Tire tread

Thus if Amontons law is obeyed, the initial velocity is determined entirely by the coefficient of friction and the length of the skid marks. The mass of the vehicle is not involved, neither is the size or width of the tire treads, nor how hard the brakes were applied, so long as the application is sufficient to maintain skidding. 

Guanidines. Guanidines (10) were one of the first aniline derivatives used as accelerators. They are formed by reaction of two moles of an aromatic amine with one mole of cyanogen chloride. Diphenylguanidine (DPG) has enjoyed a resurgence ia demand as an activator for sulfenamides and a co-accelerator ia tire tread compounds which employ siUca fillers for low rolling resistance. Guanidines alone show too Htde activity to be extensively used as primary accelerators. There were no U.S. producers as of mid-1996. 

Natural mbber was also used extensively in its oil-extended form in winter tires in the 1970s (57). Use of oil-extended natural mbber treads, found to have excellent traction on ice and snow, superseded studded synthetic mbber treads when studs were banned in certain countries and states owing to the damage they cause to partially cleared roads. This concept has been extended into aH-season tires, which account for over 75% of original equipment and replacement tires in the United States. It has been shown (58) that part replacement of styrene—butadiene mbber (SBR) in the formulation of aH-season tire tread compounds with oil-extended natural mbber increases ice and snow traction, reduces rolling resistance, and has no effect on normal wet grip. Also, there is only a minor trade-off in wear performance, because below a tire surface temperature of approximately 32°C, the wear of natural mbber is superior to SBR, whereas above this temperature the reverse is tme (59). Thus, wear of an aH-season tire ultimately depends on the surface temperature of the tread over its annual cycle of temperatures. 

Special tire treads, airplane, off-the-road racing passenger, off-the-road, special service tire treads... 

Processings and Properties. Polybutadiene is compounded similarly to SBR and vulcanised with sulfur. The high cis-1,4 type crystallizes poorly on stretching so it is not suitable as a "gum" stock but requires carbon black reinforcement. It is generally used for automotive tires in mixtures with SBR and natural mbber. Its low T (—OS " C) makes it an excellent choice for low temperature tire traction, and also leads to a high resilience (better than natural mbber) which ia turn results ia a lower heat build-up. Furthermore, the high i j -polybutadiene also has a high abrasion resistance, a plus for better tire tread wear. 

Lauf-flache, /. bearing surface (Mach.) journal (of tires) tread, -gewicht, n. sliding weight, -glasur, /. (Ceram.) flow glaze, -gummi, n. tread (of a rubber tire). 

The 6-function makes sure that if two segments and 2 meet on the huge network chain they can form a permanent constraint R( i) = R( 2)- Hence, this process will produce a network junction of functionality/n = 4, usually realized as sulfur bridges in technical elastomers like, for example, tire treads. 

FE simulations of the stress-strain properties of fiUer-reinforced elastomers are an important tool for predicting the service live performance of mbber goods. Typical examples are the evaluation of rolling resistance of tires due to hysteresis energy losses, mainly in the tire tread or the adjustment of engine mounts in automotive applications. 

On the dusted track the diminished adhesion friction component is clearly apparent for all three rabbers when comparing them with the master curves on the clean track The friction plateau observed for the rubbers filled with 50 pphr black which is typical for tire tread compounds is observed for most rubbers, as shown in Figure 26.5. 

Friction Coefficients and Relative Ratings of Four Tire Tread Compounds at 4.5°C Ice Surface Temperature and a Speed of 0.5 km/h... 

Figure 26.33 shows the side force coefficient as function of log speed for different temperatures at a constant load and slip angle for a tire tread compound based on 3,4 cw-poly-isoprene, a polymer... 

FIGURE 26.36 The side force coefficient of an OESBR black-fiUed tire tread compound on wet blunt Alumina 180 as function of log a v obtained at three speeds and five temperatures (black open squares) with a quadratic equation fitted to the data (black solid line). The red marked points were obtained at one speed for five temperatures with the dotted red line the best fitting quadratic equation, indicating the risk of extrapolation with a limited set of data. 

Experiments carried out at a constant speed over a range of temperatures showed, however, that for tire tread compounds the temperature dependence of abrasion, although smaller reaches in this case, too, a minimum at a particular temperature as shown in Figure 26.51 and rises sharply with a further decrease in temperature. 

FIGURE 26.55 Abrasion surface appearance of a natural rubber (NR) black-fiUed tire tread compound for sliding abrasion at different temperatures. 

FIGURE 26.61 Log (abrasion) of an OESBR and a natural rubber (NR) tire tread compound as function of load at different slip angles at a speed of 19.2 km/h. left Abrasion loss of the OESBR compound as function of load. Right the relative wear resistance rating of natural rubber (NR) to the OESBR as function of load for different slip angles. 

Also shown is the relative rating between the OESBR compound and an NR + black tire tread compound. At the smallest slip angle the rating of the NR is better than the OEBR but decreases with the load. As the slip angle is increased the rating reverses. 

FIGURE 26.65 Log (abrasion) as function of log (energy dissipation) for a commercial tire tread compound at three different speeds. Surface Alumina 60. 

FIGURE 26.66 Log (abrasion) as function of log speed for three different tire tread compounds. Load 76 N, slip angle 14.6°. Surface Alumina 60. (From Grosch, K.A. and Heinz, M., Proc. IRC 2000, Helsinki, 2000, paper 48.)... 

FIGURE 26.68 Log abrasion as function of log energy and log speed for a tire tread compound. 

Relative Ratings of Four Passenger Commercial Tire Tread Compounds for Which Road Test Ratings Were Available as Function of Log Energy and Log Speed... 

FIGURE 26.72 Log tire wear as function of log slip angle obtained with the MRPRA trailer for three tire tread compounds. 

During the last 50 years the understanding of the very complex phenomenon of friction and abrasion of tire tread compounds and their relation to traction and wear has progressed steadily. This chapter tries to trace the main strands of this story. Some details may still be missing but the main points are now clear. 

This basic mbber friction process is present on all surfaces, dry, wet or icy, being modified only by the external conditions. On wet surfaces this is primarily water lubrication which itself is influenced by the water depth, roughness of the road surface, and the state of the tire tread pattern. The low friction on ice near its melting point is mainly due to the properties of the ice. 

Experiments were performed using a tire-tread composition as shown in Table 29.1, representing a common silica recipe corresponding to the fuel-saving green-tire technology [2,24]. 

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