TGA Decomposition Kinetics

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Ultimate benefit is predictive curves “Lifetime Plots”. 80. Kinetic Analysis. ▫The rate at which a ... DTGA Heating Rate Comparison-Time. 20°C/min. 500°C/min .... TA Instruments Universal Analysis software supports the importation of. MS (trend ...

TGA Decomposition Kinetics

Decomposition Kinetics Background  Includes isothermal and constant heating rate methods.

 Constant heating rate method is the fastest and will be discussed here.  Based on method of Flynn and Wall – Polymer Letters, 19, 323, (1966). Requires collection of multiple curves at multiple heating rates.  Ultimate benefit obtained in ‘Life-Time’ plots.

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TA Specialty Library -- TGA Kinetics  Requires at least 3 TGA runs at different heating rates or 1 Modulated TGA® run  Calculates Activation energy & conversion curves  Ultimate benefit is predictive curves “Lifetime Plots”

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Kinetic Analysis  The rate at which a kinetic process proceeds depends not only on the temperature the specimen is at, but also the time it has spent at that temperature.  Typically kinetic analysis is concerned with obtaining parameters such as activation energy (Ea), reaction order (k), etc. and/or with generating predictive curves.

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Kinetic Analysis, con’t. Activation energy (Ea) can be defined as the minimum amount of energy needed to initiate a chemical process. State 1

Ea

State 2

With Modulated TGA, Ea can be measured directly.

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TGA Kinetics - Wire Insulation Thermal Stability

℃ ℃ ℃ ℃

℃ 82

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TGA Kinetics - Heating Rate vs. Temperature 460

440

420

400

380

360

Ln (HEAT RATE) (°C/min)

10

Conversion

5

20 10

5

2.5

1.0

0.5

2

1 1.4

1000/T (K)

1.5

1.6

Activation Energy (Ea)  Slope

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TGA Kinetics - Estimated Lifetime TEMPERATURE (°C)

260 280 300 320 340 360 1 century

ESTIMATED LIFE (hr.)

100000

1 decade 1 yr.

10000

1 mo.

1000

1 week

ESTIMATED LIFE

1000000

100 1 day 10 1.9

1.8 1.7 1000/T (K)

1.6

1.5 84

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Thermogravimetry Under Extreme High Heating Rate Conditions

What Constitutes Extreme Conditions? High Heating Rates Kinetic Studies Sample Throughput

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Rapid Heating Thermal Analysis  Gasification, combustion, and volatilization are complex processes.  Thermal treatments by different heating rates and time/temperature relationships can result is different chemical decomposition products.  As an example, heating at a high rate can result in the thermal degradation of component that would otherwise volatilize at a slow heating rate.  Rapid heating rates, as on the TA Instruments Discovery TGA and pyrolysis GC/MS, provide powerful techniques to investigate the time/temperature relationships

Discovery TGA & Q5000 IR Innovative IR-Heating Furnace

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DTGA Ballistic Heating Performance 800

2000

#1 #2 #3 #4

Temperature (°C)

600

1500

Equilibrate method segment is very repeatable and achieves rates approaching 2000°C/min in this application

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1000

200

500

0

0 0

2

4

6

Time (min)

DTGA Heating Rate ComparisonTemperature

500°C/min

20°C/min

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8

[ – – – – ] Deriv. Temperature (°C/min)

Run Run Run Run

DTGA Heating Rate Comparison-Time

20°C/min 500°C/min

High Heating Rate TGA: Kinetic Studies

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Effect of Heating Rate on Decomposition Temperature of Polystyrene Polystyrene 20°C/min Polystyrene 10°C/min Polystyrene 5°C/min Polystyrene 1°C/min

100

80

Weight (%)

60

40

20

0 0

100

200

300

400

500

Temperature (°C)

600 Universal V4.2D TA Instruments

TGA: Copier Paper in Air 100

80 0.5 to 50 °C/min =======>

Weight (%)

60

BREAK

40

PLATEAU

20

RESIDUE

0 0

200

400

600

Temperature (°C)

