Characterization of the ageing of HTPB bonded HMX based insensitive high explosive charge

by Heat Flow Microcalorimetry (HFC), Chemiluminescence, Gap test and Dynamic Mechanical Analysis (DMA)

Dr. Manfred A. BohnFraunhofer-Institut fuer Chemische Technologie, ICT

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn / Titel 1

Presented on

NDIA 2009 Insensitive Munitions and Energetic Materials Technology Symposium

May 11 to 14, 2009, Ventana Canyon

Tucson, Arizona, USA

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 2

Content

Composition of high explosive charge (HEC) HTPB-HMX

Objectives

Basic stability data

Time-temperature (ageing) program for HEC

Sensitiveness by gap-test

Glass transition temperature determined by torsion DMA

Heat generation rate between 120°C and 150°C

Chemiluminescence in air between 100°C and 140°C

Summary and conclusions

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 3

What is HEC of type KS 32

KS32 is a polymer bonded high explosive charge (HEC), manufactured by EADS-TDW, Schrobenhausen, Bayern, Germany (now part of MBDA)

Typical composition

Energetic material HMX 85.0 mass-%

Binder HTPB cured with IPDI 13.7 mass-%

Plasticizer DOA 1.0 mass-%

Antioxidant protected phenol type 0.1 mass-%

Curing catalyst DBTL 0.001 mass-%

Additionals 0.199 mass-%

HTPB hydroxy terminated polybutadiene

IPDI ísophorone diisocyanate

DOA di-(iso-octyl) adipate (DiOA)

DBTL di-(n-butyl) tin dilaureate (DnBTDL) (CH3CH2CH2CH2)2 Sn [OCO(CH2)10CH3]2

H3C (CH2)3 CH CH2 O C (CH2)4 C O CH2 CH (CH2)3 CH3

C2H5O O C2H5

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 4

Objectives

● To age the material accelerated up to the equivalent loads with regard to in-service loads

● To age at the two extremesunder air and under oxygen-free atmosphere (here under argon)

● To get information about the Arrhenius parameters valid at accelerated andin-service temperatures.

The minus centigrade region was not included because the chemical and diffusionprocesses are very slow there and are expected of minor to no influence.

● To look at some properties if they can be used as ageing monitor

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Basic stability data of HEC of type KS32

Autoignition temperature determined in Wood metal bath

5°C/min heat rate 244°C

20°C/min heat rate 243°C

Holland Mass Loss test at 110°C

0-8 h 0.02 %

0-72 h 0.01 %

8-72 h -0.01 % ( limit value: 2 % )

Vacuum Stability Test, 100°C, 40h

2.5g 0.03 ml/g ( limit value: 1.2 ml/g )

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 6

Time-temperature or ageing program for KS 32

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Accelerated ageing at thermal equivalent loads

The best way to perform accelerated ageing on a material for prediction purpose is to do it in such a way that the thermal load at in-service will be covered.

This is named equivalent load ageing.

The equivalent load must be calculated from given or demanded in-service loads for the test conditions at elevated temperatures.The in-service loads can be assumes as isothermal over a set usetime as 20 years or stored at time-temperature profile as experienced during missions

For this one needs a temperature parameterization of properties of the material

What to do if you do not known them at the beginning?

Recommended procedureAssume a ageing at low activation energies in a two step mechanism.

Such a two-step mechanistic ageing can be simulated quite reasonably with thegeneralized van’T Hoff rule

Equivalent load relation between ‘test time - test temperature’ and ‘in-service time - in-service temperature

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn / 8

d25.365/F]d[t]a[t FET T/)TT(TE

∆−⋅=tE time in years at temperature TE

tT test time in days at test temperature TT

F reaction rate change factor per 10°C temperature changerate decreases with temp. decrease / rate increases with temp. Increase

TT test temperature in °C

TE in-service (environmental) temperature in °C

∆TF temperature interval for actual value of F, here ∆TF is always 10°C

For chemically caused ageing processes the following formula has proven by experience as suitable (Ea about 80 to 120 kJ/mol, temperature range 30°C to 90°C)

Generalized formulated van’T Hoff rule

For details and worked out examples with two mechanisms seeManfred A. BohnPrediction of equivalent time-temperature loads for accelerated ageing to simulate preset in-storage ageing and time-temperature profile loads.Paper 78, 40th Conference of ICT, 2009.

