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Polymers and Ceramics

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Title: Polymers and Ceramics


1
Polymers and Ceramics Team 6 Christopher
Chavez Steve De La Torre David Jaw Matthew
Witkowski September 21, 2005 ME260L
2
Topics
  • Polymers (S. De La Torre)
  • Additives and Properties (M. Witkowski)
  • Glass and it Properties (D. Jaw)
  • Properties and Applications of Reinforced Plastic
    (C. Chavez)
  • References (Team 6)
  • Questions (Team 6)

3
Polymers
  • Things To Know (General Overview)
  • General Information on Polymers (Plastics)
  • Designing with Plastics
  • Did you know? Facts

4
Things To Know
  • Polymers (Plastics) Material capable of being
    shaped or molded.
  • Synthetic Manmade polymer
  • Monomer Basic building block of a polymer, one
    unit (short molecules)
  • Polymerization Monomer linked into a repeating
    unit (long molecules)
  • Amorphous Short Chain polymers, no crystallinity
    in solid state
  • Crystallinity Long chain polymer, dense
    molecular alignments
  • Glass Temp (Tg) Temp at which a transition
    occurs (hard vs rubbery)
  • Thermoplastics Long chains polymers, Plastics
    that can be repeatedly softened and harded by
    heating or cooling. E.g. polyethylene,
    polypropylene
  • Thermosets Crosslinked polymers, Plastics that
    can not be softned without degrading the material.

5
Polymers (Plastics)
  • What are Plastics? Any one of a large and varied
    group of materials consisting wholly or part of a
    combination of carbon and hydrogen (hydrocarbons)
    e.g. Polyethylene and Polypropylene. Also a
    combination of oxygen, nitrogen and other organic
    and inorganic elements. e.g. Polyvinyl Chloride
    (PVC) and Nylon The invention of new plastics is
    so rapid that approximately three new plastics
    are developed each week.
  • Characteristics of Plastics Plastics are divided
    into two distinct groups, thermoplastics and
    thermosets. Chemical resistant (cleaning
    fluids), thermal and electrical insulators
    (Cookware handles, thermal underwear). Light
    weight and varying degrees of strength (toys to
    space station, pantyhose to Kevlar)
  • Additives In order to impart certain properties,
    polymers usually are compounded with additives.
    Additives modify and improve certain
    characteristics of the polymer, e.g. stiffness,
    strength, color, weatherability

6
Polymers (Plastics)
  • Producing Plastics Plastics can be injected
    molded with great accuracy or machined into
    components, Extrusion for tube or rod shapes, hot
    temperature formed, blow molding compressed air
    blown. In some case, plastics have replaced metal
    as the material in components for the reason that
    they are easy to work with and relative
    inexpensive.
  • Where are Plastics? Whether you are aware of it
    or not, plastics play an important part in your
    life. Plastics versatility allow it to be used
    in everything, in fact about nearly every thing
    we generally use contains plastic. Plastic makes
    life easier and better. The applications for
    plastics are almost limitless. e.g.
    shopping, packaging, home construction.

7
Polyethylene
  • Molecular Structure
  • Common Products Packaging, Electrical
    insulation, milk and water bottles, packaging
    film, house wrap, agricultural film
  • Good gas, chemical and moisture barrier
    properties, High temperature (high density)
    allowance, toughness, flexibility, Low melting
    point (low density).
  • Lower cost than polypropylene

8
Polypropylene
  • Molecular Structure
  • Common Products Carpet fibers, automotive
    bumpers, microwave containers,
  • Has excellent chemical resistance, high melting
    point, flexible to rigid.
  • Low cost and moisture absorption

9
Designing with Plastics
  • The number of variations or formulations possible
    by combining the many chemical elements is
    virtually endless. This variety also makes the
    job of selecting the best material for a given
    application a challenge. The plastics industry
    provides a dynamic and exciting opportunity.
  • The plastic industry has classified plastics as
    Durable (3 years or longer of usage e.g.
    automobiles, electronics, building materials)
    Non-Durable (3 years or less e.g. trash bags,
    cups, most toys).
  •   A designer or engineer will often use design
    equations that work with metals while a part is
    being designed. Metals behave like a spring that
    is, the force generated by the spring is
    proportional to its length.
  •   When a material actually works this way it is
    called "LINEAR" behavior. This allows the
    performance of metals and other materials that
    work like a spring to be quite accurately
    calculated. A problem occurs when the designer
    tries to apply these same equations directly to
    plastics. Plastics DO NOT BEHAVE LIKE A SPRING
    (not a straight line), that is they are
    "non-linear." Temperature changes the behavior
    even more. The equations should be used only with
    very special input. A material supplier may have
    to be consulted for the correct input.

