Kinetics of Self-Heat Build-Up in Carbon Black Filled Natural Rubber Caused by Cyclic Mechanical Loading

The fact that heat is generated in viscoelastic materials like rubber progressed by energy dissipation while cyclically loaded is well known as self-heat build-up (HBU). In addition, the rubber components are reinforced with various types of fillers, the most used being carbon black (CB), which significantly affects the viscoelastic properties and therefore the development of heat. The exact course of heat generation depending on individual load cycles has not yet been sufficiently described in general terms, let alone defined with regard to the influence of different types of CB. More detailed knowledge would therefore be of great importance for the development of materials for many rubber applications. For this reason, the aim of this study is to describe in detail the kinetics of HBU in natural rubber reinforced with 10 different types of CB under varied cyclic loading conditions. In order to understand the effect of different filler reinforcements on the HBU behavior, the fundamental characterization of the studied materials, namely hardness, tensile properties as well as the determination of viscoelastic behavior with respect to the Payne effect, was first performed. The kinetic of HBU was characterized using a unique method of cyclic alternating tensile and compressive loading of a rotating bent rubber cylinder with in-situ temperature analysis inside as well as on the surface of the sample. Simple mathematical functions describing the heat evolution as a function of the type of CB and loading frequency were defined and these were discussed in relation to the fundamental properties of the materials studied. An increasing temperature rise with increasing CB volume as well as aggregate surface area has been found which fully corresponds with increasing hardness and stiffness of the rubber. Moreover, it has been shown that the course of HBU kinetics as a function of CB type and amount is fully consistent with the G’values obtained in the Payne effect analyses.