## 1 Introduction  
Since the discovery of carbon nanotubes (CNTs) by [PERSON] in 1991 [1], their excellent mechanical [2; 3], thermal [4; 5], and electrical properties [6; 7] have promoted their use as fillers in composites. Especially after the first preparation of epoxy resin/CNT by [PERSON] et al. [8], nanocomposites have been extensively studied. Polyethylene (PE) is an important plastic material, which has the advantages of a wide range of raw materials, low price and stable chemical properties, but its service life is reduced due to low strength, easy deformation, and heat resistance [9]. Thus, it is necessary to study PE nanocomposites. In nanocomposites, the interface plays the role of transmitting the load from polymer to CNTs under the action of external force; therefore, the interface interaction is crucial. The orderly arrangement degree of the polymer molecular chains on the surface of the CNT directly affects the interface crystallization behavior and interface interaction [10, 11]. Therefore, the orientation and conformation of molecular chains on the surface of the CNT can be studied to regulate and control the interface structure and improve interface interaction. In recent years, the molecular simulation method has been applied to the study of nanocomposites [12, 13, 14, 15, 16], and many molecular simulation studies have been conducted on the molecular chain orientation and conformation evolution induced by CNT. [PERSON] et al. analyzed the orientation process of multiple short PE chains induced by the CNT [17]. [PERSON] et al. studied the orientation process of a single PE chain induced by the CNT, and found that the ordered structures formed by PE chains with different lengths were all almost parallel to the axis of the CNT, with a shorter chain forming an ordered single-layer structure, and a longer chain forming an ordered multi-layer structure [18]. [PERSON] et al. studied the adsorption and diffusion behavior of molecular chains on the surface of semi-metallic and semiconductor CNTs. The results showed that the adsorption position and conformation of molecular chains are mainly related to the temperature and the radius of the CNT, not the type of CNT [19]. [PERSON] et al. found that only the structure of local polymer molecular chains close to the CNT was more orderly, while the overall chain conformation did not change significantly [20]. [PERSON] et al. found that the molecular chains in the adsorption layer tended to be parallel to the axis of the CNT, and improvement of the structure order degree strengthened the nanocomposites [11]. These studies mainly focused on the individual effect of the CNT inducing the orientation of molecular chains under static conditions. In addition, [PERSON] et al. compared and discussed the degree of orientation and the interface crystallization behavior when the specific initial orientation angles of molecular chains and the CNT were \(0^{\circ}\), \(45^{\circ}\), or \(90^{\circ}\)[10]. However, shear flow inevitably occurs in the melt during the injection molding of nanocomposites [21, 22]. For the thermoplastics with a linear flexible molecular chain structure, under different process conditions of injection molding, the molecular chains will have different degrees of orientation under the induction of shear flow, thus affecting the degree and morphology of crystallization at the interface. The molecular mechanism of the orientation of multiple random molecular chains in melt under the combined effect of shear flow and the CNT has not been reported. In this study, the dynamic evolution process of the conformation of molecular chains at the interface of nanocomposites was more intuitively observed using molecular simulation technology. The micro-mechanism of molecular chains orientation, synergistically induced by carbon nanotube and shear flow, is discussed.