Study of the hydrolysis of an industrial radio-oxidized poly(ester urethane)

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Study of the hydrolysis of an industrial radio-oxidized

poly(ester urethane)

E. Fromentin, J. Frey, S. Legand, J. Pielawski, P. Reiller, D. Doizi, C. Aymes-Chodur, S. Esnouf, M. Ferry

To cite this version:

E. Fromentin, J. Frey, S. Legand, J. Pielawski, P. Reiller, et al.. Study of the hydrolysis of an industrial radio-oxidized poly(ester urethane). (IRaP) - The 12th meeting of the “Ionizing radiation and polymers” symposium 2016, Sep 2016, Porquerolles, France. �hal-02442285�

IRaP 2016, 25-30th_September

Porquerolles Island, source: the Internet

E. Fromentin*, J. Frey, S. Legand, J.J. Pielawski,

P. E. Reiller, D. Doizi, C. Aymes-Chodur, S. Esnouf, M. Ferry

INTRODUCTION

Nuclear waste management

Several countries are considering a deep

geological disposal.

Switzerland,

www.nagra.ch

Opanilus clay, 300-900 meters depth

France,

www.cigéo.com

Callovo-Oxfordian clay, 500 meters depth

Finland,

www.posiva.fi

Migmatic gneiss + bentonite clay, 400-450 meters depth

Radio-oxidation, then alkaline hydrolysis Production of water-soluble molecules Increase of the radionuclides solubility?

INTRODUCTION

Polymers in nuclear waste packages

Polyvinyl chloride, cellulose, ion-exchange resins, polyethylene…

What will become polymers inside the geological disposal?

An example of an Intermediate Level Long-Lived waste package

Considered polymer

Poly(ester urethane) (PUR)

Constituent of gloves for glove boxes

Composed of 3 segments synthesized from these precursors:

hard segment extender soft segment

+ 8.9% inorganic fillers

+ 1,8% cross linking agents

+ 0,4% pigments

INTRODUCTION

1,4-butandiol

4,4’-methylene diphenyl diisocyanate _{poly(1,4-butylene adipate)}

H O O O O O H n

25.5%

_w

63.4%

_w

Objectives

Characterizing and quantifying water-soluble molecules created by the alkaline hydrolysis of the non-irradiated and irradiated PUR at different doses

Understanding the degradation mechanisms PUR under radiolysis

Irradiated PUR under hydrolysis

Identifying the products than can complex the radionuclides

Being able to model the complexant release kinetics

Objectives

Characterizing and quantifying water-soluble molecules created by the alkaline hydrolysis of the non-irradiated and irradiated PUR at different doses

Understanding the degradation mechanisms PUR under radiolysis

Irradiated PUR under hydrolysis

Identifying the products than can complex the radionuclides

Being able to model the complexant release kinetics

MATERIALS: A TWO-STEP PREPARATION

1st _{step: PUR is irradiated under air using} g rays by LABRA (60_{Co source), dose}

rate: ~ 0.9 kGy.h-1_{, doses: 500 kGy and 1,000 kGy}

2nd _{step: non-irradiated and irradiated PUR are then hydrolyzed}

3 temperature values: room temperature (≈23°C), 40 and 60°C ∆t is variable and depends on the degradation rate

alkaline water 10 mL polymer 1g inert atmosphere ∆t T

Alkaline water composition: 0.16 mol/L KOH, 0.07 mol/L

NaOH

ANALYSES

Filtration

dried at 50°C in vacuum for 24h and WEIGHTED

MATERIALS: A TWO-STEP PREPARATION

1st _{step: PUR is irradiated under air using} g rays by LABRA (60_{Co source), dose}

rate: ~ 0.9 kGy.h-1_{, doses: 500 kGy and 1,000 kGy}

2nd _{step: non-irradiated and irradiated PUR are then hydrolyzed}

3 temperature values: room temperature (≈23°C), 40 and 60°C ∆t is variable and depends on the degradation rate

alkaline water 10 mL polymer 1g inert atmosphere ∆t T

Alkaline water composition: 0.16 mol/L KOH, 0.07 mol/L

NaOH

ANALYSES

Filtration

dried at 50°C in vacuum for 24h and WEIGHTED

EXPERIMENTAL DATA

Mass loss

3 temperatures, 3 doses Room temperature ≈ 23°C 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0 20 40 60 80 1,000 kGy, room T 500 kGy, room T 0 kGy, room T PUR mass lo ss(%)

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0 20 40 60 80 1,000 kGy, 40°C 500 kGy, 40°C 0 kGy, 40°C 1,000 kGy, room T 500 kGy, room T 0 kGy, room T PUR mass lo ss (%)

hydrolysis time (days)

Mass loss

3 temperatures, 3 doses

Room temperature ≈ 23°C 40°C

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0 20 40 60 80 1,000 kGy, 60°C 500 kGy, 60°C 0 kGy, 60°C 1,000 kGy, 40°C 500 kGy, 40°C 0 kGy, 40°C 1,000 kGy, room T 500 kGy, room T 0 kGy, room T PUR mass lo ss (%)

hydrolysis time (days)

