Engineering Materials

General Physical Properties

Density

Density is one of the most fundamental physical properties of any material. It is defined as the ratio of an objects mass to its volume. Because most designs are limited by either size and or weight density is an important consideration in many calculations.

Density is a function of the mass of the atoms making up the materials and the distance between them. Massive, closely packed atoms characterize high density materials such as Tungsten or Neptunium. In contrast light, relatively distant atoms compose low density materials such as Beryllium or Aluminum. Density on a macroscopic level is also a function of the microscopic structure of a material. A relatively dense material may be capable of forming a cellular structure such as a foam which can be nearly as strong and much less dense than the bulk material. Composites including natural constituents such as wood and bone, for example, generally rely on microscopic structure to achieve densities far lower than common monolithic materials.

Availability/Manufacturability

Availability and manufacturability requirements are often unseen limiting factors in materials selection. The importance of a material being available is obvious. Materials which are not available cannot be used. The importance of processibility is not always so obvious.

Any other desirable qualities are useless if a material cannot be processed into the shape required to perform its function. Most engineering materials in use today have well known substitutes which would perform better and often at lower cost but processes for forming, cutting, machining, joining, etc. are not available or commercially viable. There is often a period of time after a new material is introduced during which its application is severely limited while processing techniques are developed which facilitate its use.

Cost

A materials cost is also generally a limiting factor. While cost is universally recognized and perhaps the easiest of all properties to understand there are specific cost considerations for materials selection. Just as materials and their processing go hand in hand so do material costs and processing costs. Understanding the entire processing sequence is critical to accurately evaluating the true cost of a material.

Appearance

Because the appearance of many mechanical components seems fairly trivial it is also easy to overlook its importance in the marketing and commercial success of a product.

Mechanical Properties

The mechanical properties of a material describe how it will react to physical forces. Mechanical properties occur as a result of the physical properties inherent to each material, and are determined through a series of standardized mechanical tests.

Strength

Strength has several definitions depending on the material type and application. Before choosing a material based on its published or measured strength it is important to understand the manner in which strength is defined and how it is measured. When designing for strength, material class and mode of loading are important considerations.

For metals the most common measure of strength is the yield strength. For most polymers it is more convenient to measure the failure strength, the stress at the point where the stress strain curve becomes obviously non-linear. Strength, for ceramics however, is more difficult to define. Failure in ceramics is highly dependent on the mode of loading. The typical failure strength in compression is fifteen times the failure strength in tension. The more common reported value is the compressive failure strength.

Elastic limit

The elastic limit is the highest stress at which all deformation strains are fully recoverable. For most materials and applications this can be considered the practical limit to the maximum stress a component can withstand and still function as designed. Beyond the elastic limit permanent strains are likely to deform the material to the point where its function is impaired.

Proportional limit

The proportional limit is the highest stress at which stress is linearly proportional to strain. This is the same as the elastic limit for most materials. Some materials may show a slight deviation from proportionality while still under recoverable strain. In these cases the proportional limit is preferred as a maximum stress level because deformation becomes less predictable above it.

Yield Strength

The yield strength is the minimum stress which produces permanent plastic deformation. This is perhaps the most common material property reported for structural materials because of the ease and relative accuracy of its measurement. The yield strength is usually defined at a specific amount of plastic strain, or offset, which may vary by material and or specification. The offset is the amount that the stress-strain curve deviates from the linear elastic line. The most common offset for structural metals is 0.2%.

Ultimate Tensile Strength

The ultimate tensile strength is an engineering value calculated by dividing the maximum load on a material experienced during a tensile test by the initial cross section of the test sample. When viewed in light of the other tensile test data the ultimate tensile strength helps to provide a good indication of a

material's toughness but is not by itself a useful design limit. Conversely this can be construed as the minimum stress that is necessary to ensure the failure of a material.

True Fracture Strength

The true fracture strength is the load at fracture divided by the cross sectional area of the sample. Like the ultimate tensile strength the true fracture strength can help an engineer to predict the behavior of the material but is not itself a practical strength limit. Because the tensile test seeks to standardize variables such as specimen geometry, strain rate and uniformity of stress it can be considered a kind of best case scenario of failure.

Ductility

Ductility is a measure of how much deformation or strain a material can withstand before breaking. The most common measure of ductility is the percentage of change in length of a tensile sample after breaking. This is generally reported as % El or percent elongation. The R.A. or reduction of area of the sample also gives some indication of ductility.

Toughness

Toughness describes a material's resistance to fracture. It is often expressed in terms of the amount of energy a material can absorb before fracture. Tough materials can absorb a considerable amount of energy before fracture while brittle materials absorb very little. Neither strong materials such as glass or very ductile materials such as taffy can absorb large amounts of energy before failure. Toughness is not a single property but rather a combination of strength and ductility.

The toughness of a material can be related to the total area under its stress-strain curve. A comparison of the relative magnitudes of the yield strength, ultimate tensile strength and percent elongation of different material will give a good indication of their relative toughness. Materials with high yield strength and high ductility have high toughness. Integrated stress-strain data is not readily available for most materials so other test methods have been devised to help quantify toughness. The most common test for toughness is the Charpy impact test.

In crystalline materials the toughness is strongly dependent on crystal structure. Face centered cubic materials are typically ductile while hexagonal close packed materials tend to be brittle. Body centered cubic materials often display dramatic variation in the mode of failure with temperature. In many materials the toughness is temperature dependent. Generally materials are more brittle at lower temperatures and more ductile at higher temperatures. The temperature at which the transition takes place is known as the DBTT, or ductile to brittle transition temperature. The DBTT is measured by performing a series of Charpy impact tests at various temperatures to determine the ranges of brittle and ductile behavior. Use of alloys below their transition temperature is avoided due to the risk of catastrophic failure.

Fatigue ratio

The dimensionless fatigue ratio f is the ratio of the stress required to cause failure after a specific number of cycles to the yield stress of a material. Fatigue tests are generally run through 10 7 or 108

cycles. A high fatigue ratio indicates materials which are more susceptible to crack growth during cyclic loading.

Loss coefficient

The loss coefficient is an other important material parameter in cyclic loading. It is the fraction of mechanical energy lost in a stress strain cycle. The loss coefficient for each material is a function of the frequency of the cycle. A high loss coefficient can be desirable for damping vibrations while a low loss coefficient transmits energy more efficiently. The loss coefficient is also an important factor in resisting fatigue failure. If the loss coefficient is too high, cyclic loading will dissipate energy into the material leading to fatigue failure.

