High Temperature Polymers for Extreme Environmental Applications

Teddy Keller, Matthew Laskoski,

Manoj Kolel-Veetil & Dawn Dominguez

Head of Advanced Materials Section, Code 6127

Chemistry Division

Naval Research Laboratory

Washington, Dc 20375

E-mail: teddy.keller@nrl.navy.mil

Classes of High Temperature Polymers

• Phthalonitrile resins –simple and oligomeric

• Oligomeric cyanate ester resins

• Aromatic ether vinyl silane terminated aryl ether oligomers (room temperature cure)

• Inorganic-organic hybrid polymers

• Copolymers of aromatic ether vinyl silane terminated aryl ether oligomers and vinyl terminated carborane siloxanes

• Conversion of high temperature polymers into carbon nanotubes

• New synthetic method for the production of refractory metal ceramics

Phthalonitriles

Phthalonitrile Monomers

Bisphenol A Phth : M.P. = 195 ºC Biphenol Phth : M.P. = 235 ºC

Sastri, S. B.; Keller, T. M. J. Polym. Sci., Part A: Polym. Chem. 1999, 37, 2105.

O O

CN

CN

NC

NCO

CH3

CH3

O

CN

CN

NC

NC

Simple bisphenol-based materials must be processed at

high temperatures High melting points which create short processing windows

Low Melting Oligomeric Phthalonitriles

PO

OOO

O

C

N

CN

C

N

C N

n

O

OO

C

N

CN

OC

N

CN

CH3H3C

CH3H3C

n

Goal: Design liquid/low melting phthalonitrile monomers that

can be injection molded to form polymers/composites with high

thermal and oxidative stability.

Examples:

Oligomeric Phth. (n=4) (m.p. 41 °C)

OnOO C

N

CN

CN

CN

P containing oligomeric Phth. (m.p. 75 °C)

Alkyne containing oligomeric Phth. (m.p. 80 °C)

Ketone containing oligomeric Phth. (m.p. 85 °C)-PEEK like Material

73 %A

B

0

20

40

60

80

100

Weig

ht

(%)

0 200 400 600 800 1000Temperature (°C)

(A) N2 : 95 % @ 520 °C

(B) Air : 95 % @ 515 °C

Properties:

• Materials have high thermal/oxidative stability above 400 °C

• Polymers have excellent mechanical properties >400 °C

• Monomers have low viscosity ideal for injection molding

• Fully cured polymers do not exhibit Tg

Thermal and oxidative stability of ketone containing

oligomeric phthalonitrile (phth.)

CH3

H3C

O

O

O H3C

CH3

O

O

n

CNC

N

CN C

N

Comparison of New Resin vs Old Resin

O

CH3

CH3

O

CN

CN

NC

NC

M.P. = 195 C

Melt processable at

temperatures above 195 C,

cures quickly at 245 C

CH3

H3C

O

O

O H3C

CH3

O

O

1

CNNC

CNCN

Tg = 85 C

Melt processable at

temperatures above 100 C,

cures slowly above 200 C

50 100 150 200 250 300 350 400

-0.2

0.0

0.2

Heat

Flo

w (

W/g

)

Temperature (oC)

50 100 150 200 250 300 350

-5

-4

-3

-2

-1

0

Heat

Flo

w (

W/g

)

Temperature (oC)

Laskoski, M.; Dominguez, D. D.; Keller, T. M. J. Poly. Sci. Part A, 43, 4136 (2005).

Oxidative Aging and Flame Studies

Temperature (C)

Total Weight

Loss for A

(%)

Total Weight

Loss for B

(%)

A 250 0.1 0.2

B 300 0.3 0.4

C 325 0.7 1.0

D 350 1.7 3.0

E 375 5.0 8.0

O O

O

O

CNNC

O CN

CN

1

CH3

H3C

O

O

O H3C

CH3

O

O

1

CNNC

CNCN

A

B

Top: Epoxy; Bottom: Phthalonitrile

Fire Resistant Properties of High Performance Phthalonitrile Carbon Composites

(DATA SUPPLIED BY USMAN SORATHIA OF NSWC CD)

MIL-STD: For submarine application (MIL-STD 2031)

at heat flux of 100 kW/m2

– Greater than 60 second ignition time (TIG)

