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Tuesday 23 February 2016

Green Fibres and Their Potential in Diversified Applications (2)

2.2.2 Green fibres/bast fibrous plants for biocomposites, based on lignocellulosics
Biocomposites include a wide range of products for different applications ranging from construction or insulation panels made of wood pieces, particles and fibres, through special textiles (geo-textiles and non-woven textiles), to plastic products based on polymers filled with lignocellulosic particles. Fibre plants are seen as promising lignocellulosic raw materials for different applications.
These lignocellulosics are biodegradable, recyclable, and, when combined with natural resin, they are as strong as steel yet of lower density. Such composites may be used in motor vehicles, building materials, furniture, machine construction, insulating materials, gardening and agricultural equipment, and other applications. Examples of applications of composite materials containing lignocellulosic components include glue-lam wood, plywood, particleboard, fibreboard, Medium Density Fibre (MDF), Oriented Strandboard (OSB), lignocellulosic-mineral particleboards and composites, special functional (water, fire, and bio resistant), thermosetting polymer composites, thermoplastic polymer composites, natural polymer composites (based on starch, polyhydroxy butyric and polylactic acid), non-woven, geo-textiles, absorption chemotextiles (bentonite, carbon active, silica, hydrogel, linoleum, etc.).

2.2.3 Utilisation of bast fibres in nonwovens.
Nonwovens appeared in the 1940s, and were later developed with different dynamics in various countries. Nonwovens technology was further improved and developed, particularly concerning bonded nonwovens based on valuable chemical fibres and synthetic binding agents facilitating manufacture of better and more useful products for technical usage, clothing and household use.
Nonwovens have a very wide range of applications from furniture to the geo- and chemotextiles.
An example of nonwovens is geotextiles for reinforcement of earth structures like landfills, slopes and embankments like grass mats.

2.2.4 Prospective applications of composites.
Composite materials find uses in car, aircraft, railway and truck industries. Polymers have displaced steel and ferric alloys in car construction from 80 percent used in 1965 to 60 percent in 1995. This field of polymers application was pioneered by Henry Ford, who designed the car body entirely in polymer, a car "made of soybean" in 1941. In 1953 a Chevrolet Corvette had many parts made of polyester resins reinforced with different fibres allowing the weight of the car to be decreased by about 85 kg.

Application of natural fibres in the automotive industry may include different types of fillings, reinforcing fibre and in some cases replacement of glass fibre, one of the components of hybrid composites, degradable composite of natural fibres and natural polymers. The great advantage of composites reinforced with fibres is that when the fibres are arranged parallel to the direction of applied forces (unidirectional laminates), the possibility of utilisation of anisotropic properties of material for structure arises (crushed fibres, embroided and 3-D weaved structures). The properties of this new material can be compared with regular glass fibre or reinforced polymers in normal conditions, for instance in the automotive industry, road construction, irrigation systems, landfills, furniture industry and also in sport. New nanobinders have been proposed for jute, hemp composites by the Institute for New Materials, Saarbrücken, Germany resulting in flame resistant construction elements with a compressive strength of 3.5 MPa by a specific weight of only 0.13 g/cm2.

2.2.5 Particleboards.
Composition boards, including particle board (extruded and plate-pressed), and fibre boards, especially medium-density fibre (MDF) board, are quite common in construction, furniture and interior panelling. The most common raw material used is wood, but many countries successfully use other agriculturally based residues like flax and hemp shives, jute stalks, bagasse, reed stalks, cotton stalks, grass-like Miscanthus, vetiver roots, rape straw, oil flax straw, small grain straw, peanut husks, rice husks, grapevine stalks and palm stalks. These cheap raw materials can be valuable in lignocellulose board production from wood particles.

