Abstract
The effects of chaotic advection on the in situ assembly of a hierarchal nanocomposite of Poly Amide 6, (nylon 6 or PA6) and platelet shape nanoparticles (NPs) were studied. The assemblies were formed by chaotic advection, where melts of pristine PA6 and a mixture of PA6 with NPs were segregated into discrete layers and extruded into film in a continuous process. The process assembles the nanocomposite into alternating pristine-polymer and oriented NP/polymer layers. The structure of these hierarchal assemblies was probed by X-rays as a processing parameter, N, was varied. This parameter provides a measure of the extent of in situ structuring by chaotic advection. We found that all assemblies are semi-crystalline at room temperature. Increasing N impacts the ratio of α to γ crystalline forms. The effects of the chaotic advection vary with the concentration of the NPs. For nanocomposites with lower NP concentrations the amount of the γ crystalline form increased with N. However, at higher NP concentrations, interfacial effects of the NP play a significant role in determining the structure, where the NPs oriented along the melt flow direction and the polymer chains oriented perpendicular to the NP surfaces.
Highlights
Controlled assembly of structured layers of polymers that contain different types of nanoparticles (NPs) offers a means to tailor multifunctional materials
We have shown that using Smart Blending of two polymer-melts, where one contains NPs, results in hierarchical nanocomposites that consist of alternating layers of a polymer and polymer-NP layers [27]
In order to set the background for the NP assembly and its impact, we first probed the pristine polymer, comparing extruded PA6 in comparison with a film formed by a melt exposed to chaotic
Summary
Controlled assembly of structured layers of polymers that contain different types of nanoparticles (NPs) offers a means to tailor multifunctional materials. Directing the assembly of NPs via chemical modifications, coupled with large-scale extrusion that can further structure the resulting composite, provide a powerful method to move processes on a lab scale to an actual technologically viable process One such a process is a blending technique often referred to as “Smart Blending”, where chaotic advection is introduced into melts of two polymers, resulting in localization of the polymers into layers of controllable thickness and number [22,23,24,25,26]. The current study presents for the first time the effects of chaotic advection on the structure of hierarchal nanocomposites; i.e., the effects of non-linear flows on the assembly, using X-ray diffraction. The study has shown that chaotic advection structured the films, and changes the ratio of the crystalline forms of the polymer depending on the concentration of the NPs, where at higher concentrations of NPs, surface effects become significant
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