Last Updated on 06.08.2024 by hrushetskyy
TIRE LIFE CYCLE
An understanding to the role of tires involves an analysis of product life cycles and specifically the tire life cycles.
A product life cycle is a forecast of product growth and length of Life based on an S-curve analysis. It depicts in effect the life of a product in a time frame. Frequently a product life cycle is projected for a new product prior to introduction. It is akin to writing an obituary at birth.
Product life cycle is related to technological forecasting and long-range planning. Life cycle analysis is used to anticipate trends and pinpoint needs. It makes possible incremental analysis (cost of growth).
Some products have life cycles of several months (hula hoops) others have life cycles of decades (autos tires aspirin nylon television etc.).
Product Life Cycle
The life cycle of a product can be generally divided into five categories.
The first stage is experimentation and development. At this point the product is a technical innovation that has been subjected to a market assessment.
Second is the commercialization stage. This is the period of product introduction to the marketplace. Needless to say many products do not survive this stage. The concept of customer orientation for example has been developed to decrease this failure rate.
Stage III is the period of growth. Product demand is increasing. The size of the total market is expanding. Often shortages occur. The presence of competitors accelerates product differentiation. Brand preference makes an appearance.
Next the product reaches maturity (Stage IV). Demand is leveling off and the market is becoming saturated. Sales growth parallels population growth. There are fierce efforts to hold brand preference. Often this stage includes product differentiation to a fine degree; a multitude of product claims; aggressive promotional practices; intensive distribution efforts; sophisticated advertising techniques; ingenious packaging; emphasis on customer service; and sometimes lowering of prices. The maturity stage of a product can be brief in time or may last for many years.
Finally the product reaches a period of decline (Stage V). The product begins to lose consumer appeal. Overcapacity exists and plants are closed. Prices deteriorate.
The demand criteria for each stage are given below:
I) Experimentation and Development: little growth
II) Commercialization: > 10-percent growth per year
III) Growth: 3- to 10-percent growth per year
IV) Maturity: 0-to 3-percent growth per year
V) Decline: negative growth
Tire Life Cycle
More than 5 billion tires have been produced in the USA from 1900 to 1972. In constructing a tire life cycle the tire demand curve has been adjusted to eliminate the depression and war years 1929 to 1948. The tire demand curve has been superimposed over the classical product life cycle curve. As can be seen tires follow the classical curve to a remarkable degree. Analysis of the tire life cycle leads to the following conclusion: Tires are currently at the middle of the growth period (Stage III) of the product life cycle. Demand growth is about 6 percent per year.
It should be noted that a product life cycle for an industry is not necessarily identical to product life cycles for individual companies within the industry.
Product Demand
A forecast of growth trends in the product life cycle requires an analysis of the determinants of demand. The basic factors affecting product demand can be discussed within the following general groupings: product mission technology fashion and product-market structure. Each of these categories will be discussed relative to tires.
Product Mission: A product seeking to assume the role of tires would of necessity be required to have load-carrying capacity have cushioning ability transmit driving and braking torque produce cornering force provide flotation provide lateral stability resist abrasion provide steering response have low rolling resistance and be durable and safe. Add to this fact that a sophisticated personal transportation system has been developed around tires and one can conclude that there is not an immediate competitive threat from a substitute product.
Technology: Maintaining a viable product is essential to product growth. The demand trend can be a function of the introduction rate of product improvements. This can be reflected in new uses for the product or modified products to better satisfy current requirements. Thus the history of innovation in a product is significant. Tires are constantly being improved in an evolutionary manner to meet ever-increasing customer demands. Some of these changes appear revolutionary in retrospect. Basic tire advances appear to occur every decade. In the teens carbon black was adopted in rubber compounds. In the 1920’s layers of parallel cord fabric were introduced. The 1930’s saw the appearance of balloon tires.
In the war years synthetic tires were born. Tubeless tires were developed in the 1950’s. Belted tires made a widespread appearance in the sixties.
Analysis of innovations in a product can lead to sub-life cycles within the major product life cycle. Although the tire life cycle is in Stage III sub-cycles can be identified in all stages.
There are three basic types of tires in using today: bias radial and bias/belted. An analysis of bias passenger tires as a sub-cycle indicates that this construction is in Stage V (decline).
Fashion: Product life cycles affected by fashion are usually characterized by a more rapid growth stage a shorter maturity stage followed by rapid decline. Tires are generally unaffected by fashion. Should a fashion occur it will affect product mix only.