– Peak heat release (PHR) less than 150 kW/m2

COMPOSITE TIG PHR

PHTHALONITRILE 90 118

PMR-15 55 85

BMI 22 270

PEEK 42 85

EPOXY 28 232

Smoke And Gas Generation, Flaming Mode (ASTM-662)

Composite* CO (ppm) CO2 (%V) HCN (ppm) HCl (ppm)

Gl/Phth. 40 0.5 tr** ND***

Gl/VE 230 0.3 ND ND

Gl/EP 283 1.5 5 ND

Gl/BMI 300 0.1 7 tr

Gl/PH 300 1.0 1 1

Gl/PI 200 1.0 tr 2

* Composite: Gl = glass fiber, Phth.= phthalonitrile, VE = vinyl ester,

EP = epoxies, BMI = bismaleimides, PH = phenolic, PI = polyimide

** tr stands for trace

*** ND stands for Not Detected or Not Defined

Technological Impact of Phthalonitriles

Matrix material for advanced high temperature, flame resistant, and carbon/carbon composites:

– Aerospace: Internal components of commercial aircraft, space vehicles, supersonic military

aircraft, missiles, rockets, turbine engine applications, 2nd generation shuttle, satellite

components, and engine components on aircraft.

– Marine: surface ship and submarine fire resistant structural components and use in

applications below deck.

Aircraft CVN21/CVN78 carrier Satellites, Space Vehicles

– High temperature adhesives

– Oil rig components

– High temperature sizing or coating material for fibers

– Tooling

– Car battery casing

– Geothermal tooling

– Microelectronic device applications up to 325C in oxidizing environment

– Printed circuit boards

Car Engine Components Off-Shore Oil Rigs

Technological Impact of Phthalonitriles Cont.

Li Battery casing Oil Rig Components

Oligomeric Cyanate Ester Resins

Structure of Known Cyanate Esters (CE) Monomers

CF3

CF3

O C NOCN

ArOCy B : M.P. = 79ºC ArOCy F : M.P. = 87ºC

CH3

CH3

O C NOCN

Problem with current commercially available cyanate

esters (CE)

High melting points which create short processing windows

Liquid/Processable Cyanate Ester (CE) Resins

Goal: Design liquid cyanate ester (CE) monomers

that can be injection molded at room temperature to

form polymers/ composites with high thermal and

oxidative stability.

Examples:

BisA6F based oligomeric CE

Resorcinol based oligomeric CE

BisA based oligomeric CE

Properties:

• Monomers are liquid and have low viscosity to permit

injection molding

• Polymers have high thermal and oxidative stability

• Good mechanical properties of cured thermosets

• Low dielectric constants

DSCs of bisphenol A based oligomeric CE

OO

n

OC

N

OC

N

OO

CF3

F3CCF3

F3C

O O

C

N

C

N1

OO

CH3

H3CCH3

H3C

O O

C

N

C

N1

2 % Cu

Neat

-0.5

1.5

He

at

Flo

w (

W/g

)

0 100 200 300 400Temperature (°C)

Ne

w N

RL

Res

in

Cu

rren

t Res

in

Dielectric constant = 2.67 at 1 GHz

Dielectric constant = 2.66 at 1 GHz

(solid, M.P. = 80C)

Properties of CE Resins

Neat

2 % Cu

-5

3

He

at

Flo

w (

W/g

)

25 125 225 325Temperature (°C)

O

CH3

CH3

OCN C N

New Resin (liquid)

OO

CH3

H3CCH3

H3C

O OC

NC

N1

2 % Cu

Neat

-0.5

1.5

He

at

Flo

w (

W/g

)

0 100 200 300 400Temperature (°C)

Water Absorption of CE Polymers

OO

CF3

F3CCF3

F3C

O OC

NC

N1

OO

CH3

H3CCH3

H3C

O OC

NC

N1A

B

0 5 10 15 20 25 30 350.0

0.3

0.6

0.9

1.2

1.5

To

tal W

ate

r A

bso

rbe

d (

%)

Time (Days)

A

B

0 5 10 15 20 25 30 350.0

0.4

0.8

1.2

1.6

2.0

2.4

To

tal W

ate

r A

bso

rbe

d (

%)

Time (Days)

A

B

Water Absorption at 25C Water Absorption at 100C

At 25C and 100C, majority of water absorbed within first 14 and 7 days, respectively

CF3 containing system absorbs small amount of water

Technological Impact of Cyanate Esters

Matrix material for advanced high temperature composites

Electronics: Circuit boards and radomes

Low dielectric constant material applications

High temperature adhesives

Structural or coating applications

Aircraft radome Circuit board

Vinyl Silane Terminated Aryl Ether Oligomers

High Temperature, Transparent, Room Temperature Curable Elastomers/Plastics

Figure 1: Room temperature cured elastomer containing bisphenol A and benzophenone moieties.

