Thermosets_ Epoxy, Polyesters, Vinyl esters, Polyurethanes, and Phenolics

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Nov 25, 2013 (3 years and 10 months ago)

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1

Thermosets_ Epoxy, Polyesters, Vinyl
esters, Polyurethanes, and Phenolics

Professor Joe Greene

CSU, CHICO

2

Composites

Reference: Appendix E.
Industrial Plastics, Modern Plastics Encyclopedia

(p142)


History


Applications


Advantages/Disadvantages


Chemistry and Chemical Structure


Mechanical Properties


Physical Properties


Processing Characteristics


Other thermosets


Review


Questions


3

Composites History


Thermosets are polymers that undergo a chemical reaction
during the polymerization.


Thermosetting reaction is not reversible under heat.


Epoxy


Standard epoxy is based on bisphenol A and epichlorohydrin.


Others based on phenols and formaldehyde or aromatic amines and
aminophenols


Curing can occur at room temperature with the use of 2 component
systems. Curing at elevated temperature with use of one
-
component.


Properties include good adhesion to many substrates, low shrinkage,
high electrical resistivity, good corrosion resistance, and thermal.


Processing is achieved without generation of volatiles.









4

Polymers Composites


Objectives


Define the components and difference types of composites.


Explain the different types of composite construction and the reasons
behind them.


Describe the various manufacturing methods used to produce
composites.


List the different reinforcing materials used in composites.


List the various matrix materials used in composites.


Excellent Web sites


Michigan State
http://islnotes.cps.msu.edu/trp/


U of Delaware
http://www.ccm.udel.edu/publications/CU/99/


Cornell University
http://www.engr.siu.edu/staff2/abrate/NSFATE/links.htm

5

Composites


Composite definition


A composite is a material comprised of two or more physically distinct
materials with at least one material providing reinforcing properties on strength
and modulus.


Natural Composites


Bone


Wood


Bamboo: Natures fiber glass due to pronounced fibrillar structure which is very
apparent when fractured.


Muscle and other tissue


Engineering Composites


Reinforced concrete beams


Thermoset composites: Thermoset resins (polyurethanes, polesters, epoxies)


Glass fibers, Carbon fibers, Synthetic fibers, metalfibers, or ceramic fibers


Thermoplastic composites (polypropylene, nylon, polyester,TPU,polyimide)


Glass fibers, Carbon fibers, Synthetic fibers, metalfibers, or ceramic fibers



6





8-25-98
M41_au25
5
Automotive Applications of
Plastics and Composites
n
Composite Intensive Vehicles
SMC

Sheet Molding

Compound:

Polyester Resin and

chopped glass

Polyester resin and Glass Mat Preform

With RTM Resin Transfer Molding

7

Automotive Plastics and Composites Use


Exterior Composite Panels


doors


Sheet Molded Compound (SMC) with compression molding: Camaro, Firebird and
Corvette


Polyester resin and glass mat preform with Resin Transfer Molding (RTM): Viper


hoods


Sheet Molded Compound (SMC) with compression molding: Camaro, Firebird, Corvette,
Ford trucks


Polyester resin and glass mat preform with Resin Transfer Molding (RTM): Viper,
Heavy duty trucks)


bumper beams


Glass Mat Thermoplastic (GMT) with compression molding : Camaro, Firebird, Venture,
Transport,


Interior


floor pan


Polyester resin and glass mat preform with Resin Transfer Molding (RTM): Corvette


Engine


Sheet Molded Compound (SMC) with compression molding: valve covers, intake
manifolds, fluid containers, etc.

8

Automotive Plastics and Composites Use



SMC

Sheet Molding

Compound

SMC

Sheet Molding

Compound

9

Recreational Plastics and Composites Use


Snow Equipment


skis, snow boards, snow mobiles, etc.



Water Sports Equipment


water skis, water crafts, snorkel equipment, fishing gear


diving equipment



Land Sports Equipment


shoes, roller blades, skate boards, tennis, golf


Air Sports Equipment


plane kits

10

Composite Reinforcement Classifications


Reinforcement Type


Discontinuous (fibers are chopped and dispersed in matrix resin)


Short fibers: fiber lengths 3mm or less (glass filled plastics, GF
-
Nylon)


Long fibers: fiber lengths greater than 6 mm. (Some injection molded materials with
6mm fibers, Sheet Molding Compound (SMC) with 1” fibers, DFP Directed Fiber
Preforms for RTM and SRIM)


Particulates: fibers is forms as spheres, plates, ellipsoids (some injection molded
materials reinforced with mineral fibers)


Continuous (fibers are throughout structure with no break points)


Glass roving: glass bundles are wound up in a packet similar to yarn.


