Tyre Industry

L.S.RAHEJA COLLEGE OF ARTS AND COMMERCE S.Y.BBI

COST ACCOUNTING

PROJECT ON COST ACCONTING (TYRE INDUSTRY) Presented by: 1. Jaisal Chachhia - 06 2. Laveit Dighe - 10 3. Bhavin Jagani - 14 4. Pushkar Kothare – 20 5. Krupa Parekh - 30 6. Afreen Sheikh - 40

Presented to: Prof. Gayatri Mam

Latex refers generically to a stable dispersion (emulsion) of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic. Latex as found in nature is the milky sap of many plants that coagulates on exposure to air. It is a complex emulsion in which proteins, alkaloids, starches, sugars, oils, tannins, resins and gums are found. In most plants, latex is white, but some have yellow, orange, or scarlet latex. The word is also used to refer to natural latex rubber; particularly for nonvulcanized rubber. Such is the case in products like latex gloves, latex condoms and latex clothing. It can also be made synthetically by polymerizing a monomer that has been emulsified with surfactants. The term latex is attributed to Charles Marie de la Condamine, who derived it from lac, the Latin word for milk.[1]

Sources The cells or vessels in which latex is found make up the laticiferous system, which forms in two very different ways. In many plants, the laticiferous system is formed from rows of cells laid down in the meristem of the stem or root. The cell walls between these cells are dissolved so that continuous tubes, called latex vessels, are formed. This method of formation is found in the poppy family, in the rubber trees (Para rubber tree and Castilla elastica), and in the Cichorieae, a section of the Family Asteraceae distinguished by the presence of latex in its members. Dandelion, lettuce, hawkweed and salsify are members of the Cichorieae. It is also present in another member of the Asteraceae, the guayule plant. In the milkweed and spurge families, on the other hand, the laticiferous system is formed quite differently. Early in the development of the seedling latex cells differentiate, and as the plant grows these latex cells grow into a branching system extending throughout the plant. In the

mature plant, the entire laticiferous system is descended from a single cell or group of cells present in the embryo. The laticiferous system is present in all parts of the mature plant, including roots, stems, leaves, and sometimes the fruits. It is particularly noticeable in the cortical tissues. Several members of the fungal kingdom also produce latex upon injury. Notable are the milk-caps such as Lactarius deliciosus. Natural function of latex

Rubber latex Many plant functions have been attributed to latex. Some regard it as a form of stored food, while others consider it an excretory product in which waste products of the plant are deposited. Still others believe it functions to protect the plant in case of injuries; drying to form a protective layer that prevents the entry of fungi and bacteria. Similarly, it may provide some protection against browsing animals, since in some plants latex is very bitter or even poisonous. It may be that latex fulfills all of these functions to varying degrees in the numerous plant species in which it occurs. Uses of latex The latex of many species can be processed to produce other materials. Natural rubber is the most important product obtained from latex; more than 12,000 plant species yield latex containing rubber, though in the vast majority of those species the rubber is not suitable for commercial use.[2].

Balatá and gutta percha latex contain an inelastic polymer related to rubber. Latex from the chicle and jelutong trees is used in chewing gum. Poppy latex is a source of opium and its many derivatives. Latex is also used to make gloves, catheters, condoms, and is used as a binding agent in latex paint. Latex clothing Latex is used in many types of clothing. Worn on the body (or applied directly by painting) it tends to be skin-tight, producing a "second skin" effect. Allergic reactions Some people have a serious latex allergy, and exposure to latex products such as latex gloves can cause anaphylactic shock. Guayule latex is hypoallergenic and is being researched as a substitute to the allergyinducing Hevea latexes. Some allergic reactions are not from the latex but from residues of other ingredients used to process the latex into clothing, gloves, foam, etc. These allergies are usually referred to as multiple chemical sensitivity (MCS).

