STANDARD TEST METHOD FOR FLAMMABILITY SCREENING OF AC MATERIALS

Fire Safety Branch AAR-440FEDERAL AVIATION ADMINISTRATION

William J. Hughes Technical CenterAtlantic City International Airport, NJ 08405

International Aircraft Materials Fire Test Working GroupTropicana Hotel-Casino, Atlantic City, NJ, March 20-21, 2006

WEB: www.fire.tc.faa.gov E-MAIL: richard.e.lyon@faa.gov

Richard E. Lyon

OUTLINE

• FLAMMABILITY PROPERTIES FROM MICROCALORIMETRY

• MICROCALORIMETRY AND:

Ignitability (Radiant Panel Flame Spread)

Heat Release Rate (OSU and Intermediate Scale Tests)

Flame Resistance (Bunsen burner tests)

Research (Product Development)

• SUMMARY AND CONCLUSIONS

Standard Test Method for Flammability Screening of AC Materials

GOAL: PREDICT RESULTS OF AC FIRE TESTING

FLAMERESISTANCE

HEAT RELEASE

INTERMEDIATESCALE

FIRE TESTSPCFC

Semi-Empirical Correlation

CombustionPropertieshc, Tign, ηc

0

MilligramsKilograms

= 10 −6 = “Microscale”

OSU Hidden Materials

FLAME SPREAD

Radiant Panel

APPROACH: Simulated Flaming Combustion

Flaming Combustion

Microscale Combustion Calorimetry• Sample heated at constant rate in N2• Complete oxidation of fuel gases• Oxygen consumption calorimetry to

measure heat release rate

Pyrolysis

Combustion

Sample

Exhaust

DAQO2

GasScrubber Gas

Flow-meter

O2Meter

N2

APPARATUS CONSTRUCTION

Combustor

Pyrolyzer

Mixing Section

Sample Cup

ScrubberFlow MeterO2 Sensor

Exhaust

Purge Gas Inlet

Sample Post & Thermocouple

Oxygen Inlet

Q(t) =ρO2

Cm0

F[O2 ]{ }(t)

hc0 = Q(t)dt

0

∞∫

= 13 kJg

Br

Cl

Cl

( ) n

-50

0

50

100

150

200

250

300

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600

Q (W

/g)

Temperature, C

elsius

Time, seconds

PCFC DATA: Example for Research Polymer

ηc = 260 W/ g1K / s

= 260 Jg −K

260 W/g

β = 1 K/s

Tmax

Tmax = 425 °C

MICRO HRR DATA FOR COMMON PLASTICS

200 300 400 500 600 700 800

0

500

1000

1500

2000

Temperature, °C

ABSPVDF

PVC

PP

POMPMMA

PET

PE

PC

Q/β

, J/g

-K

PPSPEI

PA66

FEP

MOTIVATION FOR MICRO SCALE TEST

Small Specimens (milligrams instead of kilograms)

Rapid Results (minutes instead of hours)

Reproducible (± 7%)

Repeatable (± 5%)

Fire Properties Measured (used with models to correlate other tests)

PROPERTIES RELATED TO FLAMMABILTIY

250 300 350 400 450 500 5500

100

200

300

400

500Qmax/β

Heat of Combustion

TmaxHea

t R

elea

se R

ate

(W/g

)

Temperature (°C)

PCFC Property

• Heat release rate• Flame resistance

(UL94 , LOI)

• Fire Load• Combustibility

• Ignitability (Tign, CHF)• Glow Wire Ignition

FlammabilityParameter

IGNITABILITY

IGNITION TEMPERATURE AND Tmax

200

300

400

500

600

700

200 300 400 500 600 700

Igni

tion

Tem

pera

ture

, �C

Tmax in PCFC, �C

40 Polymers

Tign ≈ Tmax(hydrocarbons)

CHF, kW/m2

Measured* σTmax4POLYMER

Tmax

(°C)

PMMA 401 � 8 11 - 12 6 - 23POM 409 �10 11 - 13 13HIPS 463 �10 15 - 17 15ABS 467 �12 16 - 18 9 - 15PET 471 �12 16 - 18 10 - 19PVC** 478 � 8 17 - 18 15 - 28

