Thermoreversible crosslinking of maleic anhydride-grafted ethylene-propylene copolymers

/department of chemical engineering and chemistry 1/24

Thermoreversible crosslinking of maleic

anhydride-grafted ethylene-propylene

copolymers

An evaluation of hydrogen bonded and ionic networks

Sun Chunxia

March 2005

Coaches:

Mark van der Mee

Han Goossens


Contents

1)Introduction: crosslinking of rubbers2)Objectives3)Modification with alkylamines - Preparation - Results - Conclusions4)Modification with metal acetylacetonates

- Preparation- Results- Conclusions

5)Future work


Crosslinking of rubbersCrosslinking of rubbers

Crosslinking transforms non-elastic base material into an elastic material

Two main commercial technologies:1) Sulphur vulcanisation:

2) Peroxide curing

s s

s s

sulphur

heating

Why?

How?


Crosslinking of rubbers

• Prevents processing in the melt

• Complicates recycling of scrap &

used products

Problems:

х


Thermoreversible crosslinking

Thermoreversible crosslinking of

rubbers:

Low temperature: crosslinked material

High temperature: crosslinks weaken or disappear

Result: A crosslinked elastomer at service temperature

that can be processed at elevated temperatures!

heating

cooling


Crosslinking of rubbers

Microphase separation into MAn-rich domains

– Driving force is strong attraction between MAn groups

and strong repulsion between polar MAn groups and

apolar EPM chains

– Domains act as physical crosslinks, increasing network

density

0.1

1

10

100

1000

-100 -50 0 50 100Temperature (ºC)

Stor

age

Mod

ulus

(MPa

) EPM

MAn-g-EPM



NH

NN

NH2

ZnAc2

O OO

Multiple Hydrogen

Bonding

(2) Melamine

(1) NH3 Triple Hydrogen

Bonding unit

Ionomer

Ureidopyrimidinone

Quadruple Hydrogen Bonding unit

Diol

Reversible ester XL formation

(1) Furfuryl amine

(2) Bismaleimide

Diels-Alder reaction

Diamine

Reversible amide XL formation

(1) Terpyridine

(2) Metal

Metal-Ligand complex

Several thermoreversible crosslinking techniques



Hardness [ Sh. A]

E-mod [MPa]

TS [MPa]

EB [%]

CS23C

[%] CS70C

[%] MAn-g-EPM 38 1.6 0.4 550 88 100 MI-g-EPM 49 2.0 0.7 450 76 100 ATA-imide 52 2.4 1.2 310 76 100 ATA-AA 54 2.5 1.4 340 38 86

MA-g-EPM 54 2.8 1.6 320 59 100 MAA-g-EPM 57 3.4 6.1 590 24 60 ATA-imide + CoAcac

51 2.4 7.5 720 - 56

Previous work in this project

So far, pure HB is very weak !



How to improve it ?(1)Combination with ionic

interactions

(2)Arrays of HB:N

O N N NR

O

H H

H

N

ONNNR

O

HH

H

Ureidopyrimidinones

(UPy’s)

(E.W. Meijer et al.)


Objectives

1) Modification of MAn-g-EPM with primary amines to an amide-salt Significantly improves properties with NH3, which is highly volatile

DECREASE IN PROPERTIESImide formation will occur at elevated temperatures

DECREASE IN PROPERTIES

2) Addition of metal acetylacetonates (MeAA) to MAn-g-EPM based

imides

Modification of MAn-g-EPM with 3-amino-1,2,4-triazole (ATA) only slightly improves

the properties

Addition of different MeAA to the ATA-imide introduces ionic interactions

Objectives

ATA

Use less volatile primary amines (C3, C6, C10, C18)

Study the mechanism for different metals (Co & Zn) and different imides


Results (I)-Alkylamines

OO

O OH NH

OO

R

1eq R-NH2

o- NH

OO

RRNH3+

O

N

R

excess R-NH2

TMAn-g-EPMamide-acid amide-salt

imide

O

Compression moulding

at 180 ºC for 20 minutes

Modification of maleic anhydride-grafted EPM with alkylamines

Preparation

Solution in THF at R.T.


Results (I)- Alkylamines

1900 1800 1700 1600 1500 1400 13000.00

0.05

0.10

0.15

0.20

Inte

nsity

(a.

u.)

Wavenumber [cm-1]

MAn-g-EPM decylamine hexylamine propylamine octadecylamine

Peak position

(cm-1)

Peak

assignment

1865 Anhydride

1785 Anhydride

1710 Acid

1640 Amide I

1555 Amide II

Synthesis

1 eq AlkylamineOH HN

OO

R



1900 1800 1700 1600 1500 1400 13000.00

0.05

0.10

0.15

0.20

Inte

nsity

(a.

u.)

wavenumber [cm-1]

hexylamine 1eq hexylamine 2eq hexylamine 5eq hexylamine 10eq

FTIR spectra hexylamine

modified MAn-g-EPM

FTIR spectra octadecylamine

modified MAn-g-EPM

Different ratios


C10 > C18 > C3 > C6


•Significant improvement in

tensile properties

•Trends in TS and modulus not

consistent with alkyl length

Two competing effects:

Long tails disturb aggregate

formation

- poor properties

Long tails can crystallize

- improved properties

Tensile tests

1 eq Alkylamine

0

0.4

0.8

1.2

1.6

2

0 200 400 600 800 1000

Engineering strain [%]E

ngin

eerin

g st

ress

[MP

a]

MAn-g-EPMhexylaminepropylamineoctadecylaminedecylamine



hexylamine octadecylamine

• Modulus and TS increase with increasing

amount of alkylamine

• C18 > C6 crystallization?

