Group 6 PresentationChapter 7, 8, and 9

Gavin Kurey

Kevin Archibeque

David Barboza

Cedric Turcotte

Marcos Gonzales

Overview of Presentation:

Structure, General Properties, and Applications of:

• Polymers (Ch. 7)

• Ceramics, Graphite, and Diamonds (Ch. 8)

• Composite Materials (Ch. 9)

Pictures from Accelrys

Chapter 7Structure, General Properties, and Applications of Polymers

• Background of Polymers

• Characteristics of Polymers

• The Structure of Polymers

• Types of Plastics and Rubbers

• Recycling Plastics

Background of PolymersTerminology:

• Polymer – Poly meaning many and mer meaning unit.

• Monomers – Basic building block of a polymer.

• Macromolecules – extremely large collections of molecules to form one unit.

• Plastics – a synonym for polymers.

• Synthetic – manmade.

Background of Polymers• The word plastic comes from the Greek word plastikos, meaning capable of being molded and shaped.

• The earliest polymers, such as cellulose, were made from natural organic materials from animals and vegetable products.

Background of Polymers• Bakelite, the earliest synthetic polymer, is made from phenolformaldehyde, a thermoset developed in 1906.

Background of Polymers• The development of modern polymer technology began in the 1920’s when raw materials necessary for making polymers were extracted from coal and petroleum products. Ethylene was the first example of such raw material.

Characteristics of Polymers

• Plastics contain large molecules

• Two common examples of how plastics can be shaped are: Forming Machine Casting

Characteristics of Polymers

Characteristics of Polymers

Characteristics of Polymers

Characteristics of Polymers

Advantages of using plastics:• Low Cost• Low Electrical and Thermal Conductivity• Low Density• High Strength-to-Weight Ratio• Resistance to Chemical Corrosion• Amount of Noise Reduction• Assortment of Colors and Transparencies• Ease of Manufacturing• Minimal Additional Surface Treatments• Forms of Availability Such As: Tubes, Films,

Sheets, Plates, Rods, etc.

Structures of Polymers

Definitions:•Molecular Weight Distribution (MWD), is the sum of the molecular weights of the mers in a chain• Degree of Polymerization (DP), is the size of the polymer chain

•MWD and DP determines the tensile strength, impact strength, and viscosity of polymers.

Structures of Polymers

• An increase in MWD, increases:

Tensile Strength Impact strength Resistance to cracking Viscosity

• The larger DP, the larger: Viscosity Cost (because harder to shape)

Structures of Polymers

• Polymers are very large molecules compared to most other organic materials• They are long chain of molecules linked together by a process called polymerization.•There are two important types of Polymerization:

Condensation Polymerization

Addition Polymerization

Structures of Polymers

• Condensation Polymerization: Known as Step-Growth or Step Reaction Is the process in which polymers are produced by the formation of bonds between two types of reacting mers. In better terms, the polymer grows step-by-step until all of one reactant is consumed. Example: Water is condensed out to make plastic.

Structures of Polymers

• Addition Polymerization: Known as chain-growth or chain-reaction Much faster than condensation method Is the process in which the chain-growth takes place without reactant by-products such as water An initiator is added to the reaction to open the double bond between the two carbon atoms

Structures of Polymers• Examples of the basic building blocks for plastics:

Structures of Polymers• Linear Polymers

Sequential structures• Branched Polymers

Increase resistance to deformation and stress cracking.

• Cross Linked Polymers(Thermosets) have a major influence in polymers. Imparting hardness, strength, stiffness, brittleness, and better dimensional stability.

• Networked Polymers(highly cross linked), have a higher strength when exposed to high energy radiation, UV light, x-rays, or electron beams.

Structures of Polymers

• Copolymers contain two types of polymers Ex: Styrene-butadiene, used in making tires

• Terpolymers contains three types of polymers

Ex: Acrylonitrile-butadiene-styrene, used to make helmets

Structures of Polymers

• Amorphous, the polymer chains exist without order.

• Crystallites, the regions arrange themselves in an orderly manner.

Structures of Polymers

• As Crystallinity increases polymers become: Stiffer Harder Less ductile More dense Less rubbery More resistant

to solvents and heat.

