Application of Rubber in Textiles
B.J.Group, Mawna, Gazipur
B.J.Group, Mawna, Gazipur
Rubber and textiles have been used together, each working with the other to give improved performance in a very wide range of applications, since the earliest days of the rubber industry in the more developed areas of the world.
For many years, rubber companies of reasonable size, using textile reinforcement, would employ their own textile technologist working alongside the rubber technologists. Over the last third of the twentieth century, faced with global competition and the need to control and reduce total costs, this luxury has largely disappeared apart from the largest companies (particularly the tyre companies). Most organisations now rely on their textile suppliers to provide technical knowledge and expertise. As a result, the textile component for many applications is now considered in much the same way as the other raw materials, that is as an existing product, which only requires introducing into the manufacturing process, without any special knowledge or understanding, and is supplied against an agreed specification, which was probably drawn up by the textile manufacturer anyway. The most important and by far the largest use of textiles in rubber is in the tyre industry.
The modern world relies to a great extent, on textile/polymer composites, the majority of which are rubber/textile compositions. In fact, it is difficult to imagine the functioning of modern everyday life without the use of such products. It is only necessary to consider the need for transport systems (relying on textile/rubber tyres), materials handling systems (relying on textile/rubber conveyor belting) and mechanical drive systems (using rubber/ textile drive belts) to see the important role played by such materials.
Whereas textiles have been produced and used for many thousands of years, it was only some 500 years ago that rubber was introduced to Europe and really only in the last two hundred years that textiles and rubber have been used together in this region. Since then, however, there has been very great development in the design and use of these materials.
Within the last 75 years, there has been a great move away from natural materials (natural rubber and cotton) to synthetic products, both as regards the fibres and the polymers used, resulting in a very wide diversity of engineered composites, to meet many and varied performance requirements.
The origin of the textile industry is lost in the past. Fine cotton fabrics have been found in India, dating from some 6-7000 years ago, and fine and delicate linen fabrics have been found from two to three thousand years ago, at the height of the Egyptian civilisations. More recent archaeological excavations, among some of Europe’s oldest
Stone Age sites, have found imprints of textile structures, dating back some 25,000 years, but in the humid conditions obtaining in these more northerly areas, all traces of the actual textiles have long disappeared, unlike those from the dry areas of India and Egypt.
Until more recent times, the spinning of the yarns and the weaving of the fabrics were generally undertaken by small groups of people, working together – often as a family group. However, during the Roman occupation of England, the Romans established a ‘factory’ at Winchester, for the production, on a larger scale, of warm woollen blankets, to help reduce the impact of the British weather on the soldiers from southern Europe.
By the eighteenth century, small co-operatives were being formed for the production of textiles, but it was really only with the mechanisation of spinning and weaving during the Industrial Revolution, that mass production started.
Up to this time, both spinning and weaving were essentially hand operations. Handlooms were operated by one person, passing the weft (the transverse threads) by hand, and performing all the other stages of weaving manually. In 1733, John Kay invented the ‘flying shuttle’, which enabled a much faster method for inserting the weft into the fabric at the loom and greatly increased the productivity of the weavers.
As the chemical industry greatly increased the types of yarns available for textile applications, so the machinery used in the industry was being developed. Whereas the basic principles of spinning and weaving have not significantly changed over the millennia, the speed and efficiency of the equipment used for this has been vastly been improved. In weaving, the major changes have been related to the method of weft insertion; the conventional shuttle has been replaced by rapiers, air and water jets, giving far higher speeds of weft insertion.
Other methods of fabric formation have similarly been developed, such as the high speed knitting machines and methods for producing fabric webs known as ‘non-wovens’.
Whereas the basic properties of rubber, or caoutchouc as it was then called, were known to the natives of South America, the first reports of it in Western Europe were given by
Christopher Columbus in 1492 and then more detailed accounts were given by Gonzalo Fernandez d’Ovideo y Valdas, in his Universal History of the Indies, in which he describes the game of ‘batos’ as like a game of balls, ‘But played differently and the balls are of other material than those used by Christians’.
