Ultralow Percolation Threshold in Poly(l-lactide)/Poly(ε-caprolactone)/Multiwall Carbon Nanotubes Composites with a Segregated Electrically Conductive Network

Abstract

Improvement on the electrical property of conductive polymer composites is dependent on the controllable dispersion of conductive additives in polymer matrices to form a conductive network. Here we show a segregated electrically conductive network is assembled in poly­(l-lactide)/poly­(ε-caprolactone)/multiwall carbon nanotubes (PLLA/PCL/MWCNTs) composites. First, the MWCNTs were dispersed in PCL to obtain the PCL/MWCNTs phase. Second, the PLLA particles were well coated with PCL/MWCNTs phase at 100 °C, which is between melting temperature of PLLA and PCL. Finally, the coated PLLA particles were compressed above the melting temperature of PLLA to form PCL/MWCNTs segregated structures. The morphological observation showed MWCNTs successful location in the continuous PCL phase, resulting in an ultralow percolation threshold of 0.0085 vol % MWCNTs. To our best knowledge, it is the lowest percolation threshold in PLLA- or PCL-based conductive composites at present. The composites with the segregated structure with only 0.05 wt % of MWCNTs loading achieved high electrical conductivity of 3.84 × 10–4 S/m. Furthermore, the composites with the segregated structure not only showed 10% higher Young’s modulus than that of the correspondingly conventional composites but also maintained high elongation at break and tensile strength. The samples with the segregated structure also show higher complex viscosity and lower crystallinity than that of the conventional composites because of the continuous PCL/MWCNTs network and the confined effects by this network.

Ecofriendly E-Nose Based in PLA and Only 0.3 wt% of CNTs

“…Different reports in literature indicate that the percolation threshold for PLA-CNTs nanocomposites occurs with conductivity values ranging from 10 -3 S m -1 to 10 -5 S m -1 . [7,17,21] Although in our work the percolation threshold was not determined, the conductivity of the sample with 0.3 wt% of CNTs (1.6 × 10 -1 S m -1 ) is much higher than those reported in percolation, indicating that our system is percolated and that we are working at a CNTs concentration much higher than that needed for percolation.…”

“…Several authors have studied polymer-CNTs nanocomposites [4,7,11,12,13]. In order to improve the filler's dispersion, different physical and chemical modifications were performed; from the realization of covalent and non-covalent functionalizations through electrostatic interactions, to modifications in the applied shear stress during the dispersion processes, or the inclusion of different additives [14,15,16,17].…”

Enhanced Dielectric and Mechanical Properties of Ternary Composites via Plasticizer-Induced Dense Interfaces

“…Apart from ferroelectric ceramics, conductive and semi-conductive materials with lower band gaps have been added into polymers to construct high-k composites as well [ 22 , 23 , 24 , 25 ], based on interface polarization [ 26 , 27 , 28 , 29 , 30 , 31 ] and electric percolation threshold [ 32 , 33 , 34 , 35 , 36 ]. Under an applied electric field, movable charges would gather in interface zones between two materials with different intrinsic dielectric constants or conducting properties.…”

The Ultraviolet-Induced Functionalization of Multi-Walled Carbon Nanotubes with Polymer Radicals Generated from Polyvinyl Benzoate Derivatives

“…They show characteristic electric conductivity based on the conjugated pi-electron system. Accordingly, they are used in organic electronic devices [2][3][4][5][6][7][8][9][10][11][12][13].…”

“…To date, various polymers have been used to prepare polymer/ nanomaterial composites: for example, poly(L-lactide) [10,13], poly(trimethylene terephthalate) [11], polycarbonate/ethylene-propylene copolymer [12], polydimethylsiloxane [14], polyvinylpyrrolidone [15], etc. Many hybrid materials have been fabricated by means of physical dispersion of nanoparticles into polymers.…”