Minh Canh Vu

Pressure-Sensitive Adhesive Composites with a Hydrophobic Form of Graphene Oxide for Enhanced Thermal Conductivity

Pressure-sensitive adhesive (PSA) composites containing oleylamine functionalized graphene oxide (OA-f-GO) fillers were prepared. The effects of the surface modification of graphene oxide (GO) on the morphology of the PSA composites and on its thermal and adhesive properties were investigated. In contrast to GO fillers, the OA-f-GO fillers were found to be uniformly dispersed in the PSA matrix without any agglomeration and voids. The hydrophobization of GO resulting from the oleylamine functionalization improved the compatibility of the GO sheets with the PSA matrix. The thermal conductivity of the OA-f-GO (5 wt%)/PSA composites at UV energy of 2,000 mJ/cm2 was 55%, 140%, and 300% greater than the thermal conductivities of the OA-f-GO (5 wt%)/PSA composites, GO (5 wt%)/PSA composites, and bare PSA at UV energy of 800 mJ/cm2, respectively. In addition, the higher peel strength of the OA-f-GO/PSA composites compared to that of the GO/PSA composites was explained by the better wetting of hydrophobic OA-f-GO fillers in the PSA matrix.

Self-Assembly of Carbon Nanotubes and Boron Nitride via Electrostatic Interaction for Epoxy Composites of High Thermal Conductivity and Electrical Resistivity

The self-assembled oxidized carbon nanotubes (oCNTs) with the silane functionalized hexagonal boron nitrides (oCNTs@fBN) via electrostatic interaction were used to improve the thermal conductivity while maintaining the electrical insulation properties of the epoxy composites. The oCNTs were separately immobilized on the edges of hexagonal boron nitride (hBN), which prevent oCNTs from continuously contacting with each other. The thermal conductivity and volume resistivity of oCNTs@fBN filler loaded epoxy composites were measured and compared with the epoxy composites with a filler of hBN, a mixed filler of oCNTs, and silane functionalized hBN (fBN). The thermal conductivity of the epoxy composites containing 20 wt% of oCNTs@fBN10 was 1.26 W·m-1·K-1, which is higher than 600% compared to that of neat epoxy and the volume resistivity of the epoxy composites was in an insulation region even at high content of oCNTs@fBN filler. The significant improvement in thermal conductivity was attributed to the formation of linkages between oCNTs and fBN and the good compatibility of oCNTs@fBN in the epoxy matrix.

Thermally conductive adhesives from covalent-bonding of reduced graphene oxide to acrylic copolymer

ABSTRACT This work reports about the enhancement of the thermal conductivity of an acrylic pressure-sensitive adhesive (PSA) with the incorporation of functionalized and reduced graphene oxide (frGO) sheet in the composition. Bifunctional isocyanatoethylmetharcylate (IEMA) was intercalated (so-called ‘functionalization’) to the GO surface mainly at its –COOH sites. The remaining oxygenated groups on the GO surface were reduced by dimethyl hydrazine. The frGO was successfully incorporated into PSA matrix through in-situ polymerization of acrylic monomers and subsequently crosslinked under UV radiation. The conductivity and the peel strength of the PSA were studied as a function of filler content, filler modification (functionalization and/or reduction), UV-radiation dosage and mode of filler insertion (through in-situ polymerization or mechanical mixing). frGO/PSA showed much better properties than the PSA system with bare or IEMA-functionalized unreduced GO. In-situ polymerization was found to be more effective method for frGO insertion. Within the range of filler content (0.0–1.0) wt% and UV-radiation dosages of (400–3000) mJcm−2, the thermal conductivity and peel strength of the acrylic PSA-system under investigation varied in the range of 0.17–1.03 Wm−1K−1 and 2831–299 gf/25 mm. This is the first report on ‘reduced GO covalently bonded to polymer chain in an adhesive-composition’ providing novel idea to make PSA-system with balanced thermal conductivity and peel strength with perspective for application in miniature electronic industries.