Weaves made of soybean fibre blends with other natural or chemical fibres have so far been used in shirting and home textiles, and a series of such products has already been developed, reveals Janarthanan M.
Soybean is one of the nature's wonderful nutritional gifts. Soybean (Glycine max) is a leguminous plant. It is one of the very few plants that provide a high quality protein with minimum saturated fat. Soybean helps people feel better and live longer with an enhanced quality of life. India is the fifth largest producer of soybeans in the world. SPF is a kind of regenerative plant fibre. SPF is the only botanic protein fibre in the world, a newly born guard to mankind's skin(1).
This fibre appears from soybean a plant which has enormous source and is abundant in nutrition. As it contains 18 amino acids beneficial to the human body and added anti-bacterial elements, SPF offers a protective function to the skin. SPF has been praised locally and internationally by industry expert as a healthy and comfortable fibre of the 21st century. The main component of soybean fibre is it possesses the superiorities of many natural fibres and synthesised ones and it is quite similar to those of cashmere and silk, featuring fine denier, low density and good tenacity and elongation. The resulting fabric can give cashmere-like hand touch, silk-like lustre, cotton-like moisture conduction and wool-like warm retentiveness(2).
The invention of SPF is the contribution of mankind to the protection of natural rare minerals, the protection of resources, the care of the environment and the consideration of the global balance. It is an active fibre, a new green textile fibres is an advanced textile fibre. It is also known as "vegetable cashmere" or "soy silk." It is made from the soybean cake after oiling by new bioengineering technology.
Firstly, the spherical protein is distilled from the soybean cake and refined. Secondly, under the functioning of auxiliary agent and biological enzyme, the space structure of spherical protein changes and then protein spinning liquid is confected by adding high polymers and then thirdly, after the liquid is cooked, the 0.9 - 3.0 dtex fibre is produced by wet spinning and stabilised by acetalising and finally cut into short staples after curling and thermoforming.
SPF is praised as a healthy, comfortable and green fibre of the new century. Its major material is soybean protein from the farmers, massive in quantity and inexpensive in price and using it will not cause the predatory development on the resources but is helpful to resources' recovery and redevelopment. The production of SPF will not bring pollution to the environment, as the accessory and auxiliary agent used are not poisonous, while the residue after the protein extracted can be still used as feed. SPF has not only the superiorities of the natural fibres but also the physical properties of synthetic ones. SPF meets the people's demand of comfortable and beautiful wearing and also conforms to the trend of easy care. It is a potential material for middle and high class clothing in textile industry(3).
Nutritional benefits of soya protein
Soybeans contain all the three macronutrients required for good nutrition, as well as fibre, vitamins, minerals. Soybean protein provides all the essential amino acids in the amounts needed for human health. Almost 40 per cent of the calories from soybeans are derived from protein, making soybeans higher in protein than any other legumes and many animal products. Protein in just 250 grams of soybeans is equivalent to protein in 3 litres of milk or 1 kg of meat or twenty-four eggs. But it is the quality of soya protein that is most remarkable. Health professionals consider soya protein as superior protein compared to a lot of vegetable proteins and at par with egg and milk protein.
The amino acid pattern of soya protein is virtually equivalent in quality to that of milk and egg protein. The 1990s FAO/WHO protein evaluation committee put soya protein at par with egg and milk protein and ahead of beef protein. Unlike many other good sources of protein, soybean not only has higher percentage of oil but also quality fatty acid profile. It has low saturated fat content with high amount of polyunsaturated fat and is a readily available source of essential fatty acids. Soybean oil is also rich in omega-3 and 6 fatty acids similar to those found in fish oils and is cholesterol-free. Soybean has more than two times the amount of most of the minerals, especially calcium, iron, phosphorus and zinc, than any other legume and very low sodium content. Soybean is a good source of B-complex vitamins. Soybeans, especially the outer hull, are an excellent(5).
SPF scanning ultra microscopy structure
Soybean fibre is a man-made regenerated protein fibre from soybean protein blended with
PVA(2). Soybean fibres have a cream colour and their diameter is around 20 µm(5). Scanning Electron Microscopy (SEM) analysis of soybean fibre indicated longitudinal striations on the surface parallel to the axis, varying in length and depth, Figure 1.
SEM micrographs of the cross-section of soybean fibre, Figure 2, showed a kidney bean-like cross-sectional shape. Recent research on the cross section of soybean correlates well with the previous finding indicating kidney form shape. Studies on cross-sectional shapes of wet-spun fibres have associated the coagulation rate with the cross-section. It was suggested that noncircular cross-sections occur due to high coagulation rate in wet spinning(6).
Soybean protein fibres
Fibre forming soybean proteins
Soybeans are very reach with proteins (about 37 - 42% of dry bean) (Krishnan et al, 2007) in comparison to milk (3.2%), corn (10%) and peanuts (25%). Soybean proteins are used for food and feed and in many industries as adhesives, emulsions, cleansing materials, pharmaceuticals, inks, plastics and also textile fibres. Raw material for spinning textile fibres is obtained from soybean remaining flakes after the extraction of oils and other fatty substances(6).
