Microelastic properties of minimally adhesive surfaces: A comparative study of RTV11™ and Intersleek elastomers™

A comparative study of two commercially available elastomers, RTV11™ and Intersleek™, has been conducted employing atomic force microscopy (AFM) and surface and bulk analysis techniques. The results confirmed the presence of $CaCO3$ (rhombohedral calcite) filler particles in RTV11 and revealed $TiO2$ (tetragonal rutile) and $Fe3O4$ (cubic magnetite) as filler particles in Intersleek formulation. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) depth profiling revealed average threshold depths of ∼100 nm for the onset of filler particles. Indentation curves obtained from AFM force-volume imaging demonstrated that the presence of these particles significantly alters the local elastic properties of the coating. While the particle-free, high-compliance regions followed Hertzian behavior to a reasonable approximation, the low-compliance domains, where the subsurface filler particles reside, showed a significant deviation from this model. The Hertzian model, applied to the particle-free regions, gave values of 3.0, 1.9, and 1.4 MPa, respectively, for the elastic moduli of thin RTV11, thick RTV11, and Intersleek. For thin and thick RTV11 the presence of subsurface particles caused a local increase in the elastic moduli of the polymers, resulting in values 2.1 and 1.7 times higher than those for the particle-free regions of the corresponding polymers. For Intersleek, this increase was only 1.3 times. TOF-SIMS analysis did not reveal local differences in the chemical composition of the polymers, hence the inhomogeneities in the microelastic properties of these polymers are explained in terms of differences in the physical properties of these regions. Subsurface filler particles undergo substantial elastic displacements under the influence of the penetrating AFM tip.