Multi-walled carbon nanotube-filled polypropylene nanocomposites: high velocity impact response and mechanical properties

Polymer nanocomposites containing 0.75, 1.0 and 1.5 wt% of multi-walled carbon nanotubes (MWNTs) in a polypropylene (PP) matrix were studied in relation to their low and high velocity impact performances. PP nanocomposites reinforced MWNTs were prepared via melt compounding in an internal mixer followed by injection molding. Transmission electron microscopy analysis confirmed well dispersed 1 wt% MWNT in the polymer nanocomposites. The same analysis showed agglomeration and cluster formation in 1.5 wt% MWNT specimens. Results showed increase in Izod impact strength in nanocomposites containing 1 wt% MWNT, which attained the highest value (with 33.4 % increment). A single stage gas gun was used to carry out high velocity impact test in velocity range of 20-150 m/s using hard steel hemispherical tip projectile of 11.34 g weight and 8.1 mm diameter. Results showed better ballistic limit velocity (the average of highest impact velocity causing perforation but unable to go through and lowest impact velocities with no residual velocity recording) and energy absorption for specimens, each containing 1 wt% MWNT, showing the highest value (with 100 % increment), compared with neat PP. Considerable increases were observed in tensile and flexural strengths and modulus for the MWNT-containing specimens as compared with neat PP.