Transcript Thermosets_ Epoxy, Polyesters, Vinyl esters, Polyurethanes, and Phenolics Professor Joe Greene CSU, CHICO

Thermosets_ Epoxy, Polyesters, Vinyl
esters, Polyurethanes, and Phenolics
Professor Joe Greene
CSU, CHICO
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Composites
Reference: Appendix E. Industrial Plastics, Modern Plastics Encyclopedia (p142)
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History
Applications
Advantages/Disadvantages
Chemistry and Chemical Structure
Mechanical Properties
Physical Properties
Processing Characteristics
Other thermosets
Review
Questions
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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.
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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
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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
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SMC
Sheet Molding
Compound:
Polyester Resin and
chopped glass
Automotive Applications of
Plastics and Composites
n
Composite Intensive Vehicles
Polyester resin and Glass Mat Preform
With RTM Resin Transfer Molding
8-25 -98
M41_au 25
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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.
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Automotive Plastics and Composites Use
SMC
Sheet Molding
Compound
SMC
Sheet Molding
Compound
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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
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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.
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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)
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Properties of Materials
• Tensile modulus
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Low alloy steel
Aluminum
Carbon fiber
Glass fiber
Aramid fiber
(Kevlar)
Density
207GPa(30Mpsi)
72GPa (10Mpsi)
300GPa(40Mpsi)
76GPa (10Mpsi)
125GPa (20Mpsi)
• Tensile strength
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Low alloy steel
Aluminum
Carbon fiber
Glass fiber
Aramid fiber
(Kevlar)
7.85 g/cc
26spGPa
2.8 g/cc
26spGPa
1.8 g/cc167spGPa
2.56g/cc
30spGPa
1.4g/cc
89spGPa
Density
1500MPa(220Kpsi)
500MPa(75Kpsi)
2400MPa(360Kpsi)
2000MPa(300Kpsi)
3000MPa (450Kpsi)
Spec Mod
Spec Str
7.85 g/cc
191spMPa
2.8 g/cc
178spGPa
1.8 g/cc4320spGPa
2.56g/cc
781spGPa
1.4g/cc
2140spGPa
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Mechanical Properties of Thermosets
Density, g/cc
Tensile Strength, psi
Tensile Modulus, psi
Tensile Elongation, %
Impact Strength ftlb/in
CLTE
10-6 mm/mm/C
HDT
264 psi
Epoxy
1.11-1.40
Polyester
1.04 - 1.46
PET (Thermoplastic)
1.29-1.40
Polyurethane
1.03 - 1.15
4,000 – 13,000
350K
3%-6%
0.20 - 1.0
600 – 13,000
300K - 640K
2% - 6%%
0.2 - 0.4
7,000 – 10,500
400K - 600K
30% - 300%
0.25 - 0.70
175 - 10,000
10K - 100K
3% - 6%
25 to no break
45-65
55 - 100
65
100 - 200
115F-550F
140F -400F
70F -100F
70F - 150F
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• Epoxy
Applications for Thermosets
– 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
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patios, swimming pool decks, and soil around oil-well drills.
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Applications
for
Thermosets
Polyester
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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
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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
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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
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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
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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
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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)
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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
O
O
C6H4(COOH)2 + (CH2)2(OH)2
terephthalic acid
+ ethylene glycol
-[(CH2)2 -O- C
- C-O]-
Polyethylene terephthalate (PET)
– Acids include: maleic, fumaric, isophthalic, terphthalic, adipic, etc.
– Anhydrides include: maleic, phthalic
– Glycols include ethylene glycol, diethylene glycol, propylene glycol
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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 CO2 and H2O
• 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
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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:
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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.
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Epoxy Chemistry
• Epoxy: O
C C
H H
epoxide group
H
H
H + H2N (C) N (C) NH2
H
H
+
amines (DETA)
epoxy
• Other epoxy resins
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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.
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As much as 15% hardener is needed
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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
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Other Thermosets
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Polyimides
Bismaleimide
Polybenzimidazoles
Phenolics
Carbon Matrices
Thermoplastic matrices
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Polyamides
Polypropylene
PEEK
Polysulfone
PPS
• Ceramic Matrices
• Metal Matrices
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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
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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
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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.
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Phenolics and Carbon Matrices
• Phenolics is an old thermoset resin
– Used for general purpose, unreinforced plastic
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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
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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 CStage 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
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Carbon Matrices
• Carbon/carbon) composites applications:
– Similar to phenolic and are used when
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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
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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
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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.
