Toughness and roughness in hybrid nanocomposites of an epoxy matrix

Abstract

The present paper investigates the relationship between roughness and toughening mechanisms in hybrid epoxy nanocomposites with carbon nanotubes (CNT) and graphene nanoplatelets (GNPs). The role of adding a block copolymer (BC) to the studied systems was also investigated. The nanocomposites were prepared by means of high-energy sonication and in situ polymerization. All nanocomposites presented higher numerical values for K Ic than untoughened systems. The system containing 0.5 wt% of CNTs presented an increase of 35% in K Ic compared to neat epoxy, and the hybrid nanocomposite, at the proportion of 1:1 (CNT:GNP), with 0.5 wt% total of nanoparticles and also containing 0.5 wt % of BC, had an increase of 34% compared to the neat epoxy. Systems with higher amounts of graphene showed the highest roughness values, having crack deflection/exfoliation between the GNP layers as the main toughening mechanism. On the other hand, systems with more CNTs presented a lower fracture surface roughness, and the main toughening mechanism was bridging/break-up of the nanotubes. Hybrid systems have more types of mechanisms than simple ones. With only one type of nanoparticle, however, some of those mechanisms are not effective in increasing the toughness, only increasing the fracture surface roughness. POLYM. ENG.

The role of carbon nanoparticles in epoxy‐based nanocomposites modified with (poly[polypropylene oxide]‐block‐poly[ethylene oxide]‐block‐poly[propylene oxide]) triblock copolymers on phase morphology and mechanical properties

“…[ 37 ] Small and irregular holes on the fracture surface are formed due to the CNT agglomerates being wrenched off by the crack propagation, severely deforming the matrix. [ 38 ] In this work, no image of the corresponding fracture part was made, mirroring the image, as in a previous work by our group, [ 11 ] but, in the region corresponding to the holes, a high‐deformation region would probably be visualized, similarly to the part marked by the parabola in Figure 5A.…”

“…[ 39 ] The small size of the nanoparticles inhibits the identification of the crack propagation mechanisms by means of microscopy, [ 31,32 ] but it is possible to identify features related to them. [ 11,39 ]…”

“…In addition to block copolymers, carbon nanoparticles can be used to improve the mechanical properties of epoxy resins and, in particular, their toughness. [ 10–12 ] The nanoparticles used in this research (carbon nanotubes [CNTs], graphene, and carbon black) were chosen because they are the most studied nanoparticles in the literature [ 10–17 ] and they are mainly composed of carbon, only changing geometry.…”

Biosourced vanillin Schiff base platform monomers as substitutes for DGEBA in thermoset epoxy

“…[ 11,12 ] The most common are polyesters, polyurethanes and epoxies. [ 9,10 ] Most epoxy resins are obtained by reacting bisphenol A (BPA) with epichlorohydrin [ 13 ] to produce a diglycidyl ether epoxide known as DGEBA. BPA is also used in the production of polycarbonate plastics for food containers, and metal lids and tin cans are often coated with epoxy.…”

Effects of adding different concentrations of block copolymers in epoxy matrix nanocomposites with carbon allotropic nanoparticles

“…In a previous work, [ 8,21 ] our group studied the behavior of epoxy nanocomposites with 0.2 and 0.5 wt% of carbon nanoparticles with the same amounts of the BCP used in this work. This amount of BCP helped the dispersion and stabilization of carbon nanoparticles and generated a synergistic effect on toughness.…”