EXPERIMENTAL DATA

Mass loss

3 temperatures, 3 doses Room temperature ≈ 23°C 40°C 60°C

EXPERIMENTAL DATA

Additional data

Error bar: σ_max= 4%

0 20 40 0 20 40 60 80 PUR ma ss loss (%)

hydrolysis time (days)

MATERIALS: A TWO-STEP PREPARATION

1st _{step: PUR is irradiated under air using} g rays by LABRA (60_{Co source), dose}

rate: ~ 0.9 kGy.h-1_{, doses: 500 kGy and 1,000 kGy}

2nd _{step: non-irradiated and irradiated PUR are then hydrolyzed}

3 temperature values: room temperature (≈23°C), 40 and 60°C ∆t is variable and depends on the degradation rate

alkaline water 10 mL polymer 1g inert atmosphere ∆t T

Alkaline water composition: 0.16 mol/L KOH, 0,07 mol/L

NaOH

ANALYSES

Filtration

dried at 50°C in vacuum for 24h and WEIGHTED

EXPERIMENTAL DATA

Additional data

Error bar: σ_max= 4%

Total Organic Carbon = TOC is proportional to mass loss

0 20 40 60 80 100 0 200 400 600 800 1000 g/kg of hyd ro lyzed po lymer time (days) Mass loss 60°C 1.8xTOC 60°C Mass loss 40°C 2xTOC 40°C Mass loss room T 2xTOC room T 1,000 kGy PUR Degradation product C_xH_yO_z 𝑚𝑎𝑠𝑠 𝑙𝑜𝑠𝑠 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑎𝑟𝑏𝑜𝑛 = 𝑥𝑚𝐶 + 𝑦𝑚𝐻 + 𝑧𝑚𝑂 𝑥𝑚𝐶 ≈ 2 → adipate C₆H₈O₄ corresponds O O O O O R R' O H O H O O R _HO O O OH _O R' + + adipic acid

Mass balance of hydrolysis solution of 1,000 kGy PUR at day 31 at room T:

For more details about mass balances: Fromentin et al. (2016) Polymer Degradation and Stability, 128, 172-181

unknown products adipic acid 62% 0 20 40 0 20 40 60 80 PUR ma ss loss (%)

hydrolysis time (days)

MODELLING THE SOLUBLE FRACTION RELEASE

Yoon’s model

Hypotheses:

- Hydrolysis of each chain occurs with equal probability. - Water diffusion into the polymer does not limit hydrolysis.

- Water-soluble products are immediatly leached out of the polymer. - Hydrolysis is a complete reaction.

Involved reactions:

Induced rates:

Yoon et al. (1997) Polymer, 38, 3573-3579

𝑃₂ + 𝑊 → 2𝑃₁ 𝑃₃ + 𝑊 → 𝑃₁ + 𝑃₂ … 𝑃_𝑛 + 𝑊 → 𝑃_𝑟 + 𝑃_𝑛−𝑟 (𝑟 = 1, … , 𝑛 − 1) 𝑑[𝑃₁] 𝑑𝑡 = 2𝑘𝐻[𝑊] 𝑖=2 ∞ [𝑃_𝑖] 𝑑[𝑃₂] 𝑑𝑡 = −𝑘𝐻 𝑊 𝑃2 + 2𝑘𝐻[𝑊] 𝑖=3 ∞ [𝑃_𝑖] … 𝑑[𝑃_𝑛] 𝑑𝑡 = −(𝑛 − 1)𝑘𝐻[𝑊][𝑃𝑛] + 2𝑘𝐻[𝑊] 𝑖=𝑛+1 ∞ [𝑃_𝑖]

MODELLING THE SOLUBLE FRACTION RELEASE

Yoon’s model

After mathematical geniuses work:

𝑃

₁

𝜆

₁

= 1 − 2 1 −

1

𝜇

_𝑛0

𝑒

−𝜏

+ 1 −

2

𝜇

_𝑛0

𝑒

−2𝜏

𝑃

₂

𝜆

₁

= 1 −

1

𝜇

_𝑛0

𝑒

−𝜏

− 2 1 −

2

𝜇

_𝑛0

𝑒

−2𝜏

+ 1 −

3

𝜇

_𝑛0

𝑒

−3𝜏

…

𝑃

_𝑘

𝜆

₁

= 1 −

(𝑘 − 1)

𝜇

_𝑛0

𝑒

−(𝑘−1)𝜏

− 2 1 −

𝑘

𝜇

_𝑛0

𝑒

−𝑘𝜏

+ 1 −

(𝑘 + 1)

𝜇

_𝑛0

𝑒

−(𝑘+1)𝜏

with

𝜆

_𝑘

=

_𝑛=1∞

𝑛

𝑘

[𝑃

_𝑛

], 𝜏 =

₀𝑡

𝑘

_𝐻

𝑊 𝑑𝑡, 𝜇

_𝑛0

=

𝑖=1 ∞ _{𝑖 𝑃} 𝑖 𝑖=1 ∞ _𝑃 𝑖

=

𝜆₁ 𝜆₀

Considering that

m

_n0

is very high and that only P

₁

is water-soluble:

