T 5   dupont ( mr. shirish)
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    T 5   dupont ( mr. shirish) T 5 dupont ( mr. shirish) Presentation Transcript

    • Assessing Coatings Durability via CO2 Generation Rates An Alternative Rapid Test of Paint DurabilityDuPont Titanium TechnologiesS.Daptardar, Michael P. Diebold30 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 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 actualoutdoor results. A new accelerated test that relies on UV exposure conditions typical of exteriorexposures. 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 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 • Conclusions1/27/2011
    • 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 occurs1/27/2011
    • 5 The TiO2 Durability Balance Destruction from Photocatalytic Degradation Protection from Direct DegradationThe balance depends on the grade of TiO2 and the resin chemistry 1/27/2011
    • 6 Existing Test Methodologies Conditions Outdoor Real Exposures Accelerated Lab Artificial Exposures Tests Appearance Actual Secondary Secondary Degradation Change Effect Reaction Response1/27/2011
    • 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)1/27/2011
    • 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 differently1/27/2011
    • 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 consumer1/27/2011
    • 10 Existing Test Methodologies Conditions Outdoor Real Exposures New Approach Accelerated Lab Artificial Exposures Tests Actual Appearance Secondary Secondary Degradation Change Reaction Effect Response1/27/2011
    • 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.1/27/2011
    • 12 Experimental Set-up - Lab “Full Spectrum” fluorescent lighting1/27/2011
    • 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 added1/27/2011
    • 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 Value1/27/2011
    • 15 7 Day Comparison of 3 Paints 250000 200000 150000 Counts 100000 50000 0Pigment A B C A B C A B C Paint A Paint B Paint C1/27/2011
    • 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 Day1/27/2011
    • 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 mechanism1/27/2011
    • 18 Thank YouDUPONT CONFIDENTIAL