Roving is woven into several weaves using a loom machine like in apparel.


Mat products: random swirl glass pattern.


Woven product: roving is woven into machine direction (warp) and cross
direction (weft)


Uni product: roving is woven in one direction with a cross thread given to
hold mat together.


11

Composites Can Have a Fiber Preform


Fiber type


Roving form that can be sprayed into a 3
-
D preform


Roving form that is woven into a glass sheet and then formed to shape
(preform)

12

Properties of Materials


Tensile modulus




Density

Spec Mod


Low alloy steel

207GPa(30Mpsi)

7.85 g/cc

26spGPa


Aluminum

72GPa

(10Mpsi)


2.8 g/cc

26spGPa


Carbon fiber

300GPa(40Mpsi)

1.8 g/cc
167spGPa


Glass fiber

76GPa

(10Mpsi)

2.56g/cc

30spGPa


Aramid fiber

125GPa (20Mpsi)

1.4g/cc


89spGPa


(Kevlar)


Tensile strength




Density

Spec Str


Low alloy steel

1500MPa(220Kpsi)

7.85 g/cc

191spMPa


Aluminum

500MPa(75Kpsi)


2.8 g/cc

178spGPa


Carbon fiber

2400MPa(360Kpsi)

1.8 g/cc
4320spGPa


Glass fiber

2000MPa(300Kpsi)

2.56g/cc

781spGPa


Aramid fiber

3000MPa (450Kpsi)

1.4g/cc


2140spGPa


(Kevlar)

13

Mechanical Properties of Thermosets



Epoxy
Polyester
PET (Thermoplastic)
Polyurethane
Density, g/cc
1.11-1.40
1.04 - 1.46
1.29-1.40
1.03 - 1.15
Tensile Strength,
psi
4,000 – 13,000
600 – 13,000
7,000 – 10,500
175 - 10,000
Tensile Modulus,
psi
350K
300K - 640K
400K - 600K
10K - 100K
Tensile Elongation, %
3%-6%
2% - 6%%
30% - 300%
3% - 6%
Impact Strength ft-
lb/in
0.20 - 1.0
0.2 - 0.4
0.25 - 0.70
25 to no break
CLTE
10-6 mm/mm/C
45-65
55 - 100
65
100 - 200
HDT 264 psi
115F-550F
140F -400F
70F -100F
70F - 150F
14

Applications for Thermosets


Epoxy


Protective coatings: maintenance coatings for industrial and marine,
tank linings, industrial floorings, beer and beverage can coatings,
food cans, appliance primers, hospital and laboratory furniture.


Bonding and adhesives: Automotive and aircraft industries adhesive
to metals and composites.


Molding, casting and tooling: Molding compounds in electrical and
electronic industries, casting resins, potting resins. Prototype and
master model tools.


Laminating and composites: Binders in fiber reinforced laminates and
composites. Laminates are used in printed wiring boards. Composite
applications include filament winding (high performance pipes in oil
fields, pressure vessels, tank and rocket motor housings), pultrusion,
casting, and molding (graphite composites for aerospace applications)


Building and construction: Flooring (seamless, self
-
leveling, or epoxy
terrazzo floors), repair of bridges and roads with glass and carbon
fiber wraps, concrete crack repair, coat reinforcing bars, binders for
patios, swimming pool decks, and soil around oil
-
well drills.












15

Applications for Thermosets


Polyester


Boat hulls, shower stalls, electrical components, appliances


Recreation vehicles, automotive body panels, floor pans; SMC


Soft tooling, patterns


Cultured marble, buttons, corrosion resistant tanks and parts,


Corrugated and flat paneling, simulated wood furniture, bowling
balls, polymer concrete, and coatings


Polyurethane


Rigid foams:
(MDI) Laminated board stock, Moldings, Bun, Foam in place
insulation, sprayed foam, packaging



Semi
-
flexible foam:
(MDI and TDI) Moldings, Integral
-
skin moldings


Flexible foam:(TDI) Moldings, integral skin molding, carpet underlay


Packaging: (TDI) Furniture cushioning


Microcellular foam: (MDI) RIM parts, shoe soles


Non
-
foam cast elastomers


Coatings, binders, thermoplastic elastomers, sealants, paints













16

Advantages of Thermosets


Epoxy


Excellent chemical and corrosion resistance


Excellent thermal properties and low creep


High stiffness and modulus properties


Polyester


Rigid, resilient to chemical and environmental exposures, corrosion
resistant, and flame retardant


