Polypropylene/carbon nanotube nano/microcellular structures with high dielectric permittivity,low dielectric loss,and low percolation threshold |
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| Affiliation: | 1. Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto M5S 3G8, Canada;2. Leibniz Institute of Polymer Research Dresden (IPF), Hohe Straße 6, D-01069 Dresden, Germany;3. Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa L1H 7K4, Canada;1. Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan, Shandong 250061, China;2. Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario M5S 3G8, Canada;3. Center of Precision Engineering, School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China;4. Key Laboratory of Eco-textiles (Ministry of Education), Jiangnan University, Wuxi, Jiangsu 214122, China;5. Key Laboratory of Chinese Education Ministry for Tropical Biological Resources, Hainan University, Haikou, Hainan 570228, China;1. College of Polymer Science and Engineering, Sichuan University, 24 Yihuan Road, Nanyiduan, Chengdu, Sichuan, 610065, People''s Republic of China;2. Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King''s College Road, Toronto, Ontario M5S 3G8, Canada;3. School of Material Science and Engineering, Shandong University, 17923 Jingshi Road, Jinan, Shandong, People''s Republic of China;1. Advanced Composites Laboratory, School of Mechanical and Materials Engineering, Washington State University Tri-Cities, 2710 Crimson Way, Richland, WA 99354, USA;2. Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Canada M5S 3G8;3. Leibniz Institute of Polymer Research Dresden (IPF), Hohe Straße 6, D-01069 Dresden, Germany;1. Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, 5 King’s College Road, Toronto, Ontario M5S 3G8, Canada;2. Leibniz Institute of Polymer Research Dresden (IPF), Hohe Straße 6, D-01069 Dresden, Germany |
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| Abstract: | Nano/microcellular polypropylene/multiwalled carbon nanotube (MWCNT) composites exhibiting higher electrical conductivity, lower electrical percolation, higher dielectric permittivity, and lower dielectric loss are reported. Nanocomposite foams with relative densities (ρR) of 1.0–0.1, cell sizes of 70 nm–70 μm, and cell densities of 3 × 107–2 × 1014 cells cm−3 are achieved, providing a platform to assess the evolution of electrical properties with foaming degree. The electrical percolation threshold decreases more than fivefold, from 0.50 down to 0.09 vol.%, as the volume expansion increases through foaming. The electrical conductivity increases up to two orders of magnitude in the nanocellular nanocomposites (1.0 > ρR > ∼0.6). In the proper microcellular range (ρR ≈ 0.45), the introduction of cellular structure decreases the dielectric loss up to five orders of magnitude, while the decrease in dielectric permittivity is only 2–4 times. Thus, microcellular composites containing only ∼0.34 vol.% MWCNT present a frequency-independent high dielectric permittivity (∼30) and very low dielectric loss (∼0.06). The improvements in such properties are correlated to the microstructural evolution caused by foaming action (biaxial stretching) and volume exclusion. High conductivity foams have applications in electromagnetic shielding and high dielectric foams can be developed for charge storage applications. |
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