Graphene Nanoplatelets ( GNP ) as a Functional Filler for Styrene‐Butadiene Rubber ( SBR )

ABSTRACT The carbon footprint of synthetic rubber is poor, including its production and the use of carbon black as a filler, which is obtained from non‐renewable feedstocks. More environmentally friendly alternatives to carbon black (CB), such as graphene nanoplatelets (GNP) are required urgently. GNP was prepared using high‐pressure homogenization to exfoliate unpurified spheronized graphite. The GNP obtained was highly crystalline, with a relatively low defect density ( I _D / I _G = 0.17) and oxygen content (8.9 atm.%) with average lateral dimensions of ~1.85 μm. The inclusion of GNP at the same loading of CB in SBR resulted in a greater maximum tensile strength ( σ _max ) and modulus at 100% strain (↑25%) compared with CB‐filled SBR, without sacrificing abrasion resistance. Moreover, the elongation at break ( ε _b ) of SBR was 40% greater on addition of 2 phr GNP compared with 10 phr CB. This behavior is derived from strong GNP‐GNP and GNP‐SBR interfacial interactions, which result in increased crosslink density and reduced SBR chain dynamics. Additionally, the infusion of the GNP in a carrier based on a liquid (at RT) or solid wax prior to mixing with the SBR compound was shown to aid GNP dispersion but not alter crosslink density greatly due to the plasticizing effect induced by the presence of the wax/oil on the SBR. The use of waxes as a carrier for GNP to assist mixing with rubbers is an effective approach to minimizing any potential negative health effects associated with the processing, storage, and transportation of GNP powders, but at the expense of reduced tensile strength.