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Epoxy Curing Chemistry

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					NEO Chemical Seminar 2007

Cross-linking = Curing

Toine Dinnissen / March 27th 2007

Page 1

NEO Chemical Seminar 2007

Reactive Sites

O O

CH3

OH O CH O CH2

CH3

O O

CH3

CH2

CH3 N

Reaction via the OH-group[s]
– Resole, Amine-formaldehyde resins – Polyisocyanates Elevated Temperature Room Temperature

Reaction via the Epoxy-groups
– Catalytic – Chemical Addition-reactions – Acids: Anhydrides, Phenols Base: Amines Polysulphides

}

Elevated Temperature Room Temperature

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Amine Reactions
• Linear Mw build-up....

O
NH2 NH2

CH3

O O

+

O
CH3

+

NH2

NH2

OH NH2 N H CH2

CH3

OH O CH2 N H

O
CH3

NH2

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Amine Reactions
• followed by Cross-linking
– Avoid vitrification
OH
CH3

OH O O CH2 N NH2
CH3

NH2

N H

CH2

O
CH3

+

O
CH3

O

H

OH

CH3

OH O

N
H

CH2

O
CH3

CH2

N
CH2 O

HO

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Amine Reactions
• possible tertiary amine catalysed hydroxyl-cure
– temperature helps
CH3

OH
O CH2

O

CH3

O
CH3

N

+

O
CH3

O

OH
O

CH3

O
CH3

CH3

O
O CH2

O
CH3

N

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Crosslink Density
Solid epoxy resin Mole wt ~ 1000 Liquid epoxy resin Mole weight ~ 380

Assuming epoxy molecules are difunctional and hardener molecules are tetrafunctional. Note: Crosslinked network always tridimensional
Toine Dinnissen / March 27th 2007 Page 6

NEO Chemical Seminar 2007

Bisphenol-A epoxy resins
Influence of molecular weight of epoxy resin on key properties

D.E.R.™ 331 D.E.R. 337 [Liquid] [Semi-solid]

D.E.R. 660 [Semi-solid]

D.E.R. 671 [Solid]

Mole weight
EEW

370

500

700

1000

Viscosity
Flexibility Acid resistance Solvent resistance

Drying time
Pot life
™ Trademark of The Dow Chemical Company

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Amine Content
• Amine Hydrogen Equivalent Weight [ AHEW ] unit: grams / equivalent. { sometimes referred to as equivalent weight per active Hydrogen } – Definition: Grams of hardener containing one equivalent of N-H groups. or: Mw of the hardener divided by the number of active hydrogen per molecule Parts per Hundred Resin [ phr ] unit: grams – Definition: grams of hardener needed per hundred grams of epoxy resin – Conversion: phr = { AHEW * 100 } / EEW Amine Value { Aminzahl } unit: mg KOH / gram hardener sometimes called amine-index – Definition: mg KOH equivalent to one gram of hardener – Conversion: NO CORRELATION WITH AHEW Amine content [ Aminwert ] unit: eq / kg – Definition: equivalents of N-H per kg hardener – Conversion: Amine content = 1000 / AHEW

•

•

•

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Calculation Example

H H H2N-CH2-CH2-N-CH2-CH2-N-CH2-CH2-NH2
• Amine Hydrogen Equivalent Weight [ AHEW ] • Amine content

Molecular Weight is 146 Functionality is 6

= 146 / 6 = 24 g / eq

= 1000 / 24 = 42 eq / kg

In order to cure100 grams of resin with EEW = 200 g / eq one would need:

phr = 24 * 100 / 200 = 12 grams
Toine Dinnissen / March 27th 2007 Page 9

NEO Chemical Seminar 2007

How to calculate Mixing-ratio

• Amine Hydrogen Equivalent Weight [ AHEW ] • Epoxy Equivalent Weight [ EEW ]

Amount of hardener needed per 100 g of epoxy resin

=

100 * AHEW EEW

The mixing ratio can be optimised in order to achieve the desired performances.

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Example

• Polypox H 043 [ex. UPPC]
• D.E.R.™ 331 epoxy resin

:

AHEW = 115

:

EEW

= 188

Theoretical amount of hardener needed per 100 g of D.E.R. 331 epoxy resin

=

100 * 115 188

= 61 g

Toine Dinnissen / March 27th 2007

™ Trademark of The Dow Chemical Company

Page 11

NEO Chemical Seminar 2007

Mixing and Pot-life
• Mixing
Quasi all ambient cure epoxy coatings are 2 pack systems. Excellent mixing of the epoxy with the hardener components and an accurate dosing are critical to achieve the expected performances

• Pot life
Amount of time available to apply the product after mixing. Pot life depends also on the temperature and amount of product.

• Induction time
With some systems, an induction time is required. Induction prevents blooming

Toine Dinnissen / March 27th 2007

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NEO Chemical Seminar 2007

Dow is “NOT” a Curing Agent supplier !!!

Toine Dinnissen / March 27th 2007

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