Product-Market Structure: The changing nature of the product market structure will affect product demand. Close attention must be paid to the demand for the primary product (motor vehicles) that uses tires.
Therefore, different tire manufacturers, such as: Milestar, Westlake, Nokian and others, will depend on the demand for the vehicles for which they produce tires.
Tire Demand Forecast
A tire demand forecast from the tire life cycle indicates a continued expansion for tires.
This can be expected since more leisure time has resulted in an increasing mobility of Americans. A study by the U.S. Department of Commerce forecasts an enormous travel expansion in this country between now and the year 2000. The bulk of this travel will be by automobile.
A major factor in this projection is the 42500 miles of interstate highway system. The interstate system represents less than 1 percent of the total highways but accounts for nearly 20 percent of the total vehicle mileage traveled.
TIRE REINFORCING SYSTEMS
A tire is a cord/rubber composite. The tire composite is in the form of a network of cord structures arranged in a parallel configuration and imbedded in a rubber matrix. Rubber as used here is defined as an elastomer compounded with carbon black and various chemical ingredients.
The cord reinforces the rubber much as steel strengthens concrete. However tire cords are very unique materials of construction due to their extremely high fatigue resistance. Tire cords give the tire shape size stability bruise resistance fatigue resistance and load-carrying capacity.
The stringent demands of tire service have limited the types of cords suitable for tires to six. The first pneumatic tires were reinforced with cotton cellulose. In the early days the cotton fabric was square-woven. One of the important advances in tire development occurred about 1920 when cotton cord replaced square-woven fabric. The use of plies of cord added tremendous durability and resiliency to the tire. Cotton continued to be the only tire fiber in the USA until 1938 when rayon regenerated cellulose was introduced. In 1942 nylon became available for military tires and in 1947 was introduced to the motoring public.
In 1955 wire made an appearance in USA-built tires although it had been in use in Europe since 1937. In 1962 polyester was introduced. Then in 1967 fiberglass joined this select group.
Terminology
Tire cord technology utilizes a special terminology.
Filament: A filament is the smallest continuous element of a tire cord material and is characterized by a high ratio of length to thickness.
Strand: A strand is an assembly of continuous filaments (often called a yarn with textile materials).
Tire Cord: Classically a tire cord is a twisted or formed structure composed of two or more strands; generally the term is applied to the structure whatever form it may be as used in a tire.
Warp: The warp is the cord in a tire fabric that runs lengthwise.
Filling: The filling is the light thread that is placed at right angles to the warp (filling is often called the pick).
Denier: Denier is a unit of measurement for textile cords. Denier is defined as the weight in grams of 9000 meters of the material. Therefore denier is a weight-per-unit-length measurement, the higher the denier the larger the cord.
Twist: Twist is the number of turns per unit of length in a cord. A cord has S twist if the spirals turn to the right or clockwise from top to bottom when the cord is held vertically. A cord has Z twist if the spirals are counterclockwise.
Strength: Strength is the ability of a cord to withstand the ultimate tensile load or force required for rupture. Quite frequently tire cord strengths are expressed in terms of grams per denier. This is called the tenacity of the cord.
V Strength (lbs) x 453.6
Tenacity (GPD) = 0)
Filament Forming
Rayon: The advent of the modern synthetic tire begins with rayon. Since cotton is a natural fiber its structure is limited. Being man made however rayon could be engineered for tires. Rayon is an organic fiber and can be described by the following Formula:Basically rayon is regenerated cellulose. It is manufactured as continuous filament by a wet-spinning process.
Sodium hydroxide is added to wood pulp in a steeping press to form alkali cellulose. The cellulose is shredded aged and treated with carbon disulfide to form cellulose xanthate. The xanthate is then treated with diluted caustic soda to form viscose. After ripening the viscose is filtered and goes to the spinning machine. The viscose is extruded through spinnerets into a regenerating bath. The yarn is composed of many tiny filaments. Each filament is approximately .010 mm in diameter. The yarn is then washed and slashed and finish is added. Finally the yarn is beamed for shipment.
A word should be said about the finish (or lubricant) on a tire yarn. The type of finish oil applied to the yarn can determine (to a degree) cord strength fatigue and adhesion properties.
Rayon tire yarn is available today in three deniers: 1110 yarn 1650 yarn and 2200 yarn. There are three producers of rayon tire yarn in the USA: American Enka Corporation Beau-nit and AVD division of FMC. Rayon has been used in tires for 35 years.
