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In this study a series of melt mixed multi‐walled carbon nanotube (MWNT)/Polyethylene composites with several carbon nanotube (CNTs) concentrations were investigated. A good dispersion of the nanotubes in the matrix was seen using scanning electron microscopy. Melt rheological measurements in dynamic mode were used to estimate the percolation state of the CNTs within the polymer and to provide information about the structure of the CNT/polymer composites. The effect of nanotubes on the non‐isothermal crystallization behaviour of the nanocomposites was also studied by differential scanning calorimetry.

The morphological, rheological and electrical properties of nanocomposites based on multi‐walled carbon nanotubes (MWNTs) and high density polyethylene (HDPE), prepared by melt mixing, have been investigated. The effects of temperature, MWNT concentration and nanotube surface treatment have been analyzed. A good dispersion of oxidized nanotubes in the HDPE matrix was found using electron microscopy investigations, as has also been found in the case of related nonfunctionalized MWNTs. The rheological oscillatory shear tests in the melt state have been carried out with strain amplitude values within the linear viscoelastic region. The rheological measurements on the nonfunctionalized MWNT/HDPEs revealed that the percolation threshold was temperature dependent with lower values at higher temperatures. At low frequencies, the oxidized MWNTs/HDPE composites showed storage modulus and complex viscosity values lower than the corresponding values measured for nanocomposites prepared with nonfunctionalized MWNTs. The conductivity decrease is more than 2 orders of magnitude for the sample with 2.5 wt% oxidized MWNTs, compared to the un‐oxidized comparator materials. A constant voltage, long‐term stability test allowed to estimate the average number of electrically active percolation paths and showed that stepwise conductivity loss is preceded by a strong increase in the noise amplitude related to the electrical current. POLYM. ENG. SCI., 57:665–673, 2017. © 2017 Society of Plastics Engineers

Rheological and electrical properties of nanocomposites based on multi-walled carbon nanotubes (MWNTs) and high density polyethylene (HDPE), prepared by melt mixing in a micro-twin screw extruder, have been investigated. The effect of MWNT concentration (0.5 and 2.5 wt %) and nanotube surface treatment (oxidative treatment in a tubular furnace at 500°C for 1 hr in a 95% nitrogen, 5% oxygen atmosphere) has been analyzed. It has been found that the sample conductivity with oxidation of the nanotubes decreases more than 2 orders of magnitude. Scanning electron microscopy showed good adhesion and dispersion of nanotubes in the matrix, independently of the surface treatment. Electrical and rheological measurements revealed that the oxidative treatment, causing some reduction of the MWNT quality, decreases the efficiency of the nanotube matrix interaction

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