Molecular dynamics simulation on performance modulation of graphene‐modified polyethylene during friction process

Abstract

Molecular dynamics simulation is an effective method to evaluate material properties at the early stage of material design, which can accurately guide the design of new materials and shorten the material development cycle. Therefore, in this study, the changes of tribological and mechanical properties of graphene reinforced polyethylene (PE) composites during friction process were simulated by molecular dynamics. The analysis results showed that the graphene induced the formation of a transfer film consisting of PE molecular chains at the friction interface, thereby reducing the interaction between the friction pair and the composites and preventing numerous molecular chains from collecting at the friction interface. Meanwhile, the graphene enhanced the free‐volume fraction to strengthen the mechanical properties of the composites‐thereby producing high‐performance composites. Thus, an appropriate graphene content could notably reduce both the coefficient of friction and wear rate of PE, and reinforce the polymer's tribological and mechanical properties. By adding 2 wt.% of graphene, the mechanical properties of the composite were significantly improved, while the coefficient of friction decreased by 29.6% and the wear rate decreased by 89.9% compared to that of pure PE, and presented the best strengthening effect. This knowledge will be useful for future designing and developing composite polymer materials with excellent tribological and mechanical properties used for key moving components.

A molecular dynamics study of 3C‐SiC/epoxy nanocomposite as a metal‐free friction material

“…Previous work 12,26 shows the same conclusion, which proves that the result in this work is persuasive. However, it should be pointed out that some researchers also found that different range of crosslinking degree and different content of nanofillers added may not always get the same result above 12,14 . Hence, a more detailed exploration is necessary to see the whole picture of the relationship between degree of crosslinking, content of nanofillers, and FFV.…”

“…Fractional free volume (FFV) is usually applied to calculate the effective movement space of molecular chains 14 . According to the free volume theory, 15 the total volume of a material is divided into free volume V f and occupied volume V w (vdWs volume).…”

“…Fractional free volume (FFV) is usually applied to calculate the effective movement space of molecular chains. 14 According to the free volume theory, 15 the total volume of a material is divided into free volume V f and occupied volume V w (vdWs volume). V w represents the space where the material occupies, while V f represents the holes and voids throughout the whole material that allowing the molecular chains to move.…”

“…However, it should be pointed out that some researchers also found that different range of crosslinking degree and different content of nanofillers added may not always get the same result above. 12,14 Hence, a more detailed exploration is necessary to see the whole picture of the relationship between degree of crosslinking, content of nanofillers, and FFV. Usually, a smaller FFV would bring better performance for the materials, given a similar degree of crosslinking.…”