Nanomechanical properties and nanoscale deformation of PDMS nanocomposites

In this study, nanoindentation technique was utilised to estimate the nanomechanical properties (hardness H, and elastic modulus E) of elastomeric polydimethylsiloxane (PDMS) samples consisting of different nanoclay concentrations (organically modified montmorillonite), namely, 0, 5 and 8 parts per hundred. The PDMS samples were also characterised by Fourier transform infrared spectroscopy, X-ray diffraction and tensile testing. In addition, the surface of the nanocomposites was characterised through scanning probe microscopy, revealing surface modification with increasing nanoclay content in the PDMS matrix. Additionally, several analyses on nanoindentation data were performed, and the exact surface region (with higher values of H and E) was clearly defined. One key problem in using the Oliver and Pharr (O&P) method is the determination of the contact area between the indenter and the sample. It is believed that the contact area is underestimated using the O&P method and Hertzian analysis for soft polymers. Therefore, calculations using the O&P method and Hertzian analysis have been performed and compared. The change in H/E slope revealed that the addition of nanoclay amount strengthens the PDMS-montmorillonite nanocomposite.