Upload
others
View
10
Download
1
Embed Size (px)
Citation preview
SCREENING FLAME RETARDANT ADDITIVESSCREENING FLAME RETARDANT ADDITIVESFOR PLASTICS USING MICROSCALE COMBUSTION FOR PLASTICS USING MICROSCALE COMBUSTION
CALORIMETRYCALORIMETRY
FEDERAL AVIATION ADMINISTRATIONAirport and Aircraft Safety R&D Division
William J. Hughes Technical CenterAtlantic City International Airport, NJ 08405
The Fifth TriennialInternational Aircraft Fire and Cabin Safety Research Conference
Atlantic City, New Jersey USAOctober 29-November 1, 2007
WEB: www.fire.tc.faa.gov E-MAIL: [email protected]
Richard E. Lyon and Richard N. Walters
PROBLEM
Need Small Scale (milligram) Screening Test for FR Additives to
Reduce Development Costs and Accelerate Discovery.
APPROACH
• Measure Properties of Complete Combustion using Microscale
Combustion Calorimetry.
• Use a “Burning Efficiency” to Account for Incompleteness of
Flaming Combustion.
• Account for Uncertainty Using Probability.
RESULTS
CONCLUSIONS
SCREENING PLASTICS FOR FLAMMABILITYSCREENING PLASTICS FOR FLAMMABILITY
PP PEPS
PET
ABSPMMA
Epoxy
POM
NYLON 66
PCPPO
PUPAR
PPSU
PPSPES
PEI LCP's
PAI
PEKPEEK
0.1 1 10 100Materials Cost* ($/lb)
Phenolic
KAPTON
1000
10
100PVF
Heat Resistant Plastics
PSU
PVC (rigid)
Commodity Plastics
*Truckload Prices, 2001
Engineering Plastics
IntrinsicallyFlame
Resistant
Flam
mab
ility
(ηc)
, J/g
-K
THE GOAL OFTHE GOAL OF THE FR ADDITIVE APPROACHTHE FR ADDITIVE APPROACH
Flame Retardant Additives
Flame Retardant Additives
Plastic
Heat fromFlame
Heat LossFrom Surface
O2
Fuel Gases From Plastic
= Heat = Heat ResistanceResistance
FLAME RETARDANTS WORK INFLAME RETARDANTS WORK IN TWO WAYSTWO WAYS
Gas Gas PhasePhaseActivity Activity
Condensed Condensed PhasePhaseActivityActivity
Need to quantify the efficiency of these modes of action
APPROACHAPPROACH
Pyrolysis
Sample
Gases analyzed for residual oxygento compute heat release rate
O2
N2
Combustion
Flaming Combustion
MicroscaleCombustionCalorimeter
1) Reproduce elements of flaming combustion in non-flaming test
3) Relate thermal combustionproperties to fire and flametests using deterministic and probabilistic models
2) Measure thermal combustion properties of materials
MICROSCALE COMBUSTION CALORIMETER (MCC)MICROSCALE COMBUSTION CALORIMETER (MCC)
Combustor
Pyrolyzer
Mixing Section
Sample Cup
ScrubberFlow MeterO2 Sensor
Exhaust
Purge Gas Inlet
Sample Post & Thermocouple
Oxygen Inlet
Heat release rate by oxygen consumption
AUTOMATED / HIGH THROUGHPUT MCCAUTOMATED / HIGH THROUGHPUT MCC
Combustor with oxygen consumptionattached to TGA with automated sampling
Capable of ≈ 50 tests/day
MCC becameASTM Standard
April 1, 2007
MCC becameASTM Standard
April 1, 2007
THERMAL COMBUSTION PROPERTIES (MCC)THERMAL COMBUSTION PROPERTIES (MCC)
250 300 350 400 450 500 5500
100
200
300
400
500
Hea
t R
elea
se R
ate
(J/g
-K)
Temperature (°C)
φ = Pyrolysis residue (Char fraction)
Heat Release Capacity, ηc (J/g-K)
Total Heat Release, HR (J/g)