Thermal Properties

Thermal conductivity

The thermal conductivity is the rate of heat transfer through a material in steady state. It is not easily measured, especially for materials with low conductivity but reliable data is readily available for most common materials.

Thermal diffusivity

The thermal diffusivity is a measure of the transient heat flow through a material.

Specific heat

The specific heat is a measure of the amount of energy required to change the temperature of a given mass of material. Specific heat is measured by calorimetry techniques and is usually reported both as C V, the specific heat measured at constant pressure, or CP, the specific heat measured at constant pressure.

Melting point

The melting point is the temperature at which a material goes from the solid to the liquid state at one atmosphere. The melting temperature is not usually a design criteria but it offers important clues to other material properties.

Glass transition temp

The glass transition temperature, or Tg is an important property of polymers. The glass transition temperature is a temperature range which marks a change in mechanical behavior. Above the glass transition temperature a polymer will behave like a ductile solid or highly viscous liquid. Below T g the material will behave as a brittle solid. Depending on the desired properties materials may be used both above and below their glass transition temperature.

Thermal expansion coefficient

The thermal expansion coefficient is the amount a material will change in dimension with a change in temperature. It is the amount of strain due to thermal expansion per degree Kelvin expressed in units of K-1. For isotropic materials " is the same in all directions, anisotropic materials have separate "s reported for each direction which is different.

Thermal shock resistance

Thermal shock resistance is a measure of how large a change in temperature a material can withstand without damage. Thermal shock resistance is very important to most high temperature designs. Measurements of thermal shock resistance are highly subjective because if is extremely process dependent. Thermal shock resistance is a complicated function of heat transfer, geometry and material properties. The temperature range and the shape of the part play a key role in the material's ability to withstand thermal shock. Tests must be carefully designed to mimic anticipated service conditions to accurately asses the thermal shock resistance of a material.

Creep resistance

Creep is slow, temperature aided, time dependent deformation. Creep is typically a factor in materials above one third of their absolute melting temperature or two thirds of their glass transition temperature. Creep resistance is an important material property in high temperature design, but it is difficult to quantify with a single value. Creep response is a function of many material and external variables, including stress and temperature. Often other environmental factors such as oxidation or corrosion play a role in the fracture process.

Creep is plotted as strain vs. time. A typical creep curve shows three basic regimes. During stage I, the primary or transient stage, the curve begins at the initial strain, with a relatively high slope or strain rate which decreased throughout stage I until a steady state is reached. Stage II, the steady state stage, is generally the longest stage and represents most of the response. The strain rate again begins to increase in stage III and rupture at tR generally follows quickly.

Different applications call for different creep responses. In situations where long life is desired minimum creep rate is the most important material consideration. Testing through stage II should be sufficient for determining minimum creep rate. Is not necessary to proceed all the way to rupture. For this type of test the longer the test the more accurate the creep rate will be. Unfortunately practicality limits most creep tests to times shorter than would be desirable for high accuracy.

For short lived applications such as rocket nozzles the time to failure may be the only consideration. The main issue is whether or not the component fails, not the amount of deformation it may undergo. For this application creep tests may be run to completion but without recording any data but the time to rupture. In this case temperatures may be elevated above expected conditions to provide a margin of safety.

The main objective of a creep test is to study the effects of temperature and stress on the minimum creep rate and the time to rupture. Creep testing is usually run by placing a sample under a constant load at a fixed temperature. The data provided from a complete creep test at a specific temperature, T, and stress includes three creep constants: the dimensionless creep exponent, n, the activation energy Q, and A, a kinetic factor.

Materials: Ferrous Metals

Ferrous Metals

As the most abundant of all commercial metals, alloys of iron and steel continue to cover a broad range of structural applications. Iron ore is readily available, constituting about 5% of the earth's crust, and is easy to convert to a useful form. Iron is obtained by fusing the ore to drive off oxygen, sulfur, and other impurities. The ore is melted in a furnace in direct contact with the fuel using limestone as a flux. The limestone combines with impurities and forms a slag, which is easily removed.

Cast Iron

Cast iron is defined as an iron alloy with more than 2% carbon as the main alloying element. In addition to carbon, cast irons must also contain from 1 to 3% silicon which combined with the carbon give them excellent castability. Cast iron has a much lower melting temperature than steel and is more fluid and less reactive with molding materials. However, they do not have enough ductility to be rolled or forged.

The precipitation of carbon (as graphite) during solidification is the key to cast iron's distinctive properties. The graphite provides excellent machinability (even at wear-resisting hardness levels), damps vibration, and aids lubrication on wearing surfaces (even under borderline lubrication conditions).

Steels and cast irons are both primarily iron with carbon (C) as the main alloying element. Steels contain less than 2% and usually less than 1% C, while all cast irons contain more than 2% C. About 2% is the maximum C content at which iron can solidify as a single phase alloy with all of the C in solution in austenite. Thus, the cast irons by definition solidify as heterogeneous alloys and always have more than one constituent in their microstructure.

In addition to C, cast irons also must contain appreciable silicon (Si), usually from 1–3%, and thus they are actually iron-carbon-silicon alloys. The high C content and the Si in cast irons make them excellent casting alloys.

Range of Compositions for Typical Unalloyed Cast Irons(Values in Percent (%))

Type of Iron

Carbon Silicon Manganese Sulfur Phosphorus

Gray 2.5 - 4.0 1.0 - 3.0 0.2 - 1.0 0.02 - 0.25 0.02 - 1.0

Ductile 3.0 - 4.0 1.8 - 2.8 0.1 - 1.0 0.01 - 0.03 0.01 - 0.1

Compacted Graphite 2.5 - 4.0 1.0 - 3.0 0.2 - 1.0 0.01 - 0.03 0.01 - 0.1

Malleable (Cast White) 2.0 - 2.9 0.9 - 1.9 0.15 - 1.2 0.02 - 0.2 0.02 - 0.2

White 1.8 - 3.6 0.5 - 1.9 0.25 - 0.8 0.06 - 0.2 0.06 - 0.2

Carbon Steel

Carbon steel is a malleable, iron-based metal containing less than 2% carbon (usually less than 1%), small amounts of manganese, and other trace elements. Steels can either be cast to shape or wrought into various mill forms from which finished parts are formed, machined, forged, stamped, or otherwise shaped. Carbon steels are specified by chemical composition, mechanical properties, method of deoxidation, or thermal treatment.

