Key Role of the Dispersion of Carbon Nanotubes (CNTs) within Epoxy Networks on their Ability to Release.

Maxime Pras,Jannick Duchet-Rumeau,Guilhem Quintard,Jean-François Gérard,Luana Golanski

doi:10.3390/polym12112530

Abstract

Carbon nanotube (CNT)-reinforced nanocomposites represent a unique opportunity in terms of designing advanced materials with mechanical reinforcement and improvements in the electrical and thermal conductivities. However, the toxic effects of these composites on human health have been studied, and very soon, some regulations on CNTs and on composites based on CNTs will be enacted. That is why the release of CNTs during the nanocomposite lifecycle must be controlled. As the releasing depends on the interfacial strength that is stronger between CNTs and polymers compared to CNTs in a CNT agglomerate, two dispersion states—one poorly dispersed versus another well dispersed—are generated and finely described. So, the main aim of this study is to check if the CNT dispersion state has an influence on the CNT releasing potential in the nanocomposite. To well tailor and characterize the CNT dispersion state in the polymer matrix, electronic microscopies (SEM and TEM) and also rheological analysis are carried out to identify whether CNTs are isolated, in bundles, or in agglomerates. When the dispersion state is known and controlled, its influence on the polymerization kinetic and on mechanical properties is discussed. It appears clearly that in the case of a good dispersion state, strong interfaces are generated, linking the isolated nanotubes with the polymer, whereas the CNT cohesion in an agglomerate seems much more weak, and it does not provide any improvement to the polymer matrix. Raman spectroscopy is relevant to analyze the interfacial properties and allows the relationship with the releasing ability of nanocomposites; i.e., CNTs poorly dispersed in the matrix are more readily released when compared to well-dispersed nanocomposites. The tribological tests confirm from released particles granulometry and observations that a CNT dispersion state sufficiently achieved in the nanocomposite avoids single CNT releasing under those solicitations.

Highlights

Carbon nanotubes (CNTs) always have been very attractive nanofillers because of their remarkable properties
The organization of CNT within the epoxy material was studied: (i) before curing, i.e., as the CNT-based masterbatch is dispersed in the diglycidyl ether of Bisphenol A (DGEBA) prepolymer, and (ii) after
This paper paper aims aims at at generating generating different different dispersion dispersion states states but but in in aa controlled controlled way way of of carbon carbon nanotubes into an epoxy–amine network

Summary

Introduction

Carbon nanotubes (CNTs) always have been very attractive nanofillers because of their remarkable properties. CNTs have a real potential for processing the polymer composites and for obtaining mechanical reinforcement and thermal and electrical conductivities improvement while making the materials more lightweight [2,3,4]. Tailoring the releasing of isolated CNT during the nanocomposites lifecycle and especially during the different steps of handling (such as friction, mechanical abrasion, or breakage) is strongly required for a responsible development of these NTC nanofilled polymers materials [9,10]. The risk caused by the exposure to CNTs has been hard to evaluate by the lack of data about the impacts on human health and the environment. The potential release of CNTs from composite materials as a result of cutting, drilling, sanding, grinding, and UV-light weathering has been investigated [11]

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