Abstract
It has been reported that the introduction of reduced graphene oxide (RGO) can enhance the crystallization and orientation of high-density polyethylene (HDPE) matrix and thus improve the mechanical properties of HDPE/RGO nanocomposites. In this study, the local microstructures and orientations in different regions of HDPE/RGO bars with varied RGO contents were further explored by two-dimensional small-angle X-ray scattering using a microbeam technique. It is unveiled that the orientation orderings of each position is intensified with increasing RGO amount, and of particular interest is the observation of the slight change of the ordering degrees in diverse zones of HDPE/RGO nanocomposite bars, indicating that RGO imposes a uniform enhancing effect upon HDPE matrix within different areas and consequently induces an effective increase of the mechanical properties of HDPE/RGO nanocomposites.
Highlights
Polymeric materials have been widely used in a number of fields due to their unique characteristics
Compared with the pure high-density polyethylene (HDPE), which has no periodic structure at the centre, the periodic structure is enhanced in the equator and meridian direction with the increase of reduced graphene oxide (RGO) content
By further investigating the microstructures via microbeam SAXS, despite the presence of weak difference in the enhancing effect at varied positions, especially for the cases of large RGO contents, we have demonstrated that the coupling between the flow-induced orientation and the RGO-depressed release of oriented chains by absorption and epitaxial crystallization imposes an approximately uniform intensifying effect on the crystallization and orientation of HDPE in the flow direction, which results in the enhancement of the mechanical performance of injection bars of HDPE/RGO nanocomposites
Summary
Polymeric materials have been widely used in a number of fields due to their unique characteristics. Injection moulding is widely employed for shaping the products and a large number of researchers have devoted themselves to studying and modelling the injection moulding process for thermoplastics [1,2,3,4]. It is commonly recognized that the shear flow enhances the crystallization process and affects the properties of polymers by improving the orientation of polymer chains [10,11,12]. The morphology, orientation and their distribution of macromolecules at distinct zones are different due to their complex thermomechanical history, which results in the highly anisotropic and nonhomogeneous structures, affecting the physical behaviour and ultimate mechanical properties of injection-moulded parts [19,20]. Extensive studies have been conducted on the structures and properties of injection bars of pure polymers [13,21,22], much less work has been reported on the promising novel polymer/nanofiller composites
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