Vulcanization One of the key steps in the manufacture is called Vulcanization, a process invented by Charles Goodyear in 1839. Natural rubber (chemical name polyisoprene) consists of long hydrocarbon chains which are randomly intertwined with one another but have no molecular links between them. By mixing molecular sulphur (a yellow solid) into the natural rubber (which is a sticky, gooey substance) and heating the mixture, sulphur cross-links are formed between the rubber molecules. This hardens the rubber and gives it the qualities of strength and elasticity that one associates with rubber tyres. Vulcanization (or vulcanisation) refers to a specific curing process of rubber involving high heat and the addition of sulfur or other equivalent curatives. It is a chemical process in which polymer molecules are linked

to other polymer molecules by atomic bridges composed of sulfur atoms or carbon to carbon bonds. The end result is that the springy rubber molecules become cross-linked to a greater or lesser extent. This makes the bulk material harder, much more durable and also more resistant to chemical attack. It also makes the surface of the material smoother and prevents it from sticking to metal or plastic chemical catalysts.

This heavily cross-linked polymer has strong covalent bonds, with strong forces between the chains, and is therefore an insoluble and infusible, thermosetting polymer. The process is named after Vulcan, Roman god of fire. Vast arrays of products are made with vulcanized rubber including ice hockey pucks, tires, shoe soles, hoses and many more. Reason for vulcanizing Uncured natural rubber is sticky, can easily deform when warm, and is brittle when cold. In this state it cannot be used to make articles with a good level of elasticity. The reason for inelastic deformation of unvulcanized rubber can be found in its chemical nature: rubber is made of long polymer chains. These polymer chains can move independently relative to each other, which results in a change of shape. By the process of vulcanization, crosslinks are formed between the polymer chains so the chains can no longer move independently. As a result, when stress is applied the vulcanized rubber will deform, but upon release of the stress, the rubber article will go back to its original shape. Description Vulcanization is generally considered to be an irreversible process (see below), similar to other thermosets and must be contrasted strongly with thermoplastic processes (the melt-freeze process) which characterize the behavior of most modern polymers. This irreversible cure reaction defines cured rubber compounds as thermoset materials, which do not melt on heating, and places them outside the class of thermoplastic materials (like polyethylene and polypropylene). This is a fundamental difference between rubbers and thermoplastics, and sets the conditions for their

applications in the real world, their costs, and the economics of their supply and demand. Usually, the actual chemical cross-linking is done with sulfur, but there are other technologies, including peroxide-based systems. The combined cure package in a typical rubber compound comprises the cure agent itself, (sulfur or peroxide), together with accelerators, activators like zinc oxide and stearic acid and antidegradants. Prevention of vulcanization starting too early is done by addition of retarding agents. Antidegradants are used to prevent degradation by heat, oxygen and ozone. Along the rubber molecule, there are a number of sites which are attractive to sulfur atoms. These are called cure sites, and are generally sites with an unsaturated carbon-carbon bond, like in polyisoprene, the basic material of natural rubber,and in styrene-butadiene rubber (SBR), the basic material for passenger tires. The active sites are allylic hydrogen atoms; that means they are hydrogen atoms connected to the first saturated carbon atom connected to the carbon-carbon double bond. During vulcanization the eight-membered ring of sulfur breaks down in smaller parts with one to eight sulfur atoms. These small sulfur chains are quite reactive. At each cure site on the rubber molecule, such short sulfur chain can attach itself, and eventually reacts with a cure site of another rubber molecule, and so forming a bond between two chains. This is named a cross-link. These sulfur bridges are typically between two and eight atoms long. The number of sulfur atoms in a sulfur crosslink has a strong influence on the physical properties of the final rubber article. Short sulfur crosslinks, with just one or two sulfur atoms in the crosslink, give the rubber a very good heat resistance. Crosslinks with higher number of sulfur atoms, up to six or seven, give the rubber very good dynamic properties but with lesser heat resistance. Dynamic properties are important for flexing movements of the rubber article, e.g., the movement of a side-wall of a running tire. Without good flexing properties these movements will rapidly lead to formation of cracks and, ultimately, to failure of the rubber article. Vulcanization methods There are various vulcanization methods. The economically most important method i.e the vulcanization of tires uses increased pressure and temperature. A typical vulcanization temperature for a passenger tire is 10 minutes at 170 degrees C. This type of vulcanization is an example of the

general vulcanization method named compression molding. The rubber article is intended to adopt the shape of the mold. Other methods for instance those used to make door profiles for cars use hot air vulcanization or microwave heated vulcanization (both continuous processes). Four types of curing systems are in common use. They are: 1. 2. 3. 4.

