A Journey along the Extruder with Polystyrene
C60 Nanocomposites: Convergence of Feeding Formulations into a Similar Nanomorphology
Hugo Gaspar (University of Minho)
Paulo Teixeira (University of Minho)
Raquel Santos (University of Minho)
Liliana Fernandes (University of Minho)
Loic Hilliou (University of Minho)
Michael P. Weir (University of Sheffield)
Andrew J. Parnell (University of Sheffield)
Kerry J. Abrams (University of Sheffield)
Christopher J. Hill (University of Sheffield)
Wim Bouwman (TU Delft - RST/Neutron and Positron Methods in Materials)
Steven Parnell (TU Delft - RST/Fundamental Aspects of Materials and Energy)
Stephen M. King (ISIS Pulsed Neutron Source)
Nigel Clarke (University of Sheffield)
Jose A. Covas (University of Minho)
Gabriel Bernardo (University of Minho)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
We investigated the effect of the feeding formulation (premixed powders of pure components versus solvent-blended mixture) of polystyrene–C60 composites on the dispersion and reagglomeration phenomena developing along the barrel of a twin-screw extruder. The dispersion of C60 in the PS matrix is studied over different length scales using a combination of optical microscopy, spin-echo small-angle neutron scattering (SESANS), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS). When a solvent-blended mixture is used as the feeding formulation, the inlet material contains essentially molecularly dispersed C60 as revealed by the nanodomains with very small phase contrast. However, C60 reagglomeration occurs along the extruder, creating a morphology still containing only nanodomains but with much higher phase contrast. In the case of mixed powders, the material evolves from the initial macroscopic mixture of pure polystyrene and C60 into a composite simultaneously containing micro- and nanoaggregates of C60 as well as C60 molecularly dispersed in the matrix. Our results show that the two different initial feeding formulations with widely different initial morphologies converge along the extruder, through opposite morphological pathways, into a similar final nanomorphology which is dictated by the interplay between the thermodynamics of the system and the flow. Correlations between the morphological evolution along the extruder and the thermorheological properties of the composites are identified.