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800

1000 Universal V4.4A TA Instruments

TGA: Quantitation of Copier Paper HEATING BREAK PLATEAU RESIDUE RATE weight % weight % weight % __°C/min__ __________ __________ __________ 0.5 40.63 16.32 9.87 1 41.09 16.64 9.85 2.3 41.27 16.70 5 41.55 16.66 9.79 10 41.82 16.57 9.74 23 41.40 16.63 9.90 50 40.35 16.70 9.88 100 37.67 17.06 10.08 230 33.53 16.68 9.83 500 31.46 9.77 Equilibrate 25.06 9.66 > 2300 °C/min Average STD DEV

41.29 0.41

16.66 0.19

9.84 0.11

TGA: Semi-Log Plot of Copier Paper 100

100

0.5 °C/min

80

80 5.0 °C/min

50 °C/min

Weight (%)

60

Weight (%)

60

500 °C/min

40

40

*

20

20 Equilibrate >2000 °C/min

0.1

* No data at 1000 °C/min

16.7 Hours

10 Minutes

6 Seconds

0 0.01

1

10

Time (min)

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100

1000

0 10000 Universal V4.4A TA Instruments

TGA: High Heating Rates of Copier Paper 100

80 BUNCHING 50 of 500 °C/min

Weight (%)

60

0.5 °C/min EQUILIBRATE > 2300 °C/min 5.0 °C/min

40

500 °C/min

EQUILIBRATE > 2300 °C/min

230 °C/min

20

0 200

400

600

Temperature (°C)

800 Universal V4.4A TA Instruments

Modulated TGA Technology A New Approach for Obtaining Kinetic Parameters

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Temperature Change in MDSC and MTGA

MTGA OF 60% EVA WITH LINEAR RAMP

120 100

2.0

Weight (%)

80

1.5

60 1.0 40

0.5

20

0.0

0 -20

-0.5 150

200

250

300

350

Temperature (℃)

100

400

450

500

[------------] Deriv. Modulated Weight (%/min)

2.5 TGA Modulated

GENERAL THEORY OF MTGA

ARRHENIUS AND GENERAL RATE EQUATIONS

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KINETIC EXPRESSION RATIO

FACTOR JUMP EQUATION AT CONSTANT CONVERSION

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FOURIER TRANSFORMATION YIELDS

MODULATED TGA EQUATION

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FIRST ORDER PRE-EXPONENTIAL FACTOR

FAST FOURIER TRANSFORMATION

• Fast Fourier Transformation yields continuous kinetic parameters

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LINEAR HEATING PROFILE FOR POLYTETRAFLUOROETHYLENE

TGA: MTGA - Activation Energy for Polytetrafluoroethylene 1,000

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600 50 400 30

[

Activation Energy (kJ/mol)

70

] Weight (%)

90

800

200

10

0

-10 400

450

500 Temperature (℃)

105

550

600

EVA(60%Vac)的分解活化能溫度歷程圖

EFFECT OF CONVERSION ON ACTIVATION ENERGY

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QUASI-ISOTHERMAL MTGA OF PTFE

QUASI-ISOTHERMAL MTGA OF PS

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MTGA OF 60% EVA WITH DYNAMIC HEATING RATE

MTGA REPEATABILITY POLY (60% ETHYLENE VINYL ACETATE)

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MTGA KINETICS COMPARISON

MTGA EXPERIMENTAL CONDITIONS • Period : > 200 seconds (temperature range dependent) • Amplitude : 4 - 5 ° C • Cycles Across Transition : > 5

Temperature Program • Isothermal or • Heating Rate : < 2 ° C/min

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DETERMINATION OF FULL WIDTH TEMPERATURE AT HALF HEIGHT

BENEFITS OF MTGA METHOD

• SINGLE EXPERIMENT • INCREASED PRODUCTIVITY • MODELFREE • EASY OF USE • OBTAIN Z WITH ASSUMPTION OF 1st ORDER MODEL • COMPLETE KINETIC INFORMATION • E & Z AS A FUNCTION OF CONVERSION • FOLLOW PROCESS CHANGES

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Evolved Gas Analysis

Why Use Evolved Gas Analysis? • TGA measures weight changes (quantitative) • Difficult to separate, identify, and quantify individual degradation products (off-gases)

