Study On The Relationship Of Microstructure–viscoelasticity–performance Of Tire Tread Composite

With the rapid development of automobile industry technology, thehigher requirement of improve the safety, the economic and environmentalefficiency of road transport gives a big challenge for tyres to promotingfuel-efficent, wet skid resistance and noise levels. Therefore, the EuropeanUnion puts forward the Tyre Labelling Regulation1222/2009. The rulesprescribe that information on certain characteristic of tyre performances(rolling resistance, wet grip and noise level) will have to be communicated tocunsumers, include passenger car tyres, light truck tyres and heavy dutyvehicle tyres. Generally speaking, higher performance tires should have goodwet skid resistance (WSR), abrasion resistance and low rolling resistance (RR),although these performances which often called “magic triangle” in the tireindustry are hard to be improved simultaneously. The improvement of treadrubber performance is depended on the material composition choose, formulation design and processing technology of the composite. Meanwhile,the tread performance can be forecasted by the viscoelastic property of thecomposite, such as the composite which owns a lower tan δ value at50to80°C and a higher tan δ in the temperatures range of-20to0°C will alwaysexhibit a better RR and WSR performance. For the viscoelastic properties ofthe rubber composites, filler and polymer are two main effecting factors, andin this research the filler-filler network and filler-rubber interaction are studieddeeply. Based on the investigation of the relationship of microstructure-viscoelasticity-performance of tire tread composite, we hope to get a way tobalance the “magic triangle” properties of the tire tread.In the first part (Chapter3,4,5), we mainly compared the mechanicalproperties, abrasion properties, RR and WSR of carbon black (CB), carbon-silica dual phase filler (CSDPF) and silica filled different type of Styrene-Butadiene Rubber (SBR). The filler-rubber interactions were investigated viabound rubber content (BRC) of the compounds and solid-state1H low-fieldNMR spectroscopy. The results indicated that the BRC of the compound washighly related to the amount of surface area for interaction between filler andrubber, while the solid-state~1H low-field NMR spectroscopy was an effectivemethod to evaluate the intensity of filler-rubber interaction. The silica filledcompound showed the highest BRC, whereas the CB filled one had thestrongest filler-rubber interfacial interaction, verified by NMR transverserelaxation. The strain sweep measurements of the compounds were conducted via a rubber process analyzer; the results showed that the CSDPF filledcompound presented the lowest Payne effect, which is mainly related to theweakened filler network structure in the polymer matrix. The temperaturesweep measurement, tested by dynamic mechanical thermal analysis,indicated that the glass transition temperature (Tg) did not change when SBRwas filled with the different fillers, whereas the storage modulus in rubberystate and the tan δ peak height were greatly affected by the filler networkstructure of the composites. For the performance of the composites, it can befound that compared with CB filled SBR composite, the composite filled withsilica which was in-situ modified by coupling agent owns a higher modulus at300%, lower elongation at break, better RR and WSR performance, while itsabrasion resistance and cutting resistance were poor.Clay, different from CB and silica, is of layered structure, and it can bedispersed on a nano-meter level in rubber matrix by latex compoundingmethod (LCM). Not only owning a good mechanical property and gas barrierproperty, the incorporation of a small amount of nano-dispersed clay (NC)prepared by LCM can greatly improved the flex-fatigue life of CB filled SBRand NR composites due to the fact that NC layers had the advantage of crackblunting compared with carbon black. In the second part (Chapter6), wemainly compared the performance of CB or silica filled composite by additionof a small amount NC. CCR of CB filled SBR was dramatically improvedmore than30%by addition of4phr NC, while not decreasing the stress at100% and the Shore A hardness of the composite. The addition of clay enhanced thefiller-filler network of CB filled composite, which also lead to the value ofAkron abrasion and heat built up of the composite increased. For themechanism of CCR improved by addition of NC, it can be summarized asfollows: the addition of NC greatly increases the deformation ability (higherelongation) and the hysteresis, which are closely related to the ability totransform the cutting energy into heat energy, and thus prevents the compositebeen ruptured from cutting. At the same time,4phr NC improve the tearstrength and thus the composites exhibit higher ability of inhibiting crackpropagation. The combination of high deformation ability, hysteresis andpreventing crack propagation, contributes largely to the increase in CCR of thecomposites with NC. However, this phenomenon is not presented in thesilica/clay filled rubber composite.In the third part (Chapter7), the abrasion resistance of CB filled SBR,isoprene rubber (IR), butadiene rubber (BR) and integrated rubber (SIBR)were measured by Akron abrasion machine, as the sequence of the abrasionresistance performance of the composites is BR-CB> SIBR-CB> SBR-CB>IR-CB. Meanwhile, the molecular weight and distribution, filler-rubberinteraction, as well as thermal degradation of the composites were investigatedvia gel permeation chromatography (GPC), bound rubber content, andthermo-gravimetric analysis (TGA). The results indicated that the existence oflow molecular weight (1×10~4) portion in the IR-CB composite should be the main reason for its worst abrasion resistance performance. For the syntheticrubber with good resistance of molecular chain rupture by the mechanicalshear force during compounding, such as BR, SBR and SIBR, the sequence ofabrasion resistance performance is in consistent with the filler-rubberinteraction order of the composites. In addition, due to the surface temperatureof the rubber sample during abrasion will not lead to the thermal degradation,the heat resistance temperature of the composite is beside the abrasionperformance.