Easily processed in low cost equipment


Cheaper than Epoxy


Polyurethane


High strength to weight ratios, resistance to flame spread, excellent
thermal insulation, low cost, easily processed


Cheaper than Epoxy or Polyester

17

Disadvantages of Thermosets


Epoxy


Moisture absorption, toxicity, not recyclable


Long processing times


Cost



Polyester


Moisture absorption, toxicity, not recyclable


Long processing times


Odor from Styrene and potential health hazards



Polyurethane


Moisture absorption, toxicity, not recyclable


Potential health hazards of Isocyanates

18

Composite Matrix Resin Classifications


Resin (or matrix) type


Thermoset resins
-

those that undergo a chemical cross
-
linking reaction


Epoxy: reaction of bisphenol A and epichlorohydrin


Polyester: reaction of difunctional acid (or anhydride) and a difunctional
alcohol (glycol)


Polyurethane: reaction of alcohol and isocyanate


Phenolic


Silicone


Melamine


Thermoplastic resins
-

those that are formed under heat


Polyamines (nylon) (short and long fibers)


Polyesters (short and long fibers)


Polypropylene (short, long fibers and continuous fibers)


Other thermoplastic resins (short and long fibers)


19

Polyester Chemistry


Unsaturated Polyesters


Thermoset reaction between a difunctional acid (or anhydride) and a
difunctional alcohol (glycol)


At least some of the acid (or anhydride) features double bonds
between adjacent carbon atoms for unsaturation.


Characteristic ester linkages are formed, hence the name Polyester


C
6
H
4
(COOH)
2
+ (CH
2
)
2
(OH)
2
-
[(CH
2
)
2

-
O
-

C
-

C
-
O]
-

terephthalic acid + ethylene glycol


Polyethylene terephthalate (PET)



Acids include: maleic, fumaric, isophthalic, terphthalic, adipic, etc.


Anhydrides include: maleic, phthalic


Glycols include ethylene glycol, diethylene glycol, propylene glycol












O

O

20

Polyester Chemistry


Heat or radiation can trigger the cross linking reaction


Catalyst (or initiator) is used. Methyl ethyl ketone (MEK)
peroxide, benzoyl peroxide, and cumene hydroperoxide


Accelerators (or promoters) speed up the reaction.


Inhibitors extend shelf life
(hydroquinone, tertiary butyl catechol)


Condensation Reaction results in CO
2

and H
2
O


Monomer required to polymerize, e.g., Styrene, to react with
the unsaturations in the polyester molecules to form 3
-
D
network.


Styrene at 30% to 50% in commercial polyester systems for polyester


vinyl toluene for vinyl ester resins


methyl methacrylate

21

Polyester Chemistry


Step 1: Create polymer and build MW of polymer chain


Condensation
Polymerization of Di
-
ACID and Di
-
ALCOHOL


Fig 2.: Condensation reaction


Connects one end of acid with one end of alcohol to form polyester bond.


The opposite end of acid reacts with another free end of alcohol, and so on .


Have water as a by
-
product means condensation.


Still have unsaturated polymer. The Carbon atom has double bonds:




22

Polyester Chemistry


Step 2: Crosslink polyester polymer with unsaturated styrene.


Addition

(free radical) reaction to connect polyester with styrene


Use a peroxide (free radical) to open the unsaturated bond to form saturation


One reaction starts, the other unsaturated bonds open up and react with the
styrene to form a saturated polymer.


The ends of the polyester
-
styrene crosslinked polymer has peroxide end
-
groups.


Peroxide is an initiator and not a catalyst since it is consumed in reaction.
Catalysts are not consumed in the reaction and can be retrieved at the end of it.

23

Epoxy Chemistry


Epoxy: O H H


C C H + H
2
N (C) N (C) NH
2


H H H H


epoxide group + amines (DETA) epoxy



Other epoxy resins


diglycidyl ether of bisphenol A (DGEBRA)


tetraglycidyl methylene dianiline (TGMDA


epoxy phenol cresol novolac


cycloaliphatic epoxies (CA)


Curing agents
(hardeners, catalysts, cross
-
linking agents)


aliphatic or aromatic amines (DETA, TETA, hexamethylene tetramine,etc.)


acid anhydrides (phthalic anhydride, pyromellitic dianhydride, etc.)


Active hydrogen react with epoxide groups.



