New UEF Emission Factors for SMC Production and Compression Molding

David Lipiro

Environmental Compliance & Risk Management

dlipiro@ecrminc.com

ECRM

Terminology

• SMC = Sheet Molding Compound• BMC = Bulk Molding Compound• LCM = Liquid Composites Molding

• UEF = ANSI/ACMA/ICPA UEF-1-2009, Estimating Emission Factors from Open Molding and Other  Composite Processes (Current Version)

Factors for VOC Emissions

• Compounding (in UEF) – from SMC machines – based on ECRM study

• Compression molding (proposed) – SMC, BMC, LCM – based on EECS studies (R. Haberlein)

Estimating Emissions • Emission Factor = ratio

– Lb emitted/lb compound used = E/C = 0.002– Lb emitted/lb styrene used = E/S = 0.02

• Equivalent Emission Models– E = 0.002*C– E = 0.02*S– Simplest model constant factor

• Derive models and factors from test data

S E E/S

100 19.55 0.20

80 15.44 0.19

60 12.28 0.20

40 8.44 0.21

20 3.89 0.19

10 1.98 0.20

0.20Average EF =

Emissions vs Styrene Run

E = 0.2S

0

5

10

15

20

25

0 50 100 150

S, lb/hr

E, lb

/hr

S E E/S

100 25.80 0.26

80 21.29 0.27

60 17.59 0.29

40 13.65 0.34

20 8.85 0.44

10 7.79 0.78

0.40Average EF =

Emissions vs Styrene Run

E = 0.2S + 5

E = 0.4S

0

5

10

15

20

25

30

35

40

0 50 100 150

S, lb/hr

E, l

b/hr

Compounding Emission Model

• Theory

• Lab weight loss experiments at MFG Research – C. Piper

• Evaluate recent VOC emission tests of 7 SMC machines

Theory• Areas where paste is not covered by

carrier film = window to environment

• Exposed area A ft2 is constant for each SMC machine

• Simplest model:E lb/hr = kA, k = constant

Upper Lower

Styrene Content?

• Affects skinover?

• Expected to be important based on UEF for open molding

Line Speed?

• Skinover effect at longer travel times lower emissions at lower linespeeds?

• Induced air velocity as paste moves under air impact depends on vent airflow patterns?

MFG Lab Tests

• Wt loss by analytical balance + datalogger, 10 readings per second, 6-8 reps

• Constant sample pan area = 0.16379 ft2

• Range of S.G. and styrene % in pastes used

• “Wind tunnel” w anemometer – simulate motion-induced airflow

• Run times cover realistic line travel times - simulate skinover

Conclusions/Predictions

• Not much skinover effect – most weight loss curves linear or near

• Styrene content will probably have little impact on emissions

• Line speed probably won’t effect emissions

• Emissions will vary with open area, temperature and air velocity - only area practical for permitting

Field Verification• Method 24 TTE emission tests

• 7 uncontrolled machines – 24”, 48”, 60”

• Wide range of open areas, styrene contents, linespeeds

• No temperature control at doctor boxes

• Doctor boxes open to nearly closed

Field Data Analysis

• Regression: Emissions vs Predictor

• Predictors compared:– Area– Styrene throughput (traditional)– SMC throughput

Emission vs Total Wet Area, withConfidence and Prediction Limits

(k=3 for Prediction Limits)E = 0.1457A - 0.1454

R2 = 0.9917

0

2

4

6

8

10

12

14

16

18

0 50 100 150

Area, ft2

Em

iss

ion

s, l

b/h

r

Actual

LCL

UCL

LPL

UPL

Figure 2. Throughput Model 1y = 0.0009x - 1.773

R2 = 0.4

0

2

4

6

8

10

12

14

16

0 5,000 10,000 15,000

SMC Run, lb/hr

Sty

rene

Em

itted

, lb/

hr

1

2

3

4

5

6

7

Compounding Emission Model in UEF

• Er = 0.1457*A-0.1454, where:– Er = emission rate of SMC machine, lb/hr– A = open wet area of machine (including

uncovered doctor box area), ft2

• Emissions = Er * t (hrs)• Permitting: E is constant when paste

on line - throughput irrelevant

Compression Molding• SMC, BMC, LCM• Emissions from charge prep only -

Once press closes, negligible emissions

• EECS Study: Charge prep emissions measured in Method 204 TTE

SMC Compression Molding

• Two “traditional” EFs proposed based on test data

• Which is best predictor?• What are underlying models?

Compound Throughput Model

C, lb/hr E, lb/hr E/C16 0.027 0.0016486 0.250 0.00292115 0.231 0.00201229 0.540 0.00236191 0.264 0.00138189 0.627 0.00332306 0.651 0.00213388 0.750 0.00193237 0.169 0.00071319 0.672 0.00211279 0.715 0.00256142 0.335 0.00235628 0.736 0.00117602 0.682 0.00113690 1.472 0.00213690 1.200 0.00174

0.0020Average EF =

Emissions vs SMC MoldedE = 0.00148C + 0.10955

R2 = 0.74233

E = 0.002C

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 100 200 300 400 500 600 700 800

SMC molded, lb/hr

Emis

sion

s lb

/hr

Styrene Throughput Model

S, lb/hr E, lb/hr E/C2.16 0.027 0.01250

12.75 0.250 0.0196115.51 0.231 0.0148931.80 0.540 0.0169823.52 0.264 0.0112228.31 0.627 0.0221549.35 0.651 0.0131954.00 0.750 0.0138927.56 0.169 0.0061338.22 0.672 0.0175833.55 0.715 0.0213115.40 0.335 0.0217567.16 0.736 0.0109674.07 0.682 0.0092195.20 1.472 0.0154673.84 1.200 0.01625

0.0152Average EF =

Emissions vs Styrene Molded E = 0.0129S + 0.0646

R2 = 0.8093

E = 0.0152S

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 20 40 60 80 100

Styrene molded, lb/hr

Emis

sion

s lb

/hr

EFs Compared• E/C = 0.002 is poorer predictor

(R2=0.74, 10% total overestimate)

• E/S = 0.0152 is better predictor (R2=0.81, 5% total overestimate), same form as published AP-42 factor

• UEF: E lb = 1.5% styrene lb run vs 2% AP-42 factor

BMC and LCM• UEF: BMC Molding Emissions = 1.15% of

styrene in compound molded

• UEF: LCM EF, lb styrene / lb paste molded =– Spread prep: 0.0072*S% + 0.008– Pour prep: 0.0022*S% + 0.008– LCM Emissions = EF * lb paste molded

Why Use These Factors?

• Best available methods to estimate emissions w/o site testing

• Most credible factors available – adopted into UEF by transparent ANSI consensus process involving industry and state/fed regulators

Thank you for attending

Questions

ECRM