Conductive natural rubber-based composite films reinforced with graphite prepared by latex aqueous microdispersion process

Abstract

In this research study, green natural rubber (NR) composites reinforced with graphite platelets and using alginate and chitosan as dispersing and thickening agents were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The method of latex aqueous microdispersion was used for the fabrication process. Graphite incorporation of up to 60 parts per hundred rubbers (phr) was accomplished without causing excessive agglomeration or phase separation. NR composite films exhibited a remarkable increase in crystallinity upon the inclusion of graphite, especially with films facilitated by chitosan demonstrating a higher degree of crystallinity than those facilitated by alginate. Graphite reinforcement significantly improved mechanical properties such as tensile strength and Young's modulus, though elongation at break was reduced. Notably, NR with 60 phr of graphite, assisted by chitosan, demonstrated the greatest improvement, reaching a Young's modulus of 58.22 MPa, roughly 470 times that of the neat NR film. Furthermore, the inclusion of graphite and alginate increased the hydrophilicity of the composite films, resulting in a higher initial water absorption rate than a neat NR film. However, the WACs of the NR composites reinforced with graphite did not increase, but significantly reduced when chitosan was used as the dispersing agent. The addition of graphite and the dispersing agents significantly improved the composite films' chemical resistance to nonpolar solvents like toluene. Biodegradability tests in soil revealed biodegradability ranging from 17% to 30% after 90 days. With the assistance of alginate, the electrical conductivity of the composite film reached 2.18 × 10−4 S/cm at a graphite loading of 60 phr. The developed composites show promise for electronic substrate applications based on the improvements in various properties.