A facile way to produce epoxy nanocomposites having excellent thermal conductivity with low contents of reduced graphene oxide

Abstract

A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was initially prepared in water. This was concentrated by centrifugation and was mixed with a liquid epoxy resin. The remaining water was removed by evaporation, leaving a GO dispersion in epoxy resin. A stoichiometric amount of an anhydride curing agent was added to this epoxy-resin mixture containing the GO nanosheets, which was then cured at 90°C for 1 h followed by 160°C for 2 h. A second thermal treatment step of 200°C for 30 min was then undertaken to reduce further the GO in situ in the epoxy nanocomposite. An examination of the morphology of such nanocomposites containing reduced graphene oxide (rGO) revealed that a very good dispersion of rGO was achieved throughout the epoxy polymer. Various thermal and mechanical properties of the epoxy nanocomposites were measured, and the most noteworthy finding was a remarkable increase in the thermal conductivity when relatively very low contents of rGO were present. For example, a value of 0.25 W/mK was measured at 30°C for the nanocomposite with merely 0.06 weight percentage (wt%) of rGO present, which represents an increase of *40% compared with that of the unmodified epoxy polymer. This value represents one of the largest increases in the thermal conductivity per wt% of added rGO yet reported. These observations have been attributed to the excellent dispersion of rGO achieved in these nanocomposites made via this facile production method. The present results show that it is now possible to tune the properties of an epoxy polymer with a simple and viable method of GO addition.

Investigation of the interfacial interactions in epoxy nano-composites filled with functionalized graphene based fillers

“…In agreement with known concensus [43] the epoxy nano-composites here are seen to have a two-step degradationbetween 350 o C -450 o C of the epoxy groups and 450 o C -485 700 o C due to char formation from the thermal degradation of the epoxy and the fillers. In the Sial T-403 cured epoxies, the onset of degradation temperature (Td, o C, at 5% weight loss, Figure 11-12 ) is seen to drop slightly by ~2-4 o C at lower GO contents before finally showing an increment of ~4 o C at 0.50wt%.…”

“…In the Sial T-403 cured epoxies, the onset of degradation temperature (Td, o C, at 5% weight loss, Figure 11-12 ) is seen to drop slightly by ~2-4 o C at lower GO contents before finally showing an increment of ~4 o C at 0.50wt%. The reduction of Td in GO filled system have already been observed and is suspected to be due to the easier thermal decomposition of the oxygen con-490 taining functionalities (OCFs) of the filler [43]. On the other hand, adding GO-ButA to the epoxy is seen to increase Td by ~15-30 o C (Figure 11, Table 2).…”

“…[ Figure 11b near here] 500 However, addition of GO do not seem to influence the thermal stability of the Sial DETA cured epoxies with only nominal increment in Td and TDTG max (~1 o C in both cases, Figure 12, Table 2, Figure S2) and indicates that interfacial interactions do have an influence on the thermal stability of the composites [5, 44,46]. Interestingly the explanation in [43] re-505 garding the presence of OCFs reducing thermal stability does not seem to hold in this fast curing epoxy.…”

Investigation on the digital image correlation and charge trap characteristics of Al/epoxy nanocomposites

“…Shape, filler dispersion and interfacial adhesion to the epoxy matrix are the crucial deciding factors for the mechanical characterization. As filler percentage is increased, particles get aggregated easily due to high specific surface area and stronger Van Der Waals forces between adjacent particles [8]. Further, filler packing density and non-uniform dispersion at higher filler concentrations create voids and weaken the bonding between filler and matrix which results in ineffective load transfer between matrix and filler, thereby fractures easily at lower loads [31].…”

“…Earlier studies revealed that the improvement in tensile behaviour of epoxy nanocomposite materials merely depends on the efficient filler dispersion and the interfacial adhesion between filler and the matrix [8][9][10]. The polymer nanocomposite materials with conductive fillers find their applications include embedded capacitance material (ECM), high energy density capacitors, and electromagnetic interference (EMI) shielding material in electronic circuits [5].…”