Alloy Steel

Steels that contain specified amounts of alloying elements -- other than carbon and the commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus -- are known as alloy steels. Alloying elements are added to change mechanical or physical properties. A steel is considered to be an alloy when the maximum of the range given for the content of alloying elements exceeds one or more of these limits: 1.65% Mn, 0.60% Si, or 0.60% Cu; or when a definite range or minimum amount of any of the following elements is specified or required within the limits recognized for constructional alloy steels: aluminum, chromium (to 3.99%), cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium or other element added to obtain an alloying effect. Technically, then, tool and stainless steels are alloy steels.

Stainless Steel

Stainless steel is the generic name for a number of different steels used primarily for their resistance to corrosion. The one key element they all share is a certain minimum percentage (by mass) of chromium: 10.5%. Although other elements, particularly nickel and molybdenum, are added to improve corrosion resistance, chromium is always the deciding factor. The vast majority of steel produced in the world is carbon and alloy steel, with the more expensive stainless steels representing a small, but valuable niche market.

Stainless steels are commonly divided into five groups:

1. martensitic stainless steels 2. ferritic stainless steels 3. austenitic stainless steels, 4. duplex (ferritic-austenitic) stainless steels 5. precipitation-hardening stainless steels

Martensitic stainless steels, typified by types 410/420/440, containing about 12Cr and 0.1C wt% as the basic composition. They are not as corrosion resistant as the other classes, but are extremely strong and tough as well as highly machineable, and can be hardened by heat treatment. They contain 11.5 to 18% chromium and significant amounts of carbon. Some grades include additional alloying elements in small quantities.

Ferritic stainless steels contain larger amounts of Cr which stabilizes the ferritic phase. Ferritic stainless steels are highly corrosion resistant, but far less durable than austenitic grades and cannot be hardened

by heat treatment. They contain between 10.5% and 27% chromium and very little nickel, if any. Typical applications may include appliances, automotive and architectural trim (i.e., decorative purposes), as the cheapest stainless steels are found in this family (type 409).

Austenitic stainless steels, such as type 304 typically contain 18Cr and 8Ni wt% (aka 18/8 stainless).. Austenitic stainless steels comprise over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy. Other standard grades have different preferred applications; for example, type 316 which contains up to 3 wt% Mo, offers an improved general and pitting corrosion resistance, making it the material of choice for marine applications and coastal environments.

Duplex stainless steels are two-phase alloys based on the Fe-Cr-Ni system. The specific advantages offered by duplex stainless steels over conventional 300 series stainless steels are strength (approximately twice that of austenitic stainless steels), improved toughness and ductility (compared to ferritic grades), and a superior chloride SCC resistance and pitting resistance. The high yield strength offers designers the use of thin-wall material (which can lead to major reductions in weight) with adequate pressure-containing and load-bearing capacity. Duplex stainless steels have found widespread use in a range of industries, particularly the oil and gas, petrochemical, and pulp and paper industries.

Specialist grades include the precipitation hardened or oxide dispersion strengthened alloys.

Properties of Stainless Steel

(Tabulated in accordance with the Unified Numbering System for Metals and Alloys (UNS), Society of Automotive Engineers, Warrendale, Pa., 1975. This reference contains the cross reference numbers for AISI, ASTM, FED, MIL SPEC, and SAE specifications. All yield strengths are obtained using the 0.2 percent offset method. Multiply strength in kpsi be 6.89 to get strength in MPa.)

See Reference Table - Properties of Stainless Steels

UPYTE RBSA515S1 712S1 111S3 115SF 114SA515S1 711SA416 1S1 712S1 111S3 111SF 118SA395 61S1 711SA395 51SA385 61SA494 61

SA514 61SA911 52SD121 54SD111 54SD121 54SD112 63SD112 62SA473 61SD111 53SD111 53SD111 53SD112 63SD812 62SD693 71SA912 62SD121 54SD111 54SD121 64SD912 62SA372 61SA373 71

Tool Steels

Tool Steels' defining properties include resistance to wear, stability during heat treatment, strength at high temperatures, and toughness. To develop these properties, tool steels are always heat treated. Because the parts may distort during heat treatment, precision parts should be semifinished, heat treated, then finished. Tool steels are classified into several broad groups, some of which are further divided into subgroups according to alloy composition, hardenability, or mechanical similarities.

Type W - Water-hardening, or carbon, tool steels rely on carbon content for their useful properties.

Type S - Shock-resisting tool steels are strong and tough, but not as wear resistant as many other tool steels.

Types O, A, and D Cold-work tool steels include oil and air-hardened types are often more costly but can be quenched less drastically than water-hardening types. Type O steels are oil hardening; Type A and D steels are air hardening (the least severe quench), and are best suited for applications such as machine ways, brick mold liners, and fuel-injector nozzles. The air-hardening types are specified for thin parts or parts with severe changes in cross section -- parts that are prone to crack or distort during hardening. Hardened parts from these steels have a high surface hardness; however, these steels should not be specified for service at elevated temperatures.

Type H - Hot-work steels serve well at elevated temperatures. Types T (tungsten alloy) and M (molybdenum alloy) - High-speed tool steels make good cutting

tools because they resist softening and maintain a sharp cutting edge at high service temperatures.

Type L - A special-purpose, low-cost, low-alloy, tool steel often specified for machine parts when wear resistance combined with toughness is important.

Type F - Carbon-tungsten alloys (Type F) are shallow hardening and wear resistant, but are not suited for high temperatures or for shock service.

Type P - A mold steel are designed specifically for plastic-molding and zinc die-casting dies.

HSLA Steel -

High-Strength Low-Alloy (HSLA) steels have a higher strength-to-weight ratio than conventional low-carbon steels for only a modest price premium. Because HSLA alloys are stronger, they can be used in thinner sections, making them particularly attractive for transportation-equipment components where weight reduction is important. HSLA steels are usually low-carbon steels with up to 1.5% manganese, strengthened by small additions of elements, such as columbium, copper, vanadium or titanium and sometimes by special rolling and cooling techniques.

Materials: Non-Ferrous Metals

Non-Ferrous Metals

Non-ferrous metals are metals that do not contain iron. There are two groups of metals; ferrous and non-ferrous. Ferrous metals contain iron, for example carbon steel, stainless steel (both alloys; mixtures of metals) and wrought iron. Non-ferrous metals don't contain iron, for example aluminium, brass, copper (which can be remembered as ABC) and titanium. You can also get non-ferrous metals as alloys eg, brass is an alloy of copper and zinc.

