Effect of modified graphite nanoflakes on curing, mechanical and dielectric properties of nitrile rubber nanocomposites.

Graphite is a naturally abundant material and thus cost effective as a raw material. The layered structure of natural graphite like silicate clay materials, allows expansion and intercalation. Graphite was expanded by heating (i.e., at 900 °C), yielding expanded graphite (EG). EG was modified with tween 80 surfactant (50 wt%) obtaining modified expanded graphite (MEG). EG and MEG fillers were separately melt mixed at different loadings (i.e., 2.0, 4.0, 6.0, 8.0 and 10.0 phr) with nitrile rubber (NBR) as a matrix. The influence of the prepared EG, MEG loading on curing, mechanical and electrical properties of NBR nanocomposites were investigated. TEM revealed the surfactant intercalation within EG layers. SEM showed a good dispersion of MEG (6 phr) in NBR matrix in comparison to EG with medium dispersion at the same loading. Heterogeneous dispersion of MEG (8 phr) was observed as filler agglomerations in the matrix. Curing characterizations reflected a faster cure rate with an increase in maximum and minimum torques and torques difference for compound with MEG (6 phr) in comparison to that with EG at the same content and unfilled NBR compound. Mechanical properties indicated nanocomposites reinforcement with 6 phr MEG supporting the curing characterizations. While Shore A hardness values were increased with filler content up to 10 phr. NBR nanocomposites filled with MEG exhibited higher values of permittivity έ, dielectric loss ε ″ and dc conductivity σ than those filled with EG. A slight increase in the dc conductivity was found with increasing filler content up to 6 phr. Beyond 6 phr (i.e., up to 10 phr) a sudden increase in the conductivity of the system was observed and its value in the order of 10–10 Ω−1 cm−1 reflected a promising application of these nanocomposites as antistatic materials. [ABSTRACT FROM AUTHOR]