Predicting the Properties of Carbon-Black Filled Rubber Compounds Using a Micro-Structural Simulation Program

  • Wulf, Hans (TU Chemnitz)
  • Ihlemann, Jörn (TU Chemnitz)

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Carbon-black filled rubber compounds have a wide range of industrial applications like tires, seals and elastic bearings. This is due to their unique properties, allowing for very large elastic deformations and providing damping under cyclic loading. Furthermore, they exhibit a characteristic softening at strains smaller than the maximum strain they experienced (Mullins effect), which smooths the stress distribution. Industrial rubbers are a very complex material with often over ten different ingredients per compound, which provides a large design space for creating materials tailored for their respective application. The filler particles are among the most influential aspects, with their quantity, their size and their surface characteristics being relevant. However, finding the combination of ingredients, which yield the desired properties, is difficult due to complex, nonlinear microstructural interactions. Therefore, simulation methods that can predict compound properties are very beneficial. A simulation program is presented which models the molecular structure of rubber in a simplified and abstract way. It is based on the theory of Self-Organizing Linkage Patterns (SOLP) by Ihlemann, which states that the rubber behavior is based on the emergence of inhomogeneous density patterns of weak physical links. Due to the microstructural foundation, variations in the compound formulation can be directly represented as simple variations of the model parameters. Moreover, as this strategy intends to capture how the ultimate compound properties emerge from the constituents, it promises a more reliable and precise interpolation than phenomenological methods. The program is used to generate predictions concerning the change in stiffness and hysteresis when varying the carbon black content of a rubber compound. Comparative measurements demonstrate the success of this approach. Furthermore, different types of carbon black as well as mixtures of different filler types in the same compound are investigated and compared to measurements.