Analysis of diffusion characteristics for aromatic solvents through carbon black filled natural rubber/ butadiene rubber blends

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Abstract
Knowledge of solvent effect on the polymer is a need, for a large number of industrial and laboratory purposes. It is well known that swelling is a serious drawback for rubber products such as seals and O‐rings. The flexible rubber chains are highly prone to diffusion and allow easy penetration of solvent molecules through it, which causes swelling in rubber products. The flexibility and molecular mobility of rubber chains are reduced by either cross‐linking/blending/ adding inclusions. This reduces the swelling of rubber products. In the present work, blending rubbers and adding inclusions are experimented and reported. Various compositions of natural rubber (NR) / butadiene rubber (BR) i.e., 70NR/30BR, 50NR/50BR,30NR/70BR with and without carbon black (CB) were compounded, cured and characterized for diffusion analysis using benzene, toluene, and xylene. To determine the effect of varying filler concentration, 70NR/30BR blend was filled with 10, 20, 30, 40, and 50phr of CB and analyzed for diffusion characteristics. Loading of CB into rubbers reduces the chain flexibility as a result of rubber/filler interactions and this leads to a dramatic reduction in the diffusion of the solvent into rubber compounds. Diffusion characteristics of CB filled rubber blends were compared with their neat counterparts and CB filled blends showed less solvent uptake. Swelling characteristics for the neat and filled rubbers and their blends were calculated to determine coefficients and index of swelling. The experimental diffusion data obtained were fitted with mathematical models for predicting the diffusion behavior through the rubber vulcanisates to understand the mechanism of transport phenomena.

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