05 Specialty Resins

8/3/2019 05 Specialty Resins

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Specialty Resins

A. Brent Strong


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Vinyl Esters

Epoxy resins that have been modified so

that they can be cured like a polyester

The modification is usually a reaction with anacrylic (acrylic modified epoxy)

The modification must substitute a carbon-

carbon double bond for the epoxy ring

The name, vinyl ester, comes from oldchemistry because the carbon-carbon

bond (called a vinyl bond) is on the end

and next to a polyester group


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Vinyl Ester Structure

C C CC

C C

()n

Unsaturated end group

Unsaturated end group


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Vinyl esters specific molecules

+

C C C O

O

C C C...C

O

H

H

CVinyl Ester

Methyl Acrylic Acid

Epoxy

C C C C...

O

CC C C O

O

C


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Specialty Vinyl Esters

C

C

C

C

O

O

C

C

C

C

O

C

C

C

C

O

O

C

C

C

C

O

C

C

C

O

O

C

C

C

C

O

OHOH OH

Epoxy Novolac Vinyl Ester Resin

CCCOCCCO

OH O

C

CC C C O C C C O

OHO

C

C

C

Bisphenol-A Epichlorohydrin-based vinyl ester

( )n


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Vinyl esters Properties

Almost all properties of vinyl esters (andcost) are intermediate betweenpolyesters and epoxies

Some of the most important propertiesinclude:

Water and chemical resistance

Electrical stability

Thermal stability Toughness

Low volatiles during manufacture

Low shrinkage


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Vinyl Esters


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Phenolics

Key properties determining most of theapplications of phenolics

Very low flammability and low smoke

Very stiff and hard Very low heat transfer

High thermal stability

Good electrical properties

Excellent adhesion Resistance to chlorinated solvents

Moderately low price (10-15% abovepolyesters)


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Phenolics polymerization and crosslinking

C......C

C

C...

OH

C

C

...C C

OHOH

C

CC

C

OH OH

...C C...

OH

OH

HHC

OOH

HHC

O

+ + + +.

3-D Phenolic

Network

Formaldehyde Phenol

Loss ofWaterVapor


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Phenolics

Applications Handles for cooking pans

Interiors of public transportation

Glue for laminates (such as plywood) Electrical switches and other equipment

Molded parts in moderately hot environments(such as near the motor of an automobile)

Billiard balls Conversion to epoxy or vinyl ester resins

Rocket exit nozzles and carbon-carboncomposites (ablation)


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Phenolic FlammabilityPhenolic Flammability

10 20 30 40

Vinyl Ester

Epoxy

FR Polyester

Phenolic

(ASTM E-162 for thermoset

composites)

Vinyl Ester

Epoxy

FR Polyester

Phenolic

(ASTM E-662 for thermoset

composites)

100

Specific Optical DensityFlame Spread Index

200 300 400 500 600


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700-

600-

500-

400-

300-

200-

100-

0 2 4 6 8 10 12 14 16 18 20 22

NBS Smoke Chamber (Smoldering)

Epoxy

Polyester

Phenolic

Optical

Density

Time (min)


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Rocket exit nozzle

Rocket Exit Throat

Exit Nozzle

Ablative

Material

10 oF

500 oF

4000 oF

Rocket

Motor

Rocket

Propellant

NoseCone


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Phenolics Processing

Problem Solution

Toxic monomer

(formaldehyde)

B-staging to novolac (solid,

2-step with hexa) or resole

(liquid,1-step)

Condensation of water Slow cures and venting ofmold (compression molding)

High shrinkage Fillers (minerals, sawdust,

wood flour, ground nut

shells, etc.)Brittleness Fillers (selected) and

thickness of parts

Inconsistent color Black pigment


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Phenolics


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Carbon-Carbon Composites

Carbon matrix and carbon fibers

Carbon matrix is made from phenolicresins that have been repeatedly charredand infiltrated with new resin Very long process (up to 6 months for a part)

Very costly

Extremely high thermal stability Needs flammability coating (ceramic) at very

high temperatures


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Production Flow Chart for


Cured Carbon/Resin Part

Carbonization

(up to 1000oC)Impregnation by

Gas or Liquid

Graphitization

2500-3000oC

Carbon/Carbon

Composite2500-3000oC

Polymer or Pitch

Binder

Carbon Fiber


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Thermal Stability106-

105-

104-

103-

102-

10-

1-0 1000 2000 3000 4000

-18 538 1093 1650 2204

Temperature

oFoC

Exposure

Time

(sec)

EpoxyComposites

Polyim

ides

Advanced

Metalics

Carbon-Carbon

Experimental

Ablative Materials(such as phenolics)


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Carbon-Carbon

Brake Pads


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Polyimides

Very high thermal stability

Excellent solvent resistance

Excellent mechanical properties

Self-extinguishing

Processing

Standard composite techniques

Cures are much longer for polyimides than epoxies orpolyesters

Bis-maleimide (BMI) processes like a polyester


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Polyimides specific molecules

N

C

C

CC

C

C

C

CC

C

CN

C

...C

O

O

O

O...C

N

C

C

CC

C

C

C

CC

C

CN

C

C...

O

O

O

OC...

O

Bismaleimide (BMI)

Crosslinked Polyimide (PMR-15)

CCC

CN

C

O

O

CC

CN

C

O

O

Crosslink sites


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Polyimides


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Cyanate esters

Superior dielectric loss properties

Radomes

Skins covering antennae arrays Low moisture absorption

Low off-gassing

Space applications


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Cyanate Esters

C C

N

N

CN

O

O

R

RO

N

C

C

N

N

C

O

R

O

C

C

N

N

C

N

O ROR

OR

OC

N

N

C

C

N

O

O

R

R

OR

R= C

C

C


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Cyanate Esters


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Polyurethanes

Very common plastic type and just now findingapplications in composites Excellent for resin infusion processes (RIM, RTM,

etc.)

Properties can be easily tailored for anapplication Varying the amount of aromatic and non-aromatic

(aliphatic) content in both polyol and isocyanate (themonomers)

Domains give additional selectivity (Spandex) Moderate cost (about like epoxies)

Tough and abrasion resistant


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Polyurethanes

HO OH C=N

O=

N=C

O=

+

HO O C

O

N=C

O==

N

H

Urethane

linkage

Polyol Di-isocyanate


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Polyurethane


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Silicones

Widely used as a mold release Can be a contamination that makes bonding difficult

with some adhesives

Silicone can be an adhesive itself

Not widely used in composites as a matrix butmight be used as a matrix for specialapplications Moderate thermal stability (Equivalent to a high-

performance epoxy)

Low moisture absorption Electrical applications

Low flammability

Tooling (flexible)


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Thank you

Brent Strong

Documents

05 Specialty Resins