H3C CH3

O

O

Si

H3C CH3

O

O

Si

O

H3C

H3C

CH3

CH3

n

A

B

0

20

40

60

80

100

Weig

ht

(%)

0 200 400 600 800 1000Temperature (°C)

Figure 3: TGA of example resin cured with a Si-H containing curing additive using hydrosilylation chemistry; heated to 1000 C, under N2 (A), under air (B).

Figure 2: Structure of resin based on bisphenol A and benzophenone - Peek like backbone.

Potential Applications

• Protective face shield and eyewear

• High performance aircraft canopy and transparent armor

• High performance optical components and electronic display screens

• High temperature impact-resistant materials

• Chemical and heat resistance for use in harsh environments

• Medical components and electronics

• Army Humvee and automotive glazing

• Custom color coatings

Materials Features

• Transparent/tough polymers

• Room temperature curable

• Can be tailored to be elastomeric-to-hard plastics

• Liquid/low melting monomers, easily processible

• High thermal and oxidative stability

Inorganic-Organic Hybrid Polymers

• Poly (carborane-siloxane-acetylenes)

• Vinyl terminated carborane siloxanes

• Polyarylacetylenes containing siloxane, silane, and carborane moieties

Properties:

Oligomeric low molecular weight precursors are liquids at room temperature

Polymeric oxidative applications up to 510oC (950oF)

Precursors to ceramic/composites for oxidative applications at least to 1500oC (2730oF)

Polymeric Protection of Navy Fighter Jet Towlines M.K. Kolel-Veetil and T.M. Keller, Chemistry Division, 2007 NRL Review 147-148

Accomplishment: Protection of the structural and conductive components of the towline

with NRL-developed PCSA.

PCSA (Poly-carborane-siloxane-acetylene)

Properties of PCSA-Based Materials

0 200 400 600 800 10000

20

40

60

80

100

WE

IGH

T (

%)

TEMPERATURE (oC)

Thermal Properties of PCSA to 1000oC

Char in air

Heat in nitrogen

Oxidative aging studies on thermoset

0 500 1000 1500 2000

100

101

102

103

104

105

106

107

We

igh

t (%

)

Time (min)

300

400

500

600

700

800

900

1000

Te

mp

era

ture

(oC

)

Oxidative aging studies on carbon fiber coated with PCSA

PCSA postcured at 510 OC (950 OF) for 4 hrs and aged in air at 950 OF for 300 hrs - no microcracks (collaboration with Pratt &Whitney)

Polyarylacetylenes-Containing Carborane-Siloxane-Silane Units

• Two step synthesis of resin

• The thermo-oxidative properties of a representative polyarylacetylene are very similar to its PCSA counterpart

• The aromatic moiety is highly desirable to further enhance the processability of the developed systems

• Enhancement in mechanical stability

• Broader curing window that starts at a lower temperature relative to PCSA

Polyarylacetylene Polymers

Some Potential High Temperature Applications

HyStrike - high speed missile

Fabricate entire turbine engine

Potential Applications Include: • Stator Vanes • Bushings • Hotter Section of Engine

Military Jet Engine Scramjet Engine

Microelectronic packaging materials

High Temperature Copolymers Based on Vinyl Terminated Aryl Ether Oligomers and Vinyl Terminated Carborane Siloxane Resins

Objective: Develop method to enhance the oxidative stability of vinyl-terminated oligomeric aromatic ether resins

Approach: Co-polymerize with a carborane containing vinyl siloxane

Accomplishments:

Significant improvement in the oxidative stability of vinyl-silane terminated aryl ether oligomeric resins

Completely protect the ceramic from oxidation with only 10 % carborane monomer

Cures under ambient conditions

Improvement of the Oxidative Stability of Vinyl-Silane Terminated Aryl Ether Oligomers

Figure 1: TGA under air of copolymers of a benzophenone containing vinyl terminated resin with a carborane containing vinyl siloxane.

