Development and Modification of Natural Rubber for Advanced Application

Development and Modification of Natural Rubber for Advanced Application

Kanoktip Boonkerd (Chulalongkorn University, Thailand)
Copyright: © 2017 |Pages: 33
DOI: 10.4018/978-1-5225-1971-3.ch003
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Abstract

Although natural rubber is a challenging elastomeric material for both dynamic and static engineering applications, there are some inherent drawbacks such as the poor oxygen, ozone, oil and heat resistance and also the low compatibility with the polar materials. To loosen these inferior properties and also to transform natural rubber into new polymeric materials, natural rubber needs to be either chemically or physically modified. Moreover, to make natural rubber become a promising elastomeric material for the advanced application, the development of natural rubber with the superior mechanical strength, the low gas permeability or the high conductivity is recently focused. And these can be done by reinforcing natural rubber with nanofillers. This chapter presents a broad review on the recent research and development of natural rubber including the modification of natural rubber and the preparation of various natural rubber nanocomposites for advanced application.
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Introduction

Natural rubber (NR) is a high molecular weight polymeric substance with viscoelastic properties. Structurally it is cis 1,4-polyisoprene. Isoprene is a diene and 1, 4 addition leaves a double bond in each of the isoprene unit in the polymer. Natural rubber is considered as a renewable resource and an environmentally friendly materials. Because of this, natural rubber shows all the reactions of an unsaturated polymer. It gives addition compounds with halogens, ozone, hydrogen chloride and several other reactants that react with olefins. An interesting reaction of natural rubber is its combination with sulfur. This is known as vulcanization. This reaction converts the plastic and viscous nature of raw rubber into elastic. Vulcanized rubber will have very high tensile strength and comparatively low elongation. Its hardness and abrasion resistance also will be high when compared to raw rubber. Because of the unique combination of these properties, natural rubber finds application in the manufacture of a variety of products.

Table 1.
Typical properties of natural rubber
PropertySpecified Values
Specific gravity0.92
Refractive index1.52
Coefficient of cubical expansion0.00062/°C
Cohesive energy density63.7 Cal/cc.
Heat of combustion10547.084 Cal/g
Thermal conductivity0.00032 Cal/sec/cm/°C
Dielectric constant2.37
Power factor (at 1000 cycles)0.15-0.2
Volume resistivity1015 ohm.cm
Dielectric strength3937 V/mm

Although natural rubber is a challenging elastomeric material, there are some inherent drawbacks. These drawbacks are attributed to the high unsaturation and also the non-polar character of natural rubber chain. Moreover, to make natural rubber become a promising elastomeric material for advanced application, the development of natural rubber with the superior mechanical strength, the low gas permeability and the high conductivity is recently focused. This broad review is contributed to the research and development of NR including the overview about modification of natural rubber and the preparation of various natural rubber nanocomposites for advanced application.

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