Composite Resins Utem 17 Ogos

8/9/2019 Composite Resins Utem 17 Ogos

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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

Composite Resins Utem 17 Ogos

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