Different ratios

0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

4

0 200 400 600 800 1000Engineering strain [%]

Engin

eerin

g str

ess [

MPa

]

MAn-g-EPM

octadecylamine 1eq

octadecylamine 2eq

octadecylamine 5eq

0

0.4

0.8

1.2

1.6

2

2.4

2.8

3.2

3.6

4

0 200 400 600 800 1000Engineering strain [%]

Engin

eerin

g str

ess [

MPa

]

MAn-g-EPMhexylamine 1eqhexylamine 2eqhexylamine 5eqhexylamine 10eq



• Imide formation gives poor properties

• Poor properties of C18-imide:

No significant crystallization!

Imide of alkyl-amide acids

OH NH

OO

Ramide-acid

O

N

R

imide

OCM

180 oC, 80 bar



• FTIR spectroscopy can be used to study reaction of MAn-g-EPM with

amines

• Modification with different primary amines improves the tensile

properties

significantly

• Modulus and TS increase with increasing amount of alkylamine

• Imide formation leads to poor properties

Conclusions


Results (II)- Metal acetylacetonates

• Metal acetylacetonate (CoAA or ZnAA) added to imide (ATA

or

C3) in THF at RT

• Definition of 1 eq and 2 eq MeAA:

1 eq MeAA: adding enough metal to coordinate with all the

oxygen atoms from the imide groups, assuming a

fourfold coordination

2 eq MeAA: adding the double amount of metal

HB with ionic interaction systems

Preparation

O

N

R

imide

O



1 eq MeAA to ATA-imide 2 eq MeAA to ATA-imide

Tensile tests

0

1

2

3

4

5

6

0 100 200 300 400 500 600Engineering strain [%]

Engin

eerin

g stre

ss [M

Pa]

MAn-g-EPMATA-imideATA-imide+2eq CoAAATA-imide+2eq ZnAA

0

1

2

3

4

5

6

0 100 200 300 400 500 600Engineering strain [%]

Engin

eerin

g str

ess [

MPa

]

MAn-g-EPMATA-imideATA-imide+1eq ZnAAATA-imide+1eq CoAA



1 eq of MeAA to propylimide 2 eq of MeAA to

propylimide

Tensile tests

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600 700 800Engineering strain [%]

Engin

eerin

g str

ess [

MPa

]

propylimide

MAn-g-EPM

propylimide+1eq CoAA

propylimide+1eq ZnAA

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600 700 800Engineering strain [%]

Engi

neer

ing

stre

ss [M

Pa]

propylimide

MAn-g-EPM

propylimide+2eq ZnAA

propylimide+2eq CoAA



N

OO

N

NNH

Co

Zn

N

OO

C3H7

Mechanism for coordination

ATA-imide propylimide

ATA-imide : 1eq Co >> 1eq Zn; 2 eq Zn ≈ 2 eq Co; 2 eq Zn > 1 eq Zn

C3-imide : Co ≈ Zn; 1 eq > 2 eq



Following mechanism was proposed to explain the results:

• In propylimide, Co and Zn can only weakly coordinate with O,

leading to comparable properties

• In ATA-imide, additional strong coordination with N from the

ATA-ring is

possible. Two different situations:

– Co likes to coordinate with N, so good properties are obtained for

both low and high amounts

– Zn likes to coordinate with O, so an excess of Zn has to be added to

force strong coordination with N to get good properties.

Conclusions


Future work

• The effect of the tail length and the amount of the primary

amines on the properties will be further investigated

• The influence of temperature and amount of

octadecylamine on crystallization and mechanical properties

will be studied

• Other systems of HB combined with ionic interactions will

be prepared and evaluated, trying to avoid imide formation

•The exact coordination mechanism of MeAA modified MAn-

g-EPM will be further investigated by EXAFS

EXAFS can get information about coordination around metals

Future work


Acknowledgements

• Otto van Asselen

• Jules Kierkels

• All other colleagues of SKT

Acknowledgement


Structures and Names

OH OHOO

O NH2

OO OONH

OH NHOO

NN

NH

NOO

NN

NHNH4

MA-g-EPM MAA-g-EPM MI-g-EPM ATA ATA-imide

+


Mechanism of 4 fourfold coordination

N

OO

N

NNH

N

O O

N

NHN Co

N

OO

N

NNH

N

O

ON

N

HN

Co

NO

O

N

NHN

ATA-imide +1 eq CoAA ATA-imide +2 eq CoAA


Mechanism of 4 fourfold coordination

N

OO

N

NNH

N

O

ON

N

HN

Zn

NO

O

N

NHN

N

O

O

N

N

NH

N

O

ON

N

HN

Zn

NO

O

N

NHN

N O

O

N

NNH

ATA-imide + 1 eq ZnAA ATA-imide+ 2 eq ZnAA


Future work

OOO OH NH

OO

R

1eq R-NH2

o- NH

OO

RRNH3+

ON

R

excess R-NH2

TMAn-g-EPMamide-acid amide-salt

O

OH HNOO

NN

NH

NOO

NN NH

ATA (amide-acid)

ATA-imide

MeAA

o- NH

OO

RM+

imide

ionomer

base

R:H, C3, C6, C10, C18

Documents

Thermoreversible crosslinking of maleic anhydride-grafted ethylene-propylene copolymers