‘sauveur‘1 st june 2006fabian käser bua lifetime prediction of solid materials using...

Fabian Käser BUA‘SAUVEUR‘ 1st June 2006

Lifetime prediction of solid materials using chemiluminescence to characterise oxidative reactions and model-free

simulation based on experimental data

Fabian Käser

Berne University of the Arts - BUA


Oxidation

- the major cause of degradation of most organic materials!

- even occurs under ambient environmental conditions

=> Aim: prediction of lifetime expectancy under given, realistic conditions


Lifetime Expectancy of organic Materials @ different isothermal conditions

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110

Time [years]

Rea

ctio

n P

rogr

ess

alph

a of

Oxi

datio

n

T = 16°C

T = 17°C

T = 18°C

T = 19°C

T = 20°C

T = 21°C

T = 22°C

T = 23°C

T = 24°C

T = 25°C

Aim: Lifetime prediction


Abstract

New approach of lifetime prediction:

- experimental data acquisition using Chemiluminescence method

- full kinetic analysis - lifetime prediction

- conclusion


Experimental data acquisitionTesting stability by high temperature

methods (conventional thermal analysis)

Disadvantage: - very high temperature profiles- high possibility of phase transitions=> doubtful correlation to long-term

stability (different kinetic behaviour)

Fabian Käser BUA 1st June 2006‘SAUVEUR‘

Chemiluminescence CL method- light emission resulting from

chemical energy- relaxation of excited electrons - especially during oxidation:

3R=O* - mechanism not yet clarified

entirely


Advances of CL method very high sensitivity moderate experimental conditions: Texp close to

RT CL-signal is not overlapped by other thermal

effects excellent baseline stability differentiation of ROOH-decay and mechanism of

oxidation acquisition of inhomogeneous character of

oxidation reactions implementation of rH% as oxidative factor below

95°C acquisition of oxidationkinetics of most organic

materials => numerous applications


CL instrumentation

oven: precise controll of T gas exchange facility

optical path: as short as possible

shutter systemdetector: PMT photon counting mode

thermoelectrically cooled%QE @ spectral range of CL


Fields of applicationOxidation of cis -1,4-Polyisoprene unstabilised

@ different isothermal conditions

0

1'000

2'000

3'000

4'000

5'000

6'000

7'000

8'000

9'000

0 10 20 30 40 50 60 70 80 90 100

Time [h]

CL-

Sig

nal [

coun

ts s

-1 m

g-1

]

iso80°C

iso90°C

iso100°C

iso110°C

iso120°C

120°C

110°C

100°C

90°C80°C

cis -1,4-Polyiroprene unstab vs. stab Irganox 565 @ 25-120°C

(heating rate = 0.0132 K min-1, O2)CL-Signal (Darkcount substracted)

0

2'000

4'000

6'000

8'000

10'000

12'000

14'000

110 111 112 113 114 115 116 117 118 119

Temperature [°C]

CL

-Sig

na

l [co

un

ts s

-1]

unstabilised

stabilised


Advanced kinetic analysis

1. baseline optimisation of experimental data

2. isoconversional kinetic analysis:

- ln (dα / dt) vs. T-1 (Arrhenius based)

- EA = slope of ln (dα / dt) vs. T-1 (α) is constant for every state of

reaction αi = isoconversional analysis


Prediction of reaction progressDescription of reaction rate

dependent of reaction progress alpha at any given temperature profile

- isothermal- non-isothermal- modulated- customised climate conditions


10

1.7

years

@ 1

6°C

76

.4 y

ears

@

17

°C

57

.5 y

ears

@ 1

8°C

43

.4 y

ears

@ 1

9°C

32

.8 y

ears

@ 2

0°C

18

.9 y

ears

@ 2

2°C

24

.9 y

ears

@ 2

1°C

8.4

years

@ 2

5°C

Lifetime prediction of β-carotene@ different isothermal conditions

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110

Time (years)

Rea

ctio

n pr

ogre

ss a

lpha

of

oxid

atio

n

Prediction: isothermal conditions


Lifetime prediction of β-carotene@ 20°C modulated (amplitudes = 0, 1, 2, 4 K per 24 hours)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

20 21 22 23 24 25 26 27 28 29 30 31 32 33

Time (years)

Rea

ctio

n pr

ogre

ss a

lpha

of

oxid

atio

n

0 K

per

24

hour

s

1 K

per

24

hour

s (

- 0.

6 ye

ars

)

2 K

per

24

hour

s (

- 2.

4 ye

ars

)

4 K

per

24

hour

s (

- 7.

4 ye

ars

)

Prediction: modulated conditions


Conclusion

Useful approach to predict lifetime and to assess treatment effects in context of conservation-restoration.

Procedure consists of:- data acquisition using CL- full kinetic analysis- prediction of oxidation reaction

progress


„… Chemiluminescence which has developed as the most sensitive

method for detection of oxidation …“ Popíšil, J. et al., Polymer Degradation and Stability., 82 (2003),

155.

‘sauveur‘1 st june 2006fabian käser bua lifetime prediction of solid materials using...

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