Direct observation of contact on non transparent viscoelastic polymers surfaces: A new way to study creep and recovery

•Direct observation of the contact during creep for non transparent samples.•Fast and accurate measurement of residual imprints on non transparent samples.•Creep/recovery analysis without being model dependent.

This work presents a new instrumentation dedicated to the study of contact creep and recovery of non transparent polymeric samples. The aim is to be able to analyze viscoelastic properties of polymeric surfaces recording the apparent contact area for the contact creep phase and the residual imprint area for the recovery phase. This gives valuable information not to be model dependant in the analysis compared to classical techniques. Indeed, for the creep phase many methods have been proposed to estimate the contact area, but rarely perform direct vizualisation as we propose. For the recovery phase two main challenges arise: avoid contact probe not to influence on recovery kinetics; get recording at early times to have information before recovery is quite finished. This study focus on indentation problems to prove the concept of viscoelastic analysis directly from experimental data without modeling. But the problematic is more larger than that and widen to more complicated rheological surface studies including indentation and scratching.

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