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Composite Resins
Dr. Hady Efendy
August 2010
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What we will discuss
Basics of composites Matrix properties in general Basics of polymers
Polyesters Epoxies Vinyl esters Phenolics
Specialty thermosets Thermoplastics Properties and Testing
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Composites
Very important in our 21st Century world
Listed as one of the top 10 greatestengineering developments of last quarterof the 20th Century
Others: Apollo moon landing, unmannedsatellites, microprocessor, CAD, CT scan,
jumbo jet, lasers, fiber-optic communication,genetic engineering
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What are composites?
Solid materials composed of a binder ormatrix that surrounds and holds in placereinforcements.
The material consists of two (or more) phases
One of the phases is continuous (the matrix)
The other phase is discontinuous (the
reinforcement) The phases can be thought of as a group of
islands (discontinuous) in a sea (continuous)
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Matrix purposes
Hold the reinforcements together
Give shape to the object
Transfer loads to the reinforcementsProtect the reinforcements Heat
Weather
Flammability Impacts
Solvent/water
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Reinforcement purposes
Carry the load (most mechanicalproperties)
Give directionality of some properties(optional)
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Types of composites
Engineering
Fiberglass reinforced
Matrix of unsaturated polyesters and vinyl esters or
common engineering thermoplastics Uses: tub/shower, boats, automotive, pipes,
architectural, etc.
Advanced
Carbon fiber, aramid fiber, or other high performancereinforcements
Matrix of epoxies and specialty resins
Uses: aerospace, sporting goods, specialty
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Periodic Table of the Elements
Metals Non-MetalsCeramics(Ionic Bonds)
Metals(Metallic Bonds)
Polymers(Covalent Bonds)
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Polymers
Polymers can be natural (like wood,cotton, wool, leather)
Polymers can be man-made (plastics)
Polymers can be easily shaped (molded)
Polymers have other advantages over
ceramics and metals
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Polymers
Made from small molecules (monomers)which are linked together mono means one
mer means unit The linked monomers form a chain-like
structure called a polymer
poly means many The links are the covalent bonds between
the atoms
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Polymers
M
M M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
Monomers
Polymer
CovalentBonds
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Polymers
H
H
C
C
H
H
C
H
H
C
H
H
C
H
HC
H
H
H
H
C
CH
H
Monomer
Polymer
H
H
C
C
H
H
C
H
H
C
H
H
C
H
HC
H
H
H
H
C
CH
H
Polymer
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Polymers
Many millions of chains exist in the typicalpolymeric part
The chains are intertwined
Like a mass of spaghetti
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What determines physical, chemicaland mechanical properties of
materials?
Molecular shape and movement
Crystallinity Thermal transitions and crosslinks
Aromaticity
Pendant groups
Chemical nature of the backbone
Bonding between matrix and reinforcements
Polarity (like attracts like)
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Polymers Physical structure
Amorphous Polymers that have no regularinternal structure (just like the spaghetti)
Semi-crystalline Polymers that have some
internal structure (regular packing) Semi-crystalline polymers vary in the amount of
packing (crystallinity)
Semi-crystalline polymers with high percentage of
packing are sometimes called crystalline No polymers are 100% crystalline
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Amorphous and Crystalline
Amorphous(random entanglement) Semi-Crystalline or Crystalline(regular packing)
CrystalRegions
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Polymers melting, molecularweight, crosslinking
Polymers are classified into two groupsdepending on whether they are crosslinked
Thermoplastics (not crosslinked)
Thermosets (crosslinked) Crosslinks are covalent bonds that link
between the polymer chains
When crosslinking occurs, the polymers will nolonger melt
When heated to a high temperature, they burn or char
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Thermoplastics Thermoplastics are not crosslinked and so they
will melt Thermoplastics are processed (molded) as
molten liquids Thermoplastics are cooled to solidify
Thermoplastics can be re-melted repeatedly Kitchen example:
candy
Examples of thermoplastics: polyethylene,polystyrene, nylon, polycarbonate, acrylic,Teflon, PET (thermoplastic polyester)
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Thermosets
Thermosets are crosslinked and do not melt Crosslinking is sometimes called curing Thermosets are processed as room
temperature liquids Thermosets are heated to solidify Kitchen example:
cake
Examples of thermosets: polyesters, vinyl
esters, epoxies, phenolics, polyimides, silicones
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Thermal Transitions
Heat Distortion Temperature (HDT) Glass transition temperature (Tg)
Melting point (Tm)
Decomposition temperature (Td)
Semi-crystallinethermoplastic
Thermoset
Temperature
HDT Tg Tm Td
HDT Tg Td(Tm)
Hard, stiff Leathery Liquid
Degraded, Char
Degraded
Hard, stiff Semi-rigid
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The Great Dilemma in Polymers
Polymers must havegood properties
Good properties are
favored by highmolecular weight
Polymers must havegood processing
Good processing is
favored by lowmolecular weight
Molecular Weight
MechanicalProp
erties
Molecular Weight
EaseofProce
ssing
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The Great Dilemma In Polymers
Thermoplastics meet the dilemma bycompromise High enough molecular weight to get adequate
properties Low enough molecular weight to process OK
Thermosets meet the dilemma bycrosslinking Low molecular weight initially (for wetout and
processing) followed by curing to increasemolecular weight
No compromise is required
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Polymers Molecular shape
Aromatic Contains the benzene group(sometimes called phenyl group)
Named aromatic because it tends to have a strongsmell (like styrene)
Increases stiffness Increases strength
Increases non-flammability
Aliphatic Does not contain the benzene group
Increases flexibility
Increases toughness
Increases weatherability
CC...C C...
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( )n
...C C C C...CC...C C...
CC
CC
C
C
C...OC
C
C
C
C
CC
C
C
C
C
C
C
OCC C
O
C......C
H
NC
C
C
C
C
C C C
C
C
C
C
C
O
OH OH
OHOHOH
C
C
CC
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
....C C...
C.......C
Polyethylene (no aromatic)
Polystyrene (pendant
aromatic)
Epoxy (aromatic backbone)
Kevlar aromatic backbone)
Phenolic (aromatic network)
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Bonding
Bonding is strongest when electrons are:
Transferred (ceramics)
Shared by many atoms (metals)
Shared by two atoms (covalent)
Weak bonding occurs without electronsbeing transferred or shared
These weak bonds depend upon polarity
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Polarity
N S S N
S N S N
...C C O
O
C...
-
-
O
HH
O
HH
C O--
C O
Polyester is attacked by water molecules
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Bonding in polymers by polarity
Polar areas on the polymers attract otherpolar areas on other molecules. Opposite charges attract
The most electronegative atoms are thosethat cause polarity
The electronegative atoms are: F, O, N, Cl
These are all in the upper right corner of theperiodic table
Non-polar areas attract other non-polarareas
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Bonding
Fiberglass
Sizing (alkylsilane)
...O Si O Si O...
OH
OH
OH
OH
....C C O C C C
O
C C...
CH3 Si O C C C
CH3
C C C C...
CH3 Nonpolar regions (weak attraction)
-
-
A highly polar molecule
Largely non-polarPolyester
Mixed polar/non-polar
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Thank you
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