Linking structure and nanomechanical properties via instrumented nanoindentations on well-defined and fine-tuned morphology poly(ethylene)

Several poly(ethylene) samples with a broad range of morphologies were studied in this work using nanoindentations. The samples had degrees of crystallinity ranging from 30 to 100% while their Young's modulus ranged from few tens of MPa up to several GPa. Experimental conditions for the correct evaluation of Young's modulus were at first identified, choosing a suitable loading rate in order to minimize viscoelastic effects on the unloading. The force curves, i.e., plots of applied load vs. penetration depth, were then analyzed following two common procedures available in the literature. None of these procedures leads to satisfying results when compared to other experimental techniques. However, it was found that a recently proposed correction factor to the Oliver and Pharr procedure allows to evaluate reliably Young's modulus of the poly(ethylene) samples exhibiting very different, fine-tuned morphologies.