Sulfur systems Peroxides Urethane crosslinkers Metallic oxides

By far the most common vulcanizing methods are those dependent on sulfur. Sulfur, by itself, is a slow vulcanizing agent. Large amounts of sulfur, as well as high temperatures and long heating periods are necessary and one obtains an unsatisfactory crosslinking efficiency with unsatisfactory strength and aging properties. Only with vulcanization accelerators can the quality corresponding to today's level of technology be achieved. The multiplicity of vulcanization effects demanded cannot be achieved with one universal substance, a large number of diverse materials is necessary. Devulcanization The rubber industry has been researching the devulcanization of rubber for many years. The main difficulty in recycling rubber has been devulcanizing the rubber without compromising its desirable properties. The process of devulcanization involves treating rubber in granular form with heat and/or softening agents in order to restore its elastic qualities, in order to enable the rubber to be reused. Several experimental processes have achieved varying degrees of success in the laboratory, but have been less successful when scaled up to commercial production levels. Also, different processes result in different levels of devulcanization: for example, the use of a very fine granulate and a process that produces surface devulcanization will yield a product with some of the desired qualities of unrecycled rubber. The rubber recycling process begins with the collection and shredding of discarded tires. This reduces the rubber to a granular material, and all the steel and reinforcing fibers are removed. After a secondary grinding, the

resulting rubber powder is ready for product remanufacture. However, the manufacturing applications that can utilize this inert material are restricted to those which do not require its vulcanization. In the rubber recycling process, devulcanization begins with the delinking of the sulfur molecules from the rubber molecules, thereby facilitating the formation of new cross-linkages. Two main rubber recycling processes have been developed: the modified oil process and the water-oil process. With each of these processes, oil and a reclaiming agent are added to the reclaimed rubber powder, which is subjected to high temperature and pressure for a long period (5-12 hours) in special equipment and also requires extensive mechanical post-processing. The reclaimed rubber from these processes has altered properties and is unsuitable for use in many products, including tires. Typically, these various devulcanization processes have failed to result in significant devulcanization, have failed to achieve consistent quality, or have been prohibitively expensive. In the mid-1990s, researchers at the Guangzhou Research Institute for the Utilization of Reusable Resources in China patented a method for the reclamation and devulcanizing of recycled rubber. Their technology, known as the AMR Process, is claimed to produce a new polymer with consistent properties that are close to those of natural and synthetic rubber, and at a significantly lower potential cost. The AMR Process exploits the molecular characteristics of vulcanized rubber powder in conjunction with the use of an activator, a modifier and an accelerator reacting homogeneously with particles of rubber. The chemical reaction that occurs in the mixing process facilitates the delinking of the sulfur molecules, thereby enabling the characteristics of either natural or synthetic rubber to be recreated. A mixture of chemical additives is added to the recycled rubber powder in a mixer for approximately five minutes, after which the powder passes through a cooling process and is then ready for packaging. The proponents of the process also claim that the process releases no toxins, by-products or contaminants. The reactivated rubber may then be compounded and processed to meet specific requirements. Currently, Landstar Rubber, which holds the North American license for the AMR Process, has built a rubber reprocessing plant and research/quality control lab in Columbus, Ohio. The plant performs