ThermoplasticsPolymers that can undergo external shaping forces and return to their original state

Ex: Acrylics, Nylons, Polyethylenes

ThermoplasticsCharacteristics and Effects on Thermoplastics:

•Effects of Temperature

•Rate of Deformation

•Orientation

•Creep/Stress Relaxation

•Crazing

•Water Absorption

•Thermal and Electrical Properties

Effects of Temperature•Glass-Transition Temperature (Tg)•Above the Tg, the thermoplastic gradually softens and eventually turns into a viscous fluid.•Repeated heat-cycling causes thermal aging or degredation.•Effects of Temp. on thermoplastics is similar to that of metals, (for increased T, Increased toughness, strength/modulus of elasticity decreases)

Rate of Deformation•Thermoplastics can undergo large uniform deformation in tension before fracture.

•This characteristic allows for thermoforming.

•Complex shapes can be made, like bottles, meat trays, etc.

Orientation•Under deformation, the molecules within thermoplastics align themselves in unison with the deformation.

•This is called Orientation.

•The specimen becomes anistropic

•Important for enhancing strength and toughness properties

Creep/Stress Relaxation•Most thermoplastics are susceptible to Creeping and/or stress relaxation

•This can even occur at room temperature!

Crazing•Localized, deformed areas that are wedge-shaped that occur under stress

•Sometimes appearing to be cracks, crazes are usually comprised of voids (50%).

•Caused by enviroment stress or other external forces, like solvents.

•Stress whitening

Water Absorption•Polymers absorb water

•Water acts as a plasticizing agent

•Lubrication

•Tg, elastic modulus, and yeild stress are all lowered when water is absorbed

•Dimensional changes

Thermal/Electrical Properties•low thermal/electrical conductivity and a high coefficient of thermal expansion

•Good as insulators and packaging for electronics

•Doping

•Electrically conducting Polymers (metal powders, iodides, salts)

•Thermally conducting Polymers (nonmetallic, conductive particles;100x more conductive)

Thermosets•When long chain molecules in a polymer become one giant molecule with strong covalent bonds and is from then on permanently set.

•The curing reaction of a thermoset is irreversible, unlike thermoplastics

•No set Tg value, rate of deformation, or response to temperature.

Additives in Plastic•Plasticizers

•Carbon Black

•Fillers

•Colorants

•Flame Retardants

•Lubricants

Plasticizers•Adds Flexibility

•Adds Softness

•Achieved by reducing secondary bond strength

•Most common use of a plasticizer is found in PVC (Polyvinylchloride)

Carbon Black•Soot

•Compounded into plastics and rubbers

•Protects against Oxidation and Ultraviolet Radiation

Fillers•Reduces overall cost of a polymer

•May improve hardness, toughness, stiffness, abrasion resistance, etc

•Common fillers include: Saw Dust, silica flour, clay, mica, talc, asbestos, etc

Colorants•Organic or Inorganic

•Dyes(organic)

•Pigments(inorganic)

•Colorant selection depends on service temperature and light exposure.

•Pigments have a higher tolerance to temp and light.

Flame Retardants•Additives to reduce the flammability of a polymer

•Common additives include phosphorus, chlorine, and boron

•Cross-linking reduces flammability as well

Lubricants•Added to reduce friction during processing.

•Typical lubricants are: Linseed oil, mineral oil, waxes, metallic soaps, etc

•Very important to keep thin polymer sheets from sticking to each other

General Applications of Thermoplastics and

Thermosets

Biodegradable Plastics•Biodegrability - microbial species can decompose the object over time

•Three different biodegradable plastics have been developed thus far: Starch-based, Lactic-based, and Fermented Sugar Systems.

Recycling•Thermoplastics can be recycled by melting them down and reshaping them into new products

•Recycling symbols/numbers1 PETE (polyethylene)

2 HDPE (high density polyethylene)

3 V (vinyl)

4 LDPE (low density polyethylene)

5 PP (polypropylene)

6 PS (polystyrene)

7 Other

Elastomers•Also known as Rubber

•Ability to undergo large elastic deformations without rupture

•Highly kinked structure

•Stretch under load, but return to original shape without load

•Vulcanization (cross-linking w/ sulfur)

•Types of elastomers: Natural Rubber, Synthetic Rubber, Silicones, Polyurethane

Ceramics

Definition: Ceramics are compounds of metallic and non-metallic elements

Two Major Categories: Traditional such as whiteware, tiles, bricks, and pottery.

Industrial uses: turbines, cutting tools, and aerospace applications.