Nonferrous metals are specified for structural applications requiring reduced weight, higher strength, nonmagnetic properties, higher melting points, or resistance to chemical and atmospheric corrosion. They are also specified for electrical and electronic applications.

Aluminum

Pure aluminum is a silvery-white metal with many desirable characteristics. It is light, nontoxic (as the metal), nonmagnetic and nonsparking. It is easily formed, machined, and cast. Pure aluminum is soft and lacks strength, but alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful properties. Aluminum is an abundant element in the earth's crust, but it is not found free in nature. The Bayer process is used to refine aluminum from bauxite, an aluminum ore.

Because of aluminum's mechanical and physical properties, it is an extremely convenient and widely used metal.

Some Common Uses -

Building & Construction Industry:

door and window frames wall cladding, roofing, awnings

Manufacture of Electrical Products:

high tension power lines, wires, cables, busbars components for television, radios, refrigerators and air-conditioners

Packaging & Containers:

beverage cans, bottle tops foil wrap, foil semi-rigid containers

Cooking Utensils:

kettles and saucepans

Aeronautical, Aviation & Automotive Industries:

propellers airplane and vehicle body sheet gearboxes, motor parts

Leisure Goods:

tennis racquets, softball bats indoor and outdoor furniture

Properties -

very lightweight (about 1/3 the mass of an equivalent volume of steel or copper) but with alloying can become very strong.

excellent thermal conductor excellent electrical conductor (on a weight-for-mass basis, aluminium will conduct more than

twice as much electricity as copper) highly reflective to radiant energy in the electromagnetic spectrum highly corrosion resistant in air and water (including sea water) highly workable and can be formed into almost any structural shape

non-magnetic non-toxic

Properties of Aluminum Alloys

Tabulated in accordance with the Unified Numbering System for Metals and Alloys (UNS), Society of Automotive Engineers, Warrendale, Pa., 1975. This reference contains the cross reference numbers for AISI, ASTM, FED, MIL SPEC, and SAE specifications. These are typical properties for sizes of about 1/2 inch. A typical value may be neither the mean nor the minimum. It is a value which can be obtained when the purchase specifications are carefully written and with continuous inspection and testing. The values given for fatigue strength, S_f, correspond to 50e7 cycles of completely reversed stress. Aluminum alloys do not have an endurance limit. The yield strength is 0.2% offset value. Multiply strength in kpsi by 6.89 to get strength in MPa.

Properties of Aluminum AlloysUNS Temper Yield Tensile Shear Fatigue Elongation Brinell

A91100 -O 5 13 9.5 5 45 23A91100 -H12 14 15.5 10 6 25 28A91100 -H14 20 22 14 9 16 40A91100 -H16 24 26 15 9.5 14 47A91100 -H18 27 29 16 10 10 55A93003 -O 6 16 11 7 40 28A93003 -H12 17 19 12 8 20 35A93003 -H14 20 22 14 9 16 40A93003 -H16 24 26 15 9.5 14 47A93003 -H18 27 29 16 10 10 55A93004 -O 10 26 16 14 25 45A93004 -H32 22 31 17 14.5 17 52A93004 -H34 27 34 18 15 12 63A93004 -H36 31 37 20 15.5 9 70A93004 -H38 34 40 21 16 6 77A92011 -T3 48 55 32 18 15 95A92011 -T8 45 59 35 18 12 100A92014 -O 14 27 18 13 18 45A92014 -T4 40 62 38 20 20 105A92014 -T6 60 70 42 18 13 135A92017 -O 10 26 18 13 22 45

A92017 -T4 40 62 38 18 22 105A92018 -T61 46 61 39 17 12 120A92024 -O 11 27 18 13 22 47A92024 -T3 50 70 41 20 16 120A92024 -T4 48 68 41 20 19 120A92024 -T36 57 73 42 18 13 130A95052 -O 13 28 18 17 30 45A95052 -H32 27 34 20 17.5 18 62A95052 -H34 31 37 21 18 14 67A95052 -H36 34 39 23 18.5 10 74A95052 -H38 36 41 24 19 8 85A95056 -O 22 42 26 20 35A95056 -H18 59 63 34 22 10A95056 -H38 50 60 32 22 15A96061 -O 8 18 12.5 9 30 30A96061 -T4 21 35 24 13.5 25 65A96061 -T6 40 45 30 13.5 17 95A97075 -T6 72 82 49 24 11 150

PROPERTIES OF ALUMINUM DIE CASTING ALLOYSAA NUMBER

A360.0 A380.0 383 A413.0 B390.0 384Ultimate Tensile 46 47 45 42 40.5 48

TensileYield Strength 24 23 22 19 35 24Elongation 3.5 3.5 3.5 3.5 1.0 Hardness 75 80 80 120 85

Shear Strength 26 27 25 29Charpy Impact Strength 4.2 3.5 2

Fatigue Strength (ksi) 18 20 19 20 20Density 0.095 0.098 0.097 0.096 0.099 0.098

Melting Range 1035- 1000- 960- 1065- 945- 960-Specific Heat 0.23 0.23 0.23

Coefficient of Thermal 11.8 11.7 11.5 10.3 11.7 11.3Thermal Conductivity 65.3 55.6 55.6 67.7 78.6 56Electrical Conductivity 29 31 23 31 25 23Modulus of Elasticity 10.3 10.3 10.3 10.3 11.9 10.3

Aluminum and its alloys are divided into two broad classes, castings and wrought (mechanically worked products). The latter is sub-divided into heat-treatable and non-heat-treatable alloys, and into various forms produced by mechanical working.

Wrought Aluminum AlloysSeries Main Alloy Alloy Properties1xxx None (99% alu) Unalloyed aluminum is highly corrosion resistant, 2xxx Copper Gives strength, hardness, machinability. Heat-3xxx Manganese Adds moderate strength, good workability. Non-

4xxx Silicon5xxx Magnesium Moderate to high strength. Corrosion resistant. 6xxx Magnesium & Increases strength, formability, corrosion 7xxx Zinc For greatest strength. Heat treatable. Other 8xxx Tin, Lithium & Other Effects vary.9xxx N/A (This series is unused presently.)

Aluminum Temper Designations

F As fabricated. No control over the amount of strain hardening.

H Strain-hardened (wrought products only) to increase strength.