All the rubber available at this time, was, of course, wild rubber, gathered from the rain forests of Central and Southern America. This rubber was mainly in the form of ‘bottles’, from the wooden formers on which the latex was dried and smoked, or roughly spherical ‘negro-heads’, consisting of many small lumps of dried rubber stuck together.
Many other uses were found for rubber; by 1825, hoses were being built on mandrels, with reinforcement of two or more plies of fabric, and with wire spiralling for suction hose.
Today, there are many synthetic polymers available, ranging from the general purpose hydrocarbons with properties largely similar to those of natural rubber; to the special purpose types with excellent resistance to ageing, oils and solvents; to highly sophisticated (albeit very expensive) polymers with outstanding resistance to the most hostile of environments, as found in aerospace, marine and oil exploration applications.
Textile and Rubber Composites:
From the very first references to rubber in South America, its use with textiles has been noted. This is not very surprising, as from the earliest times, one of the major drawbacks of textiles was their performance under wet conditions; in the dry, they gave excellent protection and warmth, but in the wet they soon became saturated and, if anything, made things seem worse. Many treatments were tried over the years to overcome this deficiency, using coatings of tars, resins and waxes; the most successful of these was the treatment with natural drying oils, to give the waterproof oilcloths. The main disadvantage of these was the stiffness and brittleness imparted to the fabrics.
With rubber, many of these disadvantages virtually disappeared, giving a soft, flexible and waterproof material (at least at normal ambient temperatures).
Now natural rubber had to be replaced with synthetic, this, of course, applied to the adhesive systems too.
Thus, over the years, the two technologies, those of rubber and of textiles, have developed side by side. Today, composites are available which satisfy the stringent performance requirements met under such diverse and hostile environments as those of outer space or the depths of the sea and at extremes of temperature.
The Application of Rubber in Textile
There are five main types of fibres used in the production of reinforcements for rubbers. Cotton, one of the original reinforcing fibre types, is still in use in many applications, but is steadily being replaced by man-made fibres.
There are wide ranges of application of rubber in textiles. In this article I will discuss briefly.
Yarn and Cord Processes:
There are very few applications where textile fibres can be used in the form in which they are originally produced. It is usually necessary to modify the yarn form or construction, in order to obtain the optimum benefit from their incorporation as reinforcement in elastomeric composites.
For some applications, single-end yarns or cords (several twisted yarns twisted together) are the preferred form, especially for hose and V-belts. In some cases (particularly in tyres) although the single-end cord is the right form of reinforcement, it is preferable for the cords to be assembled together into a cord-fabric. This represents a halfway stage between the single cord and the fully woven constructions. For most other applications, woven fabrics provide the most satisfactory form of textile reinforcement, but even in these constructions, it is generally necessary to modify the yarn, rather than using the asproduced form.
The final yarn processing step, prior to fabric formation, is the preparation of the warp (or weaver’s) beam, to assemble the required number and lengths of yarns onto one carrier, ready for the fabric formation process.
Fabric Formation and Design of Fabrics:
As previously mentioned, for many industrial reinforcement applications, it is desirable for the yarns to be assembled together into a coherent form rather than as single-ends.
There are several methods whereby such assemblies can be prepared, but the majority of industrial reinforcements are in the form of woven fabrics, although other methods of production, such as knitting.
Heat-Setting and Adhesive Treatments:
With the increasing use of the artificial fibres, the need for additional treatments, before the textile can be satisfactorily used for elastomer reinforcement, has greatly increased. With cotton, the only pretreatment needed was drying to reduce the moisture content and so eliminate porosity in the final composite. With the introduction of rayon, this remained necessary and further processes to improve the adhesion were found to be essential.
With the synthetics, although moisture was not such a problem, adhesion treatment was needed, but also it was soon found that shrinkage presented difficulties and methods had to be developed to overcome this, which gave rise to the heat-setting operations. Heat setting and adhesive treatment are usually combined into one process, which is normally the final stage in the manufacture of the textile component.
