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Silane Impact on Color
Stability of a Silane Modified
Polyether (SMP) Sealant
Dr. Tim Biggs
October 2016
Outline
• Study Objective
- Evonik Silanes Background
• Project Design
- Silanes Evaluated
- Preparation of SMP Sealant
- Preparation of Test Coupons
- Weathering Conditions
• Results
- Analysis of Weathered Samples
- Conclusions
ASC October 2016 Page | 2
Study Objective:
What options do formulators have for low yellowing sealants?
• Traditional aminosilane adhesion promoters cause yellowing over time
• Conventional wisdom is, only hindered aminosilane adhesion promoters
with dimethyl branching adjacent to nitrogen significantly reduces yellowing
• This limits formulations to one type of adhesion promoter and restricts
formulation design
Compare Evonik low yellowing silane adhesion promoters to hindered
aminosilanes in an opaque SMP sealant
• Compare in Various Weathering Scenarios
• Examine Visual Color Change
• Test Color Change via Colorimetry Analysis
ASC October 2016 Page | 3
Organofunctional Silanes are
Bifunctional Molecules…
Y (CH2)nSi (OR)3
n = 0,3
R = CH3, C2H5, (CH2)2OCH3
Y = Organofunctional group
Y (CH2)n
Si OR
OR
ORhydrolyzablenon hydrolyzable
Organofunctional group can
react with polymers, resins…
Silicon functional group
can react with inorganic
fillers, metals, glass…
ASC October 2016 Page | 4
Five Generations of Functional
Silanes Developed by Evonik
Time
Traditional
Silanes
Dynasylan®
VTMO
Technology
1970 2010
Water - Borne
Silanes
Dynasylan®
HYDROSIL
2627
2909
Low VOC
Oligomeric
Silanes
Dynasylan®
40
9896
1146
Special
Silanes
Dynasylan®
11894148
1124
SIVO®
Technology
Unique Silanes
Dynasylan®
ASC October 2016 Page | 5
E 1 SilaneProprietary silane for critical substrates
Technologies
• MS-Polymer
• Silane modified polymers (SMP)
• RTV-1/-2 silicones
Applications
• Construction
• Transportation
• Industrial Assembly
• DIY
Benefits
• Better adhesion on critical substrates (PVC, PET)
• Higher cohesion
• Higher flexibility
• Less tendency towards yellowing
ASC October 2016 Page | 6
0
50
100
150
200
250
300
PC PMMA PET
Standard
SIVO 203
AF AF
E 1 Silane presented excellent adhesion on plastics !
Filled Sealant with 1 % Adhesion Promoter
E 1 Silane:Adhesion on Critical Polymer Substrates
ASC October 2016 Page | 7
E 1 Silane
E 1 Silane showed highest flexibility in SMP sealant !
E 1 Silane:“High-Elastic” Bonding
ASC October 2016 Page | 8
0
20
40
60
80
100
120
140
Standard E 3 Silane
E 1 Silane
Filled Sealant with 0.5 % Adhesion Promoter
0
1
2
3
4
5
E 2 Silane Standard
E 2 Silane:Unique silane co-oligomer
• Diamino/Alkyl Co-oligomer
• Improved water resistance at interface
• Reacts like a silane monomer
• Reduced VOCA = diamino, B = alkyl
OR = methoxy
R O Si
A
OR´
O Si O R
B
OR´a b
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
3 7 14 21 28
Storage in water [days]
Wa
ter
up
tak
e
[%]
Dynasylan® DAMO-T
Dynasylan® 1146
Excellent
Acceptable
Very Poor
Sealant Aged in Water: Water Uptake and Adhesion
Dry
Adhesion
Wet
Adhesion
Standard
E 2 Silane
Hindered Aminosilane
Theoretical Low Yellowing Mechanism:
• Dimethyl groups adjacent or near amine reduce or prevent formation of radicals
• Radicals lead to the formation of azo compounds
• Azo Compounds are highly colored
Selected a Typical Commercial Hindered Aminosilane:
ASC October 2016 Page | 10
Formulation Details
Parts [wt. %] Raw material
30.0 – 40.0 Hybrid Polymer
15.0 – 20.0 Plasticizer
0.5 – 1.0 Moisture Scavenger
45.0 – 55.0 CaCO3
1.5 Silane Adhesion Promoter
0.06 Tin Catalyst
Formulation Details:SMP Sealant
ASC October 2016 Page | 11
Sealant Batch Preparation:Pigment Grind Equipment
Planetary Mixer Centrifugal Mixer
ASC October 2016 Page | 12
Preparation of Test Coupons:Sealant patches on aluminum panels
Aluminum Panels were used as the testing substrate. Adequate cleaning and
substrate preparation is critical:
• Wipe the aluminum panel with isopropanol
• Prepare Alkaline Solution
• Turn on stirring to the speed 6 or 7
• Heat the solution to 140-150°F
• Dip the panel in the solution for 3 min until
a break free water surface is noticed
• Take out the panel and immediately put in
the water and shake it
• Wash with DI water and air-blow dry
Aluminum Panels: dimensions: 3 in x 6 in x 0.032 in)
ASC October 2016 Page | 13
ASC October 2016 Page | 14
Preparation of Test Coupons:Patches and Curing
After cleaning, the sealant was
applied to panels with a PTFE frame
Samples were placed in a humidity
chamber (50% moisture & 23°C) for a
curing time of 21 days
Simulating Long-term Exposure: Weathering Chamber and Test Cycles
Test Coupons were exposed to UV-light,
heat, and water:
• Equipment: QUV
• UV-Lights: UV-A 340, chosen to simulate lights
contained in sunlight radiation between 295-365
nm
• Simulated long-term weather exposure by
applying cycles of high temperatures and UV
light, as well as condensation of water
• During weathering cycle, UV radiation happens
at a higher temperature (60°C) and
condensation happens at a slightly lower
temperature (50°C). During condensation mode
the UV light is turned off.
