Medium-density polyethylene/multiwall carbon nanotube (MDPE/MWCNT) nanocomposites were produced by a mechanical milling method using a highenergy ball mill. The MDPE and MWCNTs were added to the ball mill at a constant 20:1 weight ratio of ball/powders and milled for 10 h to obtain polyethylene matrix nanocomposites reinforced with 0.5, 1, 2.5, and 5 weight percent of MWCNTs. To clarify the role of both MWCNT content and milling time on the morphology of MDPE, some nanocomposite samples were investigated by using a scanning electron microscope. To evaluate the role of milling on the microstructure of the nanocomposites, very thin films of MDPE/MWCNTs were prepared and studied by transmission electron microscopy. Thermal behavior of these nanocomposites was investigated by using differential scanning calorimetry (DSC). Standard tensile samples were produced by compression molding. The dependence of the tensile properties of MDPE on both milling time and MWCNT content was studied by using a tensile test. The results of the microscopic evaluations showed that the milling process could be a suitable method for producing MDPE/MWCNT nanocomposites. The addition of carbon nanotubes to MDPE caused a change in its morphology at constant milling parameters. The results of the DSC tests showed that the crystallization temperature of MDPE increased as MWCNTs were added, although no dependency was observed as milling time increased. Crystallization index changed from 50 to 55% as MWCNT content increased from 0 to 5%. The results of the tensile tests showed that both the Young’s modulus and the yield strength of MDPE increased as MWCNTs were added.

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