Although graphene is often dubbed “the panacea”, it is undeniable that it does have excellent optical, electrical and mechanical properties, which is why the industry is so keen to disperse graphene as a nanofiller in polymers or inorganic matrice. Although it does not have the legendary effect of “turning a stone into gold”, it can also improve part of the performance of the matrix within a certain range and expand its application range.
At present, the common graphene composite materials can be mainly divided into polymer-based and ceramic-based. There are more studies on the former.
Epoxy resin (EP), as a commonly used resin matrix, has excellent adhesion properties, mechanical strength, heat resistance and dielectric properties, but it contains a large number of epoxy groups after curing, and the crosslinking density is too high, so the obtained products are brittle and have poor impact resistance, electrical and thermal conductivity. Graphene is the hardest substance in the world and has excellent electrical and thermal conductivity. Therefore, the composite material made by compounding graphene and EP has the advantages of both and has good application value.
Nano Graphene has a large surface area, and the molecular-level dispersion of graphene can form a strong interface with the polymer. Functional groups such as hydroxyl groups and the production process will turn graphene into a wrinkled state. These nanoscale irregularities enhance the interaction between graphene and polymer chains. The surface of functionalized graphene contains hydroxyl, carboxyl and other chemical groups, which can form strong hydrogen bonds with polar polymers such as polymethyl methacrylate. Graphene has a unique two-dimensional structure and many excellent properties, and has great application potential in improving the thermal, electromagnetic and mechanical properties of EP.
1. Graphene in epoxy resins – improving electromagnetic properties
Graphene has excellent electrical conductivity and electromagnetic properties, and has the characteristics of low dosage and high efficiency. It is a potential conductive modifier for epoxy resin EP. The researchers introduced surface-treated GO into EP by in-situ thermal polymerization. The comprehensive properties of the corresponding GO/EP composites (such as mechanical, electrical and thermal properties, etc.) were significantly improved, and the electrical conductivity was increased by 6.5 order of magnitude.
Modified graphene is compounded with epoxy resin, adding 2% of modified graphene, the storage modulus of epoxy composite material increases by 113%, adding 4%, the strength increases by 38%. The resistance of pure EP resin is 10^17 ohm.cm, and the resistance drops by 6.5 orders of magnitude after adding graphene oxide.
2. Application of graphene in epoxy resin – thermal conductivity
Adding carbon nanotubes(CNTs) and graphene to epoxy resin, when adding 20 % CNTs and 20%GNPs, the thermal conductivity of the composite material can reach 7.3W/mK.
3. Application of graphene in epoxy resin – flame retardancy
When adding 5 wt% organic functionalized graphene oxide, the flame retardant value increased by 23.7%, and when adding 5 wt%, increased by 43.9%.
Graphene has the characteristics of excellent rigidity, dimensional stability and toughness. As a modifier of epoxy resin EP, it can significantly improve the mechanical properties of composite materials, and overcome the large amount of ordinary inorganic fillers and low modification efficiency and other shortcomings. The researchers applied chemically modified GO/EP nanocomposites. When w(GO)=0.0375%, the compressive strength and toughness of the corresponding composites increased by 48.3% and 1185.2% respectively. The scientists studied the modification effect of fatigue resistance and toughness of the GO/EP system: when w(GO) = 0.1%, the tensile modulus of the composite increased by about 12%; when w(GO) = 1.0%, The flexural stiffness and strength of the composite were increased by 12% and 23%, respectively.