production runs on a demonstration basis or at small commercial levels. The recycled rubber from the Ohio plant is currently being tested by an independent lab to establish its physical and chemical properties. Whether or not the AMR Process succeeds, the market for new raw rubber or equivalent remains enormous, with North America alone using over 10 billion pounds (circa 4.5 million tons) every year. The auto industry consumes approximately 79% of new rubber and 57% of synthetic rubber. To date, recycled rubber has not been used as a replacement for new or synthetic rubber in significant quantities, largely because the desired properties have not been achieved. Used tires are the most visible of the waste products made from rubber; it is estimated that North America alone generates approximately 300 million waste tires annually, with over half being added to stockpiles that are already huge. It is estimated that less than 10% of waste rubber is reused in any kind of new product. Furthermore, the United States, the European Union, Eastern Europe, Latin America, Japan and the Middle East collectively produce about one billion tires annually, with estimated accumulations of three billion in Europe and six billion in North America. One company that has had commercial success with its devulcanisation technology is Green Rubber, based out of Malaysia. The company, which owns a patented mechano-chemical devulcanisation process called DeLink, recently signed a deal with Timberland, the footwear giant, to supply devulcanised compound made from tire waste. Timberland's Fall 09 range will contain boots with soles made from 50% Green Rubber compound. The company has two plants in Malaysia and one about to become operational in the US. Recently a new method of devulcanization was developed by Coral GROUP, in Dnepropetrovsk, Ukraine. This method of devulcanization, includes impregnation of rubber with special solvent with additives of catalysts and reagents. In this process rubber is restructured, sulfuric "bridges are torn up, sulfur chemically connects, and rubber becomes plastic, suitable for molding. All that remains is to add 2-4% of sulfur, and new rubber products can be made. The quality of the obtained rubber compound is not worse than obtained from the initial materials, i.e. it is completely possible to make new automobile tires or other rubber products from the devulcanized rubber.

Tire Uniformity Tire Uniformity refers to the dynamic mechanical properties of pneumatic tires as strictly defined by a set of measurement standards and test conditions accepted by global tire and car makers. These measurement standards include the parameters of radial force variation, lateral force variation, conicity, plysteer, radial runout, lateral runout, and sidewall bulge. Tire makers worldwide employ tire uniformity measurement as a way to identify poorly performing tires so they are not sold to the marketplace. Both tire and vehicle manufacturers seek to improve tire uniformity in order to improve vehicle ride comfort. Force variation background The circumference of the tire can be modeled as a series of very small spring elements whose spring constants vary according to manufacturing conditions. These spring elements are compressed as they enter the road contact area, and recover as they exit the footprint. Variation in the spring constants in both radial and lateral directions cause variations in the compressive and restorative forces as the tire rotates. Given a perfect tire, running on a perfectly smooth roadway, the force exerted between the car and the tire will be constant. However, a normally manufactured tire running on a perfectly smooth roadway will exert a varying force into the vehicle that will repeat every rotation of the tire. This variation is the source of various ride disturbances. Both tire and car makers seek to reduce such disturbances in order to improve the dynamic performance of the vehicle.

] Tire uniformity parameters Axes of measurement

Force Variation Axes Tire forces are divided into three axes: radial, lateral, and tangential (or fore-aft). The radial axis runs from the tire center toward the tread, and is the vertical axis running from the roadway through the tire center toward the vehicle. This axis supports the vehicle’s weight. The lateral axis runs sideways across the tread. This axis is parallel to the tire mounting axle on the vehicle. The tangential axis is the one in the direction of the tire travel. Radial Force Variation Insofar as the radial force is the one acting upward to support the vehicle, radial force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the force will change. Consider a tire supporting a 1,000 pound load running on a perfectly smooth roadway. It would be typical for the force to vary up and down from this value. A variation between 995 pounds and 1003 pounds would be characterized as an 8 pound radial force variation, or RFV. RFV can be expressed as a peak-to-peak value, which is the maximum minus minimum value, or any harmonic value as described below.