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn / 9

Ageing scheme for KS32

33282419149.54.7in days90

2.72.31.91.51.2in mo

83715947362412in days80

6.85.84.93.92.91.9in mo

207177148118895930in days70

17.014.612.29.77.34.92.4in mo

51844437029622214874in days60

42.636.530.424.318.212.26.1in mo

12941109924739554370185in days50

106.491.276.060.845.630.415.2in mo

32342772231018481386924462in days40

ageing temp. [°C]

3530252015105years at 25°C ->

one month: 365/12 = 30.4 days; ageing equivalent of 20 years at 25°C is 24.3 months at 50°C

The factor of 2.5 is assumed for KS32, this gives a conservative estimate of storage times to reach preset ageing times at 25°C; means longer storage times than with factor 3.

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 10

Test on sensitiveness by gap-test

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 11

Scheme of ICT-Gap-test, 21mm

Actual length of KS32 samples were 42 mm

Donor with one booster HX charge:

diam. 21 mm, length 21 mmRDX / wax / graphite (94.5 % / 4.5 % / 1 %)pressing force 50 kN

detonator in central bore: T-CU-30-T11U

Electric Detonator

Plexiglas

Acceptor Charge

Witness Plate(Aluminium)

40m

m

21mm

Donor Charge

21m

mX

mm

Plexiglas Tube

10 mm thick

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 12

Assembly of charges in 21 mm ICT-gap-test

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Ageing of gap-test samples

Left:

Ageing in air.

Full air access by removing of the not sealed stopper two to three times per week.

Right:

Ageing in argon, applied with a glove box.

Full sealing (grease in ground surfaces) and securing the stopper.

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 14

Results of 21mm gap-test in detonation pressure

21mm gap-test at ICTaged at 80°C over 12d, 24d, 36d in air

at 80°C over 24d in argon

30

32

34

36

38

40

42

44

46

48

50

0 5 10 15 20 25 30 35 40

time [d]

deton. pressure [kbar]

go, airno go, airgo, argonno go, argon

no go

go region

no go, air

go, air

no go, argon

go, argon

38 kbar

35 kbar

44.4 kbar

41.2 kbar

14% reduction in ‘go‘

15% reduction in ‘no go‘

36 days at 80°C correspond to 15 years at 25°C

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Glass transition temperature determined by torsion DMA

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 16

DMA instrument ARESTM – sample mounting, measurement in torsion mode

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 17

Samples for DMA measurements – ageing procedure – visible influence on samples

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 18

Shear modulus and tan(δ) – different definitions of glass transition temperature TG

aged at 90°C, 30d, Argon, Pr110 Hz

1.E+05

5.E+08

1.E+09

2.E+09

2.E+09

3.E+09

3.E+09

-90 -80 -70 -60 -50 -40 -30

T [°C]

G', G'' [Pa]dG'/dT [Pa/°C]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8tan(δ) [-]

30d G'30d G''Tg in G'', -64.97°C30d dG'Tg in dG', -66.50°C30d tdTg in td, -55.99°C

TG in tan(δ) = -55.99°C

TG in G'' = -64.97°C

TG in dG'/dT = -66.50°C

G' tan(δ)

G''

dG'/dT

Temperature sweep with measurement at 3 frequencies: 0.1 Hz, 1 Hz and 10 Hz

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Shear modulus and loss factor tan(δ) – aged sample, 90°C over 30 days

aged at 90°C, 30d, Argon, Pr110 Hz

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50

T [°C]

G', G'' [Pa]dG'/dT [Pa/°C]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8tan(δ) [-]

30d G'30d G''30d dG'30d td

G'

G''

dG'/dT

tan(δ)

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 20

Shear modulus and loss factor tan(δ) – aged at 90°C under argon, 10d, 20d, 30d

90°C, Argon10 Hz

aged over 10d, 20d, 30d

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50

T [°C]

G', G'' [Pa]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

tan(δ) [-]30d G'20d G'10d G'NP1 G'NP3 G'30d G''20d G''10d G''NP1 G''NP3 G''30d td20d td10d tdNP1 tdNP3 td

tan(δ)

G'

G''

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 21

DMA results for glass transition temperatures - 90°C in argon, 10d, 20d, 30d

argon, 90°C, 10Hz

-70

-68

-66

-64

-62

-60

-58

-56

-54

NP1 NP2 NP3 NP mean 90°C, 10d 90°C, 20d 90°C, 30d

sample

TG [°C]

