Using the Atomic Force Microscopy for nanocomposites local mechanical characterization: Towards the interphase measurement

The nanocomposite materials development represents a very attractive route to upgrade polymer properties commonly used in electrical insulation systems. It was recently shown that some fundamental insulation features such as breakdown strength, partial discharge resistance, treeing lifetime or space charge accumulation may be significantly modified by using nanocharged materials. The origin of these modifications is often attributed to a nanoscale transition zone between a nanoparticle and surrounding matrix called the interphase. In spite of this importance, one can hardly find quantitative data on the transitional zone properties. In the current study, we show that it is possible to quantitatively evaluate the interphase mechanical properties by using the Peak Force Quantitative Nano-Mechanical (PF QNM) mode of the Atomic Force Microscopy (AFM) on polyimide/hexagonal-boron nitride nanocomposites. Local mechanical results allow the interphase thickness measurement. Experimental results show a perfect correlation with theoretical models.