Temperature at Max HRR, Tmax (°K)
FORCED AND UNFORCED COMBUSTIONFORCED AND UNFORCED COMBUSTION
Cone Calorimeter (ASTM E 1354)
OSU Calorimeter (14 CFR Part 25)
ForcedCombustion
UnforcedCombustion
Vertical Flame Test (ASTM D 3801)
Oxygen Index (ASTM D 2863)
FLAMING COMBUSTION: FLAMING COMBUSTION: Gas Phase ChemistryGas Phase Chemistry
Complete Combustion (Oxidation) of Fuel Gases
CcHhOmNnXx + m O2
900 °CCO2 + H2O + N2 + HX
10 secFuel Gases
Incomplete Combustion of Fuel Gases in Diffusion Flame
CcHhOmNnXx + n O2
Flame
Fuel Gases + CO + CxHy + soot
n O2
m O2< 1χ =Flaming Combustion Efficiency,
MicroscaleCombustionCalorimetry
CO2 + H2O + N2 + HX Fires and Flames
FLAMING COMBUSTION: FLAMING COMBUSTION: Condensed PhaseCondensed Phase PhysicsPhysics
Heat Transfer Efficiency, θ = =q″net− κ(ΔT/Δx) char layer
− κ(ΔT/Δx) resin
Tem
pera
ture
Tsurface
Tdecomp
ΔT
Δx Δx Δx
VirginResin
GasChar Slope = Heat Transfer RateΔT
Δx∝
Char Layer Depth =
q″net0
Heat Release Rate (HRR) for Steady Burning:
Hc = Heat of CombustionOf Fuel Gases
0
χ = Combustion Efficiencyin Flame
θ = Heat Transfer Efficiencyat Surface
HRR = χ Hc0
Lgθ ′ ′ q flame − ′ ′ q rerad( ) + χ Hc
0
Lgθ ′ ′ q ext
HRR0
HR
R (k
W/m
2 )
q″ext (kW/m2)0
Cone Calorimeter
Data
STEADY BURNING MODEL: MacroSTEADY BURNING MODEL: Macro
HRP
HRP = = ηg
HRR = ηcηg
( ′ ′ q flame − ′ ′ q rerad ) + ηcηg
′ ′ q extHeat Release
Rate:
Heat Release Capacity
Flaming Combustion Efficiency
HcLg
HRR AND THERMAL COMBUSTION PROPERTIESHRR AND THERMAL COMBUSTION PROPERTIES
χθ0 ηcχθ
hg
ΔTp
Fire Response
FORCED FLAMING COMBUSTIONFORCED FLAMING COMBUSTION
HEAT RELEASE RATE:HEAT RELEASE RATE: Macro Vs. MicroMacro Vs. Micro
ConeCalorimeter
Natural PlasticsMicro-compositesNano-compositesGFRP (PA6, PBT, PC, PPS)
0
500
1000
1500
2000
0 500 1000 1500 2000
Heat Release Capacity ηc (J/g-K)
R = 0.93
PVC
PEIPPS
POM
PET
PVDF
PC
PMMA
ABSPA66
HIPSPP
HDPE
50 kW/m2
FEPPeak
HR
R in
Con
e C
alor
imet
er
(kW
/m2 )
PC/ABS BlendsFR Compounds
At large external heat flux, HRR ∝ ηc
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 HEAT RELEASE RATE:OSU HEAT RELEASE RATE: Macro Vs.Macro Vs. MicroMicro
Flame Resistance
UNFORCED FLAMING COMBUSTIONUNFORCED FLAMING COMBUSTION
FLAME EXTINCTION CRITERIAFLAME EXTINCTION CRITERIA
HRP ≤
MACRO Extinction Criterion for Flame Tests
ηcηg HRR*
Flame Extinction Occurs at Critical HRR:
MICRO Extinction Criterion for Flame Tests
HRR* ≈100 kW/m2 (Downward Burning)
60 kW/m2 (Upward Burning)
(q″flame- q″rerad)≤
(q″flame- q″loss)HRR*
= ηc*
[O2∗ ] = ′ ′ q rerad
a+
HRR∗ ηg / aηc
≈ 12% + 2.8 kJ / g − Kθ χ ηc
(%)
Limiting Oxygen Index (LOI) = [O2*]
q″flame ∝ [O2] = a [O2]
a = 1.4 kW/m2-%O2
ηg =hg / ΔTp
χθ= ( 2 kJ / g ) /(50K )
χθ= 40 J / g − K
χθ
HRR* = 100 kW/m2 (downward burning)
FLAME RESISTANCE TEST (ASTM D2863)FLAME RESISTANCE TEST (ASTM D2863)
LOI EXTINCTION CONDITION:
′ ′ q rerad = σTmax4 ≈17kW/m2
EFFECTEFFECT OF BURNING EFFICIENCY ON L.O.I.OF BURNING EFFICIENCY ON L.O.I.