Nylon: Nylon is a synthetic thermoplastic organic fiber derived from petroleum as contrasted with rayon which is a man-made fiber but not a true synthetic. Chemically nylon tire yarn is a continuous filament aliphatic polyamide.
Although there are hundreds of nylon polymers only two are in commercial use in tires: nylon 66 and nylon 6. Both have the same empirical formula (C^Hj JON) n. Nylon 66 is composed of two recurring units with six carbon atoms (derived from adipic-acid and hexamethylenediamine). Nylon 6 is composed of one recurring unit with six carbon atoms (derived from caprolactam). Nylon 66 is manufactured as follows:
Cyclohexane and ammonia are the basic raw materials. Cyclohexane is oxidized in the presence of a catalyst to form adipic acid. Part of the adipic acid is vaporized over a catalyst and sprayed into superheated ammonia. Adiponitrile is formed. The Adiponitrile is hydrogenated over a catalyst and reduced to hexamethylene diamine. Equal molar quantities of adipic and hexamethylene diamine are dissolved in water to give a nylon salt.
This salt is concentrated and then polymerized to a suitable molecular chain length. The molten polymer is then extruded through stainless steel spinnerets to form filaments. This is called spinning. Each filament is approximately .024 mm in diameter. The filaments are cooled finish is applied and they are combined into a yarn. The nylon yarn is then drawn (or stretched) approximately 500 percent. The drawing takes place suddenly at a “neck point.” This drawing operation orients the molecules in the axial direction and regulates the crystalline. An X-ray diagram of an undrawn nylon yarn is shown on the left and a drawn oriented yarn on the right. After drawing the yarn is beamed for shipment.
Nylon 6 is manufactured as follows: The basic raw material is caprolactam which in turn is synthesized from Cyclohexane. The caprolactam is melted and five percent water is added. These react to form aminocaproic acid. The aminocaproic acid polymerizes to form nylon 6. The water is removed as the reaction progresses.
The molten polymer is then extruded to form filaments in much the same manner as in nylon 66. Nylon tire yarn is available in four deniers: 840 yarns 1050 yarn 1260 yarn and 1680 yarn. There are five producers of nylon tire yarn in the USA: Allied Chemical DuPont Fiber Industries Firestone and Monsanto.
Polyester: Polyester is also a synthetic thermoplastic continuous filament fiber derived from petroleum and is manufactured in a melt process similar to nylon. Polyester is an organic fiber that differs chemically from nylon however in that polyester contains aromatic groups (or ring structures) in the fiber backbone.
As with nylon there are hundreds of polyester polymers. The only polyester used in tires is polyethylene terephthalate.
-O-(CH2) -O-C -C-
The starting raw materials for polyesters are ethylene glycol and dim-ethyl terephthalate (DMT). In some processes terephthalic acid (TPA) is used in lieu of DMT), the DMT is melted with glycol and an ester interchange takes place.
The glycol ester is then polymerized through poly-condensation to polyethylene terephthalate. Molten polymer is extruded through stainless steel spinnerets to form filaments. Each filament is approximately .024 mm in diameter. The filaments are cooled finish is applied and they are combined into a yarn. The polyester yarn is then drawn to the desired orientation and crystalline. After drawing the yarn is beamed for shipment.
Polyester tire yarn is available in four deniers: 1000 yarn 1300 yarn 1600 yarn and 2000 yarn. There are eight polyester tire yarn producers: Allied Chemical Beau-nit DuPont Fiber Industries Firestone Goodyear, IRC Fibers and Monsanto.
Fiberglass: Considerable effort was expended by the tire industry since the thirties to develop fiberglass as a tire cord material. Fiberglass was introduced commercially into tire belts in 1967.
Fiberglass is an inorganic fiber. The fiberglass currently being used for tire cord is E-glass. A typical composition of glass for tire cord is as follows:
| Silicon dioxide | 53% |
| Calcium oxide | 21 |
| Aluminum oxide | 15 |
| Boron oxide | 9 |
| Magnesium oxide | 0.3 |
| other oxides | 1.7 |
Thus fiberglass is a lime-alumina-borosilicate glass consisting of a three-dimensional silica network containing oxides.
