industrial FRCA 2002 - Pennsylvania State Universityzeus.plmsc.psu.edu/~manias/PDFs/frca2002.pdf · 1 [email protected] The role of nm-thin layered inorganic fillers as flame retardants

1

manias@ psu.edu

The role of nmThe role of nm--thin layeredthin layeredinorganic fillers asinorganic fillers as

flame retardants in polymersflame retardants in polymers

E. Manias E. Manias && T.C. ChungT.C. ChungMaterials Science & Engineering dept.Materials Science & Engineering dept.

Penn State University, University Park, PAPenn State University, University Park, PA

J.W. GilmanJ.W. GilmanBuilding & Fire Research Lab, NISTBuilding & Fire Research Lab, NIST

OutlineOutline

Flame retardancy by layered silicate filler addition

✦ brief review of previous findings

✦ clues about the physical origins of FR

Effect of polymer & surfactant chemistry in FR

Syndiotactic Polystyrene / montmorillonite

nanocomposites as a promising high-T material

Concluding RemarksBuilding & Fire Research Laboratory

2

Flame Retardant CharacterFlame Retardant Character

0

200

400

600

800

1000

1200

1400

1600

0 120 240 360 480 600

PP intercalated (2 % silicate) PP pure (PP-g-MA, 0.4 % MA)PP intercalated (4 % silicate)

Hea

t Rel

ease

Rat

e (k

W/m

2 )

Time (seconds)

Flux = 35 kW/m2

Cone calorimeter studies(at NIST)

Gilman, J. W.; et al Chemistry of Materials 12, 1866 (2000)

“Universal” Enhancement:✦ PS ✦ nylon-6 ✦ PE✦ PP ✦ PI ✦ various epoxies

Origins:

formation of surface-char✦ barrier (O2, fumes)✦ thermal isolation

Char StructureChar Structure

Gilman, J. W.; et alChemistry of Materials 12, 1866 (2000)

nanocomposite structure char structure

3

Effect of filler dispersionEffect of filler dispersion

Flux = 35 kW/m 2

0

200

400

600

800

1000

1200

1400

1600

0 40 80 120 160 200 240 280

PS purePS immiscible (3 % NaMMT)

PS intercalated/delaminated (3 % 2C18-MMT) extruded at 170 oC

PS intercalated (3 % C14-FH) extruded at 170 oC

Hea

t Rel

ease

Rat

e (k

W/m

2 )

Time (seconds)Gilman, J. W.; et al

Chem. Mater.12, 1866 (2000)

Origins of the flame retardancyOrigins of the flame retardancy

Gilman, J. W.; et al Chemistry of Materials 12, 1866 (2000)

Nanoscale Dispersion is important/necessaryGeneral Improvement for many polymers

HRRs of thermoplastic/thermoset are reduced by 40-60% in nanocomposites of only 2-6% filler. This approach does not increase the carbon monoxide or soot produced during the combustion, and oftentimes it retards “dripping”.

The physical properties are not degraded by the sillicateadditive, instead many of them are improved.. FR originates from a surface char developmentduring combustion.

This char layer acts as an insulator and a mass transport barrier, as the polymer decomposes.

4

Achieving Dispersion Achieving Dispersion (for melt blending)(for melt blending)

Generally, Polymers and Clays do not mix

and thus, clays must be organically modified

“Rule of thumb” : favorable excess interactionsi.e. polymer-clay interactions better than

clay-surfactant interactions

Vaia & Giannelis, Macromolecules, 30, 7990 (1997)Balazs et al, Macromolecules, 31, 8370 (1998)

General Hybrid StructureGeneral Hybrid Structure

For naturally occuring fillers (e.g. montmorillonite)there coexist intercalated/exfoliated filler structures

A: intercalated layersB: exfoliated/disordered

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Barrier propertiesBarrier properties

0 2 4 6 8

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

wat

er p

erm

eabi

lity

[10-5

g*m

/m2 h]

φ MMT [wt%]

0 1 2 3 4 5 6 7

0

10

20

30

40

neat PVA φ MMT : 2 wt% 4 wt% 6 wt%

Wat

er V

apor

Tra

ns.

