Identification of the thermal response of confined fluids to mechanical shear deformation
Résumé
Anisotropic nature (rod-like geometry) allows carbon nanotubes (CNTs) to establish randomly connected web (network) in polymer matrices,
which can be utilized as mechanical reinforcement or conducting pathway in numerous present and future-emerging technologies, from multifunctional structural elements to flexible electronic devices, sensors, etc. (Oseli et al., Macromolecules, 2021). However, functional performance
of CNT-polymer nanocomposites mainly depends on the established network and its configuration (dispersed-high reinforcement, aggregatedhigh conductivity) driven by nanofiller geometry, content, as well as various mechanisms during nanocomposite productions (rupture, erosion,
diffusion, etc.). Within this study, we report on the underlying physical principles of such network formation utilizing single-walled carbon
nanotubes (SWCNT) in low- and high-density polyethylene matrices. Mechanisms were experimentally observed through plasma etching coupled
with electron microscopy as well as rheological flow tests, where Doi-Edwards theory served as theoretical platform explaining particle behavior.
Results showed, that established network is constructed from SWCNT bundles, which geometrically entangle at critical volume fraction Φv,crit
(number of rods: β≈30). Below Φv,crit, bundles behave as individual units, mainly interacting with host material. However, above Φv,crit, the rotation
of bundles is constrained by neighboring units, leading to random network configuration. This "meso-scale superstructure" exhibits long-range
particle interactions which result in profound rheological changes (increase η0,rel for ~700×). Moreover, the theory successfully explains SWCNT
bundle behavior as Brownian entity and predicts networks formation through diminishing thermo- and hydro-dynamically driven diffusion, which
can be manipulated during the production to enhance reinforcing/conductive functional performance of such materials.
Domaines
Physique [physics]
Origine : Fichiers produits par l'(les) auteur(s)