Effect of Functionalization of Carbon Black on Rubber Properties
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Effect of Functionalization of Carbon Black on Rubber Properties

Effect of Functionalization of Carbon Black on Rubber Properties Effect of Functionalization of Carbon Black on Rubber Properties

cabot.corp.com
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09.01.2013 Views

Introduction The tire industry requires continuous development in the areas ong>ofong> • Increased durability; • Better fuel economy; and • Improved safety. 2 CRX4XXX-012-FTF’01-Simp.doc These requirements can only be met by improvement ong>ofong> wear resistance, rolling resistance and skid resistance, especially in wet conditions. From the compounding point ong>ofong> 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 ong>ofong> a material that increases modulus and improves the tensile strength ong>ofong> 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 ong>ofong> filled rubber is essentially determined by the polymer-filler interaction. For fillers having similar morphologies, the increase in polymer-filler interaction, either through enhancement ong>ofong> physical adsorption ong>ofong> polymer chains on the filler surface or via creation ong>ofong> chemical linkages between filler and polymer, is crucial to the enhancement ong>ofong> wear resistance. It has also been established that there is a good correlation between the rolling resistance ong>ofong> tires and the hysteresis ong>ofong> 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 ong>ofong> 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 tradeong>ofong>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 cong>ofong>uming process. Among others a new material, carbon-silica dual phase filler (CSDPF), has been commercialized under the trade name ong>ofong> 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 ong>ofong> the carbon domain ong>ofong> the filler and creating chemical bonding via coupling reaction between polymer chains and silanols on the silica domain. 2 Consequently, the tradeong>ofong>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 ong>ofong> Cabot Corporation, it has been recognized that for wet skid resistance, while the dynamic hysteresis at low temperature due to the high-frequency nature ong>ofong> the dynamic strain involved in the skid process, is ong>ofong> 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 ong>ofong> load for passeger tire tread compounds with a variety ong>ofong> fillers ECOBLACK and CRX are the trademarks ong>ofong> Cabot Corporation. 3 SSBR/BR 75/25, filler 80 phr, oil 32.5 phr CSDPF ong>Carbonong> black Silica Load, N

carb<strong>on</strong> blacks to improve the trade<str<strong>on</strong>g>of</str<strong>on</strong>g>f between wear resistance and rolling resistance.<br />

These include chemically modified carb<strong>on</strong> blacks with different functi<strong>on</strong>al groups and<br />

carb<strong>on</strong>-metal oxide-multiphase composites produced by the c<str<strong>on</strong>g>of</str<strong>on</strong>g>uming process. Am<strong>on</strong>g<br />

others a new material, carb<strong>on</strong>-silica dual phase filler (CSDPF), has been commercialized<br />

under the trade name <str<strong>on</strong>g>of</str<strong>on</strong>g> ECOBLACK CRX TM 2XXX 2,3 group which are also referred to<br />

as CSDPF 2000 family. With this material, the filler-filler interacti<strong>on</strong> is substantially<br />

reduced due to the surface modificati<strong>on</strong>, and the polymer-filler interacti<strong>on</strong> is enhanced by<br />

increasing the surface energy <str<strong>on</strong>g>of</str<strong>on</strong>g> the carb<strong>on</strong> domain <str<strong>on</strong>g>of</str<strong>on</strong>g> the filler and creating chemical<br />

b<strong>on</strong>ding via coupling reacti<strong>on</strong> between polymer chains and silanols <strong>on</strong> the silica domain. 2<br />

C<strong>on</strong>sequently, the trade<str<strong>on</strong>g>of</str<strong>on</strong>g>f between rolling resistance and wear resistance is greatly<br />

improved, significantly enhancing <strong>on</strong>e without sacrificing the other.<br />

With regard to wet skid resistance, the mechanism is more complicated. Based <strong>on</strong> the<br />

comprehensive studies carried out in the laboratories <str<strong>on</strong>g>of</str<strong>on</strong>g> Cabot Corporati<strong>on</strong>, it has been<br />

recognized that for wet skid resistance, while the dynamic hysteresis at low temperature<br />

due to the high-frequency nature <str<strong>on</strong>g>of</str<strong>on</strong>g> the dynamic strain involved in the skid process, is <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

importance, the elasto-hydrodynamic lubricati<strong>on</strong> (EHL) and boundary lubricati<strong>on</strong> (BL),<br />

especially in the micro scale, are also critical. 4 It was also found that besides dynamic<br />

properties, namely dynamic hysteresis and modulus, the test c<strong>on</strong>diti<strong>on</strong>s, such as vehicles<br />

type (passenger vs. truck), braking system (locked wheel vs. anti-lock brake system<br />

140<br />

130<br />

120<br />

110<br />

100<br />

90<br />

80<br />

Relative fricti<strong>on</strong> force<br />

<strong>on</strong> wet surface, %<br />

Passenger tire Truck tire<br />

3°C , 1.44 km/hr, 25° slip angle<br />

0 50 100 150<br />

Figure 1. wet skid resistances measured by GAFT as a functi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> load for passeger tire tread compounds with a variety <str<strong>on</strong>g>of</str<strong>on</strong>g> fillers<br />

ECOBLACK and CRX are the trademarks <str<strong>on</strong>g>of</str<strong>on</strong>g> Cabot Corporati<strong>on</strong>.<br />

3<br />

SSBR/BR 75/25,<br />

filler 80 phr,<br />

oil 32.5 phr<br />

CSDPF<br />

<str<strong>on</strong>g>Carb<strong>on</strong></str<strong>on</strong>g> black<br />

Silica<br />

Load, N

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