Effect of aerogel on the properties of acrylonitrile-butadiene rubber (NBR) vulcanizates
Polimery 2012, No 2, 117
The effect of the addition of commercial silica aerogel (Table 1) on the mechanical properties of peroxide cured acrylonitrile-butadiene rubber (NBR) was studied. Two series of rubber compounds (NBR 1 and NBR 2) were prepared, filled respectively with silica (70 phr) and aerogel (76 phr), additionally NBR 1 contained novolak resin (50 phr). The aerogel was introduced into the rubber compound in a manner typical for fillers in rubber industry. In spite of the very large surface area of the aerogel in comparison with the silica, the reinforcing effect was significantly weaker than expected. Slight changes in the hardness and tensile strength were observed, the character of these changes was dependent on the presence of novolak resin in the rubber compound (Table 2, 3, Fig. 1). The replacement of silica by aerogel resulted in the increased impact resilience and decreased loss angle in the simple shear dynamic tests as a function of the shear amplitude (Figs. 4, 5) or the aerogel content (Figs. 8, 9). Changes in the dynamic modulus were relatively minor and dependent on the presence of novolak resin in the rubber compound (Figs. 6, 7, 10, 11). The comparable density values for the vulcanizates with the silica and the aerogel may indicate that a part of the porous structure of the aerogel was destroyed during the preparation of rubber compounds and vulcanizates.