MICROSTRUCTURE OF CB/SIO2 HYBRID REINFORCED SOLID TYRE TREAD COMPOUND CONTAINING GROUND TYRE RUBBER AND THEIR EFFECT ON FATIGUE RESISTANCE

Abstract

The possibility of improving the properties of rubber compounds containing ground tyre rubber (GTR) is an active research area. This study investigates the microstructure of carbon black filled tyre tread compound containing 20 phr GTR and compares the microstructure with those of similar compounds reinforced with hybrid carbon black/precipitated silica (CB/SiO2). In the compounds reinforced with hybrid filler, amount of the GTR was maintained at 20 phr, while the amount of the hybrid filler (CB/SiO2) were in the ratios 55/5, 50/10 and 45/15 respectively. The compounds were mixed by two-step mixing method using internal mixer and two-roll mill. The vulcanisation of each rubber compound was carried out on a compression moulding machine at 150. Results obtained from scanning electron microscopy of the fractured surfaces showed that the ingredients in the control sample that was not filled with GTR were well dispersed and distributed. The micrograph of the sample containing GTR and mixed at 60showed that GTR was not very compatible with the matrix. Improved mixing was achieved with increased mixing temperature. The addition of precipitated silica at 5 phr resulted in poor dispersion. The dispersion improved as the amount of silica increased to 10 phr and 15 phr respectively. Results obtained from flex fatigue test show that the compounds filled with hybrid CB/SiO2 in the ratios 50/10 and 45/15 phr exhibited no crack after 1000 cycles due to good dispersion. It is recommended that hybrid CB/SiO2 reinforcement at optimal amount of silica should be utilised to fill rubber compounds containing GTR in order to improve the properties of the vulcanisates.