OPTIMIZATION OF MIXING CONDITIONS FOR SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS

摘要

The dump temperature and mixing interval between rubber, silica, and silane coupling agent for silica-filled natural rubber (NR) lire tread compounds using bis-triethoxysilylpropyl tetrasulfide (TESPT) as silane were optimized. The dump temperature tums out to be the key parameter governing the properties of the silica-filled NR compounds. The increase in viscosity of the compounds by changing the dump temperature from 100 to 150℃ indicates that inevitably some crosslinking of NR occurs by sulfur contained in TESPT, simultaneous with the silanization reaction between silica and silane. However, the viscosity decreases again when dump temperatures above 150℃ are applied, indicating a dominant occurrence of degradation of the NR molecules. The results are in good agreement with bound rubber contents. The overall properties indicate that a dump temperature in the range of 135-150℃ and a silica-silane-rubber mixing interval of 10 min are the most appropriate mixing conditions for silica-filled NR compounds with TESPT as coupling agent.