Transcript Epoxy Curing Chemistry

NEO Chemical Seminar 2007
Cross-linking = Curing
Toine Dinnissen / March 27th 2007
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NEO Chemical Seminar 2007
Reactive Sites
O
OH
CH3
O
CH3
CH2
O
O
CH
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
Toine Dinnissen / March 27th 2007
}
Elevated Temperature
Room Temperature
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NEO Chemical Seminar 2007
Amine Reactions
• Linear Mw build-up....
O
NH2
NH2
+
N
+
O
O
NH2
NH2
CH3
OH
NH2
O
CH3
CH2
OH
CH3
O
O
CH2
N
NH2
CH3
H
Toine Dinnissen / March 27th 2007
H
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NEO Chemical Seminar 2007
Amine Reactions
• followed by Cross-linking
– Avoid vitrification
OH
NH2
N
O
O
O
CH2
OH
CH3
CH2
N
NH2
CH3
H
+
CH3
O
O
CH3
H
OH
N
CH2
OH
CH3
O
O
CH2
N
CH3
H
CH2
HO
Toine Dinnissen / March 27th 2007
O
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NEO Chemical Seminar 2007
Amine Reactions
• possible tertiary amine catalysed hydroxyl-cure
– temperature helps
OH
CH3
O
O
O
CH2
+
N
CH3
CH3
CH3
OH
O
O
CH3
O
O
CH3
O
CH3
O
O
CH2
N
CH3
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
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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]
Mole weight
370
D.E.R. 660
[Semi-solid]
D.E.R. 671
[Solid]
700
1000
500
EEW
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
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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]
:
AHEW = 115
• D.E.R.™ 331 epoxy resin
:
EEW
= 188
Theoretical amount of hardener needed per 100 g of D.E.R. 331
epoxy resin
=
100 * 115
188
Toine Dinnissen / March 27th 2007
= 61 g
™ Trademark of The Dow Chemical Company
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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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