H1 Strain-hardened only. Products are strain-hardened to achieve the strength desired without additional thermal treatment.

H1x,H2x,H3x The second digit following the designations H1, H2, H3 indicate the final degree of strain

Casting Alloys

Series Main Alloy Alloy Notes1xx.x None Unalloyed aluminum.2xx.x Copper Used extensively for applications where excellent strength and 3xx.x Silicon Other alloying elements such as copper and magnesium are specified. 4xx.x Silicon5xx.x Magnesiu Alloys possess a high and stable combination of strength, shock 6xx.x N/A (This series is unused presently.)7xx.x Zinc Employed when a combination of good mechanical properties without 8xx.x Tin9xx.x N/A (This series is unused presently.)

hardening. The number 8 has been assigned to tempers having a final degree of strain-hardening equivalen to that resulting from approxiamtely 75 % reduction in area. Tempers between that of the 0 Temper (annealed) and 8 (full hard) are designated by the numbers 1 through 7. A number 4 (which is halfway between 0 and 8) designation is considered half-hard; number 2 is considered quarter-hard; and the number 6 is three-quarter hard. When the number is odd, the limits of ultimate strength are exactly halfway between those of the even numbered tempers.

Hxxx The third digit indicates a variation of the two digit H temper. It is used when the degree of temper is close to the 2 digit H temper.

H111 Applies to alloys which are strain-hardened less than the amount required for a controlled H11 temper.

H112 Applies to alloys that acquire some temper from shaping processes which do not have special control over the amount of strain-hardening or thermal treatment, but for which there are mechanical property limits.

H2

Strain-hardened and partially annealed. Applies to alloys which are strain-hardened more than the desired final amount and then reduced in strength to the desired level by partial annealing. For alloys that soften with age at room temperature, the H2 tempers have the same minimum tensile strength as the corresponding H3 tempers. For other alloys, the H2 tempers have the same minimum tensile strength as the corresponding H1 tempers and slightly higher elongation.

H3

Strain-hardened and stabilized. Applies to alloys that are strain-hardened and whose mechanical properties are stabilized by a low temperature thermal treatment that results in slightly lowered tensile strength and improved ductility. This designation is applicable only to those alloys that unless they are stabilized, will gradually soften with age at room temperature.

H311 Applies to alloys which are strain-hardened less than the amount required for a controlled H31 temper.

H321 Applies to alloys which are strain-hardened less than the amount required for a controlled H32 temper.

H323 Applies to products which are fabricated to have good resistance to stress corrosion cracking.

H343 Applies to products which are fabricated to have good resistance to stress corrosion cracking.

O Annealed, recrystallized (wrought products only). Applies to wrought alloys which are annealed to obtain the softest temper, and to cast alloys which are annealed to improve ductility and dimensional stability.

T Thermally treated to produce stable tempers other than F, O or H.

T1 Naturally aged. Product is cooled from an elevated temperature shaping process and naturally aged to a substantially stable condition.

T2 Annealed (cast products only). Applies to alloys which are cold worked to improve

strength after cooling from an elevated temperature shaping process, or in which the effect of cold work in flattening or straightening is significant in mechanical property limits.

T3 Solution heat-treated, cold worked and naturally aged to a substantially stable condition to improve strength.

T4 Solution heat-treated and naturally aged to a substantially stable condition.

T5 Cooled from an elevated temperature shaping process and the artificially aged.

T51

Stress relieved by stretching. Applies to the following products when stretched the indicated amounts after solution heat-treatment or cooled from a high temperature shaping process: Plate—1.5-3% permanent set; Rod, bar, shapes, and extruded tubes—1-3% permanent set; Drawn tubes— 1.5-3% permanent set. Applies directly to plate, and rolled or cold finished rod and bar which receive no further straightening after stretching. Applies to extruded rod, bar, shapes, tubing, and to drawn tubing when designated as follows: T510 Products that receive no further straight ending after stretching; T511 Products that may receive minor straightening after stretching to comply with standard tolerances.

T52 Stress-relieved by compressing. Applies to alloys which are stress-relieved by compressing after solution heat-treatment, or cooled from a high temperature shaping process to produce a permanent set of 1 to 5%.

T54 Stress-relieved by combined stretching and compressing. Applicable to die forging which are stress-relieved by restring cold in the finish die.

T6 Solution heat-treated and then artificially aged. T62 indicates material is solution heat-treated from the O or F temper to demonstrate response to heat-treatment, and artificially aged.

T7 Solution heat-treated and then stabilized to carry them beyond the point of maximum strength to provide control of some special property.

T8 Solution heat-treated, cold worked, and then artificially aged.

T9 Solution heat-treated, artificially aged, and then cold worked.

T10 Artificially aged and then cold worked.

T42 (Wrought products only). Applicable to products solution heat-treated and naturally aged which have mechanical properties different from those of the T4 temper.

T62 (Wrought products only). Applicable to products solution heat-treated and artificially aged which have mechanical properties different from those of the T6 temper.

W Solution heat treated. An unstable temper applied only to alloys which spontaneously age at room temperature after solution heat-treatment.

Beryllium

Beryllium has one of the highest melting points of the light metals. The modulus of elasticity of beryllium is approximately 1/3 greater than that of steel. It has excellent thermal conductivity, is nonmagnetic and resists attack by concentrated nitric acid. It is highly permeable to X-rays, and neutrons are liberated when it is hit by alpha particles, as from radium or polonium (about 30 neutrons/million alpha particles). At standard temperature and pressures beryllium resists oxidation when exposed to air (although its ability to scratch glass is probably due to the formation of a thin layer of the oxide). Beryllium is a very light weight metal with a high modulus of elasticity (five times that of ultrahigh-strength steels), high specific heat, and high specific strength (strength to weight ratio).

Uses -

Beryllium is used as an alloying agent in the production of beryllium-copper because of its ability to absorb large amounts of heat. Beryllium-copper alloys are used in a wide variety of applications because of their electrical and thermal conductivity, high strength and hardness, nonmagnetic properties, along with good corrosion and fatigue resistance. These applications include the making of spot-welding electrodes, springs, non-sparking tools and electrical contacts.

Due to their stiffness, light weight, and dimensional stability over a wide temperature range, beryllium-copper alloys are also used in the defense and aerospace industries as light-weight structural materials in high-speed aircraft, missiles, space vehicles and communication satellites.

