Resistance to aggressive environment of rubbers based on isoprene rubber, filled with silicon dioxide from rice husks

Silicon dioxide is a well-known reinforcing filler for rubbers, and its modification, called 'white soot', is often used. This filler is expensive, therefore it is of practical interest to replace it with significantly cheaper amorphous silicon dioxide obtained from rice husk. However, there is practically no scientific research concerning the use of rice husk carbonation products in isoprene rubber vulcanizates (IRV). Due to relatively low gasoline resistance of the rubber products based on IRV, it was interesting to study the effect of amorphous silicon dioxide obtained from rice husks on the swelling of vulcanizates filled with it in standard aggressive liquids. Our experiments have shown that replacing ‘white soot’ with silicon dioxide can significantly reduce (by almost 1.5-2 times) the degree of swelling of vulcanizates based on isoprene rubber. This occurs in all investigated liquids, with the least degree of swelling occurring in water and the greatest degree in toluene. Thermal aging of the samples increases the degree of swelling in all studied media, regardless of the type of filler used. At the same time, after thermal aging, the samples remain more resistant to aggressive influences when using silicon dioxide from rice husk. We associate the increase in resistance to aggressive media with a slight increase in the density of the network of vulcanizates when 'white soot' is replaced by amorphous silicon dioxide. This can be attributed to the fact that vulcanization is accelerated in alkaline environment, and the studied filler based on rice husk has the pH value in an aqueous extract of 9.97; therefore, it is able to influence the formation of rubber cross-links.