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Supramolecular bionanocomposites, part 2: Effects of carbon nanoparticle surface functionality on polylactide crystallization



Two types of supramolecular carbon nanostructures, carbon nanospheres (CNS) and multiwalled carbon nanotubes, (MWCNTs) are investigated for their potential as nanofillers in the bioplastic polylactide (PLA). Modification of the surfaces of both carbon nanostructures by covalent attachment of dodecylamine is accomplished and the effects of this compatibilizing functionality are explored. Crystallization kinetics, thermal properties, and mechanical properties are investigated. Addition of a small amount of carbon to the PLA increases the thermal stability by as much as 20–30°C. Incorporation of the MWCNT and CNS increases the heat distortion temperature by up to 10°C. Speed up in crystallization rate is observed for small to intermediate loading levels; however, at higher nanofiller loading, the rate decreases. Functionalized nanostructures are more effective at increasing crystallization rates than unfunctionalized nanostructures. It is concluded that the dodecylamine (DDA) grafted to the carbon surfaces aids in dispersing the materials and preventing aggregation, thereby providing higher surface area for heterogeneous nucleation of the biopolymer. The resulting materials are composed of the supramolecular carbon nanostructure embedded in a semicrystalline biopolymer matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011