As much as 15% hardener is needed





















24

Polyurethane Chemistry


Reaction between isocyanate and alcohol (polyol).


Crosslinking occurs between isocyanate groups (
-
NCO) and
the polyol’s hydroxyl end
-
groups (
-
OH)


Thermoplastic PU (TPU) have some crosslinking, but purely
by physical means. These bonds can be broken reversibly by
raising the material’s temperature, as in molding or extrusion.


Ratio between the two give a range of properties between a
flexible foam (some crosslinking) to a rigid urethane (high
degree of crosslinking).


In PUR foams density can range from 1 lb/ft3 to 70 lb/ft3.


Foams are produced by chemical blowing agents.


Catalyst are used to initiate reaction.


RIM process is used to produce fenders and bumper covers


25

Other Thermosets


Polyimides


Bismaleimide


Polybenzimidazoles


Phenolics


Carbon Matrices


Thermoplastic matrices


Polyamides


Polypropylene


PEEK


Polysulfone


PPS


Ceramic Matrices


Metal Matrices


26

Polyimides



For temperature stability up to 600 F


Polyimides or polybenzimidazole (PBI) rather than epoxy


Aerospace applications due to high cost


Chemical Structure


Polyimides


Characterized by cyclic group containing a nitrogen and two
carbonyl groups (C with double bond with oxygen)


PBI


Characterized by a five member ring containing two nitrogens
and is attached to a benzene ring.


Polyimids and PBI are structurally planar and very rigid. Large
aromatic groups are added into polymer to make stiffer.



27

Polyimides



Formed with two step condensation. Fig 2
-
5


First step: An aromatic dianhydride is reacted with an
aromatic diamine to form polyamic (polamide) acid.


Second step: Curing of the polyamic acid.


Formation of imide group by closing of 5
-
member ring


Condensation step of solvent molecules: water, alcohol, solvents


Chain extension


Cross
-
linking


High viscosities of polyamid acids require use of prepregs.


Impregnating the fiber mat with monomer solutions of diamines
and diester acids.


Long times and gradual increase in temperature are needed.




28

Polyimides



Major condensation polyimids, Dupont’s Avimid N & K


are marketed as Prepreg polyimids


Avimid N Tg = 675F (360C), and


Avimid K: Tg = 490F (254C)


Linear polyimids are produced which have thermoplastic
behavior above the Tg.


They process like thermoplastics for a few heat cycles.


Advantages of thermoplastic nature


Tractable nature of resins when hot facilitates the removal of
volatiles.


Voids, formed as result of the evolution of gases, can be
eliminated by applying pressure while heating the resins above Tg.


Applications


Wing skins for high performance aircraft.




29

Polyimides



Addition Polyimides


Many polyimids are cross linked with an addition reaction


Two general cross
-
linking reactions are widely used


End group reactions


Bismaleimide reactions


Reactive End Group Resin Fig 2
-
6


First phase (imidization): results in the formation of the oligomeric (small
polymer) imide


Second phase (consolation): is when the oligomer melts and flows to fill
voids that were created from volatiles depart.


Third phase (crosslinking): oligomer builds MW & crosslinks

»
MW = 1500


Shorter polymer chains gave lower viscosity and better wet
-
out

»
Wet
-
out is defined as uniform coating and soaking of resin in fiber.


Commercial end group resin (PMR) is PMR 11, PMR 15 and PMR 20

»
PMR
-
11 has more end groups and higher cross
-
linking density and
higher stiffness

»
PMR
-
20 gave better thermal stability.

»
PMR
-
15 has the best physical properties balanced.




30

Polyimides



Second type of endgroup crosslinking has acetylene
endgroups and is called Thermid 600


Crosslinking in Fig 2
-
7


First step: joining two polyimid oligomers to form a butadiene
linkage which results in chain extension. Each double bond can
react with double or triple bonds to form highly crosslinked.


Addition reaction


Problems is with too fast a cure and chain extension competing
with cross
-
linking mechanism thus causing MW to build too fast.


Alleviated with proper solvents.


Disadvantage is the loss of tackiness in prepregs as the solvent
evaporates.



31

Polyimides



Bismaleimide (BMI) resins


Addition polymerization


Reactions involving bismaleimide (BMI) derivatives: Fig 2
-
8


Case 1


Carbon
-
Carbon double bond in the maleimide group reacts
with the carbon
-
carbon double bond in the olefin co
-
reactant
(similar to maleic acid is crosslinked with styrene in polyester)


Case 2


An aromatic diamine adds to the carbon
-
carbon double bond
of the maleimide in what is called Michaels Reaction.


