Effect of cell structure on Solvent Absorption Capacity of Nitril rubber composite foams

Polymer foams are composite in which gas bubbles are dispersed inside the polymer substrate. Rubber foams have properties such as low weight, buoyancy, cushioning performance, impact damping, effective packaging, moderate energy absorption, and low cost. The characteristics of rubber foams depend on its density, microstructure of cells (i.e. size, morphology and shape) and the mechanical properties of the base polymer. The foam structure can be controlled by the proper selection of blowing agents. Sodium bicarbonate was appplied in this study. Closed-cell NBR rubber foams with different amounts of blowing agent (۳, ۶, ۹, ۱۲ phr) were produced by two-step method (pre-heat foaming and curing) to investigate their compression molding and equilibrium uptake. The foam density was independent of the amount of blowing agent. The optical microscope results showed that the blowing agent increasing from ۳ to ۱۲ phr reduced the size of the cells from ۳۷۹.۳ to ۱۵۵.۵ μm with the enhancement in the number of cells per unit volume. Moreover, swelling experiments revealed that the higher the cell size, the more the equilibrium uptake.