Friction on ice

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. 

Most polybutadiene is used in tyre applications, and the majority of this use is in blends with other polymers, such as NR and SBR, where polybutadiene reduces heat build-up and improves the abrasion resistance of the blend. The friction on ice of winter tyres is also improved by using higher levels of polybutadiene in the tread blend. 

L. Makkonen, A theoretical approach to rubber friction on ice. In ARTTU Final Report, Helsinki University of Technology, Laboratory of Automotive Engineering, J. Vainikka and H. Pirjola, Eds, 2003, 12. 

J. Harrison (Goodyear Tire and Rubber Co.) Continuing the comparison of the coefficients of friction on ice between chemically different types of rubbers, have observations been made which would compare the effect of more or less methyl group substitutions than natural rubber possesses, e.g. butadiene versus di-methyl butadiene rubber ... 

The coefficient of friction between two unlubricated solids is generally in the range of 0.5-1.0, and it has therefore been a matter of considerable interest that very low values, around 0.03, pertain to objects sliding on ice or snow. The first explanation, proposed by Reynolds in 1901, was that the local pressure caused melting, so that a thin film of water was present. Qualitatively, this explanation is supported by the observation that the coefficient of friction rises rapidly as the remperarure falls, especially below about -10°C, if the sliding speed is small. Moreover, there is little doubt that formation of a water film is actually involved [3,4]. 

FIGURE 26.15 Friction force on ice as function of the (a) load at a constant ice temperature of —5°C and a speed of 1.5 km/h, for two compounds showing the experimental points and the fitted power function (h) showing the calculated power functions of seven compounds. Their main ingredients are shown helow. (c) Shows the relative ratings with compound 1 as reference, (d) to (f) Show similar graphs for the speed dependence at a load of 75 N. 

Another area of much interest is the adhesion of ice to solids. This system is obviously of much interest in general everyday phenomena (tire friction on road surfaces, ice on metal surfaces, ships, etc.). Especially of interest is the adhesion of ice on ships sailing in the cold areas, and on wings of airplanes. Investigations have shown that the adhesive bonds between clean metal surface and ice are very strong. When the ice is removed by force, it breaks, leaving a thin layer of ice on the solid layer. 

Friction on snow and ice and the development of some fast-running skiis. Nature (London) 176, 946-947 (1955). 

A valuable resource is Colbeck s bibliography, which lists 192 references on ice friction, dating from 1900 to 1991. Nevertheless, Colbeck has overlooked some significant work such as Fitz et al., and he lists no publications for the past fifteen years. Rosenberg traces published scientific interest in ice slipperiness and ice adhesion as far back as W. and J.J. Thomson in the 1850 s and Michael Faraday in 1859, and there are trails leading back to Rene Descartes in the 1630 s. ... 

The friction coefficient when walking on ice may be too small to permit enough force to propel a body forward. 

Friction, however, offers an even deeper line of thought. Friction produces heat, which can melt ice in a very thin layer. However, friction can only produce heat during movement. Ice is known to be shppeiy even for objects that are stationary, there is no extra effort needed to begin the movement. And forces of friction tend to be quite small on ice— this is the very reason why it is slippery, and small forces can only generate a small amount of heat. 

Friction is the resistance between things, such as between work shoes and a walking surface. Without friction, workers are likely to slip and fall. Probably fhe best example of this phenomenon is slipping on ice. On icy surfaces, shoes can t grip the surface normally, causing a loss of traction and a fall. 

---