Both cases: the coreactants (olefin or diamine) form bridges
between the imide molecules to form a crosslinked structure


Commericial products


Ciba
-
Geigy uses an olefinic compound with two olefins



32

Polyimides



Bismaleimide (BMI) resins


Advantages


Low processing temperature versus polyimides (Cured at
350F)


Standard epoxy processing equipment can be used since
same T.


Postcure of 475 F is required to complete
polymerization.


BMI are fully formed polyimides when reacted to form
composite


Thus, no volatiles are removed and no consolidation
problems


Tack and drape are quite good because of the liquid
component of the reactants



33

Polyimides



Polybenzimidazole (PBI) resins


Less prevalent than the polyimides, PBI have equivalent and
sometimes superior physical and thermal properties


Formation reaction
-

fig 2
-
9


Five member ring containing two nitrogens is formed with
accompanying aromatic groups.


Groups are flat and stiff leading to good physical properties and
aromatics result in high thermal.


Problems are expensive, difficult process, toxicity


Some have been alleviated and is commercially available


Resin is thermoplastic with a Tg over 800F (427C)


It does not burn, contribute fuel to flames or produce smoke


Forms a tough char


Resins are toxic and need to be handles with care.


34

Phenolics and Carbon Matrices


Phenolics is an old thermoset resin


Used for general purpose, unreinforced plastic


electrical switches


junction boxes


automotive molded parts


consumer appliance parts, handles, billiard balls


Fillers are required due to high shrinkage and brittle nature.


Sawdust, nut shells, talc, or carbon black


Fiber reinforced Phenolics have aerospace applications


Rocket nozzles, nose cones due to ablative nature (Goes from solid
to gas during burning)


High temperature aircraft ducts, wings, fins, and muffler repair kits


Carbon matrixes are new in applications requiring excellent
heat resistance


Carbon matrixes are often made from phenolics




35

Phenolics and Carbon Matrices


Phenolic chemical structure
-

Fig 2
-
10


Formed by reaction between phenol and formaldehyde


Condensation reaction releases water as a byproduct.


Initially low molecular weight, soluble and fusible,
A
-
Stage

resin


Condensation reaction involves more and more phenol molecules
that causes the resin to pass through a rubbery, thermoplastic state
that is only partially soluble phase called
B stage
.


Resin is cured and cross
-
linked thermoset resin,
C
-

Stage
.


Other terms describing phenolic formation


Resole
:
If phenol/formaldehyde reaction is carried out in excess formaldehyde
and base catalyst is called
resole

at low molecular weight stage.



Requires just heat to convert to C
-
stage (1 step)


Novolac
:
If phenol/formaldehyde reaction is carried out in excess phenol with
an acid catalyst is called
novolac
.


Requires addition of a hardener (hexamethylenen tetramine) to achieve C
-

Stage in 2 steps. It provides acid to both reactants which speeds up reaction.


Reinforcements are mixed with novolacs for composites. Bstaging is when
any other resin is cured to an intermediate stage

and cured by heating






36

Carbon Matrices


Carbon/carbon) composites applications:


Similar to phenolic and are used when


Very high temperature protection or toughness are needed.


Rocket nozzles and nose cones.


Brakes for aerospace, trucks, and race cars.


Carbon matrix material with carbon fibers on opposing brake parts


Produced from carbon fiber reinforced phenolics that have
been charred in a process called pyrolysis.


Charring process results in a porous structure because the phenolic
ablates from solid to gas and does not go into a liquid phase.


The porous material is impregnated with pitch, phenolics, or directly
with carbon by vapor deposition.


Resulting material is carefully charred again and the process is
repeated to fill the remaining voids with material.


Process can take as long as 6 months to prevent matrix damage








37

Carbon Matrices


Some produced from chemical vapr deposition (CVD)


Using several layers of carbon fabric as the base material


Methane is blown into fabric under controlled cracking conditions.


Carbon plates out like a metal in the analogous metal vapor deposition
process.


The deposition fills the voids in the cloth to create the finished structured


Must be careful that outer layers fill at the same rate as the inner layers.


Limited to structures no thicker than 5mm (3/16 in)


Insulative uses of carbon matrix materials


Similar to phenolics except that a higher more uniform and
predictable thermal insulation.


Best in small rockets (nozzle diameter less than 12”) where
fewer safety factors are used as in larger rockets.


