SPECTROSCOPIC ANALYSIS OF ARCHITECTURAL COATINGS FOR IMPROVED WEATHERING Karl Booth Western Coatings Show October 23, 2019
SPECTROSCOPIC ANALYSIS OF ARCHITECTURAL COATINGS FOR IMPROVED WEATHERING
Karl Booth
Western Coatings Show
October 23, 2019
Exterior Product Development Pain Points
Formulation & Stability
3 months
QUV evaluation/ qualifications
3+ months
Exterior exposure & Validation
24+ months
Exterior Exposure
• Gold standard for product validation
• Dirt pickup• Grain crack• Adhesion• Gloss retention• Mildew
• Disadvantages• Multi-year investment• Variability within and
between studies
EPS Exposure Progam
Los Angeles, CA Marengo, IL Ft Myers, FL
Climate: Dry-Subtropical• Dirt Pickup Resistance• Gloss Retention
Climate: Continental• Grain-Crack Resistance• Chalk Adhesion• Alkaline Substrates
Climate: Subtropical Savanna• Gloss Retention• Mildew Resistance
Exposure Study for Gloss Retention
Main objectives:1. Identify the conditions that are most
challenging to gloss retention performance.
2. Identify conditions that are most stable, consistent and reproducible.
Polymer Substrate Location Color
1 Primed Aluminum California White
2 Primed Cedar Florida Yellow Oxide
3 Galvanized Illinois Lamp Black
4 Primed Hardie
5 Bare Aluminum
6 SYP
7
Paints were all <50 g/L and adjusted to pass LTC 972 individual panels 3,400 readings taken over 6 months
Exposure Study for Gloss Retention
Location Selection• Florida shows the largest
variation, highest mean• California shows lowest gloss
• Gloss evaluated both washed & unwashed
• Dirt pickup responsible for gloss reduction
Sample Mean Std. Dev Grouping
California 17.2 3.7 A
Florida 36.7 7.3 B
Marengo 30.0 6.1 C
60o
Glo
ss -
6 M
onth
s
Florida ILCalifornia
Location
Exposure Study for Gloss Retention
• Substrate Selection• Dimensionally stable types
showed lowest Std. Dev• Primed aluminum & cement
board were most consistent
60o
Glo
ss -
6 M
onth
s St
d D
ev
Primed Aluminum
Primed Cedar
Primed Galv.
Primed Hardie.
SYP
Substrate
Sample n Mean Std. Dev Grouping
SYP 162 3.1 2.0 A
PrimedCedar 143 2.0 1.4 B
PrimedHardie 107 1.8 1.1 B C
Primed Galvanized 108 1.6 1.6 B C
PrimedAluminum 108 1.4 1.1 C
Primed Aluminum, Florida Selected
Std. Dev. 60o Gloss at 6 Months Exterior Exposure
Accelerated Approaches
• QUV-A (340nm)• Industry Standard for coatings• 8hr UV, 4 condensation; 60/50oC• Mimics higher energy portion of solar
radiation, 340nm
• Xenon Arc (290-800)• Stronger match for full range solar
radiation• Less common than QUVA
• QUV-B (313nm)• Highest energy wavelength, 313nm• Typically only used for extremely
durable materials
Onset of Gloss Loss in Cyclic Testing
• High performance architectural coatings tend to maintain constant gloss over a period of time
• After a exposure, sufficient UV induced degradation has occurred that film erosion and roughness is detectable by gloss measurement
• It is important to validate QUVA with true exterior weathering 0
10
20
30
40
50
60
70
80
90
0 500 1000 1500 2000 2500
60 G
loss
Uni
ts
Hours
QUVA
Relating QUV to Exterior Exposure
0
10
20
30
40
50
60
0 1000 2000 3000 4000 5000
60 G
loss
Hours
Cyclic QUVA
White
Black
Yellow Oxide
0
10
20
30
40
50
60
0 2 4 6 8 10 12 14 16 18 20
60 G
loss
Months
Florida Exposure – Primed Aluminum
Modes of UV-Degradation
γ-Lactone - 1780cm-1
Ketone - 1710cm-1
Carboxy Acid - 1705cm-1
Ester - 1735cm-1
