Nano-mesh superstructure from single-walled carbon nanotubes in semi-crystalline polymers

date: 08.06.2020

category: Sporočila za javnost

 

Carbon nanotubes are one of the fundamental geometrical configurations (allotropes) of carbon, i.e. tube- or rod- like structures, exhibiting superior strength and other functionalities, such as electrical conductivity, which enables them to act as ideal multi-functional fillers in polymer matrices. Moreover, their anisotropic nature allows them to establish randomly connected web (network), serving as mechanical reinforcement or conducting pathway, which can be applied in numerous technologies, from multi-functional structural elements to flexible electronic devices, sensors, etc. Within the scope of the research, we studied the underlying mechanisms of network formation in semi-crystalline polymers utilizing advanced plasma etching methods coupled with electronic microscopy, and its macroscopic effect observed through physical properties (rheological, thermal, mechanical). It was shown that the network mostly incorporates bundles from single-walled carbon nanotubes, resulting from interparticle attraction (van der Waals attractive forces), which cannot be ruptured or eroded by conventional processing techniques without damaging the nano-filler or matrix material. Based on the results, the network is established at critical concentration, i.e. φcrit ≈ 0.3 wt.%. Below the critical concentration (in dilute regime), these entities can freely rotate about their center mass and mainly act on matrix material. However, above critical concentration (in semi-dilute regime), bundles establish randomly connected web. Established network or so-called “meso-scale superstructure” exhibits long range particle interactions that ranges from nano- to macro-scale fundamentally changing the material behavior and the properties of nanocomposites. In addition, bundles “arrange” themselves in mesh formation, i.e. nano-mesh, which is the result of two mechanisms: i.) alignment of the bundles in the melt flow direction, forming network backbone and ii.) Sish-kebab induced crystallization, forming network net. Although the established superstructure profoundly improves reinforcing properties of the material, it reduces its reinforcing potential as it limits or slows down (topologically/geometrically hinders) crystal growth in nanocomposites.

lidija

The results of the research are the fruit of a successful collaboration between teams of Faculty of mechanical engineering, Faculty of polymer technology, Jozef Stefan institute, and National institute of chemistry, which were published in prestige scientific journal Composites Part A: Applied science and manufacturing (IF 6.282).

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