OO

n

O O

O

R R Si

CH3

CH3

Si

H3C

CH3

Si-H containing crosslinkerPt catalyst

Crosslinked polymer

+

SiO

CH3

CH3

CB10H10C Si O

CH3

CH3

SiSi

CH3

CH3

CH3

CH3

72%

B

100%A

70

75

80

85

90

95

100

We

ight

(%)

0 200 400 600 800 1000Temperature (°C)

Figure 2: TGA under air of the chars of copolymer containing 10 wt % carborane monomer (A) and of neat benzophenone-containing vinyl terminated resin (B)

Conversion of High Temperature Polymers into Carbon Nanotubes in Bulk Carbonaceous Solid and Fibers

NRL-patented methods: Melt-processable organometallic precursor composition for formation of shaped carbon nanotubes (CNT) and/or carbon nanofibers (CNF) during the carbonization process upon thermal treatment to elevated temperatures

NRL Synthetic Approach to Carbon Nanotube/Nanofiber solids

Bulk CNT/CNF solid

Organometallic Precursor Thermoset

Degradation of Organometallic Composition to Metal Nanoparticles

Carbonization and Formation of Carbon

NanoparticlesCNT/CNF Solids

150-400 oC

300-700 oC

800-1300 oC

(Presence of carbon source in excess)

Air 300-500 oC

Purified CNT/CNF Solids

500-750 oC

In situ deposition of metal nanoparticles in polymeric precursor is the key to multi-walled carbon nanotubes (MWNTs) in carbonaceous shaped composition.

• XRD diffraction studies show metal nanoparticle sizes

of 6-25 nm

• Metal particle size and concentration can be

controlled

– Metal particles (1-4 nm) could afford SWNTs

CNT Shaped Samples Prepared by Carbonization of Organometallic-Carbon Composition in Bulk Solid

Advantages: o Large-scale, low-cost production of CNTs/CNFs

o Formation of active metal nanoparticles in a porous carbon

o Moldable shapes (solid, film, and fiber)

o Production from commodity chemicals, resins, and polymers

o Amenable to incorporation of heteroatoms and various metal nanoparticles

Melt-processible

organometallic

catalyst (< 2 wt. %)

Melt-processable

carbon precursors +

Synthetic Routes to CNT/CNF Solids Using Various Carbon Sources

Co2(CO)8

Fe2(CO)9

Ni[COD]2

Examples:

As a general rule, any

organic material that

chars leads to carbon

nanotube/nanofiber

formation in specific

shapes

O

O

OO O

NC

NC

CN

CNn

OOO O

OO

CH2 CH2

n

1. Mix with amine and

Fe or Co compound

2. Cure

3. Heat to 1000 oC

4. Purifyphthalonitrile

epoxy

CNT/CNF Solid

1. Mix with amine and

Fe or Co compound

2. Cure

3. Heat to 1000 oC

4. Purify

CNT/CNF Solid

C

C

C

C

CPh

CPh

PhC

PhC

1. Mix with Fe or Co compound

2. Cure

3. Heat to 1000 oC

4. Purify

CNT/CNF Solid

TPEB

CH2 CH

CN

n

polyacrylonitrile

1. Mix with

Fe or Co compound

2. Heat to 1000 oC

CNT/CNF Solid

NRL Synthetic Approach to Carbon Nanotube/Nanofiber Solids

1. Mixed with various

amounts of Ni(COD)22. Cured to 375 C

3. Carbonization

°CNT/CNF Solids

C

C

C

C

CPh

CPh

PhC

PhC Co2(CO)8 +

carbon

source

graphitization

catalyst

Initial reaction

mixture

with melt-

processable

precursors

Nanocomposite of

graphitic and amorphous carbon

Carbonization

800 – 1300 C

under argon

or nitrogen

Thermoset resin with embedded metal

nanoparticles

Thermoset

formation

150 – 400 C

under argon

or nitrogen

“Carbon nanotube formation in situ during carbonization in shaped bulk solid cobalt nanoparticle compositions,” T.M. Keller, S.B. Qadri, and C.A. Little, J. Mater. Chem. 14 (2004) 3060.