Continuous filament fiberglass is manufactured as follows: Sand clay limestone and borax are fed from raw material hoppers into a blender. After blending the mix moves to a direct gas-fired furnace for melting. The molten glass at 2500 deg F is gravity fed through a platinum rhodium bushing where strands of continuous glass filaments are attenuated or drawn. Filament diameters are approximately .009 mm. The filaments are then solidified by a water quench. Next a coupling agent and forming size (binder) is applied to the surface of the glass filaments as the strand passes to a high-speed take-up.
Fiberglass for tires is impregnated by the fiberglass manufacturers before shipment to a fabric mill. Fiberglass is used in tires in the form of a strand with low twist and is not normally twisted into a cord structure.
Fiberglass is produced in three text sizes: 330 strand 460 strands and 660 strands. Tex is a metric system to replace the use of denier. Tex is equal to denier divided by nine. That is text is the number of grams per 1000 meters of yarn. There are two producers of fiberglass for tires in the USA. These are Owens Corning Fiberglas and PPG Industries.
Wire: Wire has been used in tires in this country since 1955. The usage has been small but consistent. Recently wire has gained wide interest in all types of tires. Like fiberglass wire is an inorganic material.
Wire manufacture begins with 6.35-mm-diameter high-carbon steel rods. Typical specification for the steel for tire cord is as follows:
| Carbon | .7% |
| Manganese | .5 |
| Silicon | .3 |
| Chromium | .05 max |
| Copper | .02 max |
| Sulfur | .03 max |
| Phosphorus | .03 max |
The rod is cleaned in acid bath rinsed and lime coated. Next the rod is drawn to reduce the diameter from 6.35 mm to 2 mm. The wire is then heat treated (called patenting) to change the grain structure. Further drawing reduces the diameter to .80 mm. The wire is then further heat treated and brass plated. Brass weight is about 7 gm per kg of steel. The brass composition is typically 70 percent copper and 30 percent zinc. The brass plating enhances the adhesion of wire cord to rubber and facilitates drawing to fine diameters. The brass plated wire is drawn to a final diameter in the range of .20 mm. Drawing is accomplished with tungsten carbide and diamond dies. The drawn wire filaments are then combined to form a strand. Several strands are combined to obtain the final wire tire cord.
In some cases an additional filament is spirally wrapped around the entire cord structure. This spiral wrap (a) resists compressive forces when the tire enters the footprint (b) improves cord tension uniformity (c) enhances mechanical adhesion (d) prevents flaring of the strands when cut and (e) reduces cord liveliness for better factory handling.
The nomenclature for this wire tire cord is described as:
3 + 5 x 7 x .20 + 1 x .20
That is the cord is composed of a core containing one bundle of three filaments of .20 mm gauge. The core is surrounded by five strands each containing seven filaments of .20 mm gauge. The entire structure is surrounded by a wrap of one filament of .20 mm gauge.
The generalized equation (2) is:
Core + intermediate part + outermost part + wrap
SxFxD+SxFxD +SxFxD + FxD (2)
Where
S = number of strands (when S = 1 it may be omitted)
F = number of filaments in each strand
D = diameter of filaments (millimeters)
In general the cord description starts with the innermost section and proceeds outward. Each layer is separated with a plus (+) sign. If the diameter is the same for two or more components the diameter is omitted except for the last component. If a strand is a single filament the numerical designation is omitted.
Quite complex cord structures can be assembled. Wire cords for passenger tire belts generally contain from 3 to 10 filaments. Large tires utilize wire cords with up to 50 filaments. In large earthmover tires one ply of steel can replace up to 40 plies of conventional textile.
The only producer of wire tire cord in the USA is National Standard. Much of the wire tire cord used in the USA is imported. Monsanto has an experimental program underway to spin steel fibers from the molten state using in-viscid technology.
Other Cords: A new tire cord material receiving wide attention is Fiber B. Fiber B is a fully aromatic continuous filament organic fiber produced by DuPont. Fiber B is characterized by extremely high strength and modulus.
Tire Cord Characteristics
Characterization of tire cords has become sophisticated in recent years. Analysis has been undertaken from a mechanical chemical thermal and energy basis.
Tire Cord Usage Pattern
This chart tabulates usage by type of tire (bias radial bias/belted) and application (passenger truck off-the-road farm and aircraft).
An asterisk indicates the predominant fiber used in each line of tire. This table indicates that tire technology is a specific engineering of different textiles for various types of tires. Note that the elastic organic fibers such as nylon are not generally used in belts. On the other hand inorganic fibers such as wire are not used in the carcass of bias or bias/belted tires.
