Bound rubber interphase in rubber reinforced with carbon black: Effect of temperature Elastomers, composed of polymeric chains above their glass transition temperature and crosslinked, owe their elasticity to an entropic effect, and their stiffness increases with temperature. The addition of carbon black, critical for industrial applications, generates an increase in elastic modulus (measured at small strain amplitude) by a at least an order of magnitude. Nevertheless, upon increasing temperature, the modulus drops significantly, with a larger drop at higher carbon black contents. I discuss here the role of the elastomer adsorbed on the carbon black surfaces, often referred to as “bound rubber”, and show direct visualization and measurement of this interphase via atomic force microscopy (AFM). In our hydrogenated nitrile butadiene rubber (HNBR) filled with CB (N330), the Young’s elastic modulus of the interphase was estimated to be 53 MPa at room temperature, more than 10 times higher than that of the rubber matrix (4 MPa), with a thickness of ca. 20 nm, that dropped by ca. 10 nm when temperature was increased to 180 C. We concluded that the decrease in the interphase content with temperature can explain the drop in macroscopic small strain elastic modulus. Finally, I argue that an elastomer filled with nanofillers such as carbon black may be understood as a random three-dimensional cellular solids where bending arms are made of carbon black clusters coated with bound rubber, and where the matrix is the free rubber.