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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.

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One of the problems for use of rubber in various industries is the surface tension at the surface of rubbers, which results in the crack on the surface, fracture of the rubber and reduces its service life. These tensions are caused by contacting the rubber component with the metal surface and the friction between two surfaces. Roughness of the surface, the composition of the rubber compound, the environmental factors, test conditions and etc. affect the friction between rubbers – metal. Surface roughness plays an important role in sliding between two surfaces and mainly controls friction behavior. On the other hand, roughness effect on the coefficient of friction is controllable using a suitable lubricant. In the present study regarding to the application of JP4 as an aviation fuel, the effect of JP4 fuel as a lubricant was investigated in the reduction of the sliding friction coefficient between the NBR and aluminum surfaces with different roughness. Experimental studies showed, friction coefficient has a good correlation with the mean surface roughness (Ra). By applying JP4 lubricant, the coefficient of friction decreased by about 75%. JP4 fuel as lubricant has changed the trend of varying friction coefficient from decreasing to increasing regard to the surface roughness.