Exfoliated graphene and its derivatives from liquid phase and their role in performance enhancement of epoxy matrix composite

• Liquid phase exfoliation of graphite was assessed. • Variables affecting physicochemical properties and exfoliation rate were summarized. • The step-wise mechanism have been discussed to understand the rate-limiting step. • The role of graphene and its derivatives upon epoxy based coatings and composite were explored. • At the end, the challenges and future roadmap have been mentioned. The present review paper emphasizes liquid-phase exfoliation (LPE) of graphene and its derivatives with the focus mainly on electrochemical exfoliation, mechanical exfoliation, and chemical exfoliation. A careful analysis of literature data on the above processes has been carried out in this review, which gives an insight into rate-controlling factors in LPE. The mechanism for each exfoliation process has been discussed. Based on these inputs, the scale-up methodology is proposed. Reduced GO (rGO) are synthesized by mainly two routes i.e. thermal and chemical. The scope and limitation of both routes are discussed in brief. Further, the applications of functionalized graphene and GO in the polymer matrix composite have been elucidated. How the bonding of the epoxy group with the functional group present on graphene affects the strength and permeation properties of epoxy composites have been explained in this review. The advantages of modifications of graphene are discussed in detail to understand the mechanism for industrial development. A future roadmap has been proposed based on the existing knowledge gap.