Influence of accelerated aging on nanomechanical properties,creep behaviour and adhesive forces of PDMS

Abstract

In the present study, the nanoindentation creep behaviour of untreated and ultraviolet (UV) treated polydimethylsiloxane (PDMS) samples was investigated, accompanied with adhesion analysis and Fourier transform infrared spectroscopy (FTIR) characterisation. Different hold times, in the range of 5–2000 s (at 10 μN of applied load), were incorporated into each nanoindentation measurement. The increase in hold time results in an increase in change in depth of the indenter in both samples. The error in hardness/modulus due to creep can be neglected for hold times of ∼400 s or more for untreated PDMS and ∼200 s or more for UV treated PDMS. The FTIR obtained data revealed surface deterioration, while the bulk nanomechanical properties were almost identical. A decrease in adhesive energy in the case of UV treated PDMS was observed, indicating that adhesive forces play a significant role at the nanometre scale in the indentation tests (real contact area determination during nanoindentation measurements).