Major types of oxide ceramics

Alumina: •Used both in its raw form or as an ingredient blended with other ceramics.

•Are the most commonly used ceramic material

•Used as an abrasive such as grinding wheels or sandpaper.

•Affordable compared to other ceramics.

Major types of oxide ceramicsZirconia: •Possesses high toughness and strength, resistance to thermal shock, wear, corrosion and low thermal conductivity.

•Excellent or good for high heat applications such as dies for hot extrusions, aerospace coatings.

Definitions: •Thermal Shock-Refers to the development of cracks after a single thermal cycle.

•Thermal conductivity- Rate at which heat flows within and through a material. Ionically or covalently bonded have poor conductivity

CarbidesTungsten Carbide

•Made from tungsten-carbide particles with cobalt as a binder

•The quantity of binder used has a major influence on the attributes of the final product.

•Cobalt increases toughness, but hardness, strength, and wear resistance decreases

Titanium Carbide

• Not as tough as Tungsten Carbide.

•Uses nickel and molybdenum as a binder.

•Most often used as cutting tools.

Silicon carbide

•Low friction coefficient while still retaining its strength at elevated temperatures.

NitridesCubic Boron Nitride •It is the second hardest known substance. •Synthetically made in a manner similar to synthetic diamonds. •It is not found in nature.•It is often used in cutting tools and abrasive wheels.

Silicon Nitride

•Used in high temperature applications since it possesses a high resistance to thermal shock and creep.

Definition •Creep is the permanent elongation of a component under a static load over a long period of time.

Nitrides

Titanium Nitride (TiN)

• Is gold in color and is very widely used as a coating for cutting tools. Drill bits, end mills, etc.

Sialon and Cermets Sialon

•It is a combination of Silicon, Aluminum, Oxygen, and Nitrogen.

•It is more thermal-shock resistant and has a higher strength than Silicon Nitride.

•It sees use as a machine cutting tool.

Cermets

•It is a combination of Ceramics phase bonded with a Metallic phase.

•They marry the high temperature oxidation resistance of ceramics with the ductility, toughness, and thermal-shock of metals.

•Introduced in the 1960’s.

•Often used in machining tools.

Silica and NanoceramicsSilica •Found in nature silica can have different crystal structures or is called a polymorphic material.

•The most common form found is quartz.

•The cubic structure is found in the ceramic refractory bricks used in high temperature furnaces.

Nanoceramics

•By reducing the size of the particles, nanoceramics are formed.

•They consist of atomic clusters containing a few thousand atoms.

•They are ductile at much lower temperatures than conventional ceramics

•Stronger and easier to machine with less flaws.

•Found in the automotive industry for valves, turbocharger rotors, and cylinder linings.

Bioceramics

Because of their strength and inertness the most common uses include replacement for human joints, prosthetic devices and teeth crowns.

Advantages/DisadvantagesAdvantages

•Ceramics tend to be very hard, abrasion resistant, able to operate in high temperatures, and resistant to corrosive chemicals.

Disadvantages •Expensive to manufacture and machine

•Due to the hardness and the abrasive nature of many ceramics diamond tools are required to machine, which is very time consuming and expensive.

•Tend to be brittle and do not take impact loads very well.

•Not as tough as metal

Section 8.4 - 8.7

•Types of Glasses

•Properties of Glasses

•Glass Ceramics

•Types of Graphite

•Diamond

Glass TerminologyTerminology:

Glass- an amorphous solid with the structure of a liquid.

Glass is an inorganic product of fusion that has been supercooled to a rigid condition without crystallizing.

Supercooled- the cooling of a liquid at a rate too high to allow crystals to form.

Types of Glasses

•Soda-lime glass- The most common type of commercial glass.

•Lead-alkali glass-

•Borosilicate glass

•Aluminosilicate glass

•96%-silica glass

•Fused silica glass

Types of Glasses

Soda-lime glass

Types of Glasses

Lead-alkali glass

Types of Glasses

Borosilicate glass

Types of Glasses

Aluminosilicate glass

Types of Glasses

96%-silica glass

Types of Glasses

Fused silica glass

Characteristics of GlassGlass is categorizied by its:

•Density

•Strength

•Resistance to thermal shock

•Electrical resistivity

•Hot workability

•Heat Treatability

•Chemical Resistance

•Impact-abrasion resistance

•Ultraviolet-light transmission

Glass Classifications•Colored

•Opaque (White or Translucent)