10
Designing with Plastics
  • Modulus Stress/Strain
  • The stress/strain equation is the equation used
    by designers to predict how a part will distort
    or change size and shape when loaded. Predicting
    the stress and strain within an actual part can
    become very complex. Fortunately, the material
    suppliers use tests that are easy to understand.
  • The information for all the parameters are
    supplied by the vendor. The designer need to
    know what to ask for. Some calculations will
    still need to be engineered.

11
Designing with Plastics
STRESSHow does one know if a material will be
strong enough for a part? If the loads can be
predicted and the part shape is known then the
designer can estimate the worst load per unit of
cross-sectional area within the part. Load per
unit area is called "STRESS". If Force or Load
is in pounds and area is in square inches then
the units for stress are pounds per square inch
12
Designing with Plastics
  • Other parameters to consider when choosing a
    plastic as your material.
  • Stiffness (Modules) How much is the part going
    to bend?
  • Strain How much will the part change under a
    load to the original shape?
  • Yield Point When a part is subject to a load, it
    may no longer return to is original shape.
  • Tensile Strength Maximum strength of a material
    with breaking (elongation).
  • Poissons Ratio Material Necks
  • Creep Load and Thermal
  • Shear Strength
  • THE PERFORMANCE OF A PLASTIC PART IS AFFECTED BY
    WHAT KIND OF LOAD THE PART WILL SEE (Tensile,
    Impact, Fatigue, etc.)HOW BIG THE LOAD IS?HOW
    LONG OR OFTEN THAT LOAD WILL BE APPLIED?HOW HIGH
    AND/OR LOW A TEMPERATURE THE PART WILL SEE?HOW
    LONG IT WILL SEE THOSE TEMPERATURES?THE KIND OF
    ENVIRONMENT THE PART WILL BE USED IN. WILL
    MOISTURE OR OTHER CHEMICALS BE PRESENT?

13
Designing with Plastics
  • THIS IS WHERE PLASTICS DIFFER IN THEIR BEHAVIOR
    WHEN COMPARED TO OTHER MATERIALS, SUCH AS METALS
    AND CERAMICS. CHOOSING STRESS AND/OR MODULI
    VALUES THAT ARE TOO HIGH AND DO NOT ACCOUNT FOR
    TIME AND TEMPERATURE EFFECTS CAN LEAD TO FAILURE
    OF THE PART.
  • THIS IS WHERE PLASTICS DIFFER IN THEIR BEHAVIOR
    WHEN COMPARED TO OTHER MATERIALS, SUCH AS METALS
    AND CERAMICS. CHOOSING STRESS AND/OR MODULI
    VALUES THAT ARE TOO HIGH AND DO NOT ACCOUNT FOR
    TIME AND TEMPERATURE EFFECTS CAN LEAD TO FAILURE
    OF THE PART.
  • Remember, MATERIALS DON'T FAIL, DESIGNS DO.
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14
Did You Know?
  • Between 1990 and 1996 the amount of waste going
    into landfills declined by more than 17 percent.
  • We are recycling more than ever before. With an
    average recycling rate of 27 percent, and over 60
    percent for some materials, we have exceeded US
    EPAs national goal.
  • For every seven trucks needed to deliver paper
    grocery bags to the store only one truck is
    needed to carry the same number of plastic
    grocery bags.
  • Plastic lumber made with recycled plastic, holds
    nails and screws better than wood, is virtually
    maintenance free and last for 50 years.
  • Today, 12,000 communities provide recycling
    service to 184 million people.

15
Biodegradable Plastics
  • Biodegradable- means that microbial species in
    the environment will degrade a portion (or all)
    of polymeric material, under the proper
    environmental conditions, and without producing
    toxic by-products.
  • 3 Biodegradable Plastics
  • 1. starch-based system farthest along in
    production capacity
  • 2. lactic-based system based in medical and
    pharmaceutical uses
  • 3. fermentation of sugar process results in
    production of a highly crystalline and very stiff
    polymer (acts similar to polymers from petroleum)

16
Crystallinity
17
  • Recycling of Plastics
  • Recycling Symbols are used to correspond with
    each plastic
  • 1. PETE (polyethylene)
  • 2. HDPE (high-density polyethylene)
  • 3. V (vinyl)
  • 4. LDPE (low-density polyethylene)
  • 5. PP (polypropylene)
  • 6. PS (polystyrene)
  • 7. Other

