Is percolation really achievable in polymeric composites by incorporating approximately 1 vol.% of CNT or other nanoparticles in bulk composite form? Or it is only observed in the thin film form at this concentration?
Yes, certainly you can have ultralow percolation thresholds as soon as you deal with particles having high aspect ratios, and provided that these particles are randomly dispersed in the polymer matrix (see attachement). As far as CNTs are concerned, it is not so easy to disperse them suitably, and they don't maintain their straight shape, but tend to curl. These phenomena tend to increase the threshold, but very low values (less than 1 vol.%) were already reported in the literature.
Alain
Yes, certainly you can have ultralow percolation thresholds as soon as you deal with particles having high aspect ratios, and provided that these particles are randomly dispersed in the polymer matrix (see attachement). As far as CNTs are concerned, it is not so easy to disperse them suitably, and they don't maintain their straight shape, but tend to curl. These phenomena tend to increase the threshold, but very low values (less than 1 vol.%) were already reported in the literature.
Alain
There is a rule of thumb that is surprisingly suitable to gain the percolation threshold, it’s called the Nan’s law: Vc = 0.7/f , where f is the aspect ratio of the fillers. Now with ultra-small particles a dynamic effect arise not visible with micronic particles. This is especially visible with carbon nanotube, but has also been reported with carbon black, especially if you add an electric field that favors agglomeration.
https://www.researchgate.net/publication/264051665_Understanding_dynamic_percolation_mechanisms_in_carbonaceous_polymer_nanocomposites_through_impedance_spectroscopy_Experiments_and_modeling?ev=prf_pub
or
https://www.researchgate.net/publication/234078453_Effect_of_filler_auto-assembly_on_percolation_transition_in_carbon_nanotubepolymer_composites?ev=prf_pub
and the references therein (especially from alig & Poetchke te al)
https://www.researchgate.net/publication/224437720_In_situ_observation_of_electric_field_induced_agglomeration_of_carbon_black_in_epoxy_resin?ev=prf_pub
Article Understanding dynamic percolation mechanisms in carbonaceous...
Article Effect of filler auto-assembly on percolation transition in ...
Article In situ observation of electric field induced agglomeration ...
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