Tg in td [°C]Tg in G'' [°C]Tg in dG'/dt [°C]M-Tg-td-NPM-Tg-tdM-Tg-G''-NPM-Tg-G''M-Tg-dG'-NPM-Tg-dG'

TG from maximum in tan(δ)

TG from maximum in G''

TG from maximum in dG'/dT

baseline samples aged samples

∆TG = 0.95°C

∆TG = 0.88°C

∆TG = 0.85°C

HFMC- and CL-measurements

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 22

HFMC Heat Flow Microcalorimetry

CL Chemiluminescence

O2-Attack sites on HTPB binder chain – resulting effect can be cross-linking

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn / 23

CH

CH

HCH

CH

H

.O - O.

H O - O.-

+.

HCC

HCH

CH

H

CH

CH

HCH

CH

CH

CH

.

CH

CH

HC

CH

CH

CH

+

+

CH

CH

CH

.

- H O - O.

.O - O.

The allylic hydrogen atoms are very susceptible for oxygen attack because the resulting radical is resonance stabilized

Recombination of two radicals on two neighbouring chains -cross-linking occurs

Heat Flow Microcalorimetry (HFMC)

Used instrument

TAM II (high temp. version), TA Instruments (formerly Thermometric AB), equipped with 4 microcalorimeter inserts (channels)high long term baseline stability, better than 1 µW over 20 days

• Measured is heat generation rate (HGR) dQ/dtHGR is proportional to chemical reaction rate

• isothermal from 120°C to 150°C• atmosphere: argon and air• HEC sampled in Duran-vials inserted in Hastelloy-C22 ampoules• sample masses around 1.0 to 1.25 g

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 24

Measurement results (HFMC)

HGR and HG of HEC (HTPB bonded HMX)

in air and argon at 120°C

-10

0

10

20

30

40

50

60

70

80

90

100

110

120

0 2 4 6 8 10 12 14 16 18 20

time [d]

dQ/dt [µW/g]

-1

0

1

2

3

4

5

6

7

8

9

10

11

12Q [J/g]

dQ-HEC-air-1dQ-HEC-air-2dQ-HEC-Ar-1dQ-HEC-Ar-2zeroQ -HEC-air-1Q -HEC-air-2Q -HEC-Ar-1Q -HEC-Ar-2

argonair

air

argon

sharp bend

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 25

Measurement results (HFMC)

HGR and HG of HEC (HTPB bonded HMX)

130°C, in aircomparison with HMX alone

-10

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18

time [d]

dQ/dt [µW/g]

-5

0

5

10

15

20

25

30Q [J/g]

dQ-HEC-air-1dQ-HEC-air-2dQ-HMX-airzeroQ -HEC-air-1Q -HEC-air-2Q -HMX-air

Q, HMXdQ, HMX

dQ, HEC

Q, HECsharp bend

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 26

Measurement results (HFMC)

HGR and HG of HEC (HTPB bonded HMX)

145°C, in air

0

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

time [d]

dQ/dt [µW/g]

0

20

40

60

80

100

120Q [J/g]

dQ-HEC-air-1dQ-HEC-air-2zeroQ -HEC-air-1Q -HEC-air-2

sharp bend

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 27

Data evaluation (HFMC) – times to sharp bend in HGR

Heat generation rate of HEC (HTPB bonded HMX)

120°C in air

0

4

8

12

16

20

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8

time [d]

dQ/dt [µW/g]

dQ-HEC-air-1dQ-HEC-air-2

zero

3.435 d3.205 d

dQ, HEC-2

dQ, HEC-1

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 28

Results of sharp bend evaluation (HFMC) from HGR (dQ/dt) curves

T [°C] ln(1/ tkdQ [1/d]) tkdQ [d]

100 - -

110 - -

120 -1.164712 3.205

120 -1.234017 3.435 130 -0.285179 1.33 130 -0.381855 1.465

135 0.088831 0.915

135 0.032523 0.968

140 0.605136 0.546

140 0.549913 0.577

145 1.114742 0.328

145 1.072945 0.342

150 1.491655 0.225

150 1.366492 0.255

EakdQ [kJ/mol] 123.7 ± 3

lg(ZkdQ [1/d]) 15.896 ± 037

R2 0.9946

Arrhenius parameterization of reciprocal times to sharp bends in HGR curves

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 29

evaluation of time tkdQ to reach the sharp bend in HGR curveHGR of HEC measured in air

