Study of the scratch resistance criteria and their relationship with mechanical properties and microstructure in a ternary thermoplastic blend

Abstract

Polymeric materials generally suffer from a low resistance to various types of surface mechanical damage, among which scratch is a prominent example. While several attempts have been made to assess the scratch resistance and its relationship with the bulk mechanical properties in simple polymeric systems, the available research on the polymeric blends is scarce. This study attempts to fill this gap by studying the link between the scratch resistance and mechanical properties in a ternary polymeric nanocomposite, which has proved to feature superior and tunable mechanical properties. For this aim, blends of polypropylene and polyamide 6 were prepared using melt blending with two different types and various amounts of compatibilizers. Their microstructure was studied using scanning electron microscopy and atomic force microscopy. It was observed that the type of morphology depends upon both compatibilizer type and content. Bulk mechanical properties were investigated at different loading conditions. The microstructure was seen to have a noticeable effect on ductility of the blends. Different scratch groove geometry parameters were seen to be affected by different mechanical properties. It was shown that relying exclusively on scratch groove geometry might lead to contradicting conclusions regarding the effect of bulk mechanical properties on scratch resistance. Instead, a heavier emphasis was placed upon the respective contribution of each parameter to the overall scratch visibility. In addition, it was shown that micro-mechanical scratch deformation mechanisms have a crucial impact on scratch visibility, and they are affected by a complex interplay among various mechanical properties. An analysis of these relationships is provided with the aim of moving towards a comprehensive understanding of scratch visibility and routes to its minimization.