Thermal

oxidation of

amorphous

carbon

400 – 500 C

in air or O2

Final Product:

Highly porous shaped

solid with graphitic nanotubes/nanofibers

and metal oxide nanoparticles

Mold to define solid shape

Advantages: o Large-scale, low-cost production of CNTs/CNFs

o Formation of metal nanoparticle compositions in thermosets and carbon

o Shaped components (solid, film, and fiber)

o Production from commodity chemicals, resins, and polymers

o Amenable to incorporation of heteroatoms and multiple metal nanoparticles

o High surface area films for sensor to TIC exposure

Conversion of Phthalonitrile Resins into Multi-Walled Carbon Nanotubes

AO O

O

AO O

NC

NC CN

CNn

1. Co2(CO)8

THERMOSET

Carbon Nanotube Compositions1c

(1000 - 1300 C)°

3

4

CH3

CH3

, n = 0

A =

CH3

CH3

A =

1a

1b

, n = 0

, n = 1

A =

20 30 40 50 60 70 80

Co

(200

)

Co

(220

)

CN

T (1

10)

2

Inte

nsity

(Arb

itrar

y U

nits

)

CN

T (1

00)

Co

(111

)

CN

T (0

04)

CN

T (0

02)

A

B

C

Formation of MWNTs from various phthalonitriles Phthalonitrile resins are commercially available

TGA thermograms of (A) BisPhth, (B) Biphenyl Phth, and (C) Oligomeric Phth.

DTA thermograms showing MWNT formation between 600-800oC

XRD for MWNTs formed from various phthalonitriles

Images of carbonized 4 after drawing of rods from melt and heating to 1000oC

SEM images of film deposited on silicon wafer showing MWNTs.

TEM images of 1:20 sample of Co2(CO)8 to 1a heated to 1000oC.

M. Laskoski, T. M. Keller, and S. B. Qadri, Polymer, 48, 7484 (2007)

Formation of CNTs from Novolac Epoxy Resin Precursor

BET surface area = 310 m2 g-1

Pore volume = 1.08 cm3 g-1

Fe-catalyzed epoxy carbon Co-catalyzed epoxy carbon

BET surface area = 261 m2 g-1

Pore volume = 0.64 cm3 g-1

OOO O

OO

CH2 CH2

n

epoxy

1. Mix with amine and

Fe2(CO)9

2. Cure

3. Heat to 1000 oC

4. Purify

CNT/CNF Solid

OOO O

OO

CH2 CH2

n

epoxy

1. Mix with amine and

Co2(CO)8

2. Cure

3. Heat to 1000 oC

4. Purify

CNT/CNF Solid

100 nm 100 nm

Bamboo CNTs Bamboo CNTs and MWNTs

Conversion of Polyacrylonitrile (PAN) to Carbon Nanotubes

CH2 CH

CN

n

polyacrylonitrile

1. Mix with

Fe or Co compound

2. Heat to 1000 oC

Carbon Nanotubes

(00

2)

(10

0)

(00

4)

(110)

XRD of CNT composition

prepared from polyacrylonitrile

SEM images of MWNTs on solid film

PAN crude rod carbonized in presence

of Fe nanoparticles

10 mm

Fiber from injection into water followed

by carbonization and formation of CNT

fiber

Fabrication of Metal Nanoparticle-Carbon Nanotube-Containing Fibers Formulated from Polyacrylonitrile (PAN)-Nothing

Optimized but Demonstrated CNTs form In Situ Within Fibers

Metal nanoparticle-carbon nanotube-containing carbon fibers

SEM image of Fe nanoparticle-carbon nanotube carbon fiber (top) SEM image of Fe nanoparticle-carbon nanotube graphitized fiber (bottom)

Technological Impact of Carbon Nanotube and Metal Nanoparticle Carbonaceous Solid Compositions

• Shaped components (solid, film, fiber, or powder) can be readily fabricated

• Large-scale, low-cost method of production opens up market using CNT, CNT-metal nanoparticle, and carbon nanoparticle-metal nanoparticle compositions

• Development of new technologies and transition to industries based on the low cost, easy-to-process CNT and metal nanoparticle compositions synthesized at the atomic and molecular levels

• Potentially the NRL developed CNT and metal nanoparticle compositions could have broad impact on the nanotechnology industry

• Nanotube and metal nanoparticle compositions may have useful structural, catalytic, electric, and/or magnetic properties

Acknowledgement

Thank the Office of Naval Research for

financial support of the research efforts.