Road adhesion

Polybutadiene vulcanizates (see Table 18.1 for typical properties) are superior to those of natural rubber with respect to resilience, heat build-up and abrasion resistance. These properties are particularly significant in tyres. On the other hand, polybutadiene vulcanizates have lower tensile strength and tear resistance and polybutadiene tyres have relatively poor road-adhesion in wet conditions. For these reasons and to aid processing, butadiene rubbers are generally used in blends with natural or styrene-butadiene rubbers such blends usually contain less than 50% polybutadiene. Because of their use in tyre production, butadiene rubbers have become significant tonnage rubbers (Table 18.2). 

However, low loss rubbers like polybutadiene are extremely resilient, which means that articles constructed of them (like rubber balls) tend to bounce very readily. Obviously, we do not want a vehicle that bounces its way along the road, so for the contact tread area we need a rubber that absorbs shocks without bouncing, and so adheres to the road. For this purpose we need a high loss rubber, and again, where cost is not a factor, a special rubber, like butyl rubber, is used. Such rubbers give better road adhesion, particularly in the wet. Once again, it is necessary to note that cheaper tyres, with the tread constructed of natural rubber, are more prone to skid on wet roads than are those constructed with a tread of special high loss rubber. 

Hydrocarbon resin is a broad term that is usually used to describe a low molecular weight thermoplastic polymer synthesized via the thermal or catalytic polymerization of coal-tar fractions, cracked petroleum distillates, terpenes, or pure olefinic monomers. These resins are used extensively as modifiers in the hot melt and pressure sensitive adhesive industries. They are also used in numerous other appHcations such as sealants, printing inks, paints, plastics, road marking, carpet backing, flooring, and oil field appHcations. They are rarely used alone. 

Hydrocarbon resins based on CPD are used heavily in the adhesive and road marking industries derivatives of these resins are used in the production of printing inks. These resins may be produced catalyticaHy using typical carbocationic polymerization techniques, but the large majority of these resins are synthesized under thermal polymerization conditions. The rate constants for the Diels-Alder based dimerization of CPD to DCPD are weU known (49). The abiHty to polymerize without Lewis acid catalysis reduces the amount of aluminous water or other catalyst effluents/emissions that must be addressed from an environmental standpoint. Both thermal and catalyticaHy polymerized DCPD/CPD-based resins contain a high degree of unsaturation. Therefore, many of these resins are hydrogenated for certain appHcations. 

Hydrocarbon resins are used extensively as modifiers in adhesives, sealants, printing inks, paints and varnishes, plastics, road marking, flooring, and oil field appHcations. In most cases, they ate compounded with elastomers, plastics, waxes, or oils. Selection of a resin for a particular appHcation is dependent on composition, molecular weight, color, and oxidative and thermal stabiHty, as weU as cost. A listing of all hydrocarbon resin suppHers and the types of resins that they produce is impractical. A representative listing of commercially available hydrocarbon resins and their suppHers is included in Table 6. 

The present invention provides a wheel cover which improves the aerodynamic properties of the hub-rim-spoke wheels. The wheel cover of the present invention is preferably made of a light weight synthetic or natural polymer, fabric or paper film which is adhesively applied to a wheel through simple manual application. In turn, the aerodynamic wheel cover of the present invention may also be easily removed and replaced to allow on-road repairs of spoke, hub, or rim. 

Bisphenol F epoxy resins are used in high-soHds-high-build systems such as tank and pipe linings, industrial floors, road and bridge deck toppings, stmctural adhesives, grouts, coatings, and electrical varnishes. Bisphenol F epoxy resins are manufactured in Europe and Japan. 

Israelachivil et al. [25] proposed a phenomenal model for describing the interrelations between friction and adhesion. Consider the system shown in Fig. 28, where a spherical molecule slides over a corrugated solid surface. The scenario is somehow like pushing the wheel of a cart over a road paved with cobblestones, so it is also known as the cobblestone model. 

When forces are transmitted between tire and road the tire is deformed to some extent. It still adheres to the road in part of the contact area, but slides locally when the ratio of tangential stress to the local pressure exceeds the friction coefficient and wear occurs. It is this partial adhesion and sliding which on the one hand allows a control over the force transmission and on the other hand leads to wear of the tire. 

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. 

Calcium chloride has several industrial applications. The major applications of this compound are in deicing of roads, dust control, imparting stability to roads and buildings, and to improve traction in tractor tires. It is mixed with ice to make freezing mixtures. Hexahydrate mixed with crushed ice can lower the temperature of the cooling bath to below -50°C. It also is used as a desiccant for dehydrating gases and liquids. It is added to cement in various proportions to manufacture different types of concrete. Other uses are in adhesives, to lower gel temperatures, and as a calcium source in liquid feed supplements for dairy cattle. Also, the compound is used to control particle size development and reduce coalescence in plastics. 

Some other practical situations where particle aggregation is important include the precipitation of colloidal mud at the mouth of a river due to the salinity of the sea-water exceeding the critical coagulation concentration, land (e.g. mountainside) stability, building and road foundations, the retention of a porous structure in filtration, mineral processing117 and paper making. Control of particle aggregation is also of primary importance in adhesives, inks, pharmaceuticals, cosmetics, foodstuffs and lubricants. 

Hot-melt adhesives based on bitumen show good adhesion to many materials and are resistant to water and weather. One important commercial use in which plastics are involved is the construction of road signs and other street furniture, where these adhesives are used to bond polyethylene sleeves to steel tubes. 

Bitumen additives to give wet adhesion to road aggregates Quaternary ammonium compounds Imidazoline derivatives Amine ethoxylates Wetting agents... 

---