Natural fibre ropes

When inspecting natural fibre ropes, discoloration and rotting must also be looked for. This includes internal as well as external fibres. 

Trace metals can be leached out of some natural fibres. To determine copper in webbing, rope and cotton duck, Simonian [184] warmed, to near boiling, 2—3 g fabric with 80—90 ml of 0.5 M hydrochloric acid. The sample was filtered and made up to 200 ml before aspiration into an air/acetylene flame. 

Whilst this type of incidental orientation may constitute a minor disadvantage, there are whole industries which are based upon the deliberate exploitation of this effect. The production of synthetic fibres, and therefore of all synthetic textiles and ropes, depends upon orientation. Also the packaging industry makes extensive use of uniaxial and biaxial orientation. Recently the drawing and subsequent fibrillation of polyol uis has produced a cheap replacement for jute and sisal with profound repercussions on the economies of India and Pakistan. The extent to which synthetic fibres have supplemented natural fibres is shown in Fig. 2. 

Issues of ecology and sustainability may lead to natural fibres making a comeback in ropes and cords. 

There is a wide variety of agro-based or natural fibres to consider for utilization. They can be subdivided based on their origin, viz. vegetable, animal or minerals. Cellulose as a material is used by the natural world in the construction of plants and trees, and by man to make shipping sails, ropes and clothes, to give but a few examples. It is also the major constituent of paper and further processing can be performed to make cellophane and rayon. Depending on the part of the plant from which they are taken, cellulose fibres can be classified as ... 

Kenaf is an herbaceous annual plant that is grown commercially in the USA in a variety of weather conditions, and it has been previously used for rope and canvas. Kenaf has been deemed extremely environmentally friendly for two main reasons (a) kenaf accumulates carbon dioxide at a significantly high rate and (b) kenaf absorbs nitrogen and phosphorous from the soil [17]. In addition, kenaf, like most other natural fibres, demonstrates low density, high specific mechanical properties, is easily recycled and maintains a competitive price. 

PVDs made of natural fibres are popular because of their economy and efficiency. A flexible natural PVD made of jute filter fabric and a coir ropes core was developed and field tested at Changi Airport in Singapore to consolidate soft compressive soil. After 2 years of observation, analysis showed that the drain had adequate discharge capacity and functioned well (Rao and Balan, 1994). 

A major use of ropes is in lifts (elevators) and cranes, where heavy weights have to be raised and lowered. The requirement is for high strength and low extensibility plus resistance to flex fatigue in motion over pulleys and to corrosion. Heat can be a problem in deep mines or in braking an elevator in free fall. As skyscrapers and deep mines came into use in the 19th century, steel wire ropes were the natural choice. Industrial conservatism means that they continue to dominate the market. The mechanics are stress-driven and extension is a nuisance so that the high-performance fibres, such as aramid and HMPE, should be contenders. 

Fibres are a class of material that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. They can be spun into filaments, rope or string. Fibres are of two types natural and synthetic. Figure 9.1 shows a general classification of fibres. 

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. 

It must be emphasized that the large standard deviations result from irregularities in bundle geometry and composition due to the natural origin of the fibre, and that the stiffness of the bundle is very low at low strains, and increases gradually to the value of 8030 MPa at and beyond a strain of 1.5 % the "rope" effect is obvious. 

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