Nanoscratching of nylon-based ternary nanocomposites

Recent developments in miniaturization of polymeric components for microelectromechanical systems (MEMS) and nanotechnology applications require that the load applied be very small in the range of μN and nN and the contact radius in nanometers to achieve certain purposes like nanofabrication, nanomachining or nanopatterning. So, it is necessary to understand the basic nanotribological mechanisms to describe the stress fields associated with the asperities, crack initiation and growth, material removal, etc. This study reveals the nano-scale nature of intimate contacts by using atomic force microscopy during nano-scratching of nylon 66/SEBS-g-MA/organoclay ternary nanocomposites produced by different blending sequences and having contrasting microstructures using a standard diamond Berkovich indenter at a low load of 1 mN and a low sliding velocity of 1 μm/s. It is shown that the constraint effect of exfoliated organoclay on the nylon matrix material is much more important than on the dispersed soft domains in resisting the nanoscratch, as indicated by the lower scratch penetration depth. However, the absence of clay in the soft SEBS-g-MA phase promotes cavitation under these nanoscratch conditions. Conversely, the presence of organoclay in SEBS-g-MA restrains the cavitation of the latter, and its absence in the nylon matrix material is deleterious as indicated by the higher scratch penetration depth. The results presented also suggest that the ternary nanocomposites are preferred to the binary nanocomposites, particularly the exfoliated nylon 66/organoclay nanocomposite. This research extends our basic knowledge and provides new insights of the nature of nano-scale processes that happen during nanoscratching of polymer nanocomposites. The outcome of the work also raises critical questions like, penetration depth versus morphology left behind the tip, which needs an in-depth understanding of a broad range of materials.