4.1 shows a brief classification of textile fibres. 

Vegetable or plant fibres used in natural geotextiles are usually extracted from woody stemmed herbaceous dicotyledons (ie, the bast fibres jute, flax, kenaf and hemp), one of Palmaceae (palms, ie, coir) and one of the monocotyledonous plants (ie, sisal). 

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