Vulcanized rubber, property tear strength

D 395 Test Method for Rubber Property - Compression Set D 412 Test Method for Vulcanized Rubber, Thermoplastic Rubbers and Thermoplastic Elastomer - Tension D 471 Test Method for Rubber Property - Effect of Liquids D 570 Test Method for Water Absorption of Plastics D 624 Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomer D 638 Test method for Tensile Properties of Plastics D 792 Test Method for Specific Gravity (Relative Density) and Density of Plastics by Displacement... 

The particles of carbon black are not discrete but are fused clusters of individual particles. The reinforcement conferred by the black is not influenced to any extent by the size of the unit but predominantly by the size of the particles within the unit. The primary particle typically has cross-sectional dimensions" of 5-100 nm. It is well established that the most appropriate way of describing the size of the primary particles is to express it as speciflc surface area/weight Particle size of itself has relatively little effect on the modulus. But tensile and tear strengths are affected by the particle size and both properties are normally enhanced as the surface area increases (i.e. surface area increases with decreasing particle size). The high surface area enhances the ability of the filler to wet the rubber and thus enhances the interaction at the rubber filler interface. It is the enhancement of the filler-rubber interface that provides the desired reinforcement in filled vulcanized rubber. 

Vulcanization is the process by which the linear rubber molecules are linked to form a three dimensional network comprising crosslinks formed by one or more sulfur atoms this is a result of heating the liquid rubber with sulfur. Crosslinking increases the elasticity and the strength of rubber about ten-fold, but the amount of erosslinking must be controlled in order to prevent the formation of brittle and inelastic rubber. The properties of rubber that are improved by vulcanization are tensile strength, elasticity, hardness, tear strength, abrasion resistance, and resistance to chemicals. The traditional... 

For many applications (e.g., automobile tires), the mechanical properties of even vulcanized rubbers are not satisfactory in terms of tensile strength, abrasion and tear resistance, and stiffness. These characteristics may be further improved by additives such as carbon black (Section 16.2). 

These losses contribute to heat buildup in the tire and consequent loss in properties such as strength and tear resistance. Since the losses increase with temperature below 100 C the rate of heat generation also increases with temperature, a very unstable situation for tires. This situation also dooms the use of polystyrene-b-polyisoprene-b-polystyrene polymers with low end-block concentrations. In terms of other physical properties, there is no compelling reason to believe that vulcanized block copolymers would be Inferior to other tire rubbers. What limits their consideration here is most likely the higher cost of the block copolymer synthesis. 

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