Graphene Additives in Biopolymers
The use of graphene to improve mechanical and fire performance
Previous studies have shown that biocomposites manufactured from natural materials such as fibres and bio-derived polymers, offer a sustainable alternative to traditional polymers and composites, but at present they are only available at industrial level for use in semi-structural applications.
The incorporation of additives to biopolymers has been studied in order to improve mechanical properties and adhesion between matrix and fibres.
The addition of graphene nanoplatelets to polymers has offered significant potential for the development of advanced materials and various applications due to their high surface area, which can have a dramatic impact on mechanical and fire resistance properties. Graphene has been regarded as one of the most promising reinforcements for the next generation of high performance composites. However, carbonaceous nanostructures’ outstanding properties have been restrained by technical challenges such as dispersion and interfacial bonding for load transfer to the resin.
Although adding graphene can greatly improve properties such modulus, toughness and fatigue properties, strong interfacial adhesion between the graphene platelet and the composite matrix is crucial to achieving these gains. Interfacial adhesion can be greatly improved by the chemical functionalisation of the graphene surface, which can also aid platelet dispersion in the matrix.
The choice of strategy is directly related to the nature of the polymeric matrix. In this way, applicable examples have used radical chemistry and a number of other chemistries for assuring an optimal compatibility degree.
In common with other composites, the processability of biocomposites can be complex and has a relatively low output. Subsequently, new technologies need to be adapted to the behaviour of the bio-based materials. Pultrusion technology is useful, but it has some limitations when used to process natural fibres and bio-based resins. Therefore, work is required to understand the new biomaterials and graphene, and to improve the proper formulation of the resin, process parameters and also to achieve a suitable dispersion of graphene as a first step of the process. In order to avoid fibre breakage other modifications such as homogeneous curing, minimised residence time and processing temperature are required.
In this project, an innovative pultrusion process was performed minimising fibre tension and reducing curing time. As a result, demonstrators of pultruded profiles have been manufactured incorporating novel materials, graphene nanoplatelets and bio-based resin.