Harmonic analysis

Harmonic Waveform Analysis RFV, as well as all other force variation measurements, can be shown as a complex waveform. This waveform can be expressed according to its harmonics by applying Fourier Transform (FT). FT permits one to parameterize various aspects of the tire dynamic behavior. The first harmonic, expressed as RF1H (radial force first harmonic) describes the force variation magnitude that exerts a pulse into the vehicle one time for each rotation. RF2H expresses the magnitude of the radial force that exerts a pulse twice per revolution, and so on. Often, these harmonics have known causes, and can be used to diagnose production problems. For example, a tire mold installed with 8 bolts may thermally deform as to induce an eighth harmonic, so the presence of a high RF8H would point to a mold bolting problem. RF1H is the primary source of ride disturbances, followed by RF2H. High harmonics are less problematic because the rotating speed of the tire at highway speeds times the harmonic value makes disturbances at such high frequencies that they are damped or overcome by other vehicle dynamic conditions. Lateral Force Variation Insofar as the lateral force is the one acting side-to-side along the tire axle, lateral force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the lateral force will change. As the tire rotates it may exert a lateral force on the order of 25 pounds, causing steering pull in one direction. It would be typical for the force to vary up and down from this value. A variation between 22 pounds and 26 pounds would be characterized as a 4 pound lateral force variation, or

LFV. LFV can be expressed as a peak-to-peak value, which is the maximum minus minimum value, or any harmonic value as described above. Lateral force is signed, such that when mounted on the vehicle, the lateral force may be positive, making the vehicle pull to the left, or negative, pulling to the right. Tangential force variation Insofar as the tangential force is the one acting in the direction of travel, tangential force variation describes the change in this force as the tire rotates under load. As the tire rotates and spring elements with different spring constants enter and exit the contact area, the tangential force will change. As the tire rotates it exerts a high traction force to accelerate the vehicle and maintain its speed under constant velocity. Under steady-state conditions it would be typical for the force to vary up and down from this value. This variation would be characterized as TFV. In a constant velocity test condition, TFV would be manifested as a small speed fluctuation occurring every rotation due to the change in rolling radius of the tire. TFV is not measured in production testing. Conicity Conicity is a parameter based on lateral force behavior. It is the characteristic that describes the tire’s tendency to roll like a cone. This tendency affects the steering performance of the vehicle. In order to determine Conicity, lateral force must be measured in both clockwise (LFCW) and counterclockwise direction (LFCCW). Conicity is calculated as one-half the difference of the values, keeping in mind that CW and CCW values have opposite signs. Conicity is an important parameter is production testing. In many high-performance cars, tires with equal conicity are mounted on left and right sides of the car in order that their conicity effects will cancel each other and generate a smoother ride performance, with little steering effect. This necessitates the tire maker measuring conicity and sorting tires into groups of like-values. Plysteer Plysteer is a parameter based on lateral force behavior. It is the characteristic that is usually described as the tire’s tendency to “crab walk”, or move sideways while maintaining a straight-line orientation. This tendency affects the steering performance of the vehicle. In order to

determine Plysteer, lateral force must be measured in both clockwise (LFCW) and counterclockwise direction (LFCCW). Plysteer is calculated as one-half the sum of the values, keeping in mind that CW and CCW values have opposite signs. Plysteer is not measured in production testing. Radial runout Radial Runout (RRO) describes the deviation of the tire’s roundness from a perfect circle. RRO can be expressed as the peak-to-peak value as well as harmonic values. RRO imparts an excitation into the vehicle in a manner similar to radial force variation. RRO is most often measured near the tire’s centerline, although some tire makers have adopted measurement of RRO at three positions: left shoulder, center, and right shoulder. Lateral runout Lateral Runout (LRO) describes the deviation of the tire’s sidewall from a perfect plane. LRO can be expressed as the peak-to-peak value as well as harmonic values. LRO imparts an excitation into the vehicle in a manner similar to lateral force variation. LRO is most often measured in the upper sidewall, near the tread shoulder. Sidewall bulge and depression Given that the tire is an assembly of multiple components that are cured in a mold, there are many process variations that cause cured tires to be classified as rejects. Bulges and depressions in the sidewall are such defects. A bulge is a weak spot in the sidewall that expands when the tire is inflated. A depression is a strong spot that does not expand in equal measure as the surrounding area. Both are deemed visual defects. Tires are measured in production to identify those with excessive visual defects. Bulges may also indicate defective construction conditions such as missing cords, which pose a safety hazard. As a result, tire makers impose stringent inspection standards to identify tires with bulges. Sidewall Bulge and Depression is also referred to as bulge and dent, and bumpy sidewall. Tire uniformity measurement machines Tire Uniformity Machines are special-purpose machines that automatically inspect tires for the tire uniformity parameters described above. They consist of several subsystems, including tire handling, chucking,