•Photochromatic (Darkens with light exposure)

•Photosensitive (Changing from clear to opaque

•Fibrous (Constructed of long fibers)

•Foam or cellular (containing bubbles)

•Hard or Soft (Thermal hardness)

•Elasticity (Modulus of elasticity 55 to 90 GPa)

•Scratch Resistance (350 to 500 HK)

Glass Ceramics•Glass Ceramics have a higher crystalline component than that of glass.•This increase in crystalline is due to the

Devitrification of the glass.•Devitrification- is the recrystallization of glass

which occurs due to the heat treating of the glass after the desired shape is

constructed.•Glass Ceramics have a hardness of 520 to

650 HK, which is significantly larger than the hardness of typical glass (350 to 500 HK).

Characteristics of Glass Ceramics

•High resistance to thermal-shock, due to their non-zero coefficient of thermal expansion

•Extremely strong due to the absence of porosity; which is typically found in traditional ceramics

•Glass ceramics are commonly used for cookware, heat exchangers in gas turbines engines, housing for radar antennas, and other electrical applications.

Background on Graphite•Graphite- a crystalline form of carbon having a layered structure with basal planes or sheet of close-packed carbon atoms.

•Lampblack (black soot) is an amorphous graphite that is used as a pigment

Characteristics of Graphite

•The strength and stiffness of graphite increases with temperature

•High electrical and thermal conductivity

•Good resistance to thermal shock and high temperature

•High resistance to chemicals

Types of Graphite and Uses•Graphite Fibers- used to reinforce plastics

•Carbon and Graphite Foams- used for core material for aircraft and ship interior panels, structural insulation, sound absorption panels, lithium-ion batteries, and for fire and thermal protection

•Buckyballs- solid lubricant particles that are made from lampblack (black soot)

•Nanotubes- used as a natural building material for new microelectromechanical systems

Types of GlassesBuckyballs Nanotubes

Diamonds•Diamond- a principal form of carbon with a covalently bonded structure

•Hardest substance known (7000 to 8000 HK)

•Very brittle, starts to decompose in air at 700oC

Chapter 9:

Composite Materials

Definition:

A composite material is a combination of two or more chemically distinct and insoluble phases with recognizable interface, in such manner that its properties and structural performance are superior to those of the constituents acting independently. (Book definition p.238)

Quick examples:

Every day use to space ship applications…

•First engineering application 1907:acid-resistant tank (Phenolic resin with asbestos fibers)

•Steel-wire reinforced tires;

•Snow boards / skis;

•Tennis raquets;

•Protective gear;

Quick examples:

Reinforced concrete;

2 x more resistant (compression)

Sailboard

(see p.249);

Quick examples:

Fiberglass;

Quick examples:

Brake pads / rotors;

Quick examples:

High speed

fan blades;

Quick examples:

High performance racing body parts;

Quick examples:

Structure of reinforced plastics (composite)

Don’t get confused by the PLASTIC appellation.

Reinforced plastics: also know as polymer-matrix composites & fiber-reinforced plastics.

Two phases:

1 . Fibers (discontinuous)

2. Matrix (continuous)

Fibers:

Known as a slender, elongated, threadlike object or structure

Fibers: (continued)

They combine high strength and high stiffness.

VarietyGraphite – Glass – Boron – Polymer;Others (boron carbide, steel, aluminium oxide, etc.)

When more then two fibers are used, the composite is called a hybrid.

Percentage of fibers in reinforced plastics varies from 10% to 60%. Anything higher then 65% usually result in lower structural properties.

Fibers are sometimes treated with a coating to increase bonding strength between fiber and matrix.

Fibers: (continued)

Cross-section usually less then 0.0004 in. (hair =0.001in)

Sensible to defects

Short & long fibers: In a given type of fiber, if the mechanical properties improve as a result of increasing the average fiber length,

then it is call a short fiber. Otherwise it’s a long fiber.

Continuous fibers: Offers a better control on composite’s reaction. Generally use for oriented forces or for increased properties.

Matrix

Known as the bonding substance.

Matrix (continued)

Tough and generally chemically inert.

Functions:• Support the fibers in place and transfer the stress to

them while they carry most of the load;• Protect the fibers against physical damage and the

environment;• Reduce the propagation of cracks in the composite

by virtue of the greater ductility and toughness of the plastic matrix.