Special machinery has been developed for these treatments, for both single-end cords and for fabrics, which allow very close control of the properties of the textile material. These treatments can be adjusted to tailor the adhesive characteristics and physical properties of the textile to meet the particular requirements for specific applications. Similarly, control must be exercised in the formulations and processes of manufacture of the composite, so that the optimum properties can be realised in the ultimate product.
Basic Rubber Compounding and Composite Assembly:In most rubber formulations, there are many ingredients which are regarded as necessary to meet performance parameters or costs, i.e., fillers, curatives, antidegradants, etc. Seldom, however, are these considered for any effects they may have on the adhesion properties of the resultant compound. Admittedly, many of these common additives do have only little effect.
Whereas it is possible to tailor the RFL system to a specific compound, to obtain optimum adhesion, it is generally more cost effective to retain a standard RFL treatment and fine tune the rubber compound for adhesion. In this way, the final control of the formulation and mixing remains within the sphere of the rubber company, rather than with the textile converter and finisher.
A large proportion of rubber/textile composites are based on the standard hydrocarbon rubbers and these will be the major types of materials considered here.
Conveyor belts are used throughout industry for transporting materials from one place to another. Their applications are very varied, from carrying small items over a metre or two, as at supermarket checkouts, to carrying bulk materials for many kilometres, as in many quarrying and mining installations.
Hoses made of rubber have been used for many years. By 1825, hoses reinforced with up to two layers of cotton fabric were being built on mandrels and spiral steel wires were incorporated, to prevent the hoses collapsing under suction or vacuum. In the late 1820s. Barclays Brewery, in London, completely replaced all its existing leather hoses, with cotton reinforced rubber ones, in spite of the opposition from the leather trade. This proved a great success, as the rubber hoses, being seamless, reduced leakage to a negligible level.
A hose is, essentially, a reinforced tube. It consists basically of three parts, the inner tube, which contains whatever medium the hose is designed to carry, the reinforcement, to impart sufficient strength to withstand the pressure of the carried medium, and the outer cover, to protect the other components from damage in service. For good performance, all three of these components must be well consolidated together during manufacture.
Frequently, especially for special applications, end fittings may be attached, the final combination being known as an assembly.
Power Transmission Belts:
Belts, of one type or another, have been used for many centuries to transmit rotational power; this was the principle of the bow drill and pole lathe. Here, a thong or strap was wrapped once around a mandrel and, on reciprocating the strap, the mandrel was rotated. A logical extension of this principle was to transmit continuous rotary motion between two shafts, by joining the strap into an endless loop. The success of these early drives depended largely on an understanding of the basic factors affecting the efficiency of the drive, such as velocity, torque ratios, slippage and, particularly, choice of materials.
Applications of Coated Fabrics:
The major applications of coated fabrics are in inflatable constructions. Such applications are well established in history; the Romans used inflated animal skins for flotation and support for bridges in the first centuries BC and AD. In 1783, the Montgolfier Brothers built their first hot-air balloons, using oiled silk as the containing membrane. In these applications, the materials available showed certain significant disadvantages; firstly the animal skins had to be stitched together and these seams treated to make them air tight but, even so, they still leaked and were of irregular size and shape and the oiled silks used later were very stiff and brittle.
Nowadays, there are many uses for such constructions, not only for inflatables but also for flexible storage tanks. Similarly, there is a wide range of applications for coated rubber sheeting, in the flat state.
Miscellaneous Applications of Textiles in Rubber:The above are the major areas of textile reinforcement of rubbers, but there are many other applications which do not fall within these groups. A very great area, outside the scope of this book, is the tyre industry, but there are other smaller, specialised applications, which could not satisfy the performance requirements without the complementary properties of both the textile and the rubber components.
Rubber also used in:
- Hovercraft Skirts
- Air Brake Chamber Diaphragms
- Snowmobile Tracks
It is just briefly described about application of rubber in textile. If you want to know more about on it. Then you should collect a book on “Applications of Textiles in Rubber” by David B. Wootton
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