measurement rims, bead lubrication, inflation, load wheel, spindle drive, force measurement, and geometry measurement. The tire is first centered, and the bead areas are lubricated to assure a smooth fitment to the measurement rims. The tire is indexed into the test station and placed on the lower chuck. The upper chuck lowers to make contact with the upper bead. The tire is inflated to the set point pressure. The load wheel advances to contact the tire and apply the set loading force. The spindle drive accelerates the tire to the test speed. Once speed, force, and pressure are stable, load cells measure the force exerted on the load wheel by the tire. The force signal is processed in analog circuitry, and then analyzed to extract the measurement parameters. Tires are marked according to various standards that may include RFV high point angle, side of positive conicity, and conicity magnitude. Other types of uniformity machines There are numerous variations and innovations among several tire uniformity machine makers. The standard test speed for tire uniformity machines is 60 rpm of a standard load wheel that approximates 5 miles per hour. High speed uniformity machines are used in research and development environments that reach 250 km/h and higher. High speed uniformity machines have also been introduced for production testing. Machines that combine force variation measurement with dynamic balance measurement are also in use. Tire uniformity correction Radial and Lateral Force Variation can be reduced at the Tire Uniformity Machine via grinding operations. In the Center Grind operation, a grinder is applied to the tread center to remove rubber at the high point of RFV. On the top and bottom tread shoulder grinders are applied to reduce the size of the road contact area, or fooprint, and the resulting force variation. Top and bottom grinders can be controlled independently to reduce conicity values. Grinders are also employed to correct or excessive radial runout. Geometry measurement systems Radial Runout, Lateral Runout, Conicity, and Bulge measurements are also performed on the tire uniformity machine. There are several generations of

measurement technologies in use. These include Contact Stylus, Capacitive Sensors, Fixed-Point Laser Sensors, and Sheet-of-Light Laser Sensors. Contact stylus Contact Stylus technology utilizes a touch-probe to ride along the tire surface as it rotates. Analog instrumentation senses the movement of the probe, and records the runout waveform. When used to measure radial runout, the stylus is fitted to a large-area paddle that can span the voids in the tread pattern. When used to measure lateral runout on the sidewall the stylus runs in a very narrow smooth track. The contact stylus method is one of the earliest technologies, and requires considerable effort to maintain its mechanical performance. The small area-of-interest in the sidewall area limits the effectiveness in discerning sidewall bulges and depressions elsewhere on the sidewall. Capacitive sensors Capacitive Sensors generate a dielectric field between the tire and sensor. As the distance between the tire and the sensor varies, the voltage and/or current properties of the dielectric field change. Analog circuitry is employed to measure the field changes and record the runout waveform. Capacitive sensors have a larger area-of-interest, on the order of 10mm compared to the very narrow contact stylus method. The capacitive sensor method is one of the earliest technologies, and has proven highly reliable; however, the sensor must be positioned very close to the tire surface during neasurement, so collisions between tire and sensor have led to longterm maintenance problems. The 10mm area-of-interest also means that bulge measurement is limited to a small portion of the tire. Capacitive sensors employ void filtering to remove the effect of the voids between the tread lugs in radial runout measurement, and letter filtering to remove the effect of raised letters and ornamentation on the sidewall. Fixed-point laser sensors Fixed-Point Laser Sensors were developed as an alternative to the above methods. Lasers combine the narrow-track area-of-interest with a large stand off distance from the tire. In order to cover a larger area-of-interest, mechanical positioning systems have been employed to take readings at multiple positions in the sidewall. Fixed-Point Laser sensors employ void

filtering to remove the effect of the voids between the tread lugs in radial runout measurement, and letter filtering to remove the effect of raised letters and ornamentation on the sidewall.