Carbon-black-filled rubber modulus, mechanism

The effects of the presence of carbon black on the dynamic mechanical properties of various types of filled rubber have been reviewed by Medalia [58]. In an early work (1939), Roelig [59] found that hysteresis increases with carbon black loading. Naunton and Waring [60] and later Gehman et al. [61] found that the elastic moduli of tread compounds decrease greatly with increases in strain. Stambaugh [62] attributed the reduction in modulus, with increases in strain, to the strain per se rather than to the increase in... 

Improvement of the mechanical properties of elastomers is usually reached by their reinforcement with fillers. Traditionally, carbon black, silica, metal oxides, some salts and rigid polymers are used. The elastic modulus, tensile strength, and swelling resistence are well increased by such reinforcement. A new approach is based on block copolymerization yielding thermoelastoplastics, i.e. block copolymers with soft (rubbery) and hard (plastic) blocks. The mutual feature of filled rubbers and the thermoelastoplastics is their heterogeneous structure u0). 

Pre-strain was included in modulated stress testing of rubber and the dimensions of the pre-strained specimens used in calculation of the loss modulus. The loss modulus was independent of pre-strain for filled and unfilled rubbers. A test specimen geometry was chosen where pure shear could be superimposed with a small strain imparted with a shear oscillation. Again, loss modulus was mostly independent of pre-strain for filled and unfilled rubbers, including those filled with carbon black. The results enable understanding of energy dissipation mechanisms in rubber composites. ... 

In the rubber industry the distribution of particle size is considered to be important as it affects the mechanical properties and performance. Aggregate size also varies with particle size. Aggregates can have any shape or morphology. The fundamental property of the filler used in a filled elastomer is the particle size. This affects the reinforcement of elastomer most strongly. One of the sources of reinforcement between the carbon black surface and the rubber matrix is the van der Waals force attraction. Also, rubber chains are grafted onto the carbon black surface by covalent bonds. The interaction is caused by a reaction between the functional group at the carbon black particle surface and free radicals on polymer chains. Hence, filler-rubber interface is made up of complex physical-chemical interaction. The adhesion at the rubber-filler interface also affects the reinforcement of rubber. When the polymer composites are filled with spherical filler (aspect ratio of the particle is equal to unity), the modulus of the composite depends on the modulus, density, size, shape, volume ratio, and number of the incorporated particles. 

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