Medium Density Fibre (MDF) Boards consist 82 percent of fibres from wood or annual plants, 9 percent gluing amino resin, 1 percent parafin and 8 percent water. There is growing interest in using annual plants to make boards because annual plants are renewed each year, and produce three times more cellulose per year than ring-growth in trees. Residues of annual plants such as rape or canola straw, oil flax straw, small grain straw, reed and reed wastes are useful for production of insulating boards for building industry, important for houses in earth-globe areas. Hemp also makes excellent insulating boards. Bast fibrous plants as a source of food, fodder, pharmaceutical products and cosmetics.

Flax and hemp seeds are perfect raw materials for agriculturally based industries such as the production and processing of food, of natural pharmaceuticals and cosmetics, or of paint varnishes.
The Institute of Natural Fibres has developed food additives based on linseed oils, which are high in lignan and unsaturated fatty acids (mainly linolenic and linolic acids). Brain, spinal cord and its branches are made up of essential fatty acids, particularly linolenic acid. We literally think with these acids - they are the brains! Linseed-based food additives also contain lignans, which seem to be capable of slowing the cell division of some tumours. Lignans also improve urinary function, helping prevent inflammation of the kidneys. Linseed proteins and mucilages are used in food products such as ice cream, powdered sauces and soups to improve smoothness and viscosity.

There is a similar market potential for pharmaceutical and cosmetic products based on linseed and hemp seed, especially in the area of "natural products", which has become a key term in marketing success. Hemp seed's nutritional values are already well documented: it is an excellent source of balanced essential fatty acids, particularly omega-3, which is responsible for the proper growth and functioning of the body. Leaves and unripe seeds can be used to produce a fodder that is rich in protein and vitamins. The amino acid and carotenoid content of hemp fodder is similar to that of traditional fodder like Lucerne and clover green meal, but with lower levels of cellulose.

2.2.6 Bast fibrous plants for fine chemicals.
Recent discoveries have shown that some of these fibrous plants are rich sources of not only phytoestrogens (lignans) mentioned above, but promising natural medicine cyclopeptides. In addition to cellulose, the main components of lignocellulosics are lignin, hemicellulose and pentosans. The uses of isolated lignin in the chemical industry grow continually. It is used as a substitute for phenol-formaldehyde resins in composites and as a natural polymer that has applications for agrochemicals, packaging, laminates, moisture barriers, stiffening agents (boxboard), friction materials (brakes, pads), wood adhesives (plywood, waferboard, particle board, fibre board), plastic moulding (automotive), foundry mould binders and antioxidants.

3 CONCLUSIONS REGARDING DIVERSIFIED USES OF GREEN FIBRES
Global trends towards sustainable development have brought to light natural, renewable, biodegradable raw materials, among them bast fibres. Science and technology continue in extending their use in textile and other industries.
Recent achievements and new applications of green fibres and associated products bast fibrous plants can provide, form the background for following conclusions:

  • Fast growing population, eco- and health awareness creates large space for future expansion of other than cottons natural cellulosic fibres.
  • Present achievements in breading/production/processing extended the use of bast fibres in textiles. To make the way for these, difficult in processing fibres, into textile products being beyond their reach for centuries, it was necessary to develop: new, refined bast fibre types, adapted to modern spinning systems; new, softer, finer 100 percent bast or bast blended yarns, amongst them knitting yarns; new crease resistant finishing treatments; new products, which could meet the needs of demanding apparel sector.
  • All the textile goods made on the basis of green fibres can boast high comfort/health properties and are ecological items. They can be labelled as "NATURAL" which is the key to market success.
  • Green fibres/bast fibrous plants are used, thanks to research and development, in growing amounts for nonwood pulps.
  • Green fibres/bast fibrous plants will also be used in growing amounts in a wide spectrum of biocomposites materials. Being lignocellulosic they can be combined with man-made or natural polymers to provide a wide range of useful composites in textiles (including geotextiles and non-woven).
Green fibrous plants provide valuable by-products like seeds, waxes, fragrances, and pigments. These may be used for food, fodder, pharmaceuticals, cosmetics, and body-care items.

Sources FAO Report, Assessed on 22 February 2016

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