Morphology and electrical properties of injection-molded PP carbon-based nanocomposites
Zaccone Marta (1)*, Armentano Ilaria (2), Cesano Federico (3), Scarano Domenica (3), Cravanzola Sara (3), Frache Alberto (4), Monti Marco (5)
(1) Proplast, Strada Savonesa 9, 15057 Tortona - Alessandria - Italy, (2) Università degli Studi di Perugia, Strada di Pentima 4, 05100 - Terni - Italy, (3) Università degli Studi di Torino, Via Pietro Giuria 7, 10125 - Torino - Italy, (4) Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 - Torino - Italy, (5) Proplast, Strada Comunale Savonesa 9, 15057, Tortona - Alessandria - Italy
CNTs are well known to be electrically conductive nanofillers that can considerably modify the electrical properties of insulating polymers [1, 2]. However, final properties of polymer nanocomposites based on CNTs, are strongly affected by the processing technologies [3]. In most of the techniques for obtaining a final polymer-based item, the morphology and the final properties of CNT-polymer nanocomposites are strongly influenced by what occurs during the shaping phase, when the polymer is in the molten state [4, 5].
In this work, PP/MWCNT nanocomposites were developed with special care to the processing condition. The MWCNT dispersion was performed in a co-rotating twin-screw extruder and the obtained nanocomposites were injection molded to obtain the desired shape of the testing specimen. Electrical characterization was then performed in the produced materials in the three main directions, i.e. the one longitudinal to the flux of the material while filling the mold - and the two transversals. Due to the fact that injection molding is one of the most important processing technique to convert polymers into objects, the aim of this work is to investigate the influence of the injection molding process conditions, on the non-conductive (or less-conductive) skin layer which is formed on the sample and its effect on the electrical properties of PP/MWCNT nanocomposites.
As a results of the electrical characterization, it was obtained that the tuning of process conditions influences the electrical properties of the produced sample. This has been explained by the multilayered morphology skin-core-skin, which was studied by SEM and also validated by a theoretical mathematical model.
Keywords: nanocomposites; carbon nanotubes; polypropylene; injection molding; skin effect
Bibliography
[1] P.C. Ma, Composites: Part A, vol. 41, pag. 1345 – 1367 (2010)
[2] S. K. H. Gulrez, Polym. Compos., vol. 35, pag. 900 – 914, (2014)
[3] S. Versavaud, Polymer, vol. 55, pag. 6811 – 6818, (2014)
[4] S. Pegel, Polymer, vol. 49, pag. 974 – 984, (2008)
[5] J. Tiusanen, Composites Science and Technology, vol. 72, pag. 1741 – 1752 (2012)