18
Elastomers (Rubbers)
  • Rubber- defined as being capable of recovering
    from deformations quickly
  • -Natural rubber latex base (milk-like sap from
    inner bark of tropical tree), resistance to
    fatigue and abrasion
  • -Synthetic rubbers better resistance to heat,
    chemicals, and gasoline than natural rubber.
  • -Silicones most useful range of temperature of
    elastomers, low resistance to oil and wear
  • -Polyurethane high strength, as well as harness
    and stiffness, good resistance to breaking and
    abrasion

19
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20
The Structure of Ceramics
  • Ceramics- compounds of metallic and nonmetallic
    elements
  • Traditional ceramics tiles, brick, sewer pipes,
    and pottery
  • Industrial ceramics (engineering ceramics) used
    in automotives, aerospace, and turbines
  • Raw Materials- clay (oldest, fine-grained
    sheet-like structure), kaolinite (white clay made
    of silicate of aluminum, slippery and moldable
    characteristics), flint (composed of fine
    silica), feldspar (crystalline minerals with
    aluminum silicates and potassium, sodium, or
    calcium)
  • Porcelain- white ceramic made of kaoline,
    quartz, and feldspar

21
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22
Types and General Characteristics of Ceramics
  • Oxide Ceramics
  • Alumina high hardness and average strength
  • Zirconia high strength and toughness
  • Carbides
  • Tungsten depend on cobalt binder content
  • Titanium nickel and molybdenum binder
  • Silicon high temperature strength and wear
    tolerance
  • Nitrides
  • Cubic boron 2nd hardest substance (1st diamonds)
  • Titanium gold in color
  • Silicon high resistance to thermal and creep
  • Sialon contains silicon nitrides and other
    oxides and carbides
  • Cermets made up of oxides, nitrides, and
    carbides
  • Silica a polymorphic material, high-temperature
    resistanc

23
Mechanical Properties
  • The tensile strength increases with decrease in
    grain size and porosity
  • UTS UTSoe-nP P volume
    fraction of pores in the solid
  • The Modulus of elasticity of ceramics is related
    to the porosity
  • E Eo( 1- 1.9P 0.9P2) Eo the modulus at zero
    porosity
  • Ceramics are have less thermal-shock tolerance
    and impact toughness than metals and
    thermoplastics. This is due to their lack of
    ductility. Ceramics have static fatigue caused
    by cyclic loading. Methods to pre-stress
    ceramics are
  • Heat treatment and chemical tempering
  • Laser treatment of surfaces
  • Coating with ceramic of different characteristics
  • Surface-finishing operations

24
Physical Properties
  • Thermal conductivity ranges and is related to
    porosity
  • k ko (1- P)
  • Thermal cracking- when a small piece or layer
    breaks off, tends to be lower with a combination
    of low thermal expansion and high thermal
    conductivity
  • Anisotropy of thermal expansion- when thermal
    expansion ranges with different directions
    through the ceramic, causes thermal stresses that
    lead to cracking
  • Bioceramics- used as biomaterials for human
    joints because of strength and inertness, they
    create a structurally strong bond

25
Glasses
  • Glass is an amorphous solid with the structure of
    a liquid.
  • Glass has no distinct melting or freezing point,
    thus its behavior is similar to that of amorphous
    alloys and amorphous polymers.

26
Is Glass a liquid?
  • Usually when a liquid is cooled to below its
    melting point, crystals form and it solidifies.

molecular arrangement in a crystal
27
Is Glass a solid?
  • If the viscosity rises enough as it is cooled
    further, it may never crystallize.
  • The molecules then have a disordered arrangement,
    but sufficient cohesion to maintain some rigidity.

molecular arrangement in a glass
28
What is in glass?
  • All glasses contain at least 50 silica, which is
    known as a glass former.
  • The composition and properties of glasses can be
    modified greatly by the addition of various other
    elements.
  • These are known as Intermediates or Modifiers.

29
Examples of Glasses
  • Soda Lime Glass
  • General purpose glass
  • Lowest cost

30
Examples of Glasses 2
  • Borosilicate Glass
  • Very resistant to chemical attack
  • Easy to cut
  • High luminous transmission
  • Uses are touch control panels, LCD, solar cells

31
Examples of Glasses 3
  • Lithium Potash Borosilicate Glass
  • Relatively high operating temperature
  • Microwave window applications
  • Low coefficient of thermal expansion
  • Excellent sealing characteristics

32
Glass Ceramics
  • Glass Ceramics have a high Crystalline component
    to their microstructure.
  • They have a near-zero coefficient of thermal
    expansion.
  • They are strong because of the absence of the
    porosity found in conventional ceramics.

33
Examples of Glass Ceramics
  • Cookware
  • Heat Exchangers
  • Gas Turbine Engines
  • Housing for Radar Antennas

34
Graphite
  • Graphite is a crystalline form of carbon having a
    sheets of close-packed carbon atoms.
  • Although brittle, graphite has a high electrical
    conductivity, thermal conductivity, and
    resistance to high temperature.

