In-situ compatibilization of polyamide 6/polycarbonate blends through interfacial localization of silica nanoparticles

Nanoparticles are used to compatibilize immiscible polymer blends. The key to success is to localize nanoparticles at polymer-polymer interfaces. This work aims to use silica nanoparticles (SiO2) to compatibilize polyamide 6 (PA6)/polycarbonate (PC) blends. The strategy to ensure the interfacial localization of the SiO2 in the blends is to graft a methacrylic monomer onto the SiO2 and then copolymerize this methacrylic monomer with styrene (St) and 3-isopropenyl-α,α′-dimethylbenzyl isocyanate (TMI). When PA6 and PC are blended in the melt in the presence of the above surface modified SiO2 (denoted as SiO2-PST), PA6 chains are grafted onto the SiO2-PST to form PA6-SiO2-PST through a coupling reaction between the terminal amine group of the PA6 and the isocyanate moieties of the PST grafts which are partially miscible with the PC. It is shown that an optimum TMI content allows for the SiO2-PST to be preferentially localized at the interfaces between the PA6 and PC. This leads to a significant decrease in the PC domain diameter from 1.6 μm to 0.6 μm without and with the SiO2-PST, respectively. The presence of the SiO2-PST (0.5 wt% with an optimum TMI content) increases the tensile strength of the PA6/PC (70/30 by weight) from 64.1 to 79.6 MPa, the elongation at break from 84.7 to 284.7%, and the notched Charpy impact strength from 10.3 to 29.4 kJ/m2.