## 3 Results and Discussion
### Molecular Chain Orientation  
It can be seen in Figure 4 above that the conformation changes in the molecular chains are accompanied by corresponding changes in the orientation of the molecular chains. In order to quantitatively study the orientation of polymer molecular chains, the bond orientation parameter \(S\)[30] is introduced, and the calculation formula is as follows,  
\[S=\frac{1}{N(n-2)}\sum_{m=1}^{N}\sum_{i=3}^{n}\frac{3\cos^{2}\psi_{i}^{m}-1}{2} \tag{4}\]  
where \(N\) is the number of PE molecular chains, \(n\) is the number of C atoms in each PE molecular chain, and \(\psi\) is the angle between two adjacent bond segment vectors and the CNT axis.  
As shown in Figure 6, the bond orientation parameter of PE molecular chains in the static composite system slowly increases. The slight change further indicates that when the CNT is surrounded by multiple random polymer chains, the orientation of molecular chains induced by the CNT is finite under the restriction of the surrounding chain segments. The conformation evolution diagram also shows that the orientation of these chain segments is inconsistent. For a sheared pure PE system, the orientation induced by shear flow is unstable. The molecular chains are clearly disoriented and the bond orientation parameter is greatly reduced after the cessation of shear. For the sheared composite system after the cessation of shear, the bond orientation parameter decreases a little in a short time and then increases slowly. The degree of disorientation is much lower than that of the sheared pure PE system, which further indicates that the orientation stability of PE chains markedly improves under the adsorption effect of the CNT on shear-induced oriented chains and the inhibition effect of the CNT on the relaxation of shear-induced oriented chains. Moreover, the degree of orientation is further improved under the induction of the CNT.  
Figure 6 also shows that, under the combined action of the CNT and shear flow, the \(S\) value (0.74) in the sheared composite system is higher than the linear addition of \(S\) values (0.31) in the sheared pure PE and \(S\) values (0.23) in the static composite system. This indicates that shear flow and the CNT have a synergistic effect on the induction of orientation of the molecular chains. This is consistent with the analysis results of the radius of gyration. During the cooling process of injection molding, the polymer melt will undergo a transition from the liquid phase to the solid phase, that is, the crystallization process including the formation of a crystal nucleus and the growth of grain. At a higher temperature, the crystal nucleus is easily destroyed by molecular thermal motion, such as in the sheared pure PE system mentioned above. For the sheared composite system, the molecular chains maintain a stable  
Figure 6: The change curve of the bond orientation parameters of PE molecular chains over time.  
orientation under the action of the CNT. Since the molecular chains with a high orientation degree induce not only the orientation of the molecule chains around them, but also are closer to a lattice structure, the molecular chains have less kinetic barriers to cross, which is conducive to the formation of the crystal nucleus. They have a better crystallization ability than the chains with low orientation, thus promoting the interface crystallization of the composite system.