Natural Rubber Production, Properties and Applications

Department of Polymer Science and Rubber Technology Cochin University of Science and Technology Kochi, Kerala, India 

Keywords Natural rubber, Hevea brasiliensis, cultivation, modification, primary processing, manufacturing techniques, pneumatic tyre, non-tyre products, vulcanization, green commodity 

Susheel Kalia and Luc Averous (eds.) Biopolymers Biomedical and Environmental Applications, (403-436) Scrivener Publishing LLC 

Prior to the identification of Hevea brasiliensis as the most important commercial source of natural rubber, plants belonging to a wide spectmm of families had been explored for extraction of rubber. Among these, extractable quantities of mbber could be obtained from a few sources as given in Table 14.1. 

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Chemical nature Isolation of casein from milk Production of casein plastics Properties of casein Applications Miscellaneous Protein Plastics Derivatives of Natural Rubber Gutta Percha and Related Materials Shellac... 

In this chapter we cover the preparation, mechanical properties, and applications of S/DPE polymers. Owing to its brittle nature this product should be rubber modified, so special emphasis will be placed on this aspect. 

This book on natural rubber presents a summary of the present state-of-the-art in the study of these versatile materials. The two volumes cover all the areas related to natural rubber, from its production to composite preparation, the various characterization techniques and life cycle assessment. Chapters in this book deal with both the science of natural rubber - its chemistry, production, engineering properties, and the wide-ranging applications of natural rubber in the modern world, from the manufacture of car tyres to the construction of earthquake protection systems for large buildings. Although there are a number of research publications in this field, to date, no systematic scientific reference book has been published specifically in the area of natural rubber as the main component in systems. We have developed the two volumes by focusing on the important areas of natural rubber materials, the blends, IPNs of natural rubber and natural rubber based composites and nanocomposites their preparation and characterization techniques. The books have also profoundly reviewed various classes of fillers like macro, micro and nano (ID, 2D and 3D) used in natural rubber industries. The applications and the life cycle analysis of these rubber based materials are also highlighted. 

Volume 1 of this book is comprised of 25 chapters, and discusses the different types of natural rubber based blends and IPNs. The first seven chapters discuss the general aspects of natural rubber blends like their miscibility, manufacturing methods, production and morphology development. The next ten chapters describe exclusively the properties of natural rubber blends with different polymers like thermoplastic, acrylic plastic, block or graft copolymers, etc. Chapter 18 deals entirely with clay reinforcement in natural rubber blends. Chapters 19 to 23 explain the major techniques used for characterizing various natural rubber based blends. The final two chapters give a brief explanation of life cycle analysis and the application of natural rubber based blends and IPNs. 

Natural rubber based-blends and IPNs have been developed to improve the physical and chemical properties of conventional natural rubber for applications in many industrial products. They can provide different materials that express various improved properties by blending with several types of polymer such as thermoplastics, thermosets, synthetic rubbers, and biopolymers, and may also adding some compatibilizers. However, the level of these blends also directly affects their mechanical and viscoelastic properties. The mechanical properties of these polymer blended materials can be determined by several mechanical instruments such as tensile machine and Shore durometer. In addition, the viscoelastic properties can mostly be determined by some thermal analyser such as dynamic mechanical thermal analysis and dynamic mechanical analysis to provide the glass transition temperature values of polymer blends. For most of these natural rubber blends and IPNs, increasing the level of polymer and compatibilizer blends resulted in an increase of the mechanical properties until reached an optimum level, and then their values decreased. On the other hand, the viscoelastic behaviours mainly depended on the intermolecular forces of each material blend that can be used to investigate the miscibility of them. Therefore, the natural rubber blends and IPNs with different components should be specifically investigated in their mechanical and viscoelastic properties to obtain the optimum blended materials for use in several applications. 

More than 500 years ago, the people of Central and South America were using a product that they collected from certain trees to make balls and to coat fabric to make it waterproof. This material they called cauchuc, which means weeping wood. Today we know the tree as the Hevea brasiliensis and the material as natural rubber. Although a number of plants produce rubber, the only significant commercial source is the Hevea tree. Natural rubber had only limited applications until 1839, when Charles Goodyear found that when combined with sulfur and heated, the material changed into cured rubber with properties much as we know them today. The development of the pneumatic tire in 1845 combined with the dramatic growth of the automotive industry led to a rapid increase in the demand for natural rubber. 

The types of processing and physical property tests that are required to assess the important characteristics referred to above are also continually cited in the later sections of this book dealing with the use of waste rubber crumb in rubber products, thermoplastics, and thermosets, for the same reasons (Chapter 7). Many other specific property tests (e.g., acoustic) are also referred to in this book but, unfortunately, there is insufficient space here to cover them. A reasonably detailed section on the characterisation of rubber crumb is provided in Chapter 6, Section 6.4, because understanding the nature of this material is as important as understanding the properties of devulcanised rubber when it comes to its re-use applications. 

There are some applications for a-sulfo fatty acid esters in the production and processing of synthetic materials or natural rubber. Emulsifiers are needed for the emulsion polymerization, antistatic agents improve the properties of polymers, and wetting agents are needed as parting components for elastomers. 

Butyl rubber is produced by a process in which isobutylene is copolymerized with a small amount of isoprene using aluminum chloride catalyst at temperatures around — 150° F. (20). The isoprene is used to provide some unsaturation, yielding a product that can be vulcanized (43). Vulcanized Butyl rubber is characterized by high tensile strength and excellent flex resistance furthermore, as a result of its low residual unsaturation (only 1 to 2% of that of natural rubber) it has outstanding resistance to oxidative aging and low air permeability. These properties combine to make it an ideal material for automobile inner tubes (3), and Butyl rubber has continued to be preferred over natural rubber for this application, even when the latter has been available in adequate supply. 

Because of its excellent high- and low-temperature properties, many products used in the arctic and tropical areas of the world are made from natural rubber. However, it is not suitable for applications where there is contact with naphtha, e.g, gasoline hoses, because the solvent swells the material. Almost all clastic bands arc made from natural rubber. Because of its excellent tack properties, the material is used in solvent and latex form as the base for adhesives. 

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