Costs of carbon matrix nozzles are 5 times that of phenolics


Under consideration as skin of space plane where thermal
stability is essential as is good toughness and thermal shock
resistance








38

Thermoplastic Matrices


Plastics are reinforced with glass and a few with carbon fiber


Nylon, PP, PBT, PEEK and PEK, and Polysulphone


Advantages


Requires less processing time since it is heated and not cured.


Thermoplastic pre
-
preg sheets have infinite shelf life versus thermoset


Disadvantages


Have lower thermal resistance than most thermoset composites


Have lower strength and modulus than some thermoset composites


Have difficulty wetting out high fiber loading composites.





Property
Thermoset
(Fiberite 931
Epoxy)
Thermoplastic
(ICI APC-2P)
Melt Viscosity
Low
High
Fiber Impregnation
Easy
Difficult
Prepreg Tack
Good
None
Prepreg Drape
Good
Poor
Prepreg Stability at 0F
6mos -1yr
Infinite
Processing Cycle
1-6hrs
15sec-6hrs
Processing Temp
350F
700F
Mechanical Props
Good
Good
Environ Durability
Good
Exceptional
Damage Tolerance
Average
Good
Database
Large
Average
39

Thermoplastic Matrices


Two types of thermoplastic composites: Discontinuous and
continuous reinforcements


Discontinuous fiber
-

Conventional thermoplastics and short (3mm) or
long fibers (6mm)


Polypropylene, nylon, PET, PBT, Polysulphone, PE, ABS, PC, HIPS, PPO


Short Glass or Carbon fiber increases


Tensile strength, modulus, impact strength, cost, thermal properties


Short Glass or carbon fiber decreases


Elongation,


CLTE,


Moisture


sensitivity





Nylon 6,6
Nylon 6,6 with
30% short glass
Nylon 6,6 with
30% long glass
Nylon 6,6 with
30% carbon fiber
Density, g/cc
1.13-1.15
1.4
1.4
1.06-1.10
Tensile Strength,
psi
14,000
28,000
28,000
32,000
Tensile Modulus,
psi
230K – 550K
1,300K
1,400 K
3,300 K
Tensile
Elongation, %
15%-80%
3%
3%
4%
Impact Strength
ft-
lb/in
0.55 – 1.0
1.6-4.5
4.0
1.5
CLTE (in/in/C
x10-
6
)
55
18
18
15
Moisture %
1.0-2.8% (24h)
8.5% (Max)
0.7-1.1 (24h)
5.5-6.5 (Max)
0.9 (24h)
5.5-6.5 (Max)
0.7 (24h)
5 (Max)
Cost $/
lb
$1.40
$1.70
$2.00
$2.70
40

Thermoplastic Matrices


Several types of resin types


Conventional plastics: Less expensive (< $2.00 per pound)


Commodity plastics : PP, PE, PVC, PS, ABS, etc.


Engineering resins: PC, PET, PBT, Nylon, etc.


High Performance Plastics: High Costs (> $10 per pound) and High
Thermal Properties


PEEK, PEK, LCP, PPS, Polyaryle Sulfone, Polysulfone, Polyether sulfone,
Polyimid


PEEK and PEK = $30 per pound


Polyarylesters


Repeat units feature only aromatic
-
type groups (phenyl or aryl groups) between
ester linkages. Called wholly aromatic polyesters




O

n

O

O

C

O

n

O

C

PolyEther
-
Ether
-
Ketone (PEEK)

PolyEther
-
Ketone (PEK)

41

Mechanical Properties of PEEK



Mechanical

Properties
PEEK
LCP Polyester
Nylon 6,6
Density, g/cc
1.30-1.32
1.35 - 1.40
1.13-1.15
Tensile Strength,
psi
10,000 – 15,000
16,000 – 27,000
14,000
Tensile Modulus,
psi
500K
1,400K - 2,800K
230K – 550K
Tensile
Elongation, %
30% - 150%
1.3%-4.5%
15%-80%
Impact Strength
ft-
lb/in
0.6 – 2.2
2.4 - 10
0.55 – 1.0
Hardness
R120
R124
R120
CLTE
10
-6
mm/mm/C
40 - 47
25-30
80
HDT 264
psi
320 F
356F -671F
180F
42

Physical Properties of PEEK



Physical Properties
PEEK
LCP Polyester
Nylon 6,6
Optical
Opaque
Opaque
Translucent to opaque
Tmelt
334 C
400 C
255C – 265C
Tg
177 C
H
2
0
Absorption
0.1-0.14% (24h)
0.5% (Max)
0.1% (24h)
0.1% (Max)
1.0-2.8% (24h)
8.5% (Max)
Oxidation
Resistance
good
Good
good
UV Resistance
Poor
good
Poor
Solvent
Resistance
good
good
Dissolved by phenol &
formic acid
Alkaline
Resistance
good
Poor
Resistant
Acid
Resistance
good
fair
Poor
Cost $/
lb
$30
$7 - $10
$1.30
43

