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

2. Composites Reference: Appendix E
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 Excellent Web sites
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
U of Delaware
Cornell University

5. Composites Composite definition Natural Composites
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)

6. Polyester resin and Glass Mat Preform
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

13. Mechanical Properties of Thermosets

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
Odor from Styrene and potential health hazards
Polyurethane
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
C6H4(COOH)2 + (CH2)2(OH) [(CH2)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

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 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

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 + H2N (C) N (C) NH2 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 Insulative uses of carbon matrix materials
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.

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

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
PolyEther-Ether-Ketone (PEEK)
PolyEther-Ketone (PEK) O n C O n C

41. Mechanical Properties of PEEK

42. Physical Properties of PEEK

43. Properties of Reinforced PEEK

44. Advantages and Disadvantages of Polyketones
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 n O n S n O C
CH3
SO2 n O
SO2 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

49. PPS and PPO Physical Properties

50. PPS and PPO Processing Properties
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 Applications
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 F 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
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