| Summary: | 碩士 === 國立中正大學 === 化學工程研究所 === 106 === Silica is used in tire tread preparation to reduce rolling resistance and thus to increase fuel efficiency. Because of rather low compatibility between hydrophilic silica and hydrophobic rubber, bi-functional coupling agent are added in rubber compounding to connect between rubber and fillers. TESPT [Bis-(triethoxysilyl-propyl)- tetrasulphide] has widely been used in tire tread manufacturing. However, the cost of commercial TESPT is rather high；therefore, the profit margin will be suppressed by addition of TESPT. In this research, TESPT was modified by substituting polyisoprenyl (PI) carbanions for the ethoxy groups at silicon center with different molecular weight (3000, 5000, 13000 g/mole); the sample is noted as PI-TESPT. For testing the roles of this substitution modification, tire-tread samples for mechanical testing were first prepared by mixing SSBR, NR, silica filler, carbon black, stearic acid, and PI-TESPT (or TESPT for comparison) in a home-made mixing and kneading machine with an in-situ torque measurement apparatus; the functions of this machine are similar to those of Brabender machine. Then, the rubber dough was mixed with sulfur and vulcanization accelerator and kneaded in a roller machine and the cross-linking properties of the resulting material were tested by a moving die rheometer. The mechanical properties of the tire-tread samples are tested by moving die rheometer, universal testing machine, and dynamic mechanical analysis (DMA). It could be due to insufficient vulcanization of double bond containing in the PI-TESPT, with the same amount of sulfur used in preparation, the experimental results show that cross-linking density in the vulcanization of PI-TESPT is decreased with increasing PI molecular weight and the physical properties of the PI-TESPT prepared samples are also inferior to those of TESPT. The drawbacks, however, can be remedied by adjusting sulfur usage. After optimizing sulfur used, the cross-linking density was greatly improved. Moreover, DMA measurements showed loss factor (tanδ) decreasing in high temperature while increasing in low temperature, indicating that both wet grip and rolling resistance are improved. To prove the necessity for the substitution reaction, physical mixing of TESPT with the equivalent amount of polyisoprene used as coupling agent was also tested. The results reveal that the performance of PI-TESPT is better than that of the mixing one, confirming polyisoprenyl (PI) substitution modification of TESPT enhance the compatibility between silica and rubber effectively.
|
|---|