Properties of Reinforced PEEK



Mechanical

Properties Reinforced
PEEK
PEEK 30%
glass fibers
PEEK with 30%
carbon fibers
Density, g/cc
1.30-1.32
1.52
1.43
Tensile Strength,
psi
10,000 – 15,000
23,000 – 29,000
31,000
Tensile Modulus,
psi
500K
1,300K – 1,600K
1,900K – 3,500K
Tensile
Elongation, %
30% - 150%
2%-3%
1% - 4%
Impact Strength
ft-lb/in
1.6
2.1 – 2.7
1.5 – 2.1
Hardness
R120
R120
CLTE
10
-6
mm/mm/C
40 - 47
12-22
15-22
HDT 264 psi
320 F
550F -600F
550F -610F
44

Advantages and Disadvantages of Polyketones


Advantages


High continuous use temperature (480F)


High toughness, especially at high temperatures.


Outstanding wear resistance


Excellent water resistance and better than thermoset composites


Excellent mechanical properties


Very low flammability and smoke generation


Resistant to high levels of gamma radiation


Higher Elongation (30%
-
100%) versus thermosets (1%
-
10%)


Disadvantages


High material cost and long processing times


High processing temperatures due to high viscosities (1 Million poise) versus
thermoset composites (Epoxy = 10 poise). Syrup = 1000 poise


Moderate or poor resistance to hot oils


Difficult to have high fiber loadings due to high viscosity


Need special processing techniques; comingle plastic powder with fiber sheet and
consolidate (impregnate resin in fiber bundle) through heated rollers.

45

Polyphenylene Materials




Several plastics have been developed with the benzene ring in
the backbone

»
Polyphenylene



»
Polyphenylene oxide


(amorphous)


»
Poly(phenylene sulfide)


(crystalline)



»
Polysulfone


»
Polyether Sulfone



O

O

O

S

S

S

O

C

CH
3

CH
3

O

SO
2

O

SO
2

n

n

n

n

n

46

PPO and PPS Materials

*Advantages of PPS


*Advantages of PPO

-

Usage Temp at 450F



-

Good fatigue and impact strength

-

Good radiation resistance



-

Good radiation resistance

-

Excellent dimensional stability


-

Excellent dimensional stability

-

Low moisture absorption



-

Low oxidation

-

Good solvent and chemical resistance

-

Excellent abrasion resistance



*Disadvantages of PPS


*Disadvantages of PPO

-

High Cost





-

High cost

-

High process temperatures


-
Poor resistance to certain chemicals

-

Poor resistance to chlorinated hydrocarbons




47

PPO and PPS Applications

*PPS Applications



*PPO Applications


-

Computer components



-

Video display terminals

-

Range components



-

Pump impellers


-

Hair dryers




-

Small appliance housings

-

Submersible pump enclosures


-

Instrument panels

-

Small appliance housings



-

Automotive parts






48

PPS and PPO Mechanical Properties



Mechanical

Properties
PPS
PPO
Nylon 6,6
Density, g/cc
1.30
1.04 – 1.10
1.13-1.15
Tensile Strength,
psi
9,500
7,800
14,000
Tensile Modulus,
psi
480K
360K
230K – 550K
Tensile
Elongation, %
1% - 2%
60% - 400%
15%-80%
Impact Strength
ft-lb/in
< 0.5
4 - 6
0.55 – 1.0
Hardness
R123
R115
R120
CLTE
10
-6
mm/mm/C
49
60
80
HDT 264 psi
275 F
118F -210F
180 F
49

PPS and PPO Physical Properties



Physical Properties
PPS
PPO
Nylon 6,6
Optical
Opaque
Opaque
Translucent to opaque
Tmelt
290 C
250 C
255 C – 265 C
Tg
88 C
110 – 140 C
H
2
0
Absorption
> 0.02% (24h)
0.01% (24h)
1.0-2.8% (24h)
8.5% (Max)
Oxidation
Resistance
good
good
good
UV Resistance
fair
fair
Poor
Solvent
Resistance
Poor in
aromatics
Poor in
aromatics
Dissolved by phenol &
formic acid
Alkaline
Resistance
good
good
Resistant
Acid
Resistance
poor
good
Poor
Cost $/
lb
$2
$1.80
$1.30
50