Thin sheets of beryllium foil are used with X-ray detection diagnostics to filter out visible light and allow only X-rays to be detected.

In the field of X-ray lithography beryllium is used for the reproduction of microscopic integrated circuits. Because it has a low thermal neutron absorption cross section, the nuclear power industry uses this metal in nuclear reactors as a neutron reflector and moderator.

Beryllium is used in nuclear weapons for similar reasons. For example, the critical mass of a plutonium sphere is significantly reduced if the plutonium is surrounded by a beryllium shell.

It is, however, brittle, chemically reactive, expensive to refine and form, and its impact strength is low compared to values for most other metals.

Copper

Copper provides a diverse range of properties: good thermal and electrical conductivity, corrosion resistance, ease of forming, ease of joining, and color. However, copper and its alloys have relatively low strength-to-weight ratios and low strengths at elevated temperatures. Some copper alloys are also susceptible to stress-corrosion cracking unless they are stress relieved. Next to silver, copper is the next best electrical conductor. It is a yellowish red metal that polishes to a bright metallic luster. It is tough, ductile and malleable. Copper has a disagreeable taste and a peculiar smell. Copper is resistant to corrosion in most atmospheres including marine and industrial environments. It is corroded by oxidizing acids, halogens, sulphides and ammonia based solutions.

Copper and its alloys -- the brasses and bronzes -- are available in rod, plate, strip, sheet, tube shapes, forgings, wire, and castings

Lead

Lead is the most impervious of all common metals to X-rays and gamma radiation and it resists attack by many corrosive chemicals, most types of soil, and marine and industrial environments. Main reasons for using lead often include low melting temperature, ease of casting and forming, high density, good sound and vibration absorption, and ease of salvaging from scrap. Sheet lead, lead-loaded vinyls, lead composites, and lead-containing laminates are used to reduce machinery noise. The natural lubricity and wear resistance of lead make the metal suitable, in alloys, for heavy-duty bearing applications such as railroad-car journal bearings and piston-engine crank bearings.

Magnesium

As the lightest structural metal available, magnesium has a high strength-to-weight ratio. With its low modulus of elasticity combined with moderate strength, magnesium alloys can absorb energy elastically, providing excellent dent resistance and high damping capacity. Magnesium has good fatigue resistance and performs particularly well in applications involving a large number of cycles at relatively low stress. The metal is sensitive to stress concentration, however, so notches, sharp corners, and abrupt section changes should be avoided. Magnesium alloys are the easiest of the structural metals to machine and they can be shaped and fabricated by most metalworking processes, including welding.

Nickel

Nickel fits many applications that require specific corrosion resistance or elevated temperature strength. Some nickel alloys are among the toughest structural materials known. When compared to steel, other nickel alloys have ultrahigh strength, high proportional limits, and high moduli of elasticity. Commercially pure nickel has good electrical, magnetic, and magnetostrictive properties.

Precious Metals

Gold is an extremely inert, soft, ductile metal, that undergoes very little work hardening. A gram of pure gold can be worked into leaf covering 6 ft^2 and only 0.0000033 in. thick. It is used chiefly for linings or electrodeposits and is often alloyed with other metals such as copper or nickel to increase strength or hardness.

Silver is a very malleable, ductile, and corrosion resistant metal that has the highest thermal and electrical conductivity of all metals and is the least costly of all the precious metals. Alloyed with copper, and sometimes with zinc, silver is also used in high-melting temperature solders.

Platinum is an extremely malleable, ductile, and corrosion resistant silver-white metal. When heated to redness, it softens and is easily worked. It is nearly nonoxidizable and is soluble only in

liquids that generate free chlorine such as aqua regia. Because platinum is inert and stable, even at high temperatures, the metal is used for high-temperature handling of high-purity chemicals and laboratory materials. Other applications include electrical contacts, resistance wire, thermocouples, and standard weights.

Refractory Metals

Refractory metals are characterized by their extremely high melting points, which range well above those of iron, cobalt, and nickel. They are used in demanding applications requiring high-temperature strength and corrosion resistance. The most extensively used of these metals are tungsten, tantalum, molybdenum, and columbium (niobium).

Tin

Tin is characterized by a low-melting point (450°F), fluidity when molten, readiness to form alloys with other metals, relative softness, and good formability. The metal is nontoxic, solderable, and has a high boiling point. The temperature range between melting and boiling points exceeds that for nearly all other metals (which facilitates casting). Upon severe deformation, tin and tin-rich alloys work soften. Principal uses for tin are as a constituent of solder and as a coating for steel (tinplate, or terneplate). Tin is also used in bronze, pewter, and bearing alloys.

Titanium

There are three structural types of titanium alloys:

Alpha Alloys are non-heat treatable and are generally very weld- able. They have low to medium strength, good notch toughness, reasonably good ductility and possess excellent mechanical properties at cryogenic temperatures. The more highly alloyed alpha and near-alpha alloys offer optimum high temperature creep strength and oxidation resistance as well.

Alpha-Beta Alloys are heat treatable and most are weldable. Their strength levels are medium to high. Their hot-forming qualities are good, but the high temperature creep strength is not as good as in most alpha alloys.

Beta or near-beta alloys are readily heat treatable, generally weldable, capable of high strengths and good creep resistance to intermediate temperatures. Excellent formability can be expected of the beta alloys in the solution treated condition. Beta-type alloys have good combinations of properties in sheet, heavy sections, fasteners and spring applications.

Zinc

Zinc, a crystalline metal with moderate strength and ductility, is seldom used alone except as a coating. In addition to its metal and alloy forms, zinc also extends the life of other materials such as steel (by hot dipping or electrogalvanizing), rubber and plastics (as an aging inhibitor), and wood (in paints). Zinc is also used to make brass, bronze, and die-casting alloys in plate, strip, and coil; foundry alloys; superplastic zinc; and activators and stabilizers for plastics.

Zirconium

Relatively few metals besides zirconium can be used in chemical processes requiring alternate contact with strong acids and alkalis. Major uses for zirconium and its alloys are as a construction material in the chemical-processing industry.

Zinc

Zinc is a silvery blue-grey metal with a relatively low melting point (419.5°C) and boiling point (907°C). When unalloyed, its strength and hardness is greater than that of tin or lead, but appreciably less than that of aluminium or copper. The pure metal cannot be used in stressed applications due to low creep-resistance. For these reasons most uses of zinc are after alloying with small amounts of other metals or as a protective coating for steel.

