Natural fibres mechanical properties

The effect of the amount of natural fibre such as corn stover, the fibre length and the amount of cross-linker such as divinylbenzene with rm-butyl peroxide on the structure and thermomechanical properties of the soybean and linseed oil-based green composites, revealed that the properties were improved with an increase in the amount of fibre and a decrease in the length of the fibre. Mechanical properties like Young s modulus and the tensile strengths of the composites increased from 291-1398 MPa and 2.1-1 A MPa, respectively for 20-80 wt% fibre loading. However, water uptake also increases under these conditions. The composites contain... 

The first high-strength carbon fibres were produced in the 1950s (see Donnet and Bansal, 1984). The early carbonized products were rayon-based, but it was soon found that the mechanical properties and the carbon yield could be improved by the use of polyacrylonitrile (PAN) as the precursor. Also, less expensive fibres of somewhat lower strength and modulus could be made from various other precursors including petroleum pitch and lignin. However, cotton and other forms of natural cellulose fibres possess discontinuous filaments and the resulting mechanical properties were consequently found to be inferior to those of the rayon-based fibres. 

In the first section of this volume we examine the fundamentals of structure at the level of the overall composite, as well as the properties of its components. The starting materials of food derive from living biological systems, whose mechanical properties have been studied in their own right. Vincent explores the extent to which biological composites can be related to other natural and manmade composites, and emphasises the difference between the properties of components (fibres and matrix) and the structure itself This engineering approach to biological structures, whether natural or fabricated, shows the fundamental difference in the materials science approach, compared with the former recipe approach to food manufacture. 

In Table 25.1 a comparison between S/DPE(30) (i.e. 30wt% DPE) and syn-diotactic polystyrene (sPS), both products containing 30 % glass fibres, is shown. It can be seen that the mechanical properties of the S/DPE product are slightly superior to those of sPS. Resistance to polar solvents, however, is probably better in sPS than in S/DPE polymers owing to its partially crystalline nature. 

Insolation in natural conditions and under artifical light source shows that in both cases change of the value of PETP molecular weight happens less intensively compared with physico-mechanical properties. Evidently, the fact, that physico-chemical properties are defined not only by chemical structure, but by complex formations of supermolecular structure, is characteristics for PETP-fibre. 

WOL 98] WoLLERDORFER M., Bader H., Influence of natural fibres on the mechanical properties of biodegradable polymers . Industrial Crops and Products, vol. 8, no. 2, pp. 105-112,1998. 

Composites reinforced with short natural fibres has been done, as a matrix used polyester resin. The natural fibres such as palm-fibre and coir-fibre have been treated with chemical and mechanical treatment. The mechanical properties of composites with treated natural fibres better than untreated natural fibres composites. 

Results from impact assessment models for silk and other fibres are smnmarized in Table 11.3. Where datasets and assessments have followed a comparable approach, the environmental impact of silk on a mass basis is notably higher than that of other fibres. It should be noted that silk has very different mechanical properties from other natural textiles (Porter and Vollrath, 2009) and has no close substitute among natural fibres. Silk is also much more valuable both as fibre, yam, and final textile. 

Sun, D., and Stylios, G. K. (2005). Investigating the plasma modification of natural fibre fabrics-the effect on fabric surface and mechanical properties, TextRe., 75, 639-644. 

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

The mechanical characteristics of the fibres well reflect the complexity of their structures. While wool shows a decrease of E-modulus and an increase of elongation at a break in the wet stage compared to the dry one, cellulosic fibres behave inversely. A summary of the mechanical properties of natural fibres is given in Table 9.6.5. 

As already mentioned, specific mechanical properties are decisive when using natural fibres in composite materials. The fact that hemp, flax, and ramie natural fibres can compete with technical fibres is demonstrated in Fig 1. 

A striking feature of poly(p-benzamide) fibre is the extremely splintered nature of the broken end of the heat treated material (Fig. 10). The tendency of the fibres to break up into fibrillar or high aspect ratio particles and to show very poor mechanical properties in a direction perpendicular to the fibre axis must clearly be related to the extremely high axial orientation of the polymer molecules. One can envisage these fibrillar particles as built up of submicroscopic fibrils, themselves built up of the ultimate linear crystallites. 

The yarns made from natural filaments had substantially fewer technical properties compared with today s synthetic products, were heavy and absorbed substantially more moisture despite being impregnated with water repellant, which also affected the life span. Textiles made from natural fibre yarns were susceptible to mould attack and rot, got dirty rapidly and were highly flammable unless impregnated with special fire retardants. With increasing demands on the durability and mechanical strength of fabrics for use in construction, the fabrication of natural fibres for use in this sector has declined over the last few decades. 

The production of composites from epoxy resins and fibres has significantly increased in recent time. Both the fiber and polymeric phases retain their original chemical and physical identities, with mechanical properties sometimes exceeding those of the constituents. The nature of the interface of the two phases is of enormous importance, particularly where high resistance to failure is sought [21]. 

I. Crivelli-Visconti and G. A. Cooper, Mechanical Properties of aNew Caibon Fibre Material, Nature 221, 754-755 (1969). 

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