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

0.00232 0.00236 0.0024 0.00244 0.00248 0.00252 0.00256 0.0026

1/T [1/K]

ln(1/ tkdQ [1/d])

EakdQ = 123.7 ± 3 kJ/mollg(ZkdQ [1/d]) = 15.896 ± 0.37 R2 = 0.9946

120°C

150°C

140°C

130°C

145°C

135°C

Chemiluminescence - instrument used

Detector

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 30

instrument from ACL Instruments Inc., SwitzerlandMeasured is light impulses per time per sample massSignal is proportional to the chemical reaction rate

• isothermal conditions from 100°C to 140°C• atmosphere: air, 30 ml/min• sample masses around 30 mg• by reaction enthalpy excited oxygen

Measurement results on HEC (CL)

ChemiluminescenceCL-rate of HEC (HMX-HTPB)in synthetic air, flow 30 ml/min

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0.1 1 10 100

time [d]

CL [cts/s/mg]

CL-100°CCL-110°CCL-120°CCL-130°CCL-140°C

100°C

110°C

130°C

120°C

140°C

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 31

Data evaluation (CL) – times to sharp bend in CL rate

Chemiluminescence of HEC (HTPB bonded HMX)120°C, in synthetic air

0

100

200

300

400

500

600

700

800

900

1000

2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4

time [d]

CL [cts/s/mg]

CL [cts/s/mg]

3.67 d

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 32

Results (CL) - reciprocal times to sharp bend

evaluation of time tkCL to reach the sharp bend in CL-rate curveCL-rate of HEC measured in air

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0.00245 0.0025 0.00255 0.0026 0.00265 0.0027 0.00275

1/T [1/K]

ln(1/ tkCL [1/d])

EakCL = 130.0 ± 2 kJ/mollg(ZkCL [1/d]) = 16.715 ± 0.22 R2 = 0.9997

130°C

120°C

110°C

100°C This result agrees with the corresponding evaluation of HGR data:EakdQ = 123.7 ± 3 kJ/mollg(ZkdQ [1/d]) = 15.896 ± 0.37R2 = 0.9946

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 33

CL-rate curves T [°C] ln(1/tkCL [1/d]) tkCL [d] 100 0.033557 29.8 110 0.101112 9.89 120 0.272479 3.67 130 0.769823 1.299

140 (1.452434) not used 0.234

EakCL [kJ/mol] 130.0 ± 2 lg(ZkCL [1/d]) 16.715 ± 0.22

R2 0.9997

Arrhenius parameterization of reciprocal times to sharp bends in CL curves

Kinetic modelling of HFMC-data and CL-data

1 Start: radical formation at binder material

•••• +→=+ HOO Y OO H-Y formation of hydroperoxides by oxygen attack 2a Chain propagation: forms further radical sites at binder

•••• →=+ YOO OO Y HOOH Y HOO H-Y +→+ •• formation of species, which can attack the starting YOOH Y OOY H-Y +→+ •• material and re-formation of attacking species

2b Chain branching: increasingly autocatalytically effective

OH OH OOHH •• +→ OHH YO YOO OOHY 2 ++→ ••

OH YO OOHY •• +→ 3 Radical neutralization by antioxidant Stabilization

•• +−→−+ A HYHA Y •• +→−+ A YOHHA YO Radical neutralizing (trapping) by forming a more

•• +−→−+ A HHOHA HO stable radical A•

AYA Y −→+ •• YOAA YO →+ •• Consumption of antioxidant A-H

The three main steps are approximated by three reactions, each summarizing the individual reactions in each step

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 34

Kinetic model: autocat. reaction + ‘side reaction’ (= stabilizing reaction)

AOby reaction gstabilizin )H(- B-O B AO

decomp. autocat. / branchingchain )H(- 2

formation radicalprimary )H(- Ox

SR,

R,2

R,1

0

2

1

∆⎯→⎯+

∆++⎯→⎯+

∆++⎯→⎯+

A

SCBBA

SCBA

k

k

k

Model for HFCM-data: ‘Q: main: first order + autocatalytic; minor: exponential‘( )

( )( ) ⎪⎪⎭⎪⎪⎬

⎫

⎪⎪⎩

⎪⎪⎨

⎧

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

⋅+⋅+

+−⋅−+

⋅−−⋅

⋅+=

t)T(k)T(kexp)T(k)T(k

)T(k)T(k1)a1(...

