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Nucleation of the β-polymorph in Composites of Poly(propylene) and Graphene Nanoplatelets

International Institute for Nanocomposites Manufacturing (IINM), WMG, University of Warwick, Coventry CV4 7AL, UK
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J. Compos. Sci. 2019, 3(2), 38; https://doi.org/10.3390/jcs3020038
Received: 12 March 2019 / Revised: 2 April 2019 / Accepted: 3 April 2019 / Published: 8 April 2019
(This article belongs to the Special Issue Recent Advances in Graphene-based Nanocomposites)
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Abstract

The effects of graphene nanoplatelets (GNPs) on the nucleation of the β-polymorph of polypropylene (PP) were studied when melt-mixed at loadings of 0.1–5 wt % using a laboratory scale twin-screw (conical) extruder and a twin-screw (parallel) extruder with L/D = 40. At low GNP loadings (i.e., ≤0.3 wt %), the mixing efficiency of the extruder used correlated with the β-nucleating activity of GNPs for PP. GNP agglomeration at low loadings (<0.5 wt %) resulted in an increase in the β-phase fraction (Kβ) of PP, as determined from X-ray diffraction measurements, up to 37% at 0.1 wt % GNPs for composites prepared using a laboratory scale twin-screw (conical) extruder. The level of GNP dispersion and distribution was better when the composites were prepared using a 16-mm twin-screw (parallel) extruder, giving a Kβ increase of 24% upon addition of 0.1 wt % GNPs to PP. For GNP loadings >0.5 wt %, the level of GNP dispersion in PP did not influence the growth of β-crystals, where Kβ reached a value of 24%, regardless of the type of extruder used. From differential scanning calorimetry (DSC) measurements, the addition of GNPs to PP increased the crystallization temperature (Tc) of PP by 14 °C and 10 °C for the laboratory scale extruder and 16-mm extruder, respectively, confirming the nucleation of PP by GNPs. The degree of crystallinity (Xc%) of PP increased slightly at low GNP additions (≤0.3 wt %), but then decreased with increasing GNP content. View Full-Text
Keywords: poly(propylene); graphene nanoplatelets (GNPs); nucleation; β-polymorph poly(propylene); graphene nanoplatelets (GNPs); nucleation; β-polymorph
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Guerra, V.; Wan, C.; McNally, T. Nucleation of the β-polymorph in Composites of Poly(propylene) and Graphene Nanoplatelets. J. Compos. Sci. 2019, 3, 38.

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