Friction and Wear Characteristics of Additive Manufactured CNT-Reinforced HDPE Composites in Dry Contact

Abstract

The tribological properties of three-dimensional (3D) printed polymeric composites are often less explored due to the complexity involved related to their softness, poor mechanical properties, and lower thermal conductivities. Keeping this in view, this work reports the influence of carbon nanotubes (CNTs) on the tribological properties of high-density polyethylene (HDPE) composites. Fused deposition modeling was adopted to develop the composites with varying CNT contents from 0.5 wt% to 2 wt%. The tribological properties were studied by subjecting them to friction-on-wear test using a pin-on-disc setup. The tests were conducted with varying applied loads (5 to 20 N) and sliding speeds (0.262 to 1.048 m/s). A scanning electron microscope (SEM) was employed to study the morphology of the filaments and to analyze the worn surfaces after testing. The printed composite parts displayed a good dispersion of CNTs, showed a good print quality, and were free from warpage or shrinkage defects. With the increase in load and sliding velocity, both the wear rate and coefficient of friction of all the developed samples tend to increase. Out of all the developed samples, some showed poor wear resistance, while composites with the highest CNT contents of 2 wt% showed significant resistance to material loss, which is attributed to the reduced contact area and the CNT acting as an anchor to prevent the polymer chain from being detached. The worn surface analysis revealed adhesive wear as the dominant mechanism for pure HDPE, and abrasive wear as the primary mechanism for HDPE composites. Overall, this work showed that CNTs can be used as an effective filler for reducing the friction coefficient and increasing the wear resistance.