Role of chemical funcionalization of carbon nanoparticles in epoxy matrices

Abstract

The effects of the silanization of multi-walled carbon nanotubes and graphene nanoplatelets with 3-APTES on thermal, mechanical and electrical properties of epoxy nanocomposites were investigated. Nanocomposites containing pristine, oxidized and silanized nanoparticles of multi-walled carbon nanotubes or graphene nanoplatelets at two different concentrations (0.15 and 0.50 vol.%) were prepared by in situ polymerization without using solvents. The functionalized nanoparticles were characterized by Fourier-transform infrared, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscope techniques. The oxidation and the silanization on the surface of both nanoparticles were confirmed by Fourier-transform infrared, X-ray photoelectron spectroscopy, Raman and transmission electron microscope analysis. The thermal properties of all studied materials were analyzed by differential scanning calorimetry and the mechanical properties by nanoindentation. The addition of both nanoparticles (pristine and functionalized) into the matrix did not show significant variations on thermal properties, but decreased values for glass transition temperature (Tg) compared to the neat resin. Higher values for modulus of elasticity and hardness of epoxy/nanocomposites were obtained when silanized multi-walled carbon nanotubes or oxidized graphene nanoplatelets were added into the matrix. Adding 0.15 vol.% of silanized multi-walled carbon nanotubes the modulus of elasticity increased in approximately 60%, whereas 0.50 vol.% this increase was greater than 90% compared to the neat resin. While adding 0.15 vol.% of oxidized graphene nanoplatelets, the modulus of elasticity increased approximately 83%, whereas 0.50 vol.% this increase was greater than 88% compared to the neat resin. The formation of percolating networks has been achieved only by pristine multi-walled carbon nanotubes addition at a concentration of 0.50 vol.% and by silanized graphene nanoplatelets at a concentration of 0.15 vol.%. However, for both carbon-based nanoparticles conductivities on the order of 10−7 S/m for frequencies near 100 Hz were observed.

Oxidation time effects of multiwalled carbon nanotubes on thermal, mechanical, and cure kinetics of epoxy‐based nanocomposites

“…Kathi et al [ 3 ] performed the oxidation of MWCNT with sulfuric and nitric acid (3:1 v/v) and subsequently subjected them to magnetic stirring for 18 hours. Although the process proved to be efficient, as reproduced by our previous work, [ 2 ] the high magnetic stirring time makes the process slow and difficult to apply on a large scale.…”

“…Oxidation process was carried out by dispersing 300 mg of pristine MWCNT in 30 mL of H 2 SO 4 /HNO 3 mixture (3:1 v/v) with magnetic stirring at room temperature for 9 and 18 hours. [ 2,3 ] The solution was vacuum filtered and washed initially with acetone and then with deionized water until the pH reach an approximately neutral value. The oxidized CNT were dried in a vacuum oven at 100°C for 24 hours.…”

“…Adding CNT into epoxy matrices to enhance its properties and obtain a multifunctional material has already been deeply studied in order to analyze the thermal [ 2–4 ] and mechanical [ 2–6 ] properties of its polymeric nanocomposites. Furthermore, several works in the literature [ 7,8 ] have devoted themselves to the study of the curing kinetics of these systems aiming a better understanding of their functioning mechanisms.…”

“…In this context, this work aims to evaluate the influence of two different levels of oxidation on the MWCNT properties, maintaining the acid concentration constant. Based on our previous study [ 2 ] that we evaluated the influence of the 18 hours oxidizing treatment on the properties of CNT and its nanocomposites, we decided to keep this treatment time and compare with its half. In addition, two different levels of concentrations (0.15% and 0.50% v/v) were investigated in order to verify the influence of this factor on the interfacial properties of epoxy/nanoparticles.…”

Role of π‐π interactions and chain flexibility in dispersion and dynamic‐mechanical properties of nanocomposites with multiple wall carbon nanotubes

“…Although these are considered weak intermolecular forces, they become significant at nanoscale due to the nanoparticle high surface area per mass unit . In order to achieve better performances in polymer nanocomposites, several researches have been aiming to increase the interfacial interaction between the polymer matrix and CNT . The CNT surface chemical modification by introducing functional groups is an effective way to induce strong interfacial interactions.…”