Thermosets: epoxies (80%) – polyester - silicon

Thermoplastics: Polyetheretherketone; thougher then thermosets, but lower temperature resistance;

Metals: aluminium – magnesium - titanium

Ceramics: silicon carbide/nitride – aluminium oxide - mullite

Matrix (continued)

Properties

The mechanical and physical properties of reinforced plastics depend on type, shape, and orientation of the reinforcing material, the length of the fibers, and the volume fraction of the reinforcing material.

Short fibers are less effective than long fibers.

Bond strength between fibers and matrix is a critical to avoid fiber pullout and delamination, and to maintain good load transmission.

Orientation of fibers

Random(5-25%) (mostly short or long fibers, not continuous)

Orthogonal (20-40%) Unidirectional (100%)

Orientation of fibers

Figure 9.7 The tensile strength of glass-reinforced polyester as a function of fiber content and fiber direction in the matrix. Source: R. M. Ogorkiewicz, The Engineering Properties of Plastics. Oxford: Oxford University Press, 1977.

Figure 9.7 The tensile strength of glass-reinforced polyester as a function of fiber content and fiber direction in the matrix. Source: R. M. Ogorkiewicz, The Engineering Properties of Plastics. Oxford: Oxford University Press, 1977.

Various fibers

Various fibers

TABLE 9.2

Type

Tensilestrength(MPa)

Elasticmodulus

(GPa)Density( kg/m

3) Relative cost

Boron 3500 380 2600 HighestCarbon High strength 3000 275 1900 Low High modulus 2000 415 1900 LowGlass E type 3500 73 2480 Lowest S type 4600 85 2540 LowestKevlar 29 2800 62 1440 High 49 2800 117 1440 HighNote: These properties vary significantly depending on the material and method of preparation.

Various metal matrix

TABLE 9.3Fiber Matrix ApplicationsGraphite Aluminum

MagnesiumLeadCopper

Satellite, missile, and helicopter structuresSpace and satellite structuresStorage-battery platesElectrical contacts and bearings

Boron AluminumMagnesiumTitanium

Compressor blades and structural supportsAntenna structuresJet-engine fan blades

Alumina AluminumLeadMagnesium

Superconductor restraints in fission power reactorsStorage-battery platesHelicopter transmission structures

Silicon carbide Aluminum, titaniumSuperalloy (cobalt-base)

High-temperature structuresHigh-temperature engine components

Molybdenum, tungsten Superalloy High-temperature engine components

References for Chapter 7• http://www.accelrys.com• http://www.edmar-co.com• http://www.mahjongmuseum.com• http://www.4to40.com• http://www.seismo.unr.edu• http://www.silverhook.co.uk• http://www.nyu.edu• http://www.euroarms.net• http://alfiesantiques.com• http://depts.washington.edu• http://www.camposgroup.com• http://www.texwipe.com• http://archives.cnn.com• http://www.sandretto.it• http://weather.wkowtv.com/ images/

• http://www.scandia-nh.com• http://www.tristanperich.com

References For Chapter 8•www.performancecoatings.com•www.ortechceramics.com•www.ceramicindustry.com•www.bearingworks.com•www.tribology.com•www.fujikin.com•www.ornl.gov

References

• HTTP://WWW.MS.ORNL.GOV/RESEARCHGROUPS/CMT/FOAMS/FOAMS.HTM

• http://handle.tamu.edu/1969.1/55 • http://uk.dk.com/static/cs/uk/11/features/mi

ller/images/aa_104_7_HAMG220304.jpg• http://www.pilkington.com/resources/floatst

ructure.jpg• http://www.beadmuseumdc.org/

beadimages/bubble.jpg• http://www.pelletlab.com/images/1870.jpg

Reference List• http://www.element-collection.com

• http://www.ecplaza.net/tradeleads/seller/3415816/fused_silica_tube.html#none

• www.dupont.com/safetyglass/ lgn/stories/2906.html

• fireartstudio.ca/ WarmGlass.htm

• www.ill.fr/dif/ 3D-crystals/bonding.html http://www.hofstra.edu/Academics/HCLAS/Chemistry/CHM_faculty_nirode.cfm

• www.npacorp.com/ products/vitrolite.html

References

•Book ‘Des Materiaux’, Jean-Paul Baïlon, Edition Polytechnique. •http://hypertextbook.com/facts/1999/BrianLey.shtml