Effect of mixing conditions and polymer particle size on the properties of polypropylene/graphite nanoplatelets micromoldings / Renze Jiang in INTERNATIONAL POLYMER PROCESSING, Vol. 37, N° 4 (2022)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 37, N° 4 (2022) . - p. 372-382 Titre : Effect of mixing conditions and polymer particle size on the properties of polypropylene/graphite nanoplatelets micromoldings Type de document : texte imprimé Auteurs : Renze Jiang, Auteur ; Piyush Lashkari, Auteur ; Shengtai Zhou, Auteur ; Andrew N. Hrymak, Auteur Année de publication : 2022 Article en page(s) : p. 372-382 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Caractérisation Composites à fibres -- Moulage par micro-injection Composites à fibres de graphite Conducteurs organiques Microstructures Nanoparticules Polypropylène Thermocinétique Index. décimale : 668.4 Plastiques, vinyles Résumé : In this study, properties of polypropylene/graphite nanoplatelets (PP/GNP) composites and corresponding micromoldings were systematically studied in terms of filler loading concentrations and mixing methods. PP of different forms, i.e., PP pellets and powders, were adopted to fabricate PP/GNP composites. Additionally, a comparative study of precoating GNP and PP powders using solvent-based solution blending and ultrasonication-assisted mixing was performed. Results showed that PP/GNP composites prepared using powder form PP resulted in at least one order of magnitude higher electrical conductivity than using pellet form PP and further reduced the percolation threshold from 12.5 to 10 wt%, which was related to the state of filler distribution within corresponding moldings. Morphology observations revealed that microparts prepared with powder-PP/GNP composites exhibited less preferential alignment of GNP particles along the flow direction when compared with those molded using pellet-PP/GNP counterparts, which was helpful in improving the overall electrical conductivity for PP/GNP micromoldings. Note de contenu : - EXPERIMENTAL SECTION : Materials - Sample preparation - CHARACTERIZATION : Electrical conductivity - Morphology - Differential scanning calorimetry - RESULTS AND DISCUSSION : Electrical conductivity - Morphology - Differential scanning calorimetry - Table 1 : Characteristic Data from DSC Scans for PP/GNP feeds (top row) and µIM microparts (bottom row). Cycle 1: 1st heating cycle. Cycle 2: cooling cycle. Cycle 3: 2nd heating cycle DOI : https://doi.org/10.1515/ipp-2022-0004 En ligne : https://drive.google.com/file/d/1qw8Ibyf-E7sqUi1vjl_V9cgnu7o1L3jN/view?usp=shari [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=37913 [article]

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Influence of mold cavity thickness on electrical, morphological and thermal properties of polypropylene/carbon micromoldings / Shengtai Zhou in INTERNATIONAL POLYMER PROCESSING, Vol. 38, N° 2 (2023)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. 38, N° 2 (2023) . - p. 214-224 Titre : Influence of mold cavity thickness on electrical, morphological and thermal properties of polypropylene/carbon micromoldings Type de document : texte imprimé Auteurs : Shengtai Zhou, Auteur ; Renze Jiang, Auteur ; Xue Lei, Auteur ; Huawei Zou, Auteur ; Andrew N. Hrymak, Auteur Année de publication : 2023 Article en page(s) : p. 214-224 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Composites -- Moulage par micro-injection Composites -- Propriétés électriques Composites -- Propriétés thermiques Conduction électrique Etudes comparatives Matériaux -- Epaisseur Micropièces Moules d'injection Nanotubes Noir de carbone Polypropylène Index. décimale : 668.4 Plastiques, vinyles Résumé : In this work, a comparative study on the electrical conductivity (σ) and thermal properties of polypropylene (PP)/carbon microparts with different part thickness (namely, 0.85 and 0.50 mm) is reported. Two different types of carbon filler (i.e., CNT and CB) were adopted to study the efficacy of different carbon fillers in improving the σ of PP/carbon microparts. In general, the σ of 0.85 mm thickness microparts were higher than the 0.50 mm thickness microparts, regardless of the carbon filler type and testing directions. This suggested that higher shearing conditions that prevailed in the microinjection molding (μIM) process were unfavorable for the formation of intact conductive pathways in corresponding moldings, albeit the distribution of carbon fillers turned better with increasing shear rates, as confirmed by morphology observations. Differential scanning calorimetry results showed that prior thermomechanical histories (including melt blending and μIM) experienced by the polymer melts had an influence on the thermal behavior of subsequent moldings. Also, there existed a strong shear flow-induced crystallization of polymer chains during μIM because the crystallinity of microparts was higher than that of feed materials. Note de contenu : - EXPERIMENTAL SECTION : Materials - Preparation of samples - CHARACTERIZATION : Electrical conductivity - Simulation - Morphology - Differential scanning calorimetry - RESULTS AND DISCUSSION : Electrical conductivity and simulation - Morphology - Melting and crystallization behavior - Table 1 : Characteristic data from DSC scans for PP/CB and PP/CNT microparts and their corresponding blends for Cycle 1 (1st heating cycle), Cycle 2 (cooling cycle), and Cycle 3 (2nd heating cycle) DOI : https://doi.org/10.1515/ipp-2022-4288 En ligne : https://drive.google.com/file/d/1-gV9hbAsnQdBcZoU1O_GQD2XlRxDejjp/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39502 [article]

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