%0 Journal Article
%T Nucleation of the ¦Â-polymorph in Composites of Poly(propylene) and Graphene Nanoplatelets
%A Chaoying Wan
%A Tony McNally
%A Valentina Guerra
%J -
%D 2019
%R https://doi.org/10.3390/jcs3020038
%X Abstract The effects of graphene nanoplatelets (GNPs) on the nucleation of the ¦Â-polymorph of polypropylene (PP) were studied when melt-mixed at loadings of 0.1¨C5 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., ¡Ü0.3 wt %), the mixing efficiency of the extruder used correlated with the ¦Â-nucleating activity of GNPs for PP. GNP agglomeration at low loadings (<0.5 wt %) resulted in an increase in the ¦Â-phase fraction (K¦Â) 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 K¦Â 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 ¦Â-crystals, where K¦Â 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 ¡ãC and 10 ¡ãC 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 (¡Ü0.3 wt %), but then decreased with increasing GNP content. View Full-Tex
%K poly(propylene)
%K graphene nanoplatelets (GNPs)
%K nucleation
%K ¦Â-polymorph
%U https://www.mdpi.com/2504-477X/3/2/38