[mg

H2O

]

time [ 103 min ]

Poly(vinyl-alcohol) / montmorillonite hybrid

K. Strawhecker & E. ManiasChemistry of Materials 12, 2943 (2000)

GeneralEnhancement:

PDMS nylon-6PP PE PETPU PUU PSPVA ...

water vapororganic solventsgases (e.g. O2 )

Origin of barrier propertiesOrigin of barrier properties

Origins:

✦ path tortuosity

✦ dispersion✦ filler effect on

polymer nature

R. Xu, E. Manias, A.J. Snyder & J. Runt Macromolecules, 34, 337-339 (2001)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

vol. fraction silicate (φ)

Rel

ativ

e Pe

rmea

bilit

y P

com

posi

te/P

poly

mer

poly(vinyl alcohol) poly(dimethyl siloxane) poly(urethane-r-urea)

α = 300

α = 1000

theoretical prediction- - - -

Origins:path tortuosity

filler effect on polymer nature

mechanicalthermalsolubility

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Effect of polymer “chemistry”Effect of polymer “chemistry”

0

200

400

600

800

1000

1200

1400

1600

0 120 240 360 480 600

PP intercalated (2 % silicate) PP pure (PP-g-MA, 0.4 % MA)PP intercalated (4 % silicate)

Hea

t Rel

ease

Rat

e (k

W/m

2 )

Time (seconds)

Flux = 35 kW/m2

0 10 20 30 40 50 60 70 80 90 100 110 1200

200

400

600

800

1000

1200

1400

1600

1800

PP pure (PP-g-OH , 0.5% OH) PP hybrid (2C18-mmt, 5.5% silicate) PP hybrid (Cloisite15A, 5.5% silicate)

Hea

t Rel

ease

Rat

e (k

W /m

2 )

Time (seconds)

PP-g-MA 0.4% / 2C18MMT PP-g-OH 0.5% / 2C18MMT

Cone calorimeter studies at NIST

Effect of surfactant chemistryEffect of surfactant chemistry

100 200 300 400 500 600 700

0

20

40

60

80

100

2C18ammmoniummmt

sPS/2C18am -mmt nanocomposite

neat sPS

Wei

ght (

%)

Temperature (oC)

nanocomposite

formation with

alkyl-ammonium

modified mmt

can deteriorate

the response of

high T polymers

(e.g. syndio-PS)

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Cationic Surfactants for Cationic Surfactants for sPSsPS

NN H

NN C16H33

NN C16H33

H+

N+

N C16H33

C16H33

C16H33I

C16H33I

THF

THF

2C16imm

C16imm

ImmidazoliumImmidazolium--alkyls as surfactantsalkyls as surfactants

nanocomposite

formation with

alkyl-immidazolium

modified mmt

can improve

the response of

syndio-PS

200 300 400 500 600

0

20

40

60

80

100

sPS / 2C16im-mmtnanocomposite

2C16-immidazmmt

neat sPS

Wei

ght (

%)

Temperature (oC)

8

200 300 400 500 600

0

20

40

60

80

100

C16imm -mmtnanocomposite

C16 immidazmmt

neat sPS

Wei

ght (

%)

Temperature (oC)

ImmidazoliumImmidazolium--alkyls as surfactantsalkyls as surfactants

Melt Processable Melt Processable sPSsPS/o/o--mmtmmt

0 5 10 15 20 25

sPS / 2C16imm-mmt nanocomposite(melt blending @ 270oC)

sPS / 2C16imm-mmtmixture

XRD

Inte

nsity

2θ

9

Melt Processable Melt Processable sPSsPS/o/o--mmtmmt

0 5 10 15 20 25

sPS / C16imm-mmt nanocomposite(melt blending @ 270oC)

sPS / C16imm-mmt mixture

XRD

Inte

nsity

2θ

Concluding RemarksConcluding Remarks

Nanoscale Dispersion is important/necessary

General Improvement for many polymers due toa surface char development during combustion

Chemistry is also importantpolymer chemistry/functionalizationorganic modification of mmt

syndio-Polystyrene / alkyl-immidazolium mmtnanocomposites seem promising high-T materials

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AcknowledgementsAcknowledgements

Who actually did the work:Who actually did the work:

Zhiming WangAhmed TounyLixin Wu

Jeff Gilman (NIST)

T.C. Chung (Chemistry)

Financial Support:Financial Support:NIST (Building & Fire Research) Air ProductsKulicke & Soffa/PolysetArrow BiomedicalCoca-Cola papers at: http://zeus.plmsc.psu.edu/

or email: manias @ psu.edu/

100 nm