PP 493 �10 18 - 20 15 - 16

PE 514 �10 20 - 22 15 - 20PVDF** 510 � 2 21 30 - 50

PC 556 � 9 25 - 28 15 - 20PPS** 551 �18 24 - 28 35 - 38PEI 576 �10 28 - 31 25 - 40FEP 600 �10 31 - 34 38 - 50

PA66 482 17 - 19 15 - 21�11**Note poor agreement for halogen (Cl, F) and

heteroatom (S) polymers for which

Tign > Tmax

CRITICAL HEAT FLUX (CHF) FOR IGNITION FROM Tmax

*D. Drysdale, A. Tewarson, R.E. Lyon

0

10

20

30

40

50

60

0 10 20 30 40 50 60

Crit

ical

Hea

t Flu

x, k

W/m

2

81 2

3

45

7 11

13

14

6 9

1012

PMMAPOMHIPSABSPETPA66PVCPPPEPVDFPCPPSPEI

123456789

10111213

FEP14

σ 4Tmax, kW/m2

CRITICAL HEAT FLUX: Graphical Comparison

100

200

300

400

500

600

700

800

0 10 20 30 40 50

Tem

pera

ture

, °C

Distance From Igniter, cm

Tmax < Ts

Surface Temperature, Ts(From Panel Calibration)

Tmax > Ts

PERFORMANCE OF HIDDEN MATERIALS

Tmax (°C) Measured in

PCFC

Heat Resistance / Tmax is a Good Predictor of Flame Spread in FAA Radiant Panel Test

HEAT RELEASE RATE

HEAT RELEASE RATE: Macro / Micro

Slope = HRP ≡

HR

R (k

W/m

2 )

q″ext (kW/m2)0

hcLg

=hc / ΔTpLg / ΔTp

= ηcηg

Fire Calorimeter Data

HRR = HRR0 + ηc

ηg′ ′ q ext

Multiply by ΔTp / ΔTp

Intercept = HRR0

From PCFC

CONE HRR AND MICROCALORIMETER ηC

ConeCalorimeter

0

500

1000

1500

2000

0 500 1000 1500 2000

R = 0.93

PVC

Heat Release Capacity ηc (J/g-K)

PEIPPS

POM

PET

PVDFPC

PMMA

ABSPA66

HIPSPP

HDPE

50 kW/m2

FEP

Peak

HR

R in

Con

e C

alor

imet

er

(kW

/m2 )

HRR ≈ (q″ext/ηg) ηc = (50 kW/m2)/(50 kJ/kg-K) ηc

= (1 kg-K/m2-s) ηc

Slope = 1 kg-K/m2-s

ASTM E 906/OSURate of Heat

Release Apparatus

1

10

100

1000

1 10 100 1000Heat Release Capacity, J/g-K

Thermoplastic Sheet (1.6 mm) Thermoset Composites (single ply)

FAR 25.853(a-1) Maximum

OSU

Pea

k H

RR

, kW

/m2

OSU HRR AND MICROCALORIMETER ηC

THERMO ACOUSTIC INSULATION

Intermediate Scale and Micro Scale Results

PVF1 (120 J/g-K)

PUF block, Baseline

MPET (262 J/g-K)

PI-O (47 J/g-K)

PET1 (138 J/g-K)

PET3 (250 J/g-K)

PET00 (155 J/g-K)

Material (HRC)

Tem

pera

ture

, °F

TEMPERATURE RISE versus HRC

Intermediate Scale Test of Thermo-Acoustic Insulation

0

200

400

600

800

1000

1200

0 100 200 300

Max

imum

Tem

pera

ture

, °C

Heat Release Capacity, J/g-K

MPET

PET3

PET00PET1

PVF1

PI-0

FLAMERESISTANCE

FLAME RESISTANCE AND MICROSCALE HRR

Bunsen Burner Tests

Isolated flame / Unforced Combustion

Limiting Oxygen Index

Extinction in flame tests (q″ext = 0) when HRR0 ≤ HRR* ≈ 50-100 kW/m2,

HR

R (k

W/m

2 )

q″ext (kW/m2)