... )tkexp(1a

)te(QOF)T,t(Q

2Q1Q1Q2Q

2Q1Q

Qo

Q

( )

( )( ) ⎪⎪⎭⎪⎪⎬

⎫

⎪⎪⎩

⎪⎪⎨

⎧

⎟⎟⎠

⎞⎜⎜⎝

⎛

⋅+⋅+

+−⋅−+

⋅−−⋅

⋅+=

t)T(k)T(kexp)T(k)T(k

)T(k)T(k1)a1(...

... )tkexp(1a

)te(IcOF)T,t(Ic

2Ic1Ic1Ic2Ic

2Ic1Ic

Ico

Ic

Model for CL-data: ‘Ic: main: first order + autocatalytic; minor: exponential’

Approximation by three reactions;

B stands for all autocatalytically effective species

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 35

Kinetic modelling of HFMC-data

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 36

Kinetic modelling of(HFMC) - results

kQ1 [1/d] kQ2 [1/d] kQo [1/d]

EaQx [kJ/mol] 160.6 ± 5.6

133.3 ± 2.4

128.4 ± 2.7

lg(ZQx [1/d]) 16.629 ± 0.71

16.666 ± 0.31

16.943 ±0.34

R2 [-] 0.9903 0.9974 0.9964

SD2 [ln(1/d)2] 0.00782 0.00145 0.00184

primary radical formation

Chain branching / autocatalyticaldecomposition

AO -stabilizing

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2008 Bohn 37

Results of kinetic modelling – HFCM data

heat generation of HEC (HMX-HTPB)modelling with model 'Q: main: first order + autocat.; minor: exponential'

-12

-10

-8

-6

-4

-2

0

2

4

6

0.00234 0.00236 0.00238 0.0024 0.00242 0.00244 0.00246 0.00248 0.0025

1/T [1/K]

ln(kQx [1/d])

kQo (minor), AO consumption

kQ2 (autocat.)

kQ1 ( intrinsic), start of oxidationEaQ1 = 160.6 kJ/mol, R2 = 0.9903

EaQ2 = 133.3 kJ/mol, R2 = 0.9974

EaQo = 128.4 kJ/mol, R2 = 0.9964

150°C145°C 140°C

135°C130°C

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 38

Kinetic modelling of CL-data

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 39

Results of kinetic modelling – integrated CL data

kIc1 [1/d] k Ic2 [1/d] k Ic0 [1/d]

EaIcx [kJ/mol 206.2 ± 21 131.9 ± 3.5 97.8 ± 9.2

lg(ZIcx [1/d]) 20.824 ± 2.80 18.137 ± 0.47 12.337 ± 1.22

R2 [-] 0.9899 0.9979 0.9743

SD2 [ln(1/d)2] 0.128 0.0753 0.0511

primary radical formation

Chain branching / autocatalyticaldecomposition

AO -consumption

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2008 Bohn 40

Discussion of kinetic modelling – CL data

chemiluminescence of HEC (HMX-HTPB)description of integrated CL-intensity Ic

by model 'Ic: main: first order + autocat.; minor: exponential'

-22

-18

-14

-10

-6

-2

2

6

10

0.00235 0.0024 0.00245 0.0025 0.00255 0.0026 0.00265 0.0027 0.00275

1/T [1/K]

ln(kIc [1/d])

kIc1 (intrinsic), start of oxidation

kIco (minor), AO consumption

kIc2 (autocat.)

100°C110°C120°C130°C140°C

EaIco = 97.8 kJ/mol, R2 = 0.9743

EaIc2 = 131.8 kJ/mol, R2 = 0.9979

EaIc1 = 206.2 kJ/mol, R2 = 0.9899

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 41

At 140°C some non-linear effects occur, means contributions to signal, which are not present at lower temperatures.

