Graphene nanoplatelet‐silica hybrid epoxy composites as electrical insulation with enhanced thermal conductivity

Abstract

The efficient management of heat is a key issue when considering the performance of electrical devices. To reduce the probability of their failure an effective heat dissipation should be ensured. The thermal conductivity of pure epoxy is low and can be improved through the addition of fillers. Graphene has been considered as an adequate filler, due to its excellent thermal conductivity. However, graphene‐based composites also show a high electrical conductivity, which limits their application as an electrical insulation considerably. The presented work shows that it is possible to enhance thermal conductivity through the incorporation of a new class of hybrid filler, namely a masterbatch of graphene nanoplatelets (GNPs) and a standard filler like silica. This unique structural design combines the advantages of both, GNPs and silica powder, resulting in composites that not only show high thermal conductivity, but also preserve electrical insulation functionality. A modified processing method leads to the improvement of thermal conductivity. GNPs‐silica hybrid epoxy composites with only 2 wt% of GNPs reached 1.54 W/mK, whereas the volume resistivity remained at the level of 1015 Ω cm. The unique scientific aspect, namely temperature dependence of thermal conductivity, was studied. The presented novel hybrid composites show great potential in applications requiring electrical insulation with enhanced thermal conductivity in high voltage devices. POLYM. COMPOS., 39:E1682–E1691, 2018. © 2017 Society of Plastics Engineers

Aluminosilicate‐epoxy resin composite as novel material for electrical insulation with enhanced mechanical properties and improved thermal conductivity

“…This ceramic material is relatively cheap and allows to receive epoxy‐silica composite with enhanced properties. Filler concentration at 31 vol% leads to three times higher thermal conductivity in relation to the pure epoxy, while filling at the level of 45 vol% enhances this parameter up to 0.99 W/mK . Higher filler content provides more effective heat transfer through the composite as more heat paths are created .…”

“…Moreover, the small particles elongate crack path and therefore increase the fracture toughness of a composite . Another kind of HTC material is graphene and even a small addition of graphene flakes result in both thermal and mechanical properties enhancement . Unfortunately, graphene possesses high electrical conductivity and there is a risk of losing the required dielectric properties of the composite .…”

“…Besides the kind of filler, also the grain size, content and alignment in the matrix strongly influence the final properties of the polymer composite [4][5][6][7][8][9][10][11]. One of the most common kind of filler used for the epoxy system is the quartz flour [5,6,8,9]. This ceramic material is relatively cheap and allows to receive epoxy-silica composite with enhanced properties.…”

“…High thermal conductivity (HTC) fillers exhibit a very HTC itself, like in example 600 W/mK for boron nitride, but they are expensive. A good solution from the economic point of view is to use them as a shell in core-shell type filler [5,14,15], or in the small amount in the hybrid fillers [6,8,16]. HTC material lowers phonon scattering which occurs at the filler-matrix interface and defects during heat transfer by phonons in nonmetallic materials [17][18][19].…”

High thermal conductivity polylactic acid composite for 3D printing: Synergistic effect of graphene and alumina

“…Due to the bridging of the graphene layer and Al 2 O 3 , it will form a three‐dimensional network structure of heat conduction in the polymer matrix more easily. Such a hybrid network can greatly reduce the thermal resistance between the fillers and effectively improve the thermal conductivity of the material . However, to the best of our knowledge, the enhancement of thermal conductivity for graphene and Al 2 O 3 hybrid fillers in literature is still limited and the synergy mechanism is not clear enough.…”