Rubbers, both natural and synthetic, are elastic materials that recover to almost their original shape after the complete release of the applied force. They have the all-round ability to be used in extension, compression, shear, torsion or a combination of these forces. A typical rubber vulcanisate is a three-dimensional flexible polymeric matrix that is cross-linked by chemical bonds in which a variety of compounding ingredients, such as the reinforcing agents, carbon black and silica, are incorporated.
Rubbers are usually, but not always, bonded with or fabricated into composite articles with steel, glass or fibre reinforcement for use in tyres, conveyor belts, hoses, etc. Special preparation methods are required for processing various fibres such as cotton, rayon, nylon, polyester, glass, aramid and steel cords for incorporation into rubber articles. Coated fibre surfaces have an interphase that is formed chemically or physically, which must be free of mechanical damages, voids and hysteresis/ chemical effects.
Light-weight and high-performance composites have replaced metals in many dynamic applications in the automobile and aeronautical industries. Flexible rubber composites require strength and toughness as well as graded stiffness for which fibres like cotton, rayon, nylon, polyester and aramid are used in conjunction with steel.
Organic fibres are mainly composed of longitudinally oriented linear macromolecules. Steel wires drawn from high-carbon steel cords and twisted into strands after brass plating are also used. In the case of uni-directional plies, it is usual to stack them in a symmetrical arrangement at angles of zero degrees, plus alpha, minus alpha and 90 degrees in the axial direction to form composites such as tyres and spiral-wound hoses. The fibre architecture may be varied by textile processing methods such as twisting, weaving, braiding and spiralling. These have different effects on load-bearing capacity, impact-energy absorption, shape retention, energy storage and durability of the rubber products such as conveyor belting. For example, 2D( planar weaves confer a degree of transverse flexibility whereas 3D knit fabrics are flexible in all directions, although at a lower strength realisation. Due to the vast differences in molecular reactivity, polarity and unsaturation of the fibre and matrix components, adhesion (the strength of the rubber-textile bond) can only be achieved by careful preparation of the textile with a coating or flexible adhesive layer and embedding in rubber before vulcanisation.
Strength, stiffness and toughness are the qualities needed for the use of rubbers in various products such as tyres, power transmission, conveyor belting and hose. In many products, the carcass composed of the reinforcing textile is durable such that a process of re-treading can replace the worn-out rubber portions, typically extending the rubber product life to withstand over seven million flexing cycles in operation at large deflections.
Local stress concentrations due to edge effects and differential coefficients of thermal expansion, modulus mismatch at fibre/matrix interfaces, crack-resistance of rubbers, heat build-up and accumulated damage effects on stiffness and strength occur throughout the life cycle of the products and are the major causes of failure in dynamic applications. The probable causes may be mechanical (cracking, localised stress), chemical (hydrolysys, aminolysis, oxidative) or thermal ( hygro-thermal).
The book is a first-of-its-kind A-Z guide to rubber engineering with fibres. It outlines how molecular order and motions translate to macro-level elastic responses at various frequencies and temperatures to external forces acting on fibre-reinforced rubber composites. The design criteria for products like tyres, belting and hose and the forces acting on the reinforcing textile elements are explained. Remedies for textile-related problems arising in processing and performance are presented. The author makes a compelling case for the need for crossover skill development and self-education. The book will be useful to material scientists, rubber product designers, and entrepreneurs and for skill upgradation programmes.
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About the author:
Kesava Siva Loganathan has degrees in Chemical Engineering from the Indian Institute of Technology, Madras (Bachelor’s) and Indian Institute of Science, Bangalore (Master’s). He is a tyre and rubber industry veteran and technical consultant. He has provided project consultancy to clients in eight countries. He is the author of the well-known book ‘Rubber Engineering’, and has written various articles on rubber topics in a career spanning five decades. He has practical experience in all types of industrial textiles, especially in fibre conversion, fabric treatment, and rubberising, and their incorporation into a wide variety of rubber goods such as tyres, belting, and industrial rubber products.
