Transcript Gold Iridescence

Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
by Bob Ohm* & Dan Patton
Lion Copolymer, LLC
Compounding and Development Center
5955 Scenic Highway, Baton Rouge, LA 70805
* Speaker
Outline
Introduction
Bloom vs. Iridescence
23 Designed Experiment: Filler, Oil & Curative
Effect of Cure Temperature & EPDM Polymer
Surface Analysis
Antioxidant Comparison
Final Experiments
Summary
Introduction
Why weatherseals are based on EPDM
Excellent Weatherability
Impervious to Ozone
Highly Resistant to Heat and Oxidation
Highly Extendable
Discoloration in Light
Initial colors blue / red / green
Change to bronze / gold
Prior Work
Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
•Best viewed at shallow angle
•A long-standing issue
•Various “solutions” proposed:
–Cure system
–Filler
–Polymer
–Additives
•Root cause & permanent fix elusive
The Iridescent Color
depends on the angle of view
Bloom and Bleed
Surface Discoloration due to powdery solid (bloom) or liquid film (bleed)
The remedy is straightforward:
1. Remove the material at the surface
2. Determine the composition of the material removed.
3. Lower the dose or eliminate the use of the material identified.
Gold Iridescence
Surface Discoloration due to???
 The discoloration can not be readily removed.
 Methylene chloride removes - but only temporarily!
Thermal Desorption Results
Eric Jourdain, Paper #42, 149th ACS Rubber Division meeting (May 1996)
2,500,000
Non-exposed Side
Abundance
2,000,000
NH
NH
S C N
O
1,500,000
N
O
S
C OH
1,000,000
HO
O
500,000
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65
Time
Thermal Desorption Results
Eric Jourdain, Paper #42, 149th ACS Rubber Division meeting (May 1996)
2,500,000
Sun Exposed Side
Abundance
2,000,000
1,500,000
NH
1,000,000
500,000
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65
Time
Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
Five Studies:
1. 23 design for: A/ filler (furnace vs. thermal)
B/ plasticizer (par oil vs. poly alpha-olefin),
C/ cure system (sulfur vs. peroxide) and
D/ cure time at 182°C (1.5 vs. 10 minutes)
2. effect of: A/ diene content (4 vs. 8%),
B/ ethylene content (60 vs. 70%) and
C/ cure temperature (230 vs. 340°C)
3. surface analysis
4. antioxidant comparison
5. polymer, filler & other variations
23 Designed Experiment
Filler / carbon black
Oil / plasticizer
Cure System (Sulfur vs. Peroxide)
Additive Package (the 3 Amigos)
Filler Comparison
A. Furnace black:
–
–
–
–
made from crude oil
made in air
contains aromatic structures (staining)
contains sulfur, nitrogen
B. Thermal black*:
–
–
–
–
made from natural gas
anaerobic manufacture (no oxygen)
minimum extractables (aromatics)
little/no sulfur, nitrogen
* plus precipitated silica to equalize hardness
Plasticizer Comparison
A. Parafinnic oil:
– made from crude oil
– contains aromatic structures
– contains sulfur, nitrogen
B. Poly a-olefin:
– made from decene
– no residual unsaturation
(removed by hydrogenation)
– no sulfur, nitrogen
Cure System Comparison
A. Sulfur cure:
– contains sulfur, nitrogen
– little/no oxygen
– accelerator fragments found on
surface
B. Peroxide cure:
– no sulfur, nitrogen
– contains oxygen
Gold Ratings: 1 = best, 5 = worst
6 days exposure per SAE J1960 (exterior)
Cure System,
(-1 = peroxide, +1 = sulfur)
2
Sulfur
1
Cure
3, 2 (PaO)
3 Am.= 5
5, 4
0
Peroxide
Cure-1
3 Am. = 1
3, 2
5, 4
-2
-2
Thermal
Furnace
-1
0
1
Black*
Black
Filler (-1 = thermal black*, +1 = furnace black)
2
* = mat surface develops during light exposure
Gold Ratings: 1 = best, 5 = worst
6 days exposure per SAE J1885 (interior)
Cure System,
(-1 = peroxide, +1 = sulfur)
2
1, 2.5
(PaO)
Sulfur
1
Cure
3 Am.= 0.5
3.5, 3.5
0
Peroxide
Cure-1
3 Am. = 1.5
2, 3
5, 5
-2
-2
Furnace
Thermal
1
0
-1
Black
Black*
Filler (-1 = thermal black*, +1 = furnace black)
2
* = mat surface develops during light exposure
Summary of 23 Experiment
A. The filler system is most important for gold
iridescence. A thermal black/ppt. silica blend
develops a low-gloss (mat) surface during
light exposure, minimizing the gold
iridescence.
B. The 3 Amigos are effective, esp./SAE J1885.
C. A peroxide cure is poorer than the sulfur cure
per SAE J1885 (no effect per SAE J1960).
D. The PAO is better than paraffinic oil per J1960
(no effect or slightly poorer by J1885).
Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
Five Studies:
1. 23 design for: A/ filler (furnace vs. thermal)
B/ plasticizer (par oil vs. poly alpha-olefin),
C/ cure system (sulfur vs. peroxide) and
D/ cure time at 182°C (1.5 vs. 10 minutes)
2. effect of diene content (4 vs. 8%),
ethylene content (60 vs. 70%) and
cure temperature (230 vs. 340°C)
3. surface analysis
4. antioxidant comparison
5. polymer, filler & other variations
Polymers Evaluated
(Cure Temperature = 230 or 340 °C)
Light Exposure = 6 days SAE J1885
Diene Content, %
9
Previous
workers
= best
7
5
EPDM
505
EPDM
563/501
EPDM
509
Previous
workers
= worst
EPDM
556
3
50
55
60
65
70
Ethylene Content, %
75
80
Gold Ratings: 1 = best, 5 = worst
Cure Temp. 10’/230, 2’/340 °C = NO EFFECT
However, 10’at 340°C = IMMEDIATE GOLD
Diene Content, %
9
UV* = 1
3 Am.= 1
2
2
7
5
UV* = 3
3 Am. = 2
4
3
3
50
55
60
65
70
75
80
Ethylene Content, %
* = heavy white bloom on molded samples
Summary of Second Study
A. The gold color can be developed by oxidation
without light exposure. (However, this
method leads to sample embrittlement.)
B. High diene polymers give lower gold ratings.
C. Gold ratings can be further lowered by
addition of the “Three Amigos”.
D. Ethylene level and cure temperature have
little effect on gold in our laboratory work.
Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
Five Studies:
1. 23 design for: A/ filler (furnace vs. thermal)
B/ plasticizer (par oil vs. poly alpha-olefin),
C/ cure system (sulfur vs. peroxide) and
D/ cure time at 182°C (1.5 vs. 10 minutes)
2. effect of diene content (4 vs. 8%),
ethylene content (60 vs. 70%) and
cure temperature (230 vs. 340°C)
3. surface analysis
4. antioxidant comparison
5. polymer, filler & other variations
Surface Analysis Methods
Scanning Electron Microscopy
SEM
TOF-SIMSTime of Flight - Secondary
Ion Mass Spectroscopy
XPS
X-Ray Photoelectron
Spectroscopy
AFM
Atomic Force Microscopy
Surface Analysis of Molded Test Pads
Scanning Electron Micrograph (SEM)
10 m
10 m
Surface Analysis Techniques
TOF-SIMS
Time of Flight
Secondary Ion
Mass Spectroscopy
Found only
siloxane
(mold release).
XPS
X-Ray
Photoelectron
Spectroscopy*
* or ESCA, electron scattering for chemical analysis
XPS - Black Area
012771130.spe: control sample A
01 Dec 17 Al mono 350.0 W 0.0 50.0° 187.85 eV 2.0460e+005 max
Sur1/Full/1
5
012771130.spe
-C1s
2.5
x 10
Evans East
4.50 min
Carbon
2
c/s
-O1s
1.5
Oxygen
0
1200
1000
800
600
400
Binding Energy (eV)
-Si2s
-Zn3s
-Si2p
-Zn3p3
-N1s
-Zn LMM
-Zn LMM
-F1s
-Zn LMM
-Zn2p1
-Zn2p3
-O KLL
-O KLL
0.5
-C KLL
1
200
XPS - Gold Area
012771120.spe: "gold" sample A
01 Dec 17 Al mono 350.0 W 0.0 50.0°
Sur1/Full/1
5
Oxygen
-C1s
2
Carbon
c/s
1.5
-Si2s
-Si2p
-S2s
800
600
400
Binding Energy (eV)
-S2p
-Zn3s
-Zn3p3
1000
-N1s
-Zn2p1
-Zn2p3
-O KLL
-O KLL
1200
0.5
-Zn LMM
-Zn LMM
-C KLL
1
0
Evans East
4.50 min
012771120.spe
-O1s
2.5
x 10
187.85 1.8553e+005
eV
max
200
Oxygen Concentration, %
XPS Oxygen Results - 2nd Study
25
20
black surface
gold surface
15
10
5
0
Royalene Royalene Royalene R-505 + R-505 + 3 10 min @
505
556
563/501 UV Stab. Amigos
650F
(GR=2)
(GR=3)
(GR=4)
(GR=1)
GR=1) (GR=10)
Nitrogen Concentration, %
XPS Nitrogen Results - 2nd Study
contains aMSDPA
amine antioxidant
2.5
2.0
black surface
gold surface
1.5
1.0
0.5
0.0
EPDM
505
(GR=2)
EPDM
556
(GR=3)
EPDM 505 + UV 505 + 3 10 min at
563/501
Stab.