Thermoset
(Fiberite 931
Property
Epoxy)
Melt Viscosity
Low
Fiber Impregnation
Easy
Prepreg Tack
Good
Prepreg Drape
Good
Prepreg Stability at 0F 6mos -1yr
Processing Cycle
1-6hrs
Processing Temp
350F
Mechanical Props
Good
Environ Durability
Good
Damage Tolerance
Average
Database
Large
Thermoplastic
(ICI APC-2P)
High
Difficult
None
Poor
Infinite
15sec-6hrs
700F
Good
Exceptional
Good
Average
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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
Density, g/cc
Tensile Strength,
psi
Tensile Modulus,
psi
Tensile
Elongation, %
Impact Strength
1.13-1.15
Nylon 6,6 with
30% short glass
1.4
Nylon 6,6 with
30% long glass
1.4
Nylon 6,6 with
30% carbon fiber
1.06-1.10
14,000
28,000
28,000
32,000
230K – 550K
1,300K
1,400 K
3,300 K
15%-80%
3%
3%
4%
0.55 – 1.0
1.6-4.5
4.0
1.5
55
18
18
15
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)
$1.40
$1.70
$2.00
$2.70
ft-lb/in
CLTE (in/in/C
x10-6)
Moisture %
Cost $/lb
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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
PolyEther-Ether-Ketone (PEEK)
O
O
O
C
PolyEther-Ketone (PEK)
O
O
n
C
n
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Mechanical Properties of PEEK
Mechanical Properties
Density, g/cc
Tensile Strength,
psi
Tensile Modulus,
psi
Tensile
Elongation, %
Impact Strength
PEEK
1.30-1.32
LCP Polyester
1.35 - 1.40
Nylon 6,6
1.13-1.15
10,000 – 15,000
16,000 – 27,000
14,000
500K
1,400K - 2,800K
230K – 550K
30% - 150%
1.3%-4.5%
15%-80%
0.6 – 2.2
2.4 - 10
0.55 – 1.0
R120
R124
R120
40 - 47
25-30
80
320 F
356F -671F
180F
ft-lb/in
Hardness
CLTE
10-6 mm/mm/C
HDT
264 psi
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Physical Properties of PEEK
Physical Properties
PEEK
Opaque
Optical
LCP Polyester
Opaque
Nylon 6,6
Translucent to opaque
400 C
255C – 265C
0.1-0.14% (24h)
0.5% (Max)
0.1% (24h)
0.1% (Max)
1.0-2.8% (24h)
8.5% (Max)
Oxidation
Resistance
UV Resistance
good
Good
good
Poor
good
Poor
Solvent
Resistance
Alkaline
Resistance
Acid
Resistance
good
good
good
Poor
Dissolved by phenol &
formic acid
Resistant
good
fair
Poor
Cost $/lb
$30
$7 - $10
$1.30
Tmelt
334 C
Tg
177 C
H2 0
Absorption
42
Properties of Reinforced PEEK
Mechanical Properties Reinforced
PEEK
Density, g/cc
Tensile Strength,
psi
Tensile Modulus,
psi
Tensile
Elongation, %
Impact Strength
1.30-1.32
PEEK 30%
glass fibers
1.52
PEEK with 30%
carbon fibers
1.43
10,000 – 15,000
23,000 – 29,000
31,000
500K
1,300K – 1,600K
1,900K – 3,500K
30% - 150%
2%-3%
1% - 4%
1.6
2.1 – 2.7
1.5 – 2.1
ft-lb/in
Hardness
CLTE
10-6 mm/mm/C
HDT 264 psi
R120
R120
40 - 47
12-22
15-22
320 F
550F -600F
550F -610F
43
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.
44
Polyphenylene Materials
•Several plastics have been developed with the benzene ring in
the backbone
»Polyphenylene
n
»Polyphenylene oxide
(amorphous)
O
O
O
»Poly(phenylene sulfide)
(crystalline)
S
S
S
»Polysulfone
O
»Polyether Sulfone
n
n
CH3
C
CH3
O
O
SO2
SO2
n
n
45
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
46
PPO and PPS Applications
*PPS Applications
- Computer components
- Range components
- Hair dryers
- Submersible pump enclosures
- Small appliance housings
*PPO Applications
- Video display terminals
- Pump impellers
- Small appliance housings
- Instrument panels
- Automotive parts
47
PPS and PPO Mechanical Properties
Mechanical Properties
Density, g/cc
Tensile Strength,
psi
Tensile Modulus,
psi
Tensile
Elongation, %
Impact Strength
PPS
1.30
PPO
1.04 – 1.10
Nylon 6,6
1.13-1.15
9,500
7,800
14,000
480K
360K
230K – 550K
1% - 2%
60% - 400%
15%-80%
< 0.5
4-6
0.55 – 1.0
R123
R115
R120
49
60
80
275 F
118F -210F
180 F
ft-lb/in
Hardness
CLTE
10-6 mm/mm/C
HDT 264 psi
48
PPS and PPO Physical Properties
Physical Properties
PPS
Opaque
Optical
PPO
Opaque
Nylon 6,6
Translucent to opaque
255 C – 265 C
Tmelt
290 C
250 C
Tg
88 C
110 – 140 C
> 0.02% (24h)
0.01% (24h)
1.0-2.8% (24h)
8.5% (Max)
good
good
good
fair
fair
Poor
Poor in
aromatics
good
Poor in
aromatics
good
Dissolved by phenol &
formic acid
Resistant
poor
good
Poor
$2
$1.80
$1.30
H2 0
Absorption
Oxidation
Resistance
UV Resistance
Solvent
Resistance
Alkaline
Resistance
Acid
Resistance
Cost $/lb
49
PPS and PPO Processing Properties
Processing Properties
Tmelt
Recommended Temp Range
(I:Injection, E:Extrusion)
Molding Pressure
Mold (linear) shrinkage (in/in)
PPS
PPO
Nylon 6,6
290 C
250 C
255C – 265C
I: 600F – 625F I: 400F – 600F
E: 420F – 500F
I: 500F – 620F
5 – 15 kpsi
12 - 20 kpsi
1 -20 kpsi
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.)
50
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.
51
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
52
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
53
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)
54
Polyurethane Processing
• Polyurethane can be processed by
– Casting, painting, foaming
– Reaction Injection Molding (RIM)
55
Structural RIM
• Fiber preform is placed into mold.
• Polyol and Isocyanate liquids are injected into a closed mold
and reacted to form a urethane.
56
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.
57
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
58
Processing of Composites
• Open Mold processes
– Hand lay-up and Spray-up
– Filament winding
59
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
60
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.
61
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
62
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
63
Properties of Reinforced Thermosets
64