Halogen containing
0
20
40
60
80
100
10 100 1,000 10,000
Heat Release Capacity ηc, J/g-K
Lim
iting
Oxy
gen
Inde
x, %
v/v
Flamm
ability
0.3
w/ FR Additives
0.6LOI =12% + 2.8 kJ / g − K
θ χ ηc(%)
θχ = 1
q″flame ≈ 30 kW/m2
ηg =hg / ΔTp
χθ= ( 2 kJ / g ) /(50K )
χθ= 40 J / g − K
χθ
HRR* = 60 kW/m2
FLAME RESISTANCE: UPWARD BURNINGFLAME RESISTANCE: UPWARD BURNING
UL 94 V EXTINCTION CONDITION:
ηc ≤HRR∗ ηg
χθ( ′ ′ q flame − εσTmax4 )
≈ 2.4 MW J m−2 g−1K −1
χθ( ′ ′ q flame − εσTmax4 )
Comparative Burning Characteristics of Plastics in Vertical Position (UL 94 V or ASTM D 3801):
q″rerad = CHF ≈ εσTmax 4
0
200
400
600
800
1000
1200
1400
200 250 300 350 400 450 500 550 600
χθ0.2
0.40.60.6
Extin
ctio
n η C
, J/g
-K
Decomposition Temperature Tmax, °C
0.81
UL 94 VFlame Test
0.30.3
Burning Efficiency
0.60.6
EFFECT OFEFFECT OF χθχθ ANDAND TTmaxmax ON EXTINCTION ON EXTINCTION ηηc c
100 1000Heat Release Capacity, J/g-K
NR / Burns
V-2
V-1
V-0 / 5V
30 300 3000
1111
0.40.40.9
θ =χ =
UL
94 V
Rat
ing
Bromine FR Natural Plastics
Phosphorus FR 0.90.40.4
Flamm
ability
EFFECT OF BURNING EFFICIENCY ON UL 94EFFECT OF BURNING EFFICIENCY ON UL 94
Gas Phase FRCondensed Phase FRUNCERTAINTY DUE TO BURNING EFFICIENCY
OODDS OF BURNINGDDS OF BURNING AND AND HRRHRR
Assume that Odds of Burning is related to HRRand probability of burning, pB
HRRHRR*
pB
1 - pB=
HRRHRR*
pB =(HRR/HRR*)
1 + (HRR/HRR*)
Then,
pB
10 0.9995 0.99
1/2 0.111/5 0.0081/10 0.001
2 0.891 0.5
3
3
3
Odds ofBurning =
OODDS OF BURNINGDDS OF BURNING ANDAND THERMAL COMBUSTION PROPERTIESTHERMAL COMBUSTION PROPERTIES
Then,
= χθ ηc
ηg
And:
′ ′ q netHRR HRR* ≈ 60 kW/m2=;ηc
ηg′ ′ q critical
*
pB = (χθ ηc / ηc )3 / χθ
1+ (χθ ηc / ηc )3 / χθ
*
*
Depends only on burning efficiency (χθ)and heat release capacity (ηc )
pB
1− pB= HRR
HRR *⎛ ⎝ ⎜
⎞ ⎠ ⎟ 3
= χθ ηc
ηc
⎛
⎝ ⎜
⎞
⎠ ⎟ 3
′ ′ q net
′ ′ q critical
⎛
⎝ ⎜
⎞
⎠ ⎟ 3
≈ χθ ηc
ηc
⎛
⎝ ⎜
⎞
⎠ ⎟ 3 / χθ
* *
Heat Release Capacity, ηc (J/g-K)
NR / HB
V-2
V-1
V-0 / 5V
UL 94 V Rating
= Burn (HB / NR / V-2 / V-1) = No Burn (V-0 / 5V)
pB = Fraction of BurnResults in HRC Bin
MEASURE PROBABILITY OF BURNING,MEASURE PROBABILITY OF BURNING, ppBB
0 200 400 600 800 1000 1200 1400 1600
HRC bin width of ≈ 50 J/g-K gives statistically valid sample (n ≥ 5)
184 test results
Heat Release Capacity, ηc (J/g-K)
Prob
abili
ty o
f Bur
ning
, pB
pB =χθ ηc / 325( )3 / χθ
1+ χθ ηc / 325( )3 / χθ
EFFECT OF BURNING EFFICIENCY ON PROBABILITYEFFECT OF BURNING EFFICIENCY ON PROBABILITY OF BURNINGOF BURNING
0
0.2
0.4
0.6
0.8
1
10 100 100030 300 3000
χθ = 1
χθ = 0.6(FR Compounds)
χθ = 0.8Best Overall Fit
(pB ±0.11)
CONCLUSIONSCONCLUSIONS
Probabilistic Models are required to reconcile MCC data with flame resistance tests because
• Intumescence, charring (θ)• Gas phase inhibition (χ)• and Dripping
are comparable in magnitude and effect to thermal combustion properties at extinction.
Incompletecombustion in flame
Deterministic Models using thermal combustion properties appear adequate for forced flaming combustion.