Slope = HRP = ηc/ ηg

Intercept = HRR0 = (q″flame- CHF) HRP = (q″flame- CHF) ηc/ ηg

0

FLAME RESISTANCE AND MICROCALORIMETRY

Cone Calorimeter Data

[O2∗ ] = CHF

a+

HRR∗ ηg / aηc

≈ 12% + 4000ηc

(%) ηc∗ ≤

HRR∗ ηg( ′ ′ q flame − CHF)

Limiting Oxygen Index = [O2*] UL 94 V Criterion

PCFC Data

q″flame ∝ [O2] = a [O2] = 1.4 kW/m2-%[O2]

Halogen containing

FLAME RESISTANCE (LOI) AND MICROCAL (ηC)

0

20

40

60

80

100

10 100 1,000 10,000

Lim

iting

Oxy

gen

Inde

x [O

2]*, %

v/v

Heat Release Capacity ηc, J/g-K

LOI = 12% + 4000ηc

(%)Predicted*

Halogencontaining

10 100 1000 10,000

HB

V2

V1

V0

Heat Release Capacity (ηc), J/g-K

UL 94Rating

Flam

mab

ility

ηc∗ ≤

HRR∗ ηg( ′ ′ q flame − CHF)200 J/g-K ≈

FLAME RESISTANCE (UL 94) AND MICROCAL (ηC)

FLAME RESISTANCE: FAR 25.853 AND 25.855

0

2

4

6

8

10

-2

0

2

4

6

8

10

0 100 200 300 400 500 600

Bur

n Le

ngth

(cm

)

Burn Tim

e (seconds)

HRC (J/g-K)

12 Second VerticalBurn Test-Aircraft Materials

Vertical FlameTest

Dripping

RESEARCH

FLAME RESISTANCE OF GFRP

ηc has maximum for non-charring plastics (PA6, PBT).

ηc decreases montonically for charring plastics (PC, PPS)

0

100

200

300

400

500

PA6

PC

PPS

Fiberglass Fraction, % w/w403020100

UL94-HB/V2

UL94-V0

FLAMERESISTANCE

PBT

Hea

t Rel

ease

Cap

acity

, J/g

-K

50

100

150

200

250

300

0 1 2 3 4 5 6

Hea

t Rel

ease

Cap

acity

, J/g

-K

Phosphorus Concentration, % w/w

Glycidylether phosphates (PO4)

Glycidylether phosphonates (PO3)

PHOSPHORUS-MODIFIED EPOXIES

Aminophosphineoxide (PO)

P-Compound (RPOx)

Efficacy Increases for Higher Oxides

Tetrabromobisphenol-A / DGEBATetrabromoDGEBA / DGEBA + EMI-24 (2 wt.%)

Heat of complete combustion of fuel gases is

independent of [Br] in epoxy

Heat Release Capacity

decreases with [Br] in epoxy

20

25

30

35

h c,v, k

J/g

0 5 10 15 20 25 30 35 40300400500600700800

Bromine Content, Wt. %

η c, J

/g-K

BROMINATED EPOXIES (Adjusted for Fuel Fraction)

No Gas Phase Activity

Condensed Phase Activity

SUMMARY

• Small (mg) Specimens = No Fabricated Products,Assemblies, Laminates.

• Physical Effects Not Captured in Test Results:

DrippingSwellingShrinkingCurlingIntumescenceBarrier (mass/heat) effectsetc.

• Complete Combustion Under Normal Operation= Limited Sensitivity to Gas Phase/Halogen FR.

CURRENT LIMITATIONS OF METHOD

Not So Important for FAA Tests(Which Tend to Be More Severe)

STATUS OF MICROCALORIMETRY: Commercial

• R&D 100 Award Submitted by FAA

• Two licensed manufacturers

The Govmark Organization, Farmingdale, NY.

Fire Testing Technology,East Grinstead, England.

• Over ten (>10) commercial units in operation in industry, government, academia.

ASTM Committee D20 (Plastics)

ISO Technical Committee TC 61 (Plastics)

FAA (?)

• “Screening Method” inFire Test Handbook?

• Adapt to AC Materials

STATUS OF MICROCALORIMETRY: Regulatory

Work Items Submitted forStandard Test Method in: