Selective Localization Of Reduced Graphene Oxide In The Immicible PLA/EVA Blend And Its Tail Oring Mechanism

Polymer blends offer combined excellent properties generated from individual polymer component to improve the disadvantages of single polymer, which are regarded as important research areas for polymer materials with multi-functionalization and high performance. Many polymer blends are thermodynamically immiscible and their blends exhibit poor mechanical properties. Incorporating inorganic nanoparticles into immiscible polymer blends, would make great effects on strengthening and toughening the polymer blends as well as endowing the new functions. On the other hand, due to its large aspect ratio, two-dimensional structure, superior electrical conductivity, thermal conductivity and mechanical property, graphene has attracted tremendous attentions since its discovery. Poly(lacticacid)(PLA), as one of ecofriendly thermoplastic polyesters, has received increasing attentions due to its excellent biocompatibility, biodegradability, comprehensive mechanical properties and processing ability, but its brittleness restricts its application. Melt blending PLA with elastomers is of practical significance to realize the toughening. And EVA is one kind of elastomers with excellent ductility. In this research, nanocomposites of PLA/EVA containing (reduced-graphene oxides, r-GOs) were prepared by two steps method.We analysis the selective localization of reduced graphene oxides in the PLA/EVA blend according to the thermodynamic and kinetic factors. The electrical properties and microstructure of nanocomposites with different distribution and selective localization states of r-GOs(at the interface or in one phase) were comparatively investigated. The main results are listed as follows:(1) A method which is related to incorporation of the third component EVA into the PLA/r-GOs composites was explored. We observed the the selective localization of r-GOs in the PLA/EVA blend using SEM and TEM. The corresponding electrical properties of the binary immiscible polymer blend PLA/r-GOs and the ternary immiscible polymer blend PLA/EVA/r-GOs were discussed. Homogeneous dispersion of the EVA directed the exfoliation and a better dispersion of the r-GOs in polymer host. Finally, r-GOs transferd to the interface and dispersed along or wrapped on the EVA droplets due to its two-dimensional structure and interface stability of r-GOs. In this case, compared with the PLA/r-GOs binary composite, the ternary composites showed a ten orders decrease of electrical resistance with a lower electrical percolation threshold than that of the binary composites.(2) The selective localization of r-GOs in immiscible blend PLA/EVA was investigated based on different mixing sequences. For the PLA/EVA/r-GOs nanocomposites prepared through two steps (PLA/r-GOs master batch), r-GOs selectively distributed at the interface between PLA and EVA. It is consistent with the thermodynamic theory prediction. For the nanocomposites prepared through EVA/r-GOs master batch, r-GOs selectively distributed in the EVA phase. The underlying mechanism for selective localization at interface was systematically investigated by combination of migration, interfacial stability of r-GOs and viscosity change. Finally, The electrical resistivity measurements show that nanocomposites with r-GOs locating at the interface is endowed much lower resistivity and percolation threshold compared to the nanocomposites with r-GOs locating at EVA component.(3) Three different size of r-GOs were introduced to the immiscible polymer blend PLA/EVA, and the mixing time was tailored to find out the migration of r-GOs in polymer blends. We observed the selective localization of r-GOs and the microstructure of the PLA/EVA/r-GOs ternary nanocomposites prepared by different mixing times, aiming at studing the effects of the influence of the size of r-GOs and mixing time on the migration of r-GOs. As for the PLA/EVA/r-GOs ternary nanocomposites with three different size of r-GOs, more r-GOs migrate to the interface of PLA/EVA with increasing the blending time, the r-GOs with larger size exhibit slower migrate migration rate than the smaller ones. The volume resistivity of three PLA/EVA/r-GOs ternary nanocomposites decreased with the mixing time increased. The electrical conductivity was dependent on the selective localization of r-GOs, but this dependence would be weakened when the size of r-GOs was large enough.