Automotive brakes

A review of the properties of phosphate fibers as related to the manufacture of brakes is presented in Table 8.2. 

It is hoped that the data given in this paper will be useful to friction materials formulators 

There is no doubt that these data should have been useful. Brake manufactures are still calling and requesting the fibers, while the EPA searches in vain for a replacement for semimetallic brake linings and is even considering returning to asbestos. It has been recognized that more people are being killed by poor brakes than ever should have died from asbestos. This should be no surprise to anyone. 

It is obvious that the cured brake blocks must be very strong if they are to withstand the abuse that friction products must endure. The horsepower of an automobile may be as high as 50 to 100, but the brakes on the same automobile must be 400 to 600 horsepower if the brakes are to stop the automobile in one-sixth the distance required to accelerate the automobile, by its engine, to speeds where brakes are applied to stop the automobile. The major fraction of the kinetic energy of the automobile is suddenly converted to heat in the brakes, and the temperature may rise abruptly from 0 °F to 1000 °F in a matter of seconds. Thermal shock alone would destroy an inferior brake pad. 

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Requirements. Automotive brakes must satisfy a certain set of consumer expectations, which iacludes safety, comfort, durabiUty, and reasonable cost. In technical terms, these expectations are translated iato a set of specific requirements such as high and stable friction, no or minimal vibration and noise, and low wear rates for the friction material and rotor mating surfaces, all of which have to be achieved simultaneously at a reasonable cost. Particularly, the performance has to be stable under varying appHcation conditions over extremes ia temperature, humidity, speed, and deceleration rate for occasional or many consecutive stops. The requirements for use ia machines are less stringent. 

In order to define the extent of emissions from automotive brakes and clutches, a study was carried out in which specially designed wear debris collectors were built for the dmm brake, the disk brake, and the clutch of a popular U.S. vehicle (1). The vehicle was driven through various test cycles to determine the extent and type of brake emissions generated under all driving conditions. Typical original equipment and aftermarket friction materials were evaluated. Brake relines were made to simulate consumer practices. The wear debris was analyzed by a combination of optical and electron microscopy to ascertain the asbestos content and its particle size distribution. It was found that more than 99.7% of the asbestos was converted to a nonfibrous form and... 

Brake linings and clutch facings. CNSL and cardanol have found extensive uses in automotive brake... 

A few years ago, a customer filed suit against a nationally known manufacturer of automotive brake fluid for supplying faulty merchandise. When the company s control chemist went before the jury with his detailed quality control records, he was able to prove that the allegedly faulty batch made two years earlier met all the requirements established for this product. The plaintiff lost his case. 

The first involves an attempt to replace a competitive plastic in an established application. Market research and market development had reported that a nylon material was being used to make tubing for such items as automotive brake cables. The market was estimated to be several million pounds and concentrated in only a few companies who were making the cables and selling directly to the end user. 

Iijima A, Sato K, Yano K, Tago H, Kato M, Kimura H, Furuta N (2007) Particle size and composition distribution analysis of automotive brake abrasion dusts for the evaluation of antimony sources of airborne particulate matter. Atmos Environ 41(23) 4908-4919... 

Pentoses contained in hemicellulose are used to produce furfural, a useful industrial chemical, used as a solvent for resins and waxes and in petrochemical refining. It is also used as a feedstock for a range of aromatic substances (it has an almond odour) including preservatives, disinfectants and herbicides. Furfural can be converted to furfuryl alcohol and used to make resins for composite applications with fibreglass and other fibres. These are of interest in the aircraft component and automotive brake sectors. Furfural is commercially derived from acid hydrolysis of waste agricultural by-products, such as sugarcane bagasse, com cobs and cereal brans. Around 450 000 tonnes is produced by this method per year. 

Friction materials are used in a variety of automotive and nonautomotive applications to control vehicle movement or for the transmission of power. This entry will limit its scope to automotive brake friction materials. Automotive friction materials are composites that are incorporated into a disk or drum brake system (a) for stopping or reducing the speed of a vehicle by converting kinetic energy into frictional heat or (b) to prevent the movement of parked vehicles. 

Halberstadt, M.L Mansfield, J.A. Rhee, S.K. Effect of potassium titanate fiber on the wear of automotive brake linings. International Conference on Wear of Materials, St. Louis, MO, Jul 2-6, 1977. 

Polyurethane products and formulated systems are used in rigid foams, flexible foams, adhesives, sealants, coatings and elastomers, as well as in many other applications. Propene glycols are used in a wide variety of end-use and industrial applications, from unsaturated polyester resins, cosmetics and household detergents, to paints and automotive brake fluids. Propene glycol ethers are commonly... 

The oxidation of an automotive brake fluid and a motor oil was studied by high-pressure DSC (38). At an air pressure of 600 psig, indicated, the relative oxidative stability of each of the types of materials was determined. 

In order to develop a beneficial application for fly ashes, automotive brake lining friction composites have been developed. These are based on phenolic resin, aramid pulp, glass fiber, potassium titanate, graphite, aluminum fiber and copper powder, in addition to fly ash. ... 

S. Mohanty and Y. Chugh. Development of fly ash-based automotive brake lining. Tribol. Int, 40(7) 1217-1224, July 2007. 

In addition to molding compoimds, phenolics are used to bond friction materials for automotive brake linings, clutch parts, and transmission bands. They serve as binders for core material in furniture, the water-resistant adhesive for exterior grade pl)nvood, binders for wood particle boards, and... 

Figure 6. pcD machining a cast metal-matrix composite automotive brake motor in A120% SiCp. 

In a hquid the molecules are close enough together that, unlike a gas, a liquid is only slightly compressible. However, the molecules remain mobile enough that the liquid flows. Because they are difficult to compress and their molecules are moving in aU directions, confined liquids can transmit applied pressure equally in aU directions. This property is used in the hydraulic fluids that operate automotive brakes and airplane wing surfaces, tail flaps, and rudders. 

Table 23.14 Typical properties for carbon-carbon friction materiai produced for automotive brake rotors,...

Commercially, a polyamide (PA6)-based thermoplastic silicone vulcanizate is currently commercialized by Multibase, a Dow Coming company under the trade name TPSiV 1180-50D. It has been evaluated for automotive brake hose... 

Autophoretic primers are novel, water-borne primers and are based on aqueous dispersions (3-5% volume solids) of either acrylic or polyvinylidene chloride (PVDC) polymers. They are used to coat ferrous metal components, such as automotive brake parts, in a dip coating process. The coating is acidic (pH 2.5-3.S) and contains an oxidizing agent, usually hydrogen peroxide. Firmly adherent films (7-25 xm in thickness), with good corrosion resistance, can be achieved. 

Fisher, M.L., K. Ramdas, K.T. Ulrich. 1999. Component Sharing in the Management of Product Variety A Study of Automotive Braking Systems. Management Science 45(3), 297-315. 

An estimated 1.3 million employees in the construction and general industry face significant asbestos exposure on the job. Heaviest exposures occur in the construction industry, particularly when removing asbestos during renovation or demolition. In the past, employees were also likely to be exposed during the manufacture of asbestos products (such as textiles, friction products, insulation, and other building materials) and during automotive brake and clutch repair work. 

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