Auxetic Nanocomposite based on Styrene Butadiene Rubber (SBR) Foam with Varying Nano-carbon Loading

Styrene-butadiene rubber (SBR) is a synthetically produced general-purpose rubber which is fabricated by copolymerization of styrene and butadiene. It is widely used in automobile tires owing to its good abrasion-resistance, enhanced crack resistance, and improved aging properties. Strength of SBR is improved by reinforcing it using fillers such as carbon black. Presence of gaseous phase in foamed structure of SBR increases volume along with improvement in various matrix characteristics. SBR matrix was transformed into foamy product during curing in the presence of chemical blowing agents. This paper presents preparation and characterization of SBR foam with varying nano-carbon loading causing development of a variety of foamy structures; processes like compounding and vulcanization altered the mechanical properties to a great extent. Mechanical characterization revealed that incorporation of 20% carbon in the SBR caused 140% rise in tensile strength and 90% increase in hardness with a corresponding decrease in elongation to about 35%, compared with neat SBR. The 'cure rate index' increased to 200% with 20% carbon concentration, whereas 'loss modulus' and 'tan δ' increased to 135% and 80%, respectively, as determined at maximum viscosity. Overall a significant improvement in mechanical properties and damping characteristics was observed.