Viscosity Ratio and Interfacial Tension as Carbon Nanotubes Distributing Factors in Melt-Mixed Blends of Polyamide 12 and High-Density Polyethylene L. ZONDER University of Massachusetts Lowell, Lowell, Massachusetts 01854 Shenkar College of Engineering and Design, Ramat-Gan 52526, Israel S. MCCARTHY University of Massachusetts Lowell, Lowell, Massachusetts 01854 F. RIOS, A. OPHIR, S. KENIG Shenkar College of Engineering and Design, Ramat-Gan 52526, Israel Correspondence to: A. Ophir; e-mail: amosophir@shenkar.ac.il. Received: April 29, 2013 Accepted: January 9, 2014 ABSTRACT: Polyamide 12 (PA12)/high-density polyethylene (PE)/carbon nanotubes (CNTs) composites were prepared by three melt mixing sequences; premixing the CNT in the PA phase, premixing the CNT in the PE phase, and simultaneous mixing of all components. The interfacial tension and viscosity ratio between the components were altered by modifying the PE minor phase with PE-graft-maleic anhydride (PE-g-MAH) and by using different melt flow rate PE minor phase. Scanning electron microscopy (SEM) and volume resistivity (VR) measurements show that when the matrix’s viscosity is greater than that of the dispersed phase, simultaneous mixing and premixing the CNT in the PE phase form a unique microstructure that yields a VR that is 4–6 decades lower than when premixing the CNT in the PA phase. When the viscosity of the dispersed PE phase is greater, kinetic restrictions limit the migration of the CNTs from the PE phase, resulting in high VR values for all mixing procedures. The wetting parameter was used to calculate the thermodynamic drive of the CNTs localization. It was found that the MAH modification reduces the interfacial tension between the CNT and the modified PE phase, which results in selective localization of CNT in there rather than in the PA phase. This observation was confirmed in SEM imaging and also expressed in high VR values of these composites. C  2014 Wiley Periodicals, Inc. Adv Polym Technol 2014, 00, 21427; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21427 KEY WORDS: Blends, Carbon nanotubes, Interfacial tension, Nanocomposites, Viscosity Introduction I mmiscible polymer blends nanocomposites represent a spe- cial class of hybrid materials due to the presence of at least two phases in which the nanoparticles can be localized. Several researchers have shown that the specific location of particulate fillers in a multiphase polymeric system has a significant ef- fect on the performance of the material; for example, improved mechanical properties can be obtained due to morphological changes induced by selective particle location. 1–3 In addition, in- corporation of conductive particulate fillers such as carbon black (CB) or carbon nanotubes (CNTs) was found to reduce the perco- lation threshold 4–7 through a mechanism of double percolation, where the conductive filler is selectively localized inside one of the phases or at the interface, thus effectively reducing the filler amount required to reach the percolation. Melt blending is currently the fastest, most convenient, and economical route to fabricate such nanocomposite, 8 in which good dispersion can be attained. Therefore, by understanding and controlling CNT localization in melt mixing operations, it is possible to achieve well-tuned morphologies that promote tailored properties. Though the mechanisms that determine the localization of fillers during melt mixing are still not completely understood, 9 it is common to rationalize particle localization on the basis of two, sometimes competing driving forces; on the one hand, ther- modynamic wetting based on polar and dispersion interactions between the solid and the polymeric phases, and on the other hand, kinetic control of the filler localization directly linked to the rate of mixing process. With regards to the thermodynamic Advances in Polymer Technology, Vol. 00, No. 0, 2014, DOI 10.1002/adv.21427 C  2014 Wiley Periodicals, Inc. 21427 (1 of 7)