Uses -

One of the most useful characteristics of zinc is its resistance to atmospheric corrosion, and just over half of its use is for the protection of steelwork. In addition to its metal and alloy forms, zinc also extends the life of other materials such as steel (by hot dipping or electrogalvanizing), rubber and plastics (as an aging inhibitor), and wood (in paints). Zinc is also used to make brass, bronze, and die-casting alloys in plate, strip, and coil; foundry alloys; superplastic zinc; and activators and stabilizers for plastics.

Mechanical and physical properties -

Tensile strength (cast) : 28MN/m² (4,000 psi)- (rolled - with grain)- (99.95% zinc soft temper) : 126MN/m² (18,000 psi)- (98.0% zinc hard temper) : 246MN/m² (35,000 psi)Elongation : - (rolled - with grain)- (99.95% zinc soft temper) : 65%- (98.0% zinc hard temper) : 5%Modulus of elasticity : 7 X 104 MN/m² (1 X 107 psi)Brinell hardness, 500 kg load : - for 30 sec. : 30Impact resistance :- (pressed zinc, elongation = 30%) : 6.5-9 J/cm² (26-35 ft-1bs/in²) Surface tension - liquid (450°C) : 0.755 N/mSurface tension - liquid (419.5°C) : 0.782 N/mViscosity-liquid (419.5°C) : 0.00385 N/mVelocity of sound (20°C) : 3.67 km/sCoefficient of friction :- (rolled zinc v rolled zinc) : 0.21Hardness : 2.5 mohs

Zirconium

Relatively few metals besides zirconium can be used in chemical processes requiring alternate contact with strong acids and alkalis. Major uses for zirconium and its alloys are as a construction material in the chemical-processing industry.

Introduction

Humans have taken advantage of the versatility of polymers for centuries in the form of oils, tars, resins, and gums. However, it was not until the industrial revolution that the modern polymer industry began to develop. In the late 1830s, Charles Goodyear succeeded in producing a useful form of natural rubber through a process known as "vulcanization." Some 40 years later, Celluloid (a hard plastic formed from nitrocellulose) was successfully commercialized. Despite these advances, progress in polymer science was slow until the 1930s, when materials such as vinyl, neoprene, polystyrene, and nylon were developed. The introduction of these revolutionary materials began an explosion in polymer research that is still going on today.

Some degree of compromise is almost always necessary in designing plastic parts. Arriving at the best compromise usually requires satisfying the mechanical, thermal, and electrical requirements of the part, utilizing the most economical resin or compound that will perform satisfactorily and be attractive, and choosing a manufacturing process compatible with the part design and material choice.

Probably no plastic will provide 100% of the requirements for the desired performance, appearance, processibility, and price. Selecting the best qualified material is not based simply on comparing numbers on published data sheets; such values can be grossly misleading. For example, choosing the most economical material for a part by comparing the cost per pound of various plastics is a mistake. Some plastics weigh twice as much per cubic inch as others and so would require twice as much to fill a given cavity and cost twice as much to ship.

Polymers have a wide range of mechanical properties. Network polymers are often quite strong and stiff (high yield strength and modulus of elasticity), although they have poor ductility. Linear polymers have much lower strength but quite high ductility, and elastomers have very large values of ductility and a variable modulus of elasticity. Polymers are generally classified according to their structure, properties and use as:

Thermoplastic Thermosetting Elastomers

Thermoplastics

Thermoplastic materials are melt processable, that is they are formed when the are in a melted or viscous phase. This generally means they are heated, formed, then cooled in their final shape. Depending upon their chemistry, thermoplastics can be very much like rubber, or as strong as aluminum. Some high temperature thermoplastic materials can withstand temperature extremes of up to 600 F, while others retain their properties at -100 F. Thermoplastics do not oxidize and some materials have no known solvents at room temperature. Most thermoplastic materials are excellent electrical and thermal insulators. On the other hand thermoplastic composites can be made to be electrically conductive with the addition of carbonor metal fibers.

In general the combination of light weight , high strength, and low processing costs make thermoplastics well suited to many applications. The most common methods of processing thermoplastics are injection molding, extrusion , and thermoforming.

Thermoplastics include:

ABS (Acrylanitrile Butadiene Styrene)ABS Polycarbonate AlloyAcetal AcrylicASA (acrylic-styrene-acrylonitrile) AlloysCellulose ButyrateETFE (Tefzel)EVA Ethylene Vinyl AcetateLCP (Polyester Liquid Crystal Polymer)Nylon 6Nylon 4-6Nylon 6-6Nylon 11Nylon 12Nylon amorphousNylon impact modifiedPolyallomerPBT Polyester (Polybutylene Terepthalate)PolycarbonatePEEK PolyetheretherkeytonePEI Polyetherimid (Ultem)PolyethersulfonePolyethylene High DensityPolyethylene Low DensityPolyethylene Medium DensityPET Polyester (Polyethylene Terepthalate)Polyimide Thermoplastic (Aurum)PolypropylenePPA Polyphthalamide (Amodel)PPO Modified Polyphenylene Oxide (Noryl)PPS Polyphenylene SulfidePolystyrene CrystalPolystyrene High Impact HIPS

Polystyrene Medium Impact MIPSPolysulfonePolyurethanePVC Polyvinyl Chloride RigidPVC FlexiblePVDF Polyvinylidene Fluoride (Kynar)SAN Styrene Acrylonitrile

TPE Thermoplastic ElastomersTPR Thermoplastic Rubbers

Thermoset Plastics

Thermoset plastics such as amino, epoxy, phenolic, and unsaturated polyesters, are so named because they experience a chemical change during processing and become "set", hard solids. Thermosets are highly cross-linked polymers that have a molecular mesh or network of polymer chains like a three-dimensional version of a net. Thermosets undergo a chemical as well as a phase change when they are heated. Once cured they cannot be melted or remolded and are resistant to solvents - that is once they are formed they are 'set' (hence the name).

Thermoset plastics, because of their tightly crosslinked structure, resist higher temperatures and provide greater dimensional stability than do most thermoplastics. Thermosets are tough, durable with high temperature performance, and have found applications in a wide variety of fields including electronic chips, fibre-reinforced composites, polymeric coatings, spectacle lenses and dental fillings.

For more specific examples of thermoset resins and their uses browse the following pages.

