Composites, jute

Doors Jute puitruded door frames, medium density composites Jute coir CBRI, Roorkee... 

In chemical composition, jute is different from linen and cotton. It is composed of a modified form of cellulose called lignocellulose (bastose). 

Most composites made using jute exploit the long fibre strand length. Commercially, both woven and non-woven jute textiles are resin- or epoxy-impregnated and moulded into fairly complex shapes. In addition, jute textiles are used as overlays over other composites. Jute stick is used for fuel, and in poor areas it is stacked on end, tied into bundles, and used as fences and walls. 

The filaments of all plant fibers consist of several cells. These cells form crystalline microfibrils (cellulose), which are connected together into a complete layer by amorphous lignin and hemi-cellulose. Multiple layers stick together to form multiple layer composites, filaments. A single cell is subdivided into several concentric layers, one primary and three secondary layers. Figure 5 shows a jute cell. The cell walls differ in their composition and in the orientation of the cellulose microfibrils whereby the characteristic values change from one natural fiber to another. 

The surface energy of fibers is closely related to the hydrophilicity of the fiber [38]. Some investigations are concerned with methods to decrease hydrophilicity. The modification, of wood cellulose fibers with stearic acid [43] hydrophobizes those fibers and improves their dispersion in polypropylene. As can be observed in jute-reinforced unsaturated polyester resin composites, treatment with polyvinylacetate increases the mechanical properties [24] and moisture repellency. 

Figure 10 Influence of silane coupling agents on the strength of jute reinforced epoxy-resin composites at different moisture contents [12],...

Figure 14 Influence of fiber drying on the characteristic values of jute reinforced epoxy-resin composites [121.

Tests by Roe et al. [63] with unidirectional jute fiber-reinforced UP resins show a linear relationship (analogous to the linear mixing rule) between the volume content of fiber and Young s modulus and tensile strength of the composite over a range of fiber content of 0-60%. Similar results are attained for the work of fracture and for the interlaminate shear strength (Fig. 20). Chawla et al. [64] found similar results for the flexural properties of jute fiber-UP composites. 

Figure 21 Compression strength as dependent on the content of GRP in jute fiber-reinforced hybrid-composites [67J.

Several of these natural fiber composites reach the mechanical properties of glass fiber composites, they are already being used in the automobile and furniture industries. Up to now, the most important natural fibers were jute, flax, and coir. 

EAC Technologies (of Belgium) produces mats of flax, hemp or jute and composites made of flax, hemp or jute reinforced polypropylene. 

The resistance of cellulose to microbial attack when it was treated with resins was attributed to chemical bonds formed between the fiber and the resin this was ascertained by treating cotton with a variety of phosphonium salt-resin compositions having different degrees of cross-linking and homopolymerization (127). Some of the more recent approaches for producing antimicrobial fibers include the use of reactive dyes (128) and mixtures of zirconyl and copper salts (15) on cotton and the bromination of jute (129). 

The large-production reinforcing agent used today is primarily glass. Other fibers include cotton, cellulosic fiber, sisal, polyamide, jute, carbon, graphite, boron, whiskers, steel, and other synthetic fibers.10 12> 289 291, 466 They all offer wide variations in composition, properties, fiber orientation/construction, weight, and cost (Tables 15.4 and 15.5... 

Use of fibers as reinforcements to make composites is, of course, well established. These are structural applications where, because of the characteristically long length of fibers, they are incorporated in a continuous medium, called the matrix. We describe some of these applications in subsequent chapters in more detail. Yet another common use of fibers of various kinds is in making ropes. In prehistoric times, ropes were made of braided leather strips and vines. Later, vegetable fibers such as jute, hemp, etc., were used to make ropes. More recently, ropes have been made of synthetic pol3nmers and metallic fibers. Ropes can be made by a variety of construction methods twisted, braided, plaited, parallel core and fiber, and wire rope. 

In recent years starch, the polysaccharide of cereals, legumes and tubers, has acquired relevance as a biodegradable polymer and is becoming increasingly important as an industrial material (Fritz Aichholzer, 1995). Starch is a thermoplastic polymer and it can therefore be extruded or injection moulded (Balta Calleja et al, 1999). It can also be processed by application of pressure and heat. Starch has been used successfully as a matrix in composites of natural fibres (flax, jute, etc.). The use of starch in these composites could be of value in applications such as automobile interiors. An advantage of this biopolymer is that its preparation as well as its destruction do not act negatively upon the environment. A further advantage of starch is its low price as compared with conventional synthetic thermoplastics (PE, PP). 

Although jute is a natural fibre like cotton, it differs in chemical composition. Unlike cotton jute contains a high percentage of non-cellulosic matter (about 40%) and the pre-treatment processes of jute are somewhat different from that of cotton. Scouring of jute with caustic soda under pressure cannot be carried out like cotton because of removal of hemi-cellulose which results in high losses of tensile strength (10-15%) and weight (6-8%). 

The forces which come into play in a filled system are not restricted to affecting the mobility of chains. They also influence the filler particle distribution. The migration of filler particles has been modeled for an injection molding process. A spectacular effect was observed when jute fiber was used as a filler. As the moisture level of jute was increased, the fibers rotated about their axes. This changes the distribution and orientation of the jute fibers and has an effect on the properties of the composite. 

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