Amino acids content of soybean proteins is given in Figure 2. Soybean proteins contain 18 different amino acids. There are about 23% of acidic amino acids (glutamic acid and aspartic amino acid), about 25% of alkaline amino acids (serine, arginine, lysine, tyrosine, threonine, tryptophane) and about 30% of neutral amino acids (leucine, phenylalanine, valine, alanine, isoleucine, proline, glycine). Sulphur containing amino acids are present also in soyproteins: about 1.0% of cysteine and 0.35% of methionine. Soybean proteins consist of various groups of polypeptides with a broad range of molecular size: about 90% are salt-soluble globulins (soluble in dilute salt solutions) and the remainder is water-soluble albumins(7). Very important as raw material for producing textile fibres are storage globulins with predominant ß-conglycinin (30 - 50% of the total seed proteins) and glycinin (ca 30% of the total seed proteins). ß-conglycinin is a heterogeneous glycoprotein composed of three subunits (a', a, ß) contained asparagine, glutamine, arginine and leucine amino acids. Subunits are non-covalently associated into trimeric proteins by hydrophobic interactions and hydrogen bonding without any disulphide bonds. Glycinin is a large hexamer, composed from acidic and basic polypeptides linked together by disulphide bonds(7,11).
On the basis of the sedimentation coefficient, a typical ultracentrifuge pattern of soybean proteins has four major fractions: 2S, 7S, 11S and 15S(5). Globular proteins are composed of segments of polypeptides connected with hydrogen bonds, electrostatic interactions, disulphide bonds and hydrophobic interactions. Conformational changes of unfolding globular proteins through denaturation process(4)and reducing the inclination of denaturised proteins to form aggregates are important for spin ability of a spinning dope with proper relative viscosity.
It is also important for later drawing of fibres and crystallisation of proteins in fibres. Denaturation (Figure 3) is modification of the secondary, tertiary and quaternary structure of protein. Exposure of soybean proteins to strong alkali/acids, heat, organic solvents, detergents and urea causes the denaturation of native globular proteins, ie, converting into unfolded polypeptide chains, which are connected with interchanging of disulphide bonds. Extruded fibres coagulate in a precipitation acid bath and new disulphide bonds are formed(14). The structure of soybean proteins and changes at converting globular proteins into fib reforming proteins are given in Figure 3.
Oils extraction with solvents used in the mid-twentieth century, was critical for the whole spinning process of soybean fibres, because the chosen temperatures, pH, urea, salts, organic solvents (hexane) and reducing agents influence on the degree of denaturation of proteins, degradation of proteins and changing of proteins colours. Protein degradation is detrimental to the production of high-strength protein fibres. Modern method of modifying soybean globular proteins is biochemical with using enzymes and auxiliary agent(12,13).
Characteristics of Soya protein Fibre
To the senses of the consumer, the appearance of a garment's shell fabric shows lustre, drapability and a fine degree of weave. The shell fabric made of soybean protein fibre shows the lustre of real silk; its drapability is also very good, giving people the sense of elegance; the textile woven with high-count yarn has fine and clear grain, suitable for high-grade shell fabric for shirts(10).
The knitting shell fabric which uses soybean protein fibre has a soft and smooth handle, and the texture is light and thin, with the sense of blending real silk and cashmere. Its moisture absorption performance is equivalent to cotton and its permeability is greatly better than cotton, ensuring comfort and health while worn(12).
The natural colour of soybean protein fibre is light yellow, very like the colour of oak silk. It can be dyed with acidic or active dyestuffs. Particularly when dyed with active dyestuff, the colour of product will be fresh and lustrous. With good fastness to light and perspiration, it also has good dyeing brilliance and dyeing fastness in comparison with real silk products(12).
Good colour fastness
The original colour of SPF is ivory like tussah colour. It can be dyed by acid dyes and active dyes especially the colour is quite fresh and lustrous with the later dyes while quite stable in the sunshine and perspiration. Compared with silk products, the problem of freshness of colour and stability of dyeing(11).
Good physical property
Breaking strength of the single SPF is over 3.0 CNdtex, which is higher than that of wool, cotton and silk and only lower than that of polyester fibre of high intension. By now, 1.27 dtex fibre can be spun into 6 dtex yarn with high quality, which can be used for high-quality and high density fabrics. Also, fabric of SPF has outstanding anti-crease, easy-wash and fast-dry property(14).
The soybean protein fibre, with its good affinity to human skin, contains several amino-acids and has good health effects. In the fibre-spinning process of the soybean protein fibre, the addition of Chinese herbal medicine with the effects of sterilisation and anti-inflammation will combine with the side chain of the protein in the manner of a chemical bond. The medical effect is outstanding and permanent, avoiding the disadvantage that the medical effect is less long-lasting when functional products of cotton goods are developed with the after-finishing method(13).
