Protein-Based Fibres

Technical barriers would also need to be overcome. All silks are protein-based fibres. Mulberry plants do not fix nitrogen, making the process dependent on external fertilization. It is open to question whether lower levels of fertilization can be employed without compromising the quality of cocoons (Kumar and Kumar, 2011). 

Organic substances that can be analysed polarographically in the raw materials, intermediates and products of the textile industry, can be divided< > into those involved in the production of cellulosic fibres, those encountered in protein-based fibres and finally those in the dyeing process. 

Protein-based nano-fibrils have been found to be very efficient gelling agents, insofar as a protein gel can be formed even at very low protein concentrations (e.g., 0.07 wt%). Applying an external shear flow can further increase the gel-forming ability of these protein nano-fibres due to their preferred orientation along the direction of the flow. The robustness of the fibres towards dilution and other physical treatments is con-... 

There are three types of regenerated natural fibres - rayon, acetate and protein -the first two are derived from cotton linters or pine wood. Wool like protein based artificial fibres may be regenerated from animal and vegetable proteins. 

Cellulose-based plastics, particularly cellulose nitrate and acetates, were the most commercially important semi-synthetics up to the 1940s and were used as the base for photographic film, textile fibres, moulded goods and in lacquers. Naturally occurring polymer cellulose in the form of cotton linters or wood pulp is chemically treated to increase its solubility. Cellulose has a high molecular weight of between 100000 and 500000 and an empirical formula C0H1OO5. Casein-formaldehyde is the only protein-based moulded plastic that achieved commercial success. It is based on cow s milk and is still produced in very small quantities for specialist items such as hand-coloured buttons. 

The two main sources of natural fibres are plants and animals. The main component of animal based fibres is various proteins examples include mohair, wool, silk, alpaca, angora, etc. The components of plant fibres are cellulose microfibrils dispersed in an amorphous matrix of lignin and hemi-cellulose examples include cotton, jute, flax, ramie, sisal, hemp, etc. 

For centuries silk is a synonym for luxury garment. It describes a woven textile made of natural protein fibres sptm by the larvae or caterpillars of the domesticated silk moth, Bombyx mori. In this context, spinning does not refer to the textile process of fabricating a yam from a bulk of single fibres by warping and but rather describes the process of transforming an aqueous protein solution into an insoluble protein filament (Kerkam et al., 1991). Thus, silk fibres ate filaments that are spun at the point-of-delivery from feedstock, which can differ widely in detail but are protein based (Vollrath and Porter, 2009). 

Studies on protein-based formulations to treat hair fibres have also been widely explored. Several patents disclose compositions capable of restoring hair health by providing excellent finishing effects. Applications of proteins such as a water-soluble compound derived from a vegetable protein derivate [170], non-naturally occurring keratin proteins [171], a mixture of a hydrolyzed protein and an amino acid with an aliphatic side chain [172], and other hydrolyzed proteins [173, 174] are also examples within this category. 

Several proteins have been extensively studied for their materials applications. Among them, soy protein is one of the most popular. Indeed, since the early 1930s it was used in phenol-formaldehyde blends for automotive applications. However, soy protein is sensitive to moisture and exhibits relatively low strength properties. Thus stabilization by plasticization, compatibilization or crosslinkage is required to maintain long-term performance of soy protein-based plastic materials. Also, several studies on soy protein-based blends with other natural polymers or their reinforcement by natural fibres have been performed. More recently studies on soy protein-nanoclay composites and polyfbutylene adipate-co-terephthalate) (PBAT) blends were also performed. 

Wheat gluten is another protein from plants, which was intensively studied for its material applications. Wheat processing requires the presence of plasticizers such as glycerol or water to disrupt disulfide bonds. To control the formation of a crosslinked network, cysteine, formaldehyde or glutaraldehyde can be added. This contributes also to an improvement in moisture sensitivity and in elongation at break. On the other hand, the wheat gluten fibres have better properties compared to other protein-based bio products for biomedical applications. 

Two processes are currently used to prepare protein-based films the wet method ( casting ), which involves the solubilization of protein and a plasticizer in a solvent followed by the formation of a protein network on evaporation of the solvent and the dry method, which is based on thermoplastic characteristics of proteins and combines the use of pressure and heat to plasticize protein chains [25, 32]. Dehulled soybean, after solvent defatting and meal grinding, becomes a fat-free, low fibre soy flour (48.5% protein). The soy flour, after leaching out of the water/alcohol soluble sugars, is termed soy protein concentrate (above 65% protein). The soy protein concentrate, if it is further extracted by alkali and reprecipitated by acidification, becomes the purest commercially available soy protein isolate (above 90% protein). 

The mechanical properties of protein-based films can be markedly improved by adding fibres (i.e., composite materials). Mechanical properties are always highly dependent on the temperature and RH of the protein material (Figure 11.9). This modification, (i.e., sharp increase in deformation at break and decrease in mechanical strength), occurs suddenly when the material crosses the Tg range [174]. 

On the basis of their manifold functionalities, proteins can be used both in various nutritional and technical applications texturized proteins as meat extenders and replacers as well as fibres for textiles, protein-stabilized emulsions and foams in food dressings as well as asphalt emulsions or fire control foams, protein-based films, and coatings for fruit moisture control as well as for packaging purposes. 

Natural fibres include those collected from natural source according to their origin, natural fibres are further grouped into three classes vegetable, animal and mineral. Vegetable fibres contain cellulose as a fundamental constituent whereas animal-based fibres are protein, eg, silk and wool. Asbestos is example of a mineral fibre. 

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