PPS and PPO Processing Properties



Processing Properties
PPS
PPO
Nylon 6,6
Tmelt
290 C
250 C
255C – 265C
Recommended Temp Range
(I:Injection, E:Extrusion)
I: 600F – 625F
I: 400F – 600F
E: 420F – 500F
I: 500F – 620F
Molding Pressure
5 – 15 kpsi
12 - 20 kpsi
1 -20 kpsi
Mold (linear) shrinkage (in/in)
0.007
0.012 – 0.030
0.007 – 0.018


PPS frequently has glass fibers loaded up to 40% by weight

»
Tensile strength = 28 kpsi, tensile modulus = 2 Mpsi, HDT = 500F



PPO is frequently blended with PS over a wide range of percentages.


(Noryl from G.E.)

51

Ceramic Matrices


If a material is a composite and the matrix is not an
organic resin and is not metallic then it is ceramic


Ceramics are solid materials which have both positive
and negative ions and typically exhibit ionic bonding


SiC has covalent bonding.


Solid material may be either crystalline, amorphous
(vitreous) or semicrystalline.


Ceramic materials have high thermal and chemical
stability


carbides, nitrides, borides, etc.







52

Ceramic Matrices


Processing


Cast from slurries or pressed into shape with an organic
binder and then fired or sintered at high temps


Materials are very brittle and sensitive to cracks or flaws.


Applications


Not used for structural parts


Whiskers or short fibers can be added to improve strength


High heat resistance applications: T
-

2000F to 4000F


Nose cones, rocket nozzles, ram
-
jet chambers.


Dimensional stability is excellent


Aerospace applications


Low dielectric constant that is trasparent to radar,
microwaves, etc.


Electrical applications








53

Metal Matrices


Metal Matrix Composites (MMC)


High performance reinforcements


particles, whiskers, or fibers



in a metallic matrix


aluminum, titanium, Mg, Cu, …


MMC first use was in the Space Shuttle boron/Al tubes


Incorporation of second phase (reinforcement) into metal
significantly affects the propogation of pressure waves through the
material by acting as sites for scattering and attenuation


Boron reinforced Al has 5 times increase in dampening capacity


High thermal conductivity of metal matrix with low thermal
expansion of reinforcement is excellent for electrical
applications





54

Thermoset Reacting Polymers


Process Window


Temperature and pressure must be set to produce chemical reaction
without excess flash (too low a viscosity), short shot (too high a
viscosity), degradation (too much heat)

55

Polyurethane Processing


Polyurethane can be processed by


Casting, painting, foaming


Reaction Injection Molding (RIM)

56

Structural RIM


Fiber preform is placed into mold.


Polyol and Isocyanate liquids are injected into a closed mold
and reacted to form a urethane.


57

Resin Transfer Molding


In the RTM process, dry (i.e.,unimpregnated ) reinforcement is
pre
-
shaped and oriented into skeleton of the actual part known
as the preform which is inserted into a matched die mold.


The heated mold is closed and the liquid resin is injected


The part is cured in mold.


The mold is opened and part is removed from mold.

58

Processing of Composites


Open Mold processes


Vacuum bag, pressure bag, SCRIMP












autoclave: Apply Vacuum Pressure and Heat in an oven which can be
5 feet to 300 feet long












59

Processing of Composites


Open Mold processes


Hand lay
-
up and Spray
-
up










Filament winding


60

Sheet Molding Compound (SMC)


SMC is the paste that is compression molded


33% polyester resin and stryrene, which polymerizes and crosslinks


33% glass fibers (1” fibers)


33% Calcium Carbonate

61

Compression Molding


Compression molding was specifically developed for replacement of metal
components with composite parts. The molding process can be carried out with
either thermosets or thermoplastics. However, most applications today use
thermoset polymers. In fact,compression molding is the most common method of
processing thermosets.

62

Injection Molding

Glass Reinforced Composites


Plastic pellets with glass fibers are melted in screw, injected
into a cold mold, and then ejected.

Glass filled resin pellets

63

Additives and Reinforcements to Polyesters


Additives
-



UV stabilizers, colorants, heat stabilizers, blowing agents


Catalyst, inhibitors, promotors



Fillers


Talc


Calcium carbonate


Reinforcements


Glass fiber
-

short fiber (1/8” or long fiber 1/4”)


Mineral fiber (wolastonite)


Mica


carbon fibers


64

Properties of Reinforced Thermosets