Thermoset Plastics

Alkyds(Polyester)

Amino ( Urea /

Melamine)Epoxies Phenolics Polyimides Polyurethane Silicone

Alkyds / Polyester

Uses - Thermosetting polyester resins are commonly used as casting materials, fiberglass laminating resins, and non-metallic auto-body fillers. Polyester is used for car body panels and fender walls (SMC - sheet molding compound), tool housings (BMC - bulk molding compound) brackets, and industrial equipment housings.

Urea Formaldehyde (UF) & Melamine Formaldehyde (MF) / Aminos

Urea formaldehyde (UF) thermosets are strong, glossy, and durable. They are not affected by fats, oils esters, ether, petrol, alcohol or acetone, nor by detergents or weak acids, and they exhibit good resistance to weak alkalis. Their high mechanical strength, heat and fire resistance, and good electrical arc and tracking resistance make them an ideal plastic for numerous industrial and household applications, from doorknoobs and toilet seats to electrical components and cosmetics enclosures.

Melamine formaldehyde (MF) thermoset plastics are similar to urea molding compounds, but melamine has even better resistance to heat, chemicals, moisture, electricity and scratching.UFs and MF plastics that have high surface hardness and gloss, brilliant and precise colors, and light fastness.

Uses - Melamine formaldehyde (MF) thermosets are ideal for dinnerware, kitchen utensils, bathroom accessories, and electrical components. Some uses include electrical breakers, receptacles, closures, knobs and handles, appliance components, adhesives, coatings and laminates. Melamine was formerly used for dishware.

Epoxy --

Epoxies have several advantages over other plastics including excellent electrical, thermal, and chemical resistance. Their strength can be further increased with fibrous reinforcement or mineral fillers. There is a huge variety of combinations of epoxy resins and reinforcements which allows a wide range of possible properties in the finished molded parts.

Generally, parts molded from epoxy are hard, rigid, relatively brittle, and have excellent dimensional stability over a broad temperature range. The combination of high mechanical strength and excellent electrical properties make them ideal for electrostructural applications.

Uses -

Coatings, casting compounds, encapsulating for electrical components, laminates, and adhesives

Phenolic (Bakelite) --

History - The first truly synthetic plastic was invented by Leo Baekeland - a Belgium chemist living in New York. Baekeland was already very rich as he had invented the first commercially successful photographic paper and sold it to George Eastman in 1898 for $1 million. With such money, Baekeland could engage himself in whatever research he decided to do.

In 1905, he found that when he combined formaldehyde and phenol, he produced a material that bound all types of powders together. He called this material Bakelite - after himself - and it was the first thermosetting plastic in the world. This was a material that once it set hard would not soften under heat. It had so many uses and so many potential uses, that it was called "the material of a thousand uses".

Bakelite was water and solvent resistant; could be used as an electrical insulator; was rock hard but could be cut by a knife and was used in 78 rpm records and telephones. It was a naturally brittle material in pure form, but it could be strengthened with fillers such as wood pulp and cellulose.

Uses - PF was used in early consumer electronic products such as telephones, radios, records. Phenolics are little used in general consumer products today due to the cost and complexity of production and their brittle nature. An exception to the overall decline is the use in small precision-shaped components where their specific properties are required, such as molded disc brake cylinders, saucepan handles, electrical plugs and switches, and electrical iron parts. Today, Bakelite is manufactured under various commercial brand names such as Micarta. Micarta is produced in sheets, rods and tubes for hundreds of industrial applications in the electronics, power generation and aerospace industries.

Polyimide --

When compared to most other organic or polymeric materials, polyimides exhibit an exceptional combination of thermal stability (>500°C), mechanical toughness and chemical resistance. In addition, they have excellent dielectric properties.

Uses -

Used a lot in wear applications, machined gears, bushings and bearings, aerospace and aircraft parts, ring seals, thrust washers, wear strips. Also, because of their high degree of ductility and inherently low CTE, polyimides can be readily implemented into a variety of microelectronic applications. Multilayer thin and thick film applications on large silicon or ceramic substrates can be readily achieved.

Polyurethane --

Polyurethanes are widely used in flexible and rigid foams, durable elastomers and high performance adhesives and sealants, fibers, seals, gaskets, condoms, carpet underlayment, and hard plastic parts. Polyurethane products are often called "urethanes".

Uses - Over three quarters of the consumption of polyurethane products is in the form of foams, with flexible and rigid types being roughly equal in market size. Polyurethane materials are also used in coatings and varnishes used in furniture manufacture, carpentry or woodworking. Polyurethane is also used as an adhesive, especially as a woodworking glue. Its main advantage over more traditional wood glues is its water resistance. It is also used in making solid tires. Modern roller blading and skateboarding became economical only with the introduction of tough, abrasion-resistant polyurethane parts.

Silicone --

Silicones are odorless, colorless, water resistant, chemical resistant, oxidation resistant, stable at high temperature, and have weak forces of attraction, low surface tension, low freezing points and do not conduct electricity. They find many uses in oils, greases, and rubberlike materials. Silicone oils are very desirable since they do not decompose at high temperature and do not become viscous.

Uses -

Silicones are use for lubricants, adhesives, sealants, gaskets, pressure compensating diaphragms for drip irrigation emitters, dishware, Silly Putty, and many other products. Silicones have a number of medical applications (e.g. breast implants) because they are chemically inert. Other silicones are used in hydraulic fluids, electrical insulators and moisture proofing agent in fabrics.

Elastomers

Elastomers and rubber are differentiated from polymers by the mechanical property of returning to their original shape after being stretched to several times their length. The rubber industry differentiates between the terms "elastomer" and "rubber" on the bases of how long a deformed material sample requires to return to its approximate original size after a deforming force is removed, and of its extent of recovery. Synthetic materials such as neoprene, nitrile, styrene butadiene (SBR), and butadiene rubber are now grouped with natural rubber. These materials serve engineering needs in fields dealing with shock absorption, noise and vibration control, sealing, corrosion protection, abrasion protection, friction production, electrical and thermal insulation, waterproofing, confining other materials, and load bearing.

As with almost any material, selecting a rubber for an application requires consideration of many factors, including mechanical or physical service requirements, operating environment, a reasonable life cycle, manufacturability of the part, and cost.

Manufacturing rubber parts is accomplished in one of three ways: transfer molding, compression molding, or injection molding. The choice of process depends on a number of factors, including the size, shape, and function of the part, as well as anticipated quantity, type, and cost of the raw material.

Elastomers are classified as follows:

Nonoil-resistant rubbers Oil-resistant rubbers Thermoplastic elastomers