Natural fibre composites protein fibres

The classical two-phase model assuming a composite arrangement of distinct crystalline and extended amorphous regions to describe the superstructure of natural fibres apparently has to be revised. Concepts like crystallinity and amorphicity are well adapted to describe homogeneous states of matter. They are, however, rather ill-defined when it comes to treating dense composite materials like cellulose, or proteins, given that intermolecular correlations do not build up or die off abruptly at some fictitious interfaces. 

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. 

The heat deflection temperature (or heat distortion temperature) is an important material property mostly used to determine a material s useful temperature operating range. It refers to the temperature below which a moulded object can hold its own shape. It can be determined using a dynamic mechanical analyser set to apply a constant force. The HDT was determined for blends of plasticized soy flour (52% protein) and polyamide (nylon) as 45 °C when plasticized with 20 wt% sorbital, 35 °C when plasticized with 20 wt% glycerol, and 39 °C when plasticized with 10 wt% of each." When such a blend is used to make composites with natural flbres, increasing content of natural fibres also increased the HDT. 

M ht scouring operations in which these surface-active compounds are commonly used varv according to the nature of the fibre and the amount and composition of the impurities to be removed. In the case of cotton the cellulose of w hich it is composed is stable to dilute solutions of alkali at the boil. I he imphrities which must be removed are natural oils and waxes, proteins, pectic substances, natural colouring matter, and adventitious dirt. The basic principle of cotton scouring is to boil the goods for several hours at atmospheric, or under elevated, pressure with a 2 per cent solution of sodium h) droxide. 

Natural polymeric fibres have (literally) supported the development of human civilisation since its prehistoric beginnings. A particularly prominent role has been played by cellulose, a polysaccharide which is one of the world s most abundant and versatile fibrous polymers. Cellulose fibres are the reinforcing component of wood, a natural composite that can be fashioned into devices used for shelter, transportation, agriculture, war, communication, ornament and recreation. Cellulose fibres have been woven into clothing, twisted into ropes and bowstrings, and processed into papyrus and paper. Fibrous proteins, especially keratin (wool, mohair), collagen (hide, parchment, catgut) and silk also have a rich history and an assured future as useful materials. 

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