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- Persson, Henrik, 1983, et al.
(författare)
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Influence of manufacturing on electrical performances of graphite nanoplatelet filled polystyrene
- 2011
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Ingår i: NT11 International Conference on Science and Applications of Nanotubes, University of Cambridge, July 11-16, Cambridge (UK), 2011.
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Konferensbidrag (refereegranskat)abstract
- Manufacturing strategy is important for the appropriate incorporation of filler into a polymeric matrix, and this in particular refers to nanofilers. Direct-graphite nanoplatelets (GNP) were used as filler in polystyrene (PS). The as-received GNP material contained microscopic size agglomerates formed by nanoscopic size graphite nanoplatelets. Refining of the microagglomerates (break-up) and production of graphene layers (exfoliation) desirably needs to take place during manufacturing. Herein, several melt processing methods used to prepare GNP/PS are in focus. The manufacturing methods used include both, melt and solvent routes, and include elongational flow mixing (EFM), high shear energy micro compounding, roll-milling/calendering, and Brabender mixing chamber, as well as sonication and surfactant assisted solvent processing using N-methyl-pyrrolidone (NMP). We analyze particle break-up and exfoliation, and the effects on electrical conductivity and surface smoothness of the composite, both of importance in high-voltage applications. The composite is characterized by melt rheology, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) with MeX surface topography software, optical microscopy with image analysis, X-ray Diffraction (XRD), and electrical resistivity measurements. We find that manufacturing processes influence the material´s morphology and properties in different ways. As could be expected, sonication and surfactant assisted solvent processing yielded both good deagglomeration and production of thin graphene stacks/layers. Elongational flow dispersive mixing, studied here using a recently developed mixer (RMX, Scamex, France), efficiently refines the GNP microagglomerates, and the particle break-up is closely comparable to that in solvent processing. Both the processes yield composites having smoother surfaces compared to the ones from other processing methods. Solvent processing and micro-compounding are more efficient than the other processes in the production of exfoliated thin graphene stacks/ layers. Thin graphene stacks/layers, particularly, provide electrical conductivity, at lower amount of filler content.Acknowledgments: The Swedish Foundation for Strategic Research (SSF) financial support is acknowledged (HP, MR, RWR).
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- Strååt, Martin, et al.
(författare)
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Improvement of melt spinning properties and conductivity of immiscible polypropylene/polystyrene blends containing carbon black by addition of styrene-ethylene-butene-styrene block copolymer
- 2011
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 51:6, s. 1165-1169
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polymeric materials prepared from immiscible blends, such as polypropylene (PP)/polystyrene (PS), together with carbon black (CB), are known to have a relatively high electrical conductivity, because of a selective distribution of CB (double percolation). Melt spinning of immiscible blends containing CB has, however, not been extensively reported on previously. An immiscible 1:1 blend of PP and PS to which 4 wt% CB was added exhibited a very low melt draw-down ratio at rupture compared wit PP with the same content of CB. By adding 5 wt% SEBS (styrene-ethylene-butene-styrene block copolymer), the ultimate melt draw-down ratio increased about 10 times, which made the material more suitable for melt spinning. As-extruded samples of the immiscible blends (with CB) did not have higher electrical conductivities than PP/CB. A heat treatment increased the conductivity of immiscible PP/PS/CB composites, and longer treatment times and higher temperatures promoted the conductivity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.
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- Strååt, Martin, et al.
(författare)
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Melt spinning of conducting polymeric composites containing carbonaceous fillers
- 2011
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 119:6, s. 3264-3272
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Tidskriftsartikel (refereegranskat)abstract
- Fibers produced by melt spinning of conductive polymer composites are attractive for several applications; the main drawback is however reduced processability at high filler concentrations. Carbon nanotubes (CNTs) are considered suitable fillers for conductive polymer composites, replacing conductive grades of carbon black (CB). In this study, the fiber-forming properties of conductive polymer composites based on a conductive grade of CB and two masterbatches with CNT in a polyethylene matrix were investigated. The CB was also used in a polypropylene matrix for comparison. The rheological properties of the filler-containing melts in shear and their extensional behavior were evaluated. A piston-driven device was used to extrude the molten materials through a capillary; different capillary geometries were tested. Fibers were produced at various draw ratios, and their conductivity was determined. To assess the ultimate extensibility, a modified Rheotens method was used. The results showed that a conductive CB grade can have a lower percolation threshold and higher conductivity than a material with CNT. Conductivity decreased with increasing melt draw ratio for both types of fillers. The spinnability of the materials decreased with increasing concentration of filler material and correlations were found between spinnability and melt elasticity.
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