EFFECTS OF ALKYLATION OF SILICA FILLER ON RUBBER REINFORCEMENT

Rubber reinforcement of silicas with different surface alkylation have been evaluated by studies of NH3-modified swelling, swelling volume fraction, stress-strain tests, and scanning electron microscopy. Effects of silica alkylation on filler dispersion has been explained on the basis of surface Energy and acid-base interactions. Bound rubber reductions have been explained according to acid-base interactions and/or physical entanglements. Hysteresis losses have been interpreted based on the reductions of polymer-filler and filler-filler interactions. The results show that the extent of reinforcement in NR and SBR vulcanizates is reduced when the silicas are alkylated, especially in the case of the hexadecyl group. However, in NBR vulcanizates the alkylation seems to have less influence on the reinforcement characteristics of the silica.