Application Of Modified Graphene In Tire Treads

In recent years, green tire with low rolling resistance and energy-saving property has attracted much attention. As the largest component of tire, tire tread is the primary factor in determining the rolling resistance for tires. Tread performance also determines both wet skid resistance and wear resistance of tire. Graphene has been the focus of attention in research communities, due to its outstanding properties in many aspects. Graphene has been widely utilized in the prepration of the advanced polymer-based composites. In this thesis, tea polyphenols were used to reduce graphene oxide(GO) and stabilize the resulted reduced graphene. Tea polyphenols modified graphene(TPG) exhibits excellent solubility and stability in water. Then the rubber/TPG composites were prepared by latex co-coagulation method and applied as the tread rubber. The structure, morphology, and properties of tread rubbers were studied fully.Firstly, the influences of TPG contents on the mechanical properties and dynamic properties for composites, in the styrene-butadiene rubber(SBR) compound(with 18 phr silica) were investigated. The results of scanning electron micorscope(SEM) and transmission electron microscope(TEM) demonstrate that TPG exhibits good dispersion in rubber matrix at a low content(lower than 5 phr). However, TPG tends to aggregate at higher contents. While TPG contents increase from 3.5 phr to 10 phr, mechanical properties of tread rubbers increase gradually. However, the dynamic properties such as heat build-up, Akron abrasion and rolling resistance deterioate gradually. After optimization design in formulation, the formulation with 3.5 phr TPG and 28 phr silica as the reinforcement has been demonstrated to possess the combination of excellent mechanical and dynamic properties. The tire tread prepared with this formulation possesses an impressively low rolling resistance coefficient of 6.81 N/k N, very close to A-rating rolling resistance for passenger car tire in European Unions.In order to blance the tread performance and the processability of tread compounds, the influence of substitution of silica by TPG, and processing oil contents on the processability were inverstigated. Viscosity of tread compound increases with increasing TPG content, and decreases as processing oil content increases. Morphological observations indicate that TPG disperses uniformly through rubber matrix at low contents(lower than 3 phr). Fitting result of Mooney-Rivlin equation illustrates that the substitution with 1 phr TPG leads to increased interfacial interaction. With increasing TPG content, both mechanical and dynamic properties appear to improve firstly, and then decrease subsequently. With substitution by 1 phr TPG, the tread rubber posseses the optimized comprehensive performance. Compared with the control sample with silica only, the heat build-up is decreased by 5 degree and the Akron abrasion loss is decreased by 37.6%. In the meanwhile, tan δ value at 60 o C decreases by 22.0%.In addition, we attempted to utilize TPG to improve the cutting and chipping resistance(CCR) of off-the-road(OTR) tire tread rubbers. The natural rubber(NR)/TPG composites masterbatch is first prepared. Then it is incoproated into NR/SBR/carbon black composites to prepare OTR tread rubbers with varied contents of TPG. Rubber Processing Analyzer(RPA) results indicate that Payne Effect is more obvious with more TPG contents. Morphological observations indicate that TPG acquires good dispersion in rubber matrix. With TPG contents increasing from 0 phr to 2 phr, there’s no notable improvement on mechanical properties, but an outstanding improvement on the flex fatigue properties and CCR properties are achieved. With 2 phr TPG, tread rubbers’ flex cycles for Grade I and Grade III are increased by 900% and 380%, respectively, compared with the blank sample. In addition, the CCR property is increased by 16.5%. This research indicates that TPG has application prospect on the improvement of CCR in OTR tread rubbers.