Thermoplastic silicone elastomers: an endless story

16 March2021, remotely © F. Ganachaud 1

Thermoplastic silicone elastomers:

an endless story

F. GANACHAUDUniversité de Lyon, Ingénierie des Matériaux Polymères, CNRS UMR 5223,

IMP@INSA, Villeurbanne, France

[email protected]

Elasto-Plast final meeting, remotely, 16 March 2021

Dedicated to the memory of Jean-Pierre PASCAULT

mailto:[email protected]


Silicone TPEs are hardly commercialized at the moment

so this speech mainly cover academic works

• F. Ganachaud, Thermoplastic silicone elastomers: an endless story,

L’actualité Chimique, n°456-458, 74-81 (2020/2021) (in French)

Submitted to JAST (2021) (in English)

• B. Yi et al, Dynamic siloxane materials: from molecular engineering to emerging applications,

Chemical engineering Journal, 405, 127023 (2021).

• Z. Wang et al, Preparation, characterization and properties of intrinsic self-healing elastomers,

Journal of Materials Chemistry B, 7, 4876-4926 (2019).

Focus mainly on mechanical properties


✓ Context

Supramolecular chemistry and silicone TPEs

Speech overview

✓ Applications

Electronics, antifouling, shape memory….

✓ Silicone urea (co)polymers

Functional silicones, multiblock copolymers, self-healing

✓ New chemistries

Ionic pairing, metal-ligand,(covalently-reversible) vitrimers


Context


✓ : High flexibility, Tg < -120°C

✓ Rubber-like, semi-organic materials, filled with silica

✓ Chemically inert, biocompatible, high gas permeability

✓ Low modulus (few MPa), hyperelasticity, large strain at break (>1000%)

Silicone elastomers


50 nmSi

O

H

O

SiSiO2

O

SiO

O

H

H

B

Réticulation

ROOR, ∆Groupements D

Groupements Dvi

A

D units

DVi units

Crosslinking

ROOR,

Conventional silicone elastomers vs TPE

C

0 200 400 600 8000

2

4

6

8

10

12

Co

ntr

ain

te (

MP

a)

Elongation (%)

A

A+B

Ten

sile

stre

ngt

h(M

Pa)


Supramolecular chemistry

ion - ion 100 - 350 kJ/mol

ion - dipole 50 - 200 kJ/mol

dipole - dipole 5 - 50 kJ/mol

Physical interactions

Covalent bond 200 - 400 kJ/mol

H bonding

(alcohol – acid)

5 - 120 kJ/mol

(15 – 60kJ/mol)

0 - 50 kJ/mol - stacking

0 - 5 kJ/molVan der Waals

A large range of available reversible links


Block copolymer nanostructuration OR association through weak interactions

Supramolecular materials

Various possibilities

H bond growing in two directions

(Pseudo)-ionic pairs very stable

Others (A/D, - stacking…) + combinations

Flexibility and robustness

Functional group location

Multiple interactions in polymers

Phase demixion helps the structuration

Reversibility

8


Self-assembly of silicones: « Silly putty » (1943)

Si-OH B

OH

OHHO

Rapid stress behaves like an elastic gel

Slow stress behaves like a viscous liquid


Self healing systems: living polymer network

P. S. Chang, M. A. Buese, US patent 5,347,028 /JACS, 1993, 115, 11475-11484.


Silicone ureas


Brief survey

✓ Two main categories

Modified silicone backbone vs multiblock copolymers

✓ Versatile chemistry

Amine + various diisocyanates…

✓ Inspired from polyurethane TPEs

Seminal work of Yilgor and Yilgor

Soft segment Urea content

(%)

Tensile strength

(MPa)

Strain at break

(%)

PSU-DY-20 PDMS 20 7.9 205

PSU-HM-20 PDMS 205 8.1 195

PSU-ED-19 PDMS 19 8.3 180

PEU-DY-20 PEO 20 25.4 1320

PEU-HM-20 PEO 20 25.8 1325

PEU-ED-19 PEO 19 26.5 1450


Functional silicones

O. Colombani et al Macromolecules 2005, 38, 1752


T decrease

T increase

Free

Free

Bonded

Bonded

1800 1750 1700 1650 1600 1550 1500 1450

0,0

0,1

0,2

Absorb

ance

30°C

50°C

70°C

90°C

110°C

130°C

160°C

Wavenumber (cm-1)