• Direct coupling to identification techniques (Mass Spec, FTIR) reduces this problem

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TGA-EGA: Typical Applications • Polymers (composition, hazard evaluation, identification) • Natural Products (contamination in soil, raw material selection {coal, clays}) • Catalysts (product/by-product analysis, conversion efficiency) • Inorganics (reaction elucidation, stoichiometry, pyrotechnics) • Pharmaceuticals (stability, residual solvent, formulation)

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Q50/Q500 EGA Furnace Schematic Balance Purge

Quartz Liner

Sample Thermocouple Sample Pan

Off-Gases

Purge Gas In Low internal Volume ~15ml Furnace Core

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Discovery TGA & TGA Q5000 IR Sample pan

Furnace Vertical Section Silicon carbide absorber

Heated EGA adapter

Quartz tube

Lower heat shields

Thermocouple plate

Discovery TGA Heated FTIR Adapter

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Mass-Spectrometry Benefits

• Additional information for the interpretation of the reactions in the TGA results

• Sensitive method for the analysis of gaseous reaction products

• Exact control of the furnace atmosphere before starting and during the experiment

• Location of air leaks around the furnace

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TGA-Mass Spectroscopy Advantages:  Higher sensitivity and wider dynamic range than FTIR (1ppm vs. 10ppm).  Measures non-IR absorbing gases.

 More rapid response. Disadvantage:  Cannot distinguish between isomers. (e.g. N2 and CO)

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TGA-MS: System Schematic

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TGA - FTIR FTIR (Fourier transformation infrared spectroscopy): Advantages: On-line measurement Hydrocarbons are easy to identify Disadvantages: No detection of inert gases (no dipole moment) Detection of inorganic gases limited

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TGA-FTIR: System Schematic

TA Instruments Universal Analysis software supports the importation of MS (trend analysis) and FTIR data (Gram-Schmidt and Chemigram reconstructions), allowing TGA and EGA data to be displayed on a common axis of temperature and/or time.

MS & FTIR Attached to Interface

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TGA of Calcium Oxalate Sample: Calcium Oxalate Monohydrate Size: 17.6070 mg Method: RT-->1000°C @ 20°C/min

TGA

120

10

8

6

Weight (%)

80

4

60 2

Deriv. Weight (%/min)

100

40 0

20 0

200

400

600

800

Temperature (°C)

-2 1000 Universal V2.7B TA Instruments

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TGA-MS Calcium Oxalate

TGA derivative weight loss

H2O m/e=18 CO m/e=28

0

200

400

CO2 m/e=44

600

800

Temperature (°C)

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TGA-MS Sample: 583-35-E Size: 19.6330 mg

TGA

98

4

3

2 94

Gas switch from N2 to 2% H2 in N2.

1

Deriv. Weight (%/min)

Weight (%)

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92 0

90

250

252

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256

258

Time (min)

260

262

264

-1 266

Universal V2.7B TA Instruments

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TGA-MS

During weight loss, a reaction occurs between H2 in purge and sample in which H2O and HO are produced. 136

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Smoke Generation in Flame Retarded Polymers (PVC)

100 80 60 MS Intensity

TGA Weight (%)

PVC

40

PVC + MoO

3

20 0

100

200 300 400 Temperature (°C)

500

Benzene (78 amu)

0

100

200 300 400 Temperature (°C)

Benzene is a component of smoke. Much reduced in the flame retardent sample. 137

Compositional Analysis by TGA-MS 1

Sample: EVA (25%) Size: 5.7390 mg Heating Rate: 20°C/min

100 17.45% Acetic Acid (1.001mg)

0.1

% VA = 17.45(86.1/60.1) % VA = 25% Hydrocarbon CxHy m/e 56 Acetic Acid m/e 60

50

0.01

25

Ion Current (nA)

Weight (%)

75

0.001

% VA= % Acetic Acid* Molecular Wt (VA) / Molecular Wt (AA)

0 0

100

200

300

400

Temperature (°C)

119

500

600

0.0001 700 Universal V3.8A TA Instruments

138

500

Thank You

Thank you for your attention!

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