Characterization of different forms of vulcanized natural rubbers as elastomer spacer and toughening agent in two-matrix filled epoxy/natural rubber/graphene nano-platelets system

This paper compares the effects of different forms of vulcanized natural rubbers on the physical, mechanical, thermal, and electrical performances of filled epoxy systems. In this study, natural rubber (NR), liquid natural rubber (LNR), and recycled natural rubber (rNR) were introduced into filled epoxy systems. The results show that flexural strength, modulus, and toughness properties of filled epoxy system were enhanced with NR phases, as compared to those with LNR and rNR. Scanning electron micrograph revealed that the particle sizes of NR phases dispersed within epoxy matrix were smaller and more uniform, as compared to those with LNR and rNR phases. Incorporation of NR phases has improved the thermal stability of filled system, followed by LNR and rNR. This is attributed to more heat energy needed to overcome good interfacial bonding between epoxy matrix and small NR phases. X-ray diffraction analysis result showed that filled epoxy/NR/GNP system has higher 2θ values, indicated that d-spacing in between GNP nano-fillers has the closer distance. Electrical bulk conductivity values of filled epoxy/NR/GNP system were the highest. Small NR phases acted as elastomer spacers, which provided better “GNP packing efficiency” and realigned the GNP nano-fillers to form more effective conductive pathways for electrons hopping. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47188.