Review of the past and recent developments in functionalization of graphene derivatives for reinforcement of polypropylene nanocomposites

Graphene has become the promising reinforcing candidate for improvement of polymer composites. However, graphene easily stacks into piles due to the presence of van der Waals forces between graphene layers and make it tremendously hard to be dispersed homogeneously in different polar polymer matrix. For years, some dispersion methods, such as chemical functionalization, melt mixing, solution mixing, in situ polymerization, to enhance the dispersion of nanofillers in polymer matrix have been demonstrated. Therefore, several functionalization methods of graphene, synthesis of composites approaches, characterizations techniques of graphene-polypropylene composites are highlighted in this comprehensive review. This review also reveals that the addition of very low amount of nanofiller able to enhance the mechanical properties of composites considerably. With this review, a clear direction is beneficial for the researchers to solve the dispersion issues and to enhance interfacial adhesion to produce better mechanical properties of composites. The application of nanocomposite, an outlook of the challenges and different approaches that can practically useful to tackle important issues are also presented.