Synergistic Effect of Carbon Nanofiber and Non-ionic Surfactant Improved Electrical Conductivity

Synergistic effect of carbon nanofiber and non-ionic surfactant for electrical, cure and mechanical properties of natural rubber composites were studied. Electrical properties of the natural rubber volcanizes were measured, according to ISO standard 2878. Cure characteristics and mechanical properties were also evaluated in the cured natural rubber vulcanizates. The results indicated that, electrical resistance was drastically decreased when incorporating carbon nanofiber and non-ionic surfactant together and the percolation threshold value was 8 phr (parts per 100 g rubber).

Considering the cure characteristics, it was found that natural rubber vulcanizate with 2 phr of carbon nanofiber and non-ionic surfactant together, showed low values of optimum cure time (t90) compared with carbon nanofiber and non-ionic surfactant alone. Natural rubber vulcanizates were achieved better mechanical properties with low loading of combination of carbon nanofiber and non-ionic surfactant. This study will lead to the manufacturing of electrically conductive natural rubber composites with low amount of carbon nanofiber, with better cure and mechanical properties. Electrically conductive polymer composites are used in electro-magnetic shielding materials, self-regulated heaters, pressure sensors etc.

Different carbon materials have been used to make electrically conductive natural rubber composites; such as carbon black, carbon nanotubes and graphene. Large quantities of carbon black have to be used to make the electrically conductive natural rubber composites. Costly methods have to be used to synthesize carbon nanotubes and graphene. Metal particles like nickel, aluminium and iron have been used to make electrically conductive polymers. Wear and tear problems of the machines have been caused when compounding metal particles into the polymer matrix.

Carbon fiber has been mainly used as an electrical conductive material in different rubber matrices; such as, silicon [6] and chloroprene rubber. Electrical and mechanical properties of NBR, EPDM and their blends were studied by incorporating acetylene black and short carbon fiber. Carbon fiber/natural rubber and carbon fiber/ ethylene vinyl acetate (EVA) composites used for electromagnetic shielding has been reported by Das et al. where percolation value was 15 phr (parts per 100 g rubber) for carbon fiber/ natural rubber composites.

Non-ionic surfactants have been used as an antistatic agent in rubber composites, because of its electrical conductive property. Non-ionic surfactants have also been used to improve the dispersion of reduced graphene oxide in rubber latex. Large amount of carbon fiber gives dark color to the rubber composite and it could be adversely affect for the application of the conductive rubber. When non-ionic surfactants are used in large quantities it could be caused the blooming phenomenon on the rubber surface. Therefore, synergistic effect of carbon nano fiber and non-ionic surfactant was studied to improve the electrical conductive property of natural rubber composites without causing color effect and blooming phenomenon.