Effect of Functionalization of Carbon Black on Rubber Properties

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Introduction The tire industry requires continuous development in the areas <strong>of</strong> • Increased durability; • Better fuel economy; and • Improved safety. 2 CRX4XXX-012-FTF’01-Simp.doc These requirements can only be met by improvement <strong>of</strong> wear resistance, rolling resistance and skid resistance, especially in wet conditions. From the compounding point <strong>of</strong> view, it has been recognized that the filler and polymer play an equally important role in governing the compound properties, thus tire performance. In fact, the term filler is misleading as it implies a material that increases the volume and reduces the compound cost. Additionally, the filler cannot only be considered to be what is commonly referred to as a “reinforcing agent” in the sense <strong>of</strong> a material that increases modulus and improves the tensile strength <strong>of</strong> the compound. What is commonly referred to as “filler” is actually a functional material or component which has a significant effect on tire performances. It has been well established that the wear resistance <strong>of</strong> filled rubber is essentially determined by the polymer-filler interaction. For fillers having similar morphologies, the increase in polymer-filler interaction, either through enhancement <strong>of</strong> physical adsorption <strong>of</strong> polymer chains on the filler surface or via creation <strong>of</strong> chemical linkages between filler and polymer, is crucial to the enhancement <strong>of</strong> wear resistance. It has also been established that there is a good correlation between the rolling resistance <strong>of</strong> tires and the hysteresis <strong>of</strong> the tread compound, characterized by the loss factor, tan δ, at high temperature. The hysteresis is in turn determined by the filler networking which is governed by polymer-filler, and especially filler-filler interactions. 1 The stronger the filler-filler interaction, the more developed is the filler network, hence the higher the rolling resistance <strong>of</strong> tires. In the last few years, in response to ever more demanding requirements from the tire industry, a great effort has been made by Cabot Corporation to develop functionalized
carbon blacks to improve the trade<strong>of</strong>f between wear resistance and rolling resistance. These include chemically modified carbon blacks with different functional groups and carbon-metal oxide-multiphase composites produced by the c<strong>of</strong>uming process. Among others a new material, carbon-silica dual phase filler (CSDPF), has been commercialized under the trade name <strong>of</strong> ECOBLACK CRX TM 2XXX 2,3 group which are also referred to as CSDPF 2000 family. With this material, the filler-filler interaction is substantially reduced due to the surface modification, and the polymer-filler interaction is enhanced by increasing the surface energy <strong>of</strong> the carbon domain <strong>of</strong> the filler and creating chemical bonding via coupling reaction between polymer chains and silanols on the silica domain. 2 Consequently, the trade<strong>of</strong>f between rolling resistance and wear resistance is greatly improved, significantly enhancing one without sacrificing the other. With regard to wet skid resistance, the mechanism is more complicated. Based on the comprehensive studies carried out in the laboratories <strong>of</strong> Cabot Corporation, it has been recognized that for wet skid resistance, while the dynamic hysteresis at low temperature due to the high-frequency nature <strong>of</strong> the dynamic strain involved in the skid process, is <strong>of</strong> importance, the elasto-hydrodynamic lubrication (EHL) and boundary lubrication (BL), especially in the micro scale, are also critical. 4 It was also found that besides dynamic properties, namely dynamic hysteresis and modulus, the test conditions, such as vehicles type (passenger vs. truck), braking system (locked wheel vs. anti-lock brake system 140 130 120 110 100 90 80 Relative friction force on wet surface, % Passenger tire Truck tire 3°C , 1.44 km/hr, 25° slip angle 0 50 100 150 Figure 1. wet skid resistances measured by GAFT as a function <strong>of</strong> load for passeger tire tread compounds with a variety <strong>of</strong> fillers ECOBLACK and CRX are the trademarks <strong>of</strong> Cabot Corporation. 3 SSBR/BR 75/25, filler 80 phr, oil 32.5 phr CSDPF <strong>Carbon</strong> black Silica Load, N
Page 1: Effect of<
Page 6 and 7: Table I. Analytical properties <str
Page 8 and 9: Before ashing After ashing Figure 4
Page 10 and 11: 12.0 10.0 8.0 6.0 4.0 2.0 0.0 Strai
Page 12 and 13: 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
Page 14 and 15: Wet skid resistance: The results <s
Page 17 and 18: compounds. With this filler, the hi
Page 19 and 20: 140 120 100 80 60 40 20 0 Wet skid

Effect of Functionalization of Carbon Black on Rubber Properties

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