Morphological, rheological, and mechanical properties of hybrid elastomeric foams based on natural rubber, nanoclay, and nanocarbon black

In this study, compression molding was used to produce elastomeric nanocomposite foams based on natural rubber (NR) with a hybrid reinforcing system containing organo-modified nanoscale (NC) and nanocarbon black (NCB). The effect of NC content (0-10 part per hundred rubber, phr) on the curing behavior, as well as the morphological and mechanical properties of elastomeric foams containing 10 phr of NCB was determined. Transmission electron microscopy and X-ray diffraction results showed that NC exfoliation occurred at low NC concentration (less than 5 phr), while increasing NC content up to 5 phr led to aggregation. Rheological data revealed that increasing the NC content up to 10 phr gradually changed the curing parameters such as 50% shorter scorch and curing time, two times faster curing rate, as well as higher initial (35%) and final (35%) torque. Scanning electron microscopy analysis also showed that increasing NC content from 0 to 5 phr produced foams with more uniform small cells, while 7 phr of NC changed the foam structure into two areas composed of different cell sizes and different cell densities. Higher NC content (10 phr) led to broken cell walls. With nanoparticles, higher foam modulus (83%) and hardness (104%) were observed. Finally, NC addition was found to improve the NR's thermal and thermo-oxidative resistance while the sound absorption coefficient was constant.