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In this research, closed-cell natural rubber foams were produced using a single-step compression molding. The effect of carbon black content on morphology, physical and mechanical properties of the foams were examined. Results showed that in this methodology, the foam density was independent of reinforcement percentage, which is a unique characteristic of single-step foams that contrasts with other previous observations. The study of curing behavior of foam compounds showed that the carbon black increasing from 0 to 30 phr increased the crosslink density (CLD) from 6.5 to 8.3*10^-5 mol/cm³, the cure rate from 16.1 to 23.2 (%/min) and the ultimate torque from 5.8 to 10.4 Nm, while, reduced curing time from 9.2 to 5.8 min. The scanning electron microscope (SEM) results showed that the reinforcement acted as a nucleation agent increasing the cell density from 8 N/cm³ to 140 N/cm³ and reducing the cell size from 579µm to 255µm. The increase of reinforcing content in the produced foams reduced the cells size and enhanced the properties of the rubber matrix. Accordingly, the modulus and hardness of the foams were increased by  0.8MPa and 40 shore A, respectively. Results of sound absorption and reflection showed that the rubber foam reflects the sound waves more than 90% and absorbs waves about 10%.

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Presence of filler in the polymeric materials changes the mechanical, dynamic-mechanical, rheological properties and even the swelling behavior of rubber composite due to mechanisms such as hydrodynamics, polymer-filler and filler-filler interactions. Swelling in rubber composites directly affects the polymer chains, also can affect indirectly other structures in composites such as the filler network and reduce mechanical properties suddenly. In this study, the nitrile rubber-nanosilica composite containing different concentrations of modified nanosilica was prepared and the composite structure was studied through rheological, mechanical, dynamic-mechanical tests. Also it was found that the filler network containing over percolation threshold 13phr of filler concentration has a significant contribution to the mechanical properties of composites. To determine the swelling effect on the prepared composite structure, with different degrees of solubility were used. The mechanical properties of the samples were measured in equilibrium swelling state for each of the solvents The decrement of the mechanical properties between the dry samples and swelled ones containing 14.4, 20 and phr 6.25 silica in solvent with 15% toluene is significant. These intensive changes in mechanical properties that happen at the low degree of swelling are attributed to the removal of the filler network. Therefore, controlling the swelling of rubber parts in adjacent to the solvent, plays the fundamental role in their performance.