Enhancing Electrical Conductivity and Mechanical Properties of Natural Rubber Composites with Graphene Fillers and Chitosan

Biopolymer films of natural rubber/chitosan (NR-CHI) composites were fabricated using a latex aqueous microdispersion process. These composites were reinforced with graphene fillers, specifically surface-modified graphene nanoplatelets (GNP) and graphene commercial grade (GC). Chitosan (CHI) was supplemented as a biocompatible and biodegradable polymer with excellent film-forming capabilities. CHI effectively acted as a dispersing agent, helping to uniformly distribute graphene within an NR polymer matrix, as confirmed by FE-SEM examinations. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses revealed interactions of hydrogen bonds, electrostatic attractions, and van der Waals forces between NR-CHI and the graphene fillers. The incorporation of these graphene fillers resulted in notable enhancements in mechanical properties, thermal stability, electrical conductivity, and resistance to nonpolar solvents. Compared to NR and NR-CHI films, the composite films exhibited higher resistance to chemical solvents like toluene. Additionally, the addition of graphene improved thermal stability, as indicated by reduced weight loss during thermal degradation, and led to a substantial increase in Young's modulus, approximately 100-fold compared to neat NR films. Moreover, the composite films demonstrated a significant increase in electrical conductivity, reaching to the range of 10-4 S/cm. The comparison between GNP and GC revealed that the integration of GNP exhibited greater electrical conductivity at lower loading levels due to its oxygen-containing functional groups and enhanced dispersion, while GC showed superior mechanical strength at higher loadings because of its higher carbon content and more ordered graphitic structure. These results suggest that the developed composites hold promise for further advancement as stretchable conductive substrate polymer films for biodegradable electronic applications.