Mechanically robust, electrically and thermally conductive graphene-based epoxy adhesives

Figures & data

Table 1 Glass transition temperatures (T_g) of the nanocomposite adhesives at different GnP content.

GnP fraction (vol%)	0	0.05	0.125	0.25	0.375	0.5
Tg (°C)	57	59.94	67	63.41	60.14	54

Figure 1. (a), (b): TEM images of GnPs and (c): XPS of GnPs.

Figure 2. TEM images of epoxy/GnP nanocomposite adhesives.

Figure 3. (a) Young’s modulus and (b) Tensile strength of the nanocomposite adhesives at various GnP contents.

Figure 4. Lap shear strength of nanocomposite adhesives with different GnP content.

Figure 5. Mode of failure of neat epoxy and GnPs reinforced epoxy adhesive joints.

Figure 6. Toughness of the nanocomposite adhesives: (a) compact tension (CT); and (b) double cantilever beam testing (DCB).

Figure 7. Fracture surface of the 0.125 vol% epoxy/GnP nanocomposite adhesives.

Figure 8. Fracture surface of the 0.375 vol% epoxy/GnP nanocomposite adhesives.

Figure 9. Dynamic mechanical analysis of epoxy/GnP nanocomposite adhesive (a) storage modulus and (b) Glass transition temperature at different GnP content.

Figure 10. Electrical conductivity of nanocomposite adhesive with different GnP content.

Figure 11. Thermal conductivity of nanocomposite adhesive with different GnP contents.

Table 2. Thermal properties of neat epoxy and its GnP-based nanocomposite adhesives.

Composite (vol%)	Thermal diffusivity, α (mm^2/s)	Specific heat, Cp (J/gK)	Density, ρ (g/cm^3)	Thermal conductivity, k (W/mK)
0	0.071	2.416	0.915	0.1569
0.5	0.083	2.414	0.965	0.1933
1	0.089	2.405	1.004	0.2149
1.5	0.094	2.401	1.024	0.2311
2	0.135	2.392	1.03	0.3326
2.5	0.167	2.367	1.145	0.4526
3	0.212	2.232	1.203	0.5692
5	0.368	2.035	1.482	1.1098
5.8	0.642	2.017	1.589	2.05

Table 3. A comparison of mechanical and functional performance of various carbon-based epoxy composites.

Materials	Filler type	Tensile strength (MPa)	Young’s moduli (GPa)	K1C ((MPa.m^0.5)	G1C (J.m^−2)	Shear strength (MPa)	Electrical conductivity (S/cm)	Thermal conductivity (W/mK)	Ref.
Epoxy composites	SWCNT (1 wt%)	10.5–74.1	0.503–3.27	0.58			7 × 10^−9		[38,39]
	MWCNT (1 wt%)	46.4–50	1.59–2.83	2.8	270			0.25–0.38	[40,41]
	TR-GO						∼10^−9	0.254	[42]
	R-GO (0.05 wt%)	53	3.0	0.48	77		1.68 × 10^−10		[43]
	GO (0.5 wt%)	66	3.0	0.75	250	–	–		[44]
	GnPs (1 wt%)	18.2–62	2.23–3.0	0.95	298				[16,45]
	m-GnPs (1 wt%)	59–63.98	2.8	0.75	245		∼10^−9	0.234	[16,46]
	m-GnPs (0.489 vol%)	49.21	3.412	1.258	557		3 × 10^−9		[15]
Epoxy composite adhesives	SWCNT (1 wt%)					10	∼10^−4		[47]
	MWCNT (1 wt%)		0.068			∼15			[48]
	CNF (0.5 wt%)				∼96	9.2	–	–	[49]
	CNT (0.25 wt%)				∼105	9.2
	GO (1 wt%)	58.98	3.025	–	–	6.36	7.4 × 10^−16	0.37	[50]
	R-GO (1 wt%)	51.31	2.894			6.174	1.6 × 10^−14	0.31
	m-GnPs (6 wt%)	53	3.4			8.9			[51]
	GnPs (1 wt%)					∼7.5		∼0.2	[52]
	GnPs (0.5 vol%)^a	33	2.64	1.68	896	12.34	4 × 10^−9	0.24	Current study

^a 0.5 vol% GnPs is equivalent to 1 wt% GnPs.

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