Results (CL) – slopes of Ic during ‘induction period’

T [°C] kIc [cts/mg/d] R2 100 1.4996E+06 0.99991 110 4.1697E+06 0.99928 120 6.9538E+06 0.99941 130 1.8886E+07 0.99913 140 3.2345E+07 0.99921

EaIc [kJ/mol] 98.5 ± 5.6

lg(ZIc [cts/mg/d] 19.949 ± 0.75 R2 0.9903

reaction rate constants kIc describing the part of stabilizer action and its consumption

kIc is obtained from the slopes of the integrated CL-intensity curves before the main oxidation peak (autocatalysis)

ChemiluminescenceHEC (HMX-HTPB) in synthetic air

integrated CL-rateshown up to 200 million counts per mg

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

2.5E+08

0 5 10 15 20 25 30 35 40

time [d]

Ic [cts/mg]

Ic-100°C

Ic-110°C

Ic-120°C

Ic-130°C

100°C

110°C120°C130°C

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 42

Results (CL) – slopes of Ic in ‘induction period’

reaction rate constants kIc describing the part of stabilizer action and its consumption

Arrhenius plot of rate constants kIc

obtained from slope of Ic curves before main oxidation peak

13.5

14

14.5

15

15.5

16

16.5

17

17.5

18

0.00235 0.0024 0.00245 0.0025 0.00255 0.0026 0.00265 0.0027 0.00275

1/T [1/K]

ln(kIc [cts/mg/d])

100°C

110°C

120°C

130°C

140°C

EaIc = 98.2 ± 5.6 kJ/mollg(ZIc [cts/mg/d]) = 19.949 ± 0.75R2 = 0.9903

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn 43

Oxygen uptake of HTPB-IPDI binder

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn / 44

120 to 130 kJ/mol

70 to 80 kJ/mol

Switch temperature: 80°C

Occurs temperature dependent at different mechanisms

Ageing of HTPB bonded HEC using a two-step mechanism

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2009 Bohn / 45

two stage mechanismageing of HTPB-bonded HEC

0.01

0.1

1

10

100

1000

10000

100000

10 20 30 40 50 60 70 80 90 100 110 120 130

T [°C]

time [d] Ea2 = 85Ea1 & Ea2Ea1 = 130F = 2.8composed

TS = 80°C

only Ea1

TE = 25°C tE = 25 years

Ea2=85 kJ/mol Ea1=130 kJ/mol

only Ea2

F = 2.8 extrapolation

Ea1 & Ea2 curve, shifted to cross point at (TS, tS)tS = 44 d

composed curve

(TS, tS)

For details and worked out examples with two mechanisms see: Manfred A. Bohn, Paper 78, 40th Conference of ICT, 2009

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2008 Bohn 46

Summary and conclusions

Basic stability

The stability test data show that HEC of type KS32 is a very stable material.

Ageing program

The ageing times calculated with F = 2.5 in the factor extrapolation method seem appropriate, because the values of relevant ageing processes (AO consumption, time to sharp bend) are in the range 70 to 130 kJ/mol. F=2.5 is therefore a conservative extrapolation.

Gap-Test

A decrease of go detonation pressure was found with ageing: After 36 days at 80°C (corresponding to 15 years at 25°C) a 14% decrease resulted. This seems independent of surrounding atmosphere.

DMA (in torsion)

No essential shifts in glass transition temperature could be detected. Very slightly shifts between 0.5 and 1.7°C to positive values have been caused by ageing.No significant difference between ageing in air and in argon.

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2008 Bohn 47

Conclusions

HFMC and Chemiluminescence (CL)

Heat generation rate and Chemiluminescence (CL) measurements under oxidizing atmosphere revealed a kind of induction period – stabilizer (antioxidant) is active

In the curves well-defined bends occurred

With CL it could be shown that the end of induction period coincides with the well-defined bends in HFMC

After AO consumption autocatalytic oxidation / decomposition starts

Both methods give similar Arrhenius parameters of the ‘reciprocal times to the bends’ of about 130 kJ/mol

AO consumption rate is measured directly with CL, activation energy of 98 kJ/mol was found in kinetic modelling and in direct evaluation of integrated CL rate

AO consumption rate and time to end of AO activity can be used as ageing monitor.

The oxygen uptake rate has shown to follow a two-step mechanism with switching (turn-over) temperature Ts at about 80°C

For extrapolation below Ts a second process with much lower activation energy must be taken into account, about 65 to 85 kJ/mol.

Above Ts: oxygen uptake proceeds with higher activation energy: 120 to 130 kJ/mol

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯2008 Bohn 48

Thank you for your attention

Questions?