Effect of grafted chains on the heat transfer between carbon nanotubes in a polyamide-6.6 matrix: A molecular dynamics study

Abstract

By employing reverse non-equilibrium molecular dynamics simulations in a united-atom resolution, the influence of grafted polyamide-6,6 (PA) chains on the heat transfer between two parallel carbon nanotubes (CNTs) in a PA matrix is analyzed by calculating the thermal resistance. We show that grafted chains can reduce the thermal resistance between the CNTs significantly. Specifically, the thermal resistance between the CNTs decreases continuously with the grafting density and grafting length. In addition, the thermal resistance between the CNTs gradually increases with the increase of the distance between the CNTs. When the CNTs are directly linked by PA chains, the thermal resistance is even more reduced. The number of linking PA chains is the main factor that controls the thermal resistance, rather than their length. The relationship between the thermal resistance and the different parameters (grafting density, grafting length, number of linking chains, the intertube distance) can be described by an empirical equation. The heat transfer process from one CNT to another can be approximately described by a thermal circuit model between the CNTs. For the grafted CNTs, the model underestimates the simulated thermal resistance, whereas for the PA-linked CNTs, it overestimates it. However, for the grafted CNTs with very high grafting density and very short grafting length, the model significantly underestimates the simulated thermal resistance because of the appearance of a new interface between grafted PA and free PA.