𝑷

_𝟏

≈ 𝝀

_𝟏

(𝟏 − 𝟐𝒆

−𝒌

𝑯

𝒕

+ 𝒆

−𝟐𝒌

𝑯

𝒕

)

MODELLING THE SOLUBLE FRACTION RELEASE

Yoon et al. (1997) Polymer, 38, 3573-3579

Yoon’s model applied to our experimental data

40 and 60°C → the model matches

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0.0 0.2 0.4 0.6 0.8 1.0 1,000 kGy, 60°C 500 kGy, 60°C 0 kGy, 60°C 1,000 kGy, 40°C 500 kGy, 40°C 0 kGy, 40°C ma ss loss (ma ss fr actio n) time (days) Dose (kGy) Activation energy between 40 et 60°C (kJ.mol-1₎ 0 64 500 59 1,000 49

𝑷

_𝟏

≈ 𝝀

_𝟏

(𝟏 − 𝟐𝒆

−𝒌𝑯𝒕

+ 𝒆

−𝟐𝒌𝑯𝒕

)

𝑘

_𝐻

= 𝐴 × 𝑒

−𝑅𝑇𝐸𝑎

MODELLING THE SOLUBLE FRACTION RELEASE

Yoon’s model applied to our experimental data

Room temperature

→ the model does not match…

→

Temperature affects the way

water-soluble products are released.

→ It is observed at

all doses

.

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 0.0 0.2 0.4 0.6 0.8 1.0 1,000 kGy, room T 500 kGy, room T 0 kGy, room T ma ss loss (ma ss fr actio n) time (days)

MODELLING THE SOLUBLE FRACTION RELEASE

Time-temperature superposition approach

Data at room temperature cannot be overlaid by data at 40 and 60°C.

→ it confirms that

the release

of water-soluble products

is different

at room temperature.

0 100 200 300 400 500 600 700 800 0.0 0.2 0.4 0.6 0.8 1.0 Ma ss loss (ma ss fr actio n) a_T x time (days) T,°C a_T 60 9 40 2 23 1 unirradiated PUR 0 100 200 300 400 500 600 700 0.0 0.2 0.4 0.6 0.8 1.0

1,000 kGy irradiated PUR

Ma ss loss (ma ss fr actio n) a_T x time (days) T,°C aT 60 7 40 2 23 1

The methodology is explained in Bernstein and Gillen (2010) Polymer Degradation and Stability, 95, 1471-1479.

0 100 200 300 0.0 0.2 0.4 0.6 0.8 1.0

500 kGy irradiated PUR

T,°C a_T 60 7 40 1.8 23 1 Ma ss loss (ma ss fr actio n) a_T x time (days)

HYPOTHESES FOR THIS DISCREPANCY

Discrepancy: the degradation at room temperature is faster than expected. Something

speeds up the reaction or the process is different at this temperature value.

Hypotheses for this discrepancy:

Some of the Yoon’s model hypotheses are not valid:

-Reaction on surface (versus bulk reaction).

-Water concentration inside the PUR depends on temperature.

There are two competing processes (hydrolysis is the predominant process at " high " temperature):

-Plasticizing by water : PUR more porous.

-Remained synthesis reactants and additives leaching at the first steps of the degradation.

-Autocatalysis by degradation products i.e. adipic acid.* 𝐷_23°𝐶 < 𝐷_40°𝐶 < 𝐷_60°𝐶

* Salazar et al. (2003) Journal of Polymer Science: Part A: Polymer Chemistry, 41, 1136-1151.

O H

O O

CONCLUSION

Unirradiated, 500 and 1,000 kGy irradiated PUR hydrolyzed at room temperature (≈23°C), 40 and 60°C:

Mass loss and Total Organic Carbon (TOC) show the same evolution.

The ratio between mass loss and TOC confirms that adipic acid is the main product.

Whatever the dose, the release of soluble fraction at 40 and 60°C follows Yoon’s

model which means that the ester groups mainly hydrolyzed with equal probability and diffusion does not limit hydrolysis.

The release of soluble fraction at 23°C does not follow Yoon’s model. Several

hypotheses to explain this discrepancy: autocatalysis? Plasticizing? Change in water concentration?

Perspectives: improving the Yoon’s model to cover the largest range of temperature.

=> Better understanding of the PUR hydrolysis kinetics. Next step: identifying the degradation products that can complex the radionuclides.

Commissariat à l’énergie atomique et aux énergies alternatives Centre de Saclay| 91191 Gif-sur-Yvette Cedex

T. +33 1 69 08 27 62 |elodie.fromentin@cea.fr

Etablissement public à caractère industriel et commercial |R.C.S Paris B 775 685 019

Thank you for your

attention.

ACKNOWLEDGMENT

This work has been financed by CEA, AREVA NC, EDF. The authors are grateful to Florence Cochin for her scientific collaboration.

Thanks to V. Dauvois, Y. Ngono-Ravache E. Zekri, M. Tabarant, J.L. Roujou, D. Durand for their

ideas and technical help.

Any questions?

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