Mechanical and physical properties of coconut shell reinforced unsaturated polyester composites in the presence of Graphene as nano-reinforcing fillers

Coconut shell (CS) reinforced unsaturated polyester (UPE) composites have been prepared by using hand lay-up and compression molding technique. To improve fiber matrix adhesion, the CS was chemically treated by two chemical treatments which are alkaline (NaOH) and alkaline-silane with concentration NaOH (6%) and silane (2%). To enhance the performance of CS-UPE composites, graphene was also added as nano filler. Fourier transform infrared (FTIR) analysis and scanning electron microscopy (SEM) were used to investigate the changes of fibers chemical constituents and morphology after chemical treatment. Mechanical characterization such as tensile and flexural tests of untreated and chemical treated CS-UPE composites were also studied and compared. Overall, the used of alkalized treated CS-UPE composites showed the best mechanical (strength and modulus) and physical (water absorption) properties compared to alkali-silane chemical treatment. Therefore, alkaline treated CS was selected to be re-prepared with graphene as nano filler in UPE composites at 0.5, 1.0 and 1.5wt.% filler loading. The presence of graphene in CS-UPE composites have demonstrated significant enhancement in strength and modulus properties. SEM morphology investigation showed that, the presence of both alkaline treated CS and graphene as reinforcement materials in UPE composites composite has better fiber-matrix interaction as a result from the improvement in fiber/matrix adhesion after chemical treatment.