Fig. 5 shows the HR-TEM images of the EG and i-MG filled rubber compositesbasedon differentsyntheticrubbers. The dark lines in the images dictate the presence of EG and i-MG nanosheets with thicknessinthe nanometerrange.It wasseen fromthe imagesthat few EG sheets were agglomerated in the different rubber matrices in the presence of CB, which was due to the utilization of direct melt blending technique for the fabrication of the rubber compositesandalsoduetominimumbasalspacingoftheEGsheets,which restricts the rubber chains to enter the intergallery spaces. i-MG flakes exhibit higher d-spacing compared to the EG. Therefore, polymer chains can easily be intercalated into the gallery space of i-MG flakes. i-MG/CB loaded rubber composites show intercalation and partial exfoliation of i-MG sheets in the different rubber matrices.
4.6. DMTA analysis
The effects of EG and isocyanate modified graphite (i-MG) on the dynamic mechanical properties of BR, SBR and SBR/BR blends were investigated by dynamic mechanical thermal analysis. The temperature dependent storage modului (E0) and loss tangents (tand) of the rubber composites are represented in the Fig. 6a–d. Both the elastic and viscous behaviors of the composite materials affect the resulting strain in the samples due to the application of an oscillating force. The storage modulus can be regarded as the elastic modulus of the rubber composites and loss tangent is interconnected to the energy drenched due to energy dissipation as heat. It can be seen from the Fig. 6a and b that EG and i-MG loaded SBR/BR composites in the presence of CB showed a drastic increase in the storage modulus in a wide range of temperature compared to the BR based nanocomposites. But, in comparison withSBRbasednanocomposites,SBR/BRbasedcompositesshowed an increase in the storage modulus only at very low temperature regionand thendecrease in the storagemodulusfrom low temperature to a high temperature region, which was due to very low transition temperature of BR. Homogeneous mixing of SBR with BRand as well asgood dispersionof nanofillers in the rubber blend increases its stiffness, which resulting in an increase in the storage modulus of the SBR/BR based nanocomposites. Fig. 6c and d displayed the temperature dependent tand curves of the various rubber composites. Conventionally, the greater tand value of the rubber composites in the region of 20 to 10C can be accounted to figure out the superior anti-skid properties of the rubber composites under wet conditions and lower tand value of the rubber materials in the range of 50–60C indicates the low rolling resistance of the rubber stuffs [34,35]. We can see from the respective figures that the tand values of the EG and i-MG filled SBR/BR based composites in the region of 20 to 10C were higher than tand values of the only BR based nanocomposites. So, after the homogeneous mixing of SBR with BR in the presence of different nanofillers, the anti-skid property under wet conditions of the BR vulcanizates was significantly improved. At the same time, rolling resistance of the SBR/BR based nanocomposites was lowered (lower tand values of the SBR/BR based composites in the temperature range of 50–60C) compared to the rolling resistance of SBR vulcanizates. EG/i-MG containing rubber composites in the presence of CB showed superior storage modulus, antiskid properties and lower rolling resistance compared to the only CB loaded rubber composites, which was due to the better interactions and interfacial adhesion between i-MG sheets and the rubber matrices.