Tire Cord Characteristics
| STRENGTH | ELASTICITY | BIREFRINGENCE |
| ELONGATION | ORIENTATION | THERMAL ANALYSIS |
| MODULUS | SHRINKAGE FORCE | MOISTURE REGAIN |
| YIELD POINT | IR ANALYSIS | HELIX ANGLE |
| DENIER | SOLVATION | FINISH COMPOSITION |
| TWIST | STRESS DECAY | ELASTIC MODULUS |
| ADHESION | LOOP STRENGTH | COEFFICIENT OF |
| IMPACT RESISTANCE | COMPRESSIBILITY | RETRACTION |
| CREEP | CONSTRUCTION | STORAGE MODULUS |
| LASE | BRITTLE POINT | COMPLEX MODULUS (E* |
| COMPLIANCE | SPECIFIC HEAT | DYNAMIC ADHESION |
| INTRINSIC VISCOSITY | STIFFNESS | BREAKING LENGTH |
| DIP PICKUP | DURABILITY | TOUGHNESS |
| RESILIENCE | HEAT RESISTANCE | FINISH CONTENT |
| GROWTH | LOSS TANGENT | ABRASION RESISTANCE |
| POISSON’S RATIO | STRAIN | TENSILE STRENGTH |
| HYSTERESIS | FATIGUE | MELTING POINT |
| THERMAL | ||
| WORK-TO-BREAK | RESERVOIR | CONDUCTIVITY |
| STABILITY | DIFFUSION | LOSS MODULUS |
| INCH-STRENGTH | DYNAMIC MODULUS | INTERNAL FRICTION |
| GAUGE | DIP PENETRATION | RESONANCE |
| FREQUENCY | ||
| SPECIFIC GRAVITY | DAMPING | S-O-T TEMPERATURE |
| ELASTIC LIMIT | HYDROLYSIS | SOUND TRANSMISSION |
| STRESS | TEX | HEAT GENERATION |
| UNIFORMITY | TORSIONAL MODULUS | BRUSH |
| CRYSTALLINITY | SOFTENING POINT | PLATING |
| WET STRENGTH | ENTROPY OF FUSION | LAY |
| SHRINKAGE | STAINING | FLARE |
| HOT LOAD | TENACITY | WILDNESS |
| FLATSPOTTING | OXIDATION | STRAIGHTNESS |
| SONIC MODULUS | CATENARY |
USA Tire Cord Usage Pattern
| TIRE TYPE BIAS | RADIAL | BIAS/BELTED | |||
| Carcass | Belt | Carcass | Belt | ||
| Passenger | Rayon | Rayon’ | Rayon | Rayon | Rayon |
| Nylon | Polyester | Wire* | Nylon | Fiberglass* | |
| Polyester’ | Polyester* | Wire | |||
| Truck | Nylon* | Polyester | Wire* | Nylon* | Fiberglass* |
| Polyester | Wire* | Polyester | Wire | ||
| Off-the-road | Nylon* | Wire* | Wire* | Nylon “ | Wire* |
| Polyester | |||||
| Farm | Rayon | ||||
| Nylon* | |||||
| Polyester | |||||
| indicates predominant fiber used in USA. | |||||
| Aircraft | Nylon* | ||||
Additional statistics used in conjunction with Table permit a complete understanding of the tires produced in the USA. The figures are given below:
Tire Cord (All Tires)
| Rayon | 15% |
| Nylon | 42 |
| Polyester | 32 |
| Fiberglass | 6 |
| Wire | 5 |
Tire Type (All Tires)
| Bias | 50% | |
| Radial | 10 | |
| Bias/Belted | 40 | |
| Tire Application | 78% | |
| Passenger | 13 | |
| Truck and off-the-road | 2 | Farm |
| Aircraft | <1 | Other |
| 6 |
Projection of Tire Reinforcing Materials
More than one billion pounds of tire cord are used throughout the world each year. About half is used in the USA.
Tire cord consumption can be characterized by individual life cycles. It should be noted that tire cord usage has been characterized by a rising peaking and declining pattern. In 1935 only cotton was used in tires. Cotton passed through stages of growth maturity and decline finally phasing out completely. Rayon was introduced in 1938 and is in Stage V (decline) today. Nylon was commercialized in 1947 and is now in Stage IV (maturity). Polyester is in Stage III (growth). Similar cycles can be constructed for fiberglass and wire cord. Analyzing sub-cycle trends is important. A study of the tire cord sub-cycle indicates that a new fiber will be introduced before 1976.
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