Document Type : Research Paper
Authors
1
Physics and Chemistry Group, Faculty of Basic Sciences, Imam Ali University, P.O. Box: 1317893471, Tehran, Iran.
2
Department of Polymer Engineering and Color Technology, Amir Kabir University of Technology, P.O. Box: 15875-4413, Tehran, Iran
Abstract
Hypothesis: Nowadays, lightening of polymer composites for specific applications and engineering purposes, especially electromagnetic wave absorber materials, has attracted research studies. In this work, polypropylene nanocomposite and hybrid foams incorporated with carbon nanotubes and glass fibers were produced through solid-state microcellular foaming using supercritical carbon dioxide.
Methods: First, the microstructure of nanocomposites, hybrids, and produced foams were examined by scanning electron microscopy. The electrical properties and electromagnetic interference shielding performance of the solid and foamed nanocomposites were investigated using a four-point probe method and a vector analyzer, respectively. The effect of glass fiber and CNT incorporation on tensile, compressive, and impact mechanical properties was also investigated.
Findings:Nanotubes were finely dispersed in the polypropylene matrix through melt compounding. By incorporation of CNTs, the average cell size reduced (from 49 to 22.5 μm), and cell density increased. Also, the SEM micrographs of the hybrid foams revealed that, in general, cell size increased by incorporating fiber due to nearby heterogeneous nucleation, and the size of cells that were not adjacent to the fiber decreased. As a result, a bimodal microstructure with two different cell sizes was
obtained. With the incorporation of 3 wt% CNTs, electrical conductivity increased
from 1.7×10-16 S/cm to 4.7×10-4 S/cm for unfoamed PS/CNT3 and from 1.6×10-18 S/cm
to 3.36×10-5 S/cm for foamed PP/CNT3-F. Also, EMI shielding effectiveness increased to 11 dB and 9.5 dB for unfoamed and foamed PP/CNT3 samples, respectively. The mechanical test results showed that the addition of nanoparticles help to improve mechanical properties, including tensile, compression and impact. In solid samples, the addition of glass fiber improves the modulus and tensile strength, but due to poor interaction with polypropylene, it reduces the tensile properties of the foams. The results of both compression and impact resistance tests of foams showed that these properties are enhanced with the addition of fibers and nanoparticles.
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