This document proposes using carbon dioxide (CO2) generation rates as an alternative method to rapidly test paint durability. Existing test methods are time-consuming or do not correlate well with real-world outdoor results. The new method exposes paint samples to UV light typical of outdoor exposures and monitors the CO2 levels, which directly correlate to degradation. Test results show CO2 rates distinguish between titanium dioxide pigment grades and degradation increases with higher light intensities, providing a simple way to predict outdoor durability performance.

1. Assessing Coatings Durability
via CO2 Generation Rates
An Alternative Rapid Test of Paint Durability
DuPont Titanium Technologies
S.Daptardar, Michael P. Diebold
30 January, 2011
© 2004 E.I. du Pont de Nemours and Company. All Rights Reserved. The DuPont oval™, the miracles of science™,
DuPont and Product Name® are trademarks or registered trademarks of E. I. du Pont de Nemours and Company.

2. 2
Abstract
Coating durability is of high importance in most outdoor applications.
Durability must, therefore, be assessed and accurately characterized
Existing Test Methods are either time consuming or having poor correlation to actual
outdoor results.
A new accelerated test that relies on UV exposure conditions typical of exterior
exposures.
With a focus on the effect of TiO2 pigment grade on paint durability.
With better correlation to exterior results than longer term accelerated tests.
DUPONT CONFIDENTIAL

3. 3
Agenda
• Effect of TiO2 on paint durability
• Paint durability test strategies
• Using [CO2] to monitor paint degradation
– Development of the technique
– Effect of exposure conditions
• Conclusions
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4. 4
Binder Degradation Mechanisms
Photocatalytic:
TiO2 + UV light mostly heat, some radicals
radicals + binder degradation products
Direct:
UV light + binder degradation products
Thermal degradation also occurs
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5. 5
The TiO2 Durability Balance
Destruction from
Photocatalytic Degradation
Protection from
Direct Degradation
The balance depends on the grade of TiO2 and the resin chemistry
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6. 6
Existing Test Methodologies
Conditions
Outdoor
Real
Exposures
Accelerated Lab
Artificial
Exposures Tests
Appearance
Actual Secondary
Secondary
Degradation
Change Effect
Reaction
Response
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7. 7
Outdoor Exposure
Description:
– Expose paints under natural conditions
Advantages:
– Measures the changes of interest (appearance)
under the conditions of interest (ambient)
Disadvantages:
– Very slow (years to decades)
– Slowest for paints of the most interest (superdurable)
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8. 8
Accelerated Exposure
Description:
– Expose paints under high UV light conditions
Advantages:
– Measures the changes of interest (appearance)
– Quicker than traditional exterior exposure
Disadvantages:
– Relatively slow (weeks to months)
– Does not measure reaction under conditions of interest
• Degradation occurs via complex reaction chains, and increased
light intensity affects each reaction rate differently
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9. 9
Lab Tests
Description:
– Measure non-appearance (physiochemical) changes
to paint on exposure
– Often under intense (accelerated) conditions
Advantages:
– Fast (hours to days)
Disadvantages:
– High intensity (accelerated) conditions
– Measures a property that is of no interest to the paint
consumer
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10. 10
Existing Test Methodologies
Conditions
Outdoor
Real
Exposures
New Approach
Accelerated Lab
Artificial
Exposures Tests
Actual
Appearance Secondary
Secondary
Degradation
Change Reaction
Effect
Response
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11. 11
Monitor the Formation of Carbon Dioxide
– Flexibility – CO2 is the eventual degradation
product for all organic resins
– Unambiguous - Does not further react
• High concentrations can only mean fast degradation
– Manifests quickly (hours to days)
• Even under ambient conditions – no need for high
intensities
• Therefore maintains proper balance of different
degradation reactions.
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12. 12
Experimental Set-up - Lab
“Full Spectrum” fluorescent lighting
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13. 13
Effect of Liquid Water
9000
8000
CO2 Amount (Arbitrary Units) 7000
6000
5000
4000
3000
2000
1000
0
1 2 3 4 5
0.0 0.25 0.5 0.75 1.0
ml water added
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14. 14
Effect of Pigment Durability
8000
7500
7000
6500
R2 = 0.9288
[CO2] ppm
6000
5500
5000
One week exposure to Summer
4500
Sunlight
Approximately 1.5x rate seen in lightbox
4000
0 5 10 15 20 25 30 35 40
Chalk/Fade Value
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15. 15
7 Day Comparison of 3 Paints
250000
200000
150000
Counts
100000
50000
0
Pigment A B C A B C A B C
Paint A Paint B Paint C
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16. 16
Effect of Light Intensity
4000
low durability pigment 0.5 intensity
3500
low durability pigment 1.0 intensity
3000 low durability pigment 2.0 intensity
2500
[CO2] (ppm)
2000
1500
1000
500
0
0 1 2 3 4 5 6 7 8
Day
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17. 17
Conclusions
• CO2 evolution rate from paint film
degradation, under ambient conditions, is
a simple, useful predictor of TiO2 grade
durability performance.
– Method appears general since most paints
ultimately degrade to CO2 and H2O
– A number of options for exposure and CO2
detection
• This technique can also be used to probe
the degradation mechanism
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18. 18
Thank You
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