Amigos
340ºC
(GR=4)
(GR=1)
GR=1) (GR=10)
Zinc Concentration, %
XPS Zinc Results - 2nd Study
2.5
black surface
gold surface
2.0
1.5
1.0
0.5
0.0
EPDM
505
(GR=2)
EPDM
556
(GR=3)
EPDM
563/501
(GR=4)
505 +
Ciba
(GR=1)
505 + 3 10 min @
Amigos
650F
GR=1) (GR=10)
High Resolution AFM Surfaces
Black
Gold Shiny
Gold Matt
Surface Analysis Summary
A. Molded samples under SEM appear to
develop raised nodules.
B. TOF-SIMS was not successful in
identifying the composition of the
nodules.
C. XPS finds the gold surface is enriched
in oxygen and, to a lesser extent,
nitrogen and zinc.
D. AFM finds black regions are smooth;
light-exposed gold regions, especially
low-gloss, are rough – nano structure.
Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
Five Studies:
1. 23 design for: A/ filler (furnace vs. thermal)
B/ plasticizer (par oil vs. poly alpha-olefin),
C/ cure system (sulfur vs. peroxide) and
D/ cure time at 182°C (1.5 vs. 10 minutes)
2. effect of diene content (4 vs. 8%),
ethylene content (60 vs. 70%) and
cure temperature (230 vs. 340°C)
3. surface analysis
4. antioxidant comparison
5. polymer, filler & other variations
Comparison of Antioxidants
in the Three Amigos
Blank
No AO
Bisphenolic
(liquid)
OH
H19C9
ODPA
CH3
OH
CH2
C9H19
NH
CH3
TMQ
C8H17
N
H
CH3
Light Exposure = 6 days SAE J1885
C8H17
CH3
CH3
n
Comparison of Antioxidants
in the Three Amigos (continued)
aMSDPA
H 3C
C
CH3
Sulfonated
Diphenylamine NH
NH
NH
SO2
H3C
C
CH3
H 3C
Bisphenol
Phosphite
Blend
NBC
S
S C N
(C4H9)2
S C N
(C4H9)2
Ni
S
Light-Induced Gold Iridescence
(Sunburn) of EPDM Weatherseals
Five Studies:
1. 23 design for: A/ filler (furnace vs. thermal)
B/ plasticizer (par oil vs. poly alpha-olefin),
C/ cure system (sulfur vs. peroxide) and
D/ cure time at 182°C (1.5 vs. 10 minutes)
2. effect of diene content (4 vs. 8%),
ethylene content (60 vs. 70%) and
cure temperature (230 vs. 340°C)
3. surface analysis
4. antioxidant comparison
5. polymer, filler & other variations
Polymer, filler & other variations
Gold Ratings = cured / uncured
N762 black
Peroxide Cures of:
EPDM 4345 (DCPD)
5/5
N990 black &
KE clay
1/1
EPM 404 Copolymer
5/4
2/2
EPDM 509 (ENB)
4*/5
1/1
EPDM 509 / sulfur cure
5*/4
rainbow/ws
The filler system of N990 & KE clay give a dull surface
After SAE J1885 exposure, similar to N990 & ppt. silica.
* Rating improves where Mylar film adhered.
Final Experiment
Photo of Test Pad with Gold Iridescence
Middle portion clamped 1 week at RT removes gold.
10 mm
However:
gold returns on oven aging or more light exposure.
Optical Properties of Nano Particles
Chad A. Mirkin, George C. Schatz, et. al., Science, 294, pages 1901-1903 (2001),
as taken from Chemical & Engineering News, page 10 (Dec. 2, 2001)
Silver nanoprisims
scatter red light.
Gold nanorods
scatter orange light.
Gold nanospheres
scatter green light.
Summary
A. Compression of the surface can
remove the gold iridescence.
B. However, this is not a practical
solution because the gold is
redeveloped during brief oven
aging or additional light exposure.
C. For future work, a permanent
solution may require both chemical
and physical (structure) control.
Thanks for your attention
Any Questions?
The papillo butterfly’s wings
are covered with small textured
scales (above right)… Tiny
concavities within these scales
(below left) create color through
constructive interference…
In the scales of the green
portion of the papillo’s wings,
each concavity reflects bright
yellow while the outer edges
reflect bright blue…
The Three Amigos
OH
H19C9
OH
CH2
C9H19
HO
O
OH
n
CH3
CH3
Carbowax 3350
Polyethyleneglycol
Naugawhite
OH
OH
OH
HO CH2
CH2 OH
R
R
n
R
Schenctady SP-1066 Phenolic Resin
Particle Size of Additives
Gold Region
Carbon N774
Black
Zinc
Oxide
Precipitated
Silica
25
0
N990
Har
d
Cla
y
Soft
Clay
Whiting
500
1000
Particle Size, nm
1500
High Resolution XPS
Main Peak = C-(C1H)
gold sample A
C-O
C=O C-N
control sample A
-O-C=O
AFM Surface Analysis
Black Surface Shiny Sample
Black Surface of Matt Sample
30 m
Gold Shiny Surface
Gold Matt Surface
High Resolution
AFM Surfaces
Black
Gold Matt
Gold Shiny
350
nm
0
-350
350
475 nm
665 nm
130 – 250 nm
nm
0
2
m
4
6
0
-350
0
2
4
6