35
Examples of Graphite
  • Electrodes
  • Heating Elements
  • Furnace parts
  • Pencil lead

36
Diamonds
  • A Diamond is a principal form of carbon with a
    covalent bond structure.
  • It is the hardest substance known.
  • Although brittle, it does resist high
    temperatures in non-oxidizing environments.

37
Uses of Diamonds
  • Jewelry
  • Heat Sinks for Computers
  • Windows for high-power lasers
  • Cutting/Grinding Tools

38
Composite Materials
  • A composite material is a combination of two or
    more chemically distinct materials to form a
    stronger material.
  • The oldest example of composites, dating back to
    4000 BC is the addition of straw to clay in the
    making of mud huts.

39
Examples of Composite Materials
  • Aircraft
  • Space Vehicles
  • Offshore Structures
  • Piping
  • Electronics
  • Automobiles
  • Boats
  • Sporting Goods

40
Fiber Reinforced Plastics
  • Fiber Reinforced plastics, also known as
    polymer-matrix composites, consist of fibers in a
    polymer matrix.
  • Reinforced plastics have improved fatigue
    resistance, greater toughness, and higher creep
    resistance than non-reinforced plastics.

41
Examples of FRP
  • Glass Fibers used most widely, and least
    expensive of all fibers
  • Graphite Fibers also known as Carbon Fiber. It
    is more expensive than Glass Fiber, but also
    stronger.
  • Boron Fibers Consists of Boron deposited onto
    Tungsten. Boron Fibers are very strong, and very
    resistant to high temperature, but also very
    heavy and very expensive.

42
Properties of Reinforced Plastics
  • The mechanical and physical properties of
    reinforced plastics depend on the type, shape,
    and orientation of the reinforcing material.
  • Physical properties of reinforced plastics and
    their resistance to fatigue, creep and wear
    depend on type and amount of reinforcement.
  • Critical factor is strength of the bond between
    fiber and polymer matrix.
  • Weak bonding causes fiber pullout and
    delamination.

43
Effect of Type on Fiber Type on Fiber Reinforced
Nylon
44
  • Highest stiffness and strength are achieved when
    fibers are aligned with tension force.
  • Unidirectional strongest, weaker transverse
    properties.
  • Optimal configuration for specific task.
  • Weaving techniques for optimal strength

45
Applications of Reinforced Plastics
  • First application of reinforced plastic was in
    1907 acid resistant tank made of phenolic resin
    and asbestos fibers.
  • Major development in1970s resulting in advanced
    composites
  • Fibers used are usually graphite, boron, aluminum
    oxide, silicon carbide or tungsten
  • Matrix Materials usually consist of aluminum,
    magnesium, copper, titanium and super alloys.

46
  • Typically used in aircrafts, rocket components,
    automobile bodies, sporting goods and various
    other structures and components.
  • Boeing 777 is made of 9 composites
  • Weight savings reduced fuel consumption by 2

47
Mercedes-Benz SLR McLaren
  • Carbon fiber body
  • Rigidity and crash performance very good
  • Light weight allows for optimal performance

48
Metal-Matrix Composites
  • Advantages of a metal matrix composite (MMC) over
    a polymer composite are higher elastic modulus,
    toughness, ductility, and higher resistance to
    elevated temperatures.
  • Limitations are higher density and greater
    difficulty in processing parts.
  • MMC Matrix materials are usually aluminum,
    magnesium, copper, titanium and super alloys.

49
Metal-Matrix Composite Materials and Applications
50
Ceramic-Matrix Composites
  • Ceramic-Matrix Composites (CMC) are important
    because of resistance to high temperature and
    corrosive environments.
  • Ceramics are strong and stiff, resist high
    temperatures, lack toughness
  • Matrix materials may retain strength up to 1700C
  • Some CMC matrix materials are silicon carbide,
    aluminum oxide
  • Some applications of CMC include jet and
    automotive engine components, structural
    components and cutting tools.

51
Other Composites
  • Composites may also consist of coatings of
    various metals
  • Plating of aluminum for decorative purposes
  • Enamels
  • Cutting tools and dies, such as cemented carbides
    and cermets.
  • Precision grinding.

52
References
  • http//www.valleydesign.com/pr16.htm
  • http//math.ucr.edu/home/baez/physics/General/Glas
    s/glass.html
  • http//www.dictionary.com
  • Kalpakjin and Shmid. Manufacturing Engineering
    and Technology. Prentice hall, 5th edition.
  • http//www.nd.edu/manufact/pdfs/
  • www.germancarfans.com/.../ eng/mercedes/1.html
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