-CH3OH
-β Scission
Chiantore, O., L. Trossarelli, and M. Lazzari. “Photooxidative Degradation of Acrylic and Methacrylic Polymers.” Polymer 41, no. 5 (March 2000): 1657
O2H2O
Functional Group Analysis
• ATR-FTIR allows semi-quantitative analysis of film degradation
• Relating C-H to C=O demonstrates trends in degradation
• ∫ 1600−1800𝑐𝑐𝑐𝑐−1
∫ 2800−3050𝑐𝑐𝑐𝑐−1=
• Comparing changes in index between samples predicts relative degradation rates
C-H= Carbonyl
Index
C-H
- The change in index predicts the relative rate of oxidative polymer degradation
QUVA and Carbonyl Index
0
1
2
3
4
5
6
Polymer 1 Polymer 2 Polymer 3 Polymer 4
1w C
arbo
nyl I
ndex
Del
ta
0102030405060708090
100
0 500 1000 1500 2000 2500 3000
60 G
loss
Hours
Polymer 1
Polymer 2
Polymer 3
Polymer 4
- Carbonyl index run on a polymer series at 0 and 7 days cyclic exposure
Delta Carbonyl Index by Polymer
Cyclic QUVA Gloss
QUVA and Carbonyl Index
0
1
2
3
4
5
6
Polymer 1 Polymer 2 Polymer 3 Polymer 4
1w C
arbo
nyl I
ndex
Del
ta
y = 5.3024e-0.002x
R² = 0.9977
0.1
1
10
0 200 400 600 800 1000 1200 1400 1600 1800 2000
1 w
eek
Carb
onyl
Inde
x
Critical Failure Hour
0102030405060708090
100
0 500 1000 1500 2000 2500 3000
60 G
loss
Hours
Polymer 1
Polymer 2
Polymer 3
Polymer 4
Delta Carbonyl Index by Polymer
Cyclic QUVA Gloss
Accelerating Development
Experiment• Replace primary monomer in polymer 1
with 3 alternatives, maintain Tg
• Expose to standard QUVA testing
• Evaluate carbonyl index at regular intervals0
0.05
0.1
0.15
0.2
0.25
0.3
Monomer 1 Monomer 2 Monomer 3 Monomer 4
24h
Carb
onyl
Inde
x De
lta
Carbonyl Index of Monomer Replacements
0
20
40
60
80
100
120
140
0 500 1000 1500 2000 2500 300060
Glo
ssHours
Gloss Retention of Monomer Replacements
Monomer 1
Monomer 2
Monomer 3
Monomer 4
Results• Carbonyl Index provides early indication of
polymer performance
• Tight formulation control allows for strongest predictive power
Cyclic QUVA vs. Alternative Exposures
• UV-only highlights the positive side of UV exposure, crosslinking, which can increase gloss
• Cyclic QUVA involves both a UV step and a humidity step, so it is valuable to determine their individual impacts
• The combination of UV and condensation provides a severe change in gloss behavior
• Humidity exposure (Cleveland) can also severely impact gloss, but carbonyl indexing is insensitive to this mode of failure
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Paint 1 Paint 2 Paint 3 Paint 4 Paint 5 Paint 6 Paint 7 Paint 8 Paint 9 Paint10
Paint11
Paint12
Delta
Car
bony
l Ind
ex
Delta Carbonyl Index by Method @1000hrs
Cyclic2/3 UV-Only1/3 Humidity Only
0
20
40
60
80
100
120
140
160
0 1000 2000 3000 4000 5000
20 G
loss
Per
cent
age
Hours
CyclicUVHumidity
Paint 1: Gloss vs Time
Summary
• Understanding the fundamentals of weathering is pivotal to developing innovative and differentiated technology
• ATR-FTIR allows for the characterization of UV degradation at a molecular level, and gives early predictions of polymer performance where carbonyl functionality is changing
• The study of separate UV or humidity cycles demonstrates that the presence of water has both a physical and chemical impact
Specials thanks to: Matt Andersson, Paige Booth, Chuck Myers, Jacob Bolton, Mike Wildman, Robert Sandoval, Gunnar Duner, Heidi Docktor
Thermo Fischer Nicolet iS10 with Smart iTR fixture
THANK YOU QUESTIONS?