A mechanistic approach toward understanding the mechanical and rheological properties of polyamide/reclaimed rubber blend containing silane-treated silica

The use of reclaimed tire rubber (RTR) as a rubber toughener for engineering plastics such as polyamide 6 (PA6) is a sustainable route for rubber recycling, and it is essential to determine how surface treatment of silica nanoparticles (NPs) contributes to the modification of the blend properties. Here, a comprehensive mechanistic view based on a knowledge of all the influencing factors including the dispersion state of NPs, NP localization, change in matrix crystallinity, and rheology is presented to understand the properties of PA6/RTR/Silica ternary blends. Using the long-chain silane hexamethyltrimethoxysilane, silica was surface-modified at low, medium, and high levels. The impact strength of PA/RTR exhibited an improvement level of 104 % compared to the PA6 system. The results indicate that the change in matrix crystallinity, which is by itself related to the rheological properties, is the primary factor behind the modification of the mechanical properties by the silica nanoparticles. Mechanical engagement interaction resulting from interpenetration of the silane tails significantly altered the rheology and PA6 crystallinity. A secondary role was also found for the NP state of dispersion and localization.