1800 1750 1700 1650 1600 1550 1500 1450

0,0

0,1

0,2

Ab

so

rban

ce

Wavenumber (cm-1)

160°C

130°C

90°C

62°C

32°C

Functional silicones (bis)

Degradation of the material above 180°C

=> Chemical cross-linking


Silicone ureas’ copolymers

GENIOMER (Wacker)

O. Schäfer, J. Weis, S. Delica, F. Csellich, A. Kneissl Polym. Prep. 2004, 45(1), 714

Synthesis in solution (IPA) or in reactive extrusion


0 200 400 600 800 1000 1200 14000

2

4

0.01 s-1

0.08 s-1

No

min

al S

tre

ss,

N,

[MP

a]

Nominal Strain, N,[%]

0.1 s-1

0 10 20 30 40 500,00

0,05

0,10

0,15

0,20

0,25

Stre

ss [

MPa]

Strain [%]

Real life properties

0 200 400 600 800 1000 1200 1400

0

1

2

3

4

5

6

Str

ess (

MP

a)

Strain (%)

G200

G145

G80

G345


Isocyanate-free silicone urea


0

0,.1

0,.2

0,.3

0 300 600 900

+

92 %

8 %

Stre

ss (

MPa

)

Strain (%)

Implementing self-healing


Other chemistries


Brief survey

✓ Pairing with metals

Direct ion pairing or metal-ligand specific interactions

✓ Reversible covalent bonds

Following the trend of vitrimers

✓ Ionic interactions put on success

As strong bonds as covalent ones

✓ Possibility to add fillers!

Little interactions with associating groups


Zwiterionic polymers

Δ

1. Acid-base reaction

2. Aza-Michael reaction

K = 2.105 – 6.107

0 1000 2000 30000.0

0.1

0.2

0.3

0.4 0.008 s-1

0.08 s-1

0.25 s-1

0.42 s-1

No

min

al S

tress,

N, (M

Pa)

Nominal Strain, N, (%)

Press

UnloadFeed


Metal ligand interactions


Thermoreversible covalent link (old version)

Diels-Alder Esters

O

+

R

O O

OHHO

nHOOC O

OR

OO COOH

CH2 X + R2N X CH2 NR2n m

NR+

NR+

NR2+

X-

X-

X-

Ionene Azlactone

Hydrazone

R1 NH NH2 + C

O

H

R2 R1 N N

H

C

O

R2


Thermoreversible covalent link (new version)

Vinylogous Imine

Disulfide


High performance applications


Brief survey

✓ High-tech applications

Batteries, dielectric actuators, electronic sensors…

✓ Coatings and bulk materials

From anti-icing to shape-memory materials

✓ Playing with specific properties

Processability, self-healing, high stretch

✓ Challenge: 3D printing

Fused deposition modeling


Coatings

Anti-icing

Anti-fouling

+Self-healing avoidsunwanted adhesion


Materials

Shape memory


Conclusion and prospects

➢ Silicone is ideal to generate TPEs

Very low polarity efficient demixing and self-assembly

➢ Versatility of chemical modifications

From weak forces to disruptable covalent links

➢ Still need improvement to compete with silicone elastomers

Weak mechanical properties fillers

Thermal resistance new chemistry?


At IMP (if you are interested)

J. Mater. Chem., 2010, 20, 10269-10276.

Chem. Commun., 2016, 52, 6681-6684

In progress

WO 2016102498 A1J Colloid Interface Sci. 2013, 408, 87-93

+ Patent pending

In Silicon Based Polymers, 2008, pp 85-98

FR2912410 (A1)

H-Bonding Others

Ionic pairing

III III


Thermoplastic silicone elastomers:

an endless story

F. GANACHAUDUniversité de Lyon, Ingénierie des Matériaux Polymères, CNRS UMR 5223,

IMP@INSA, Villeurbanne, France

[email protected]

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Thermoplastic silicone elastomers: an endless story