Its anti-ultraviolet property is superior to cotton fibre, much more superior to viscose and silk. The absorptive of ultraviolet radiation could reach up to 99.7 per cent.
Far infrared function
The emissivity of far-infrared could reach up to 87 per cent, have the function of heat-effect, promoting micro circulation of skin and enforcing the immunity, etc.
Its amino acid can activate the collagen protein in the skin, resist tickling and evaporate the skin.
Soybean protein fibre has antibacterial properties that resist colibacillus, staphylococcus aurous and candica albicans. Fabrics made from soya protein fibre and linen or other fibres are ideal for functional underwear and summer wear.
Applications of soybean fibre
Spinning methods have already been established for 100 per cent soybean fibre, its blends with natural (cotton, linen, wool, cashmere and silk) and chemical (modified polyester, viscose, tencel, polynosic etc) fibres, and used in plants dealing with cotton, silk and wool. Production of 100 per cent soybean fibre yarns in the range of 21S - 80S and blended yarns (28/72, 30/70, 45/55, 60/40, 70/30, 85/15 etc) is possible(14).
Soybean protein contained in the fibre remakes a superior, soft hand endowed with both moisture absorbency and permeability, which makes best application in knits and innerwear. Finishes with an anti-bacterial agent, health-care functionalities are also given. It has great potential in its use in high-grade knits and innerwear.
Weaves made of soybean fibre blends with other natural or chemical fibres have so far been used in shirting and home textiles. A series of such products, too, has already been developed. Their special feature is the lustre and soft hand found in silk. Their economic effects are extremely high. SPF are soft and smooth as well as absorbent it is ideal for products that are worn close to the skin such as underwear, sleepwear, sportswear and children's and infant's clothes, bed sheets, towels and blankets(11).
The undergarment made by SPF and spandex, has incomparable and unimaginable softness and comfortableness. Wearer's skin enjoys the pleasing breath after wearing SPF fabric, easy stretch and fine caring especially "skin on skin” feeling.
Eco-friendly soybean baby clothing offers many benefits to baby. The breathability, warmth and comfort are outstanding(10).
SPF has lustre of silk which is joyful and an excellent drape which makes the fabric elegant; fabrics of yarn with high count has fine and clear appearance and is ideal for top-level shirt.
Protein fibres of soybean have various specifications and lengths. They are developing filaments from soybean protein and are planning to extract protein for spinning from crops such as peanut, rape seed and cotton seed with the same technical method. If such development is successful, it will increase the varieties of protein fibres of crops, form series of new products and will be beneficial to the industrialisation of agriculture.
1. Aarons R (1960): UK Patent, 2,935,471.
2. Agricultural Statistics Board (1990), Agricultural Prices Report, NSSA, USDA.
3. Arrese E L, D A Sorgentini, J R Wagner and M C Anon (1991): Electrophoretic, Solubility and Functional-Properties of Commercial Soya protein Isolates, Journal of Agricultural and Food Chemistry, 39 (6): pp 1029 - 1032.
4. Atwood F C (1940): Natural Protein-Base Spun Fibres, Industrial and Engineering Chemistry, 32, pp 1547 - 1549.
5. Barman B G, J R Hansen and A R Mossey (1977): Modification of the Physical Properties of Soya protein Isolate by Acetylation, Journal of Agricultural and Food Chemistry, 25 (3): pp 638.
6. Boyer R A (1940): Soybean Protein Fibres; Experimental Production, Industrial and Engineering Chemistry, Vol 32, pp 1549 - 1549, April 27, 2011.
7. Brooks M M (2005): Soybean Protein Fibres – Past, Present and Future, In: Biodegradable and Sustainable Fibres, R S Blackburn, pp 398 - 440, Woodhead Publishing Series in Textiles, No 47, ISBN 1-85573-916-X (Woodhead Publishing), Cambridge.
8. Fletcher H A (1942): Synthetic Fibres and Textiles, Kansas Bulletin 300, pp 8 - 10.
9. Huakang Ltd (2005), www.soybeanfibre.com.
10. Huppert O (1944): Modified Soybean Protein fibre, US Patent 2,364,035.
11. Jiang Y, Y Wang, F Wang and S Wang (2004): The Ultra Structure of Soybean Protein Fibre, Textile Asia, 35 (7): pp 23.
12. Kajita, T and R Inoue (1940a): Process for Manufacturing Artificial Fibre from Protein Contained in Soybean, US Patent 2,192,194.
13. Petersen H (1983): Cross Linking with Formaldehyde-Containing Reactants, Handbook of Fibre Science and Technology, Vol II, Functional Finishes Pt A Chemical Processing of Fibres and Fabrics
14. M Lewin and S B Sello: New York, Marcel Dekker Saltzberg H P (1985): Encyclopedia of Polymer Science and Engineering, New York, John Wiley and Sons.
Department of Fashion Technology
Angel college of Engineering and Technology
Tirupur, Tamil Nadu 641665.