Abstract
For the degree of orderly arrangement of the molecular chains at the interface of nanocomposites, the static and sheared polyethylene (PE)/carbon nanotube (CNT) models and the sheared pure PE model were constructed, and molecular simulation experiments were carried out in comparison. The micro-mechanism of molecular chains orientation, synergistically induced by the carbon nanotube and shear flow in injection molding, was discussed by analyzing the radius of gyration, molecular chain motion, conformation evolution of molecular chains, bond orientation parameter, interface binding energy and atom distribution. The results show that, for the static composite system, the conformation adjustment of PE molecular chains induced by CNT is limited due to the hindrance from the surrounding chains. Thus, the orientation and radius of gyration of molecular chains increase slightly. For the sheared pure PE system, the orientation induced by shear flow is unstable. After the cessation of shear, the molecular chains undergo intense thermal movement and relax quickly. The disorientation is obvious, and the radius of gyration decreases considerably. It is worth noting that for the sheared composite system, shear flow and the CNT have a synergistic effect on the orientation of the molecular chains, which is due to the adsorption effect of the CNT on shear-induced oriented chains and the inhibition effect of CNT on the relaxation of shear-induced oriented chains. Thus, the orientation stability of PE chains is greatly improved, and interface crystallization is promoted. Moreover, because of the more regular arrangement of molecular chains in the sheared composite system, more H atoms and C atoms are close to the surface of the CNT, which increases the van der Waals force, and correspondingly increases the interface binding energy.
Highlights
Since the discovery of carbon nanotubes (CNTs) by Iijima in 1991 [1], their excellent mechanical [2,3], thermal [4,5], and electrical properties [6,7] have promoted their use as fillers in composites
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]
Since the influence of the length of PE chain, the radius and chirality of the CNT on molecular chains orientation, and the aspect ratio of the CNT on the reinforcement effect of composite materials, had been investigated [18,19,23], in the constructed PE/CNT model, each PE chain contained 120 repeating units, and the single-walled carbon nanotube was (10,10) armchair type terminated by hydrogen atoms at both ends, with a length of 241.03 Å
Summary
Since the discovery of carbon nanotubes (CNTs) by Iijima in 1991 [1], their excellent mechanical [2,3], thermal [4,5], and electrical properties [6,7] have promoted their use as fillers in composites. 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. Wei 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. 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, affecting the degree and morphology of crystallization at the interface. The findings provide theoretical guidance for regulating and controlling the interface structure and improving the interface interaction of nanocomposites by controlling the processing condition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
