Improving Impact Toughness of Polylactide/Ethylene-co-vinyl-acetate Blends via Adding Fumed Silica Nanoparticles: Effects of Specific Surface Area-dependent Interfacial Selective Distribution of Silica

Adding fumed silica(SiO_2) has been considered as an effective method for tailoring the phase morphology and performance of elastomer-toughened plastic binary blends. It has been demonstrated that the selective distribution of SiO_2 plays a decisive role in the mechanical properties of plastic/elastomer/SiO_2 nanocomposites, especially for the impact toughness. In this work, we aim to illuminate the role of specific surface area in controlling their selective distribution of fumed SiO_2 and consequent mechanical properties of plastic/elastomer binary blends. Three types of SiO_2 with different specific surface areas were incorporated into polylactide/ethylene-co-vinyl-acetate(PLA/EVA) model blends by melt blending directly. It was found that the selective distribution of SiO_2 is largely determined by their specific surface areas, i.e. SiO_2 nanoparticles with low specific surface area has a stronger tendency to be located at the interface between PLA matrix and EVA dispersed phase as compared to those with high specific surface area. The specific surface area-dependent interfacial selective distribution of SiO_2 is mainly attributed to the extent of increased viscosity of EVA dispersed phase in which SiO_2 nanoparticles are initially dispersed and resultant migration rate of SiO_2 nanoparticles. The interfacial localized SiO_2 nanoparticles induce an obvious enhancement in the impact toughness with strength and modulus well maintained. More importantly, in the case of the same interfacial distribution, toughening efficiency is increased with the specific surface area of SiO_2. Therefore, this is an optimum specific surface area of SiO_2 for the toughening. This work not only provides a novel way to manipulate the selective distribution of SiO_2 in elastomer-toughened plastic blends toward high-performance, but also gives a deep insight into the role of interfacial localized nanoparticles in the toughening mechanism.