Electrical, rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

• Published in: Polymer international 2013-10, Vol.62 (10), p.1477-1484
• Main Authors: Ramôa, Sílvia DAS, Barra, Guilherme MO, Oliveira, Ricardo VB, de Oliveira, Márcia G, Cossa, Mateus, Soares, Bluma G
• Format: Article
• Language: English
• Subjects: Applied sciences; carbon black; carbon nanotubes; Composites; Electrical conductivity; Electrical resistivity; Electromagnetic interference; electromagnetic interference shielding; Exact sciences and technology; Fillers; Forms of application and semi-finished materials; percolation threshold; Polymer industry, paints, wood; Polymer matrix composites; Polyurethane resins; Resistivity; Technology of polymers; Urethane thermoplastic elastomers
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.4446

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range −22 to −20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry Carbon nanotube‐filled polyurethane composites were prepared through melt mixing. The electrical conductivity and electromagnetic interference shielding were strongly dependent to the formation of a conductive network within the polyurethane matrix.