UVH2O
ASC October 2016 Page | 15
Sample Exposure Conditions
ASC October 2016 Page | 16
Condition 1
• UV Light
• Oxygen
• Moisture
Condition 2
• Oxygen
• Moisture
Condition 3
• UV Light
Condition 4
• No Exposure
Colorimetry Analysis:Determining the degree of yellowing
Surface Colorimeter:
• Measures the amount of light reflected in three wavelength ranges across the visible
spectrum. In our case we measured the yellowness of our samples.
• These measurements were performed after 21 days of curing and then periodically after
combinations of UV-light / water / oxygen exposure.
• For this project, yellowness is measured using the standard E313 index. The more yellow
the sample gets, the larger the number.
ASC October 2016 Page | 17
Samples After 21 Days:UV, Oxygen and Moisture Exposure
Condition 1
ASC October 2016 Page | 18
0 days
10 days
21 days
0
1
2
3
4
5
6
7
8
9
10
UV H2O O2 UV H2O O2 UV H2O O2 UV H2O O2
Blank E 1 Silane E 2 Silane Hindered Silane
Yello
wn
ess
E31
3
0 days 10 days 21 days
Samples After 21 Days:UV, Oxygen and Moisture Exposure
Blank E 1 Silane E 2 Silane Hindered Silane
ASC October 2016 Page | 19
Samples After 21 Days:Oxygen and Moisture Exposure
Condition 2
ASC October 2016 Page | 20
0 days
10 days
21 days
0
1
2
3
4
5
6
7
8
9
10
O2 O2 O2 O2
Blank E 1 Silane E 2 Silane Hindered Silane
0 days 10 days 21 days
Blank E 1 Silane E 2 Silane Hindered Silane
Samples After 21 Days:Oxygen and Moisture Exposure
ASC October 2016 Page | 21
Samples After 21 Days:UV Exposure
Condition 3
ASC October 2016 Page | 22
0 days
10 days
21 days
0
5
10
15
20
25
30
35
UV UV UV UV
Blank E 1 Silane E 2 Silane Hindered Silane
UV
0 days 10 days 21 days
Blank E 1 Silane E 2 Silane Hindered Silane
Samples After 21 Days:UV Exposure
ASC October 2016 Page | 23
Samples After 21 Days:No Exposure
Condition 4
ASC October 2016 Page | 24
0 days
10 days
21 days
0
1
2
3
4
5
6
7
8
9
10
None None None None
Blank E 1 Silane E 2 Silane Hindered Silane
0 days 10 days 21 days
Samples After 21 Days:No Exposure
Blank E 1 Silane E 2 Silane Hindered Silane
ASC October 2016 Page | 25
Amine Oxide
Colorless
Discoloration in Sealants:Azo vs Amine Oxide
Analysis of Results:
• Yellowing of adhesives and sealants may be caused azo compounds.
• The absence of oxygen causes an even worse discoloration, possibly due to
oxygen forming colorless amine oxides instead of azo compounds.
Yellow
Azo Compound
ASC October 2016 Page | 26
Benefit of Oligomeric Silanes:Steric or Shielding Effect
R O Si
A
OR´
O Si O R
B
OR´a b >
E 2 Silane
ASC October 2016 Page | 27
Analysis of Results:
• Steric bulk reduces yellowing of adhesive and sealants
• E 2 Silane alkyl groups and oligomeric structure provides the highest degree
of steric bulk and shield the amine from Azo formation.
• Hindered aminesilanes offer shielding as well, but not the magnitude of E 2
Silane.
Conclusion
ASC October 2016 Page | 28
Key Points Learned:
• E 2 Silane performed significantly better than the Hindered Silane when exposed to
UV light in vacuum
• Under all other conditions, the three silanes gave similar low yellowing results.
• Hindered silanes do not out-perform E 1 Silane and E 2 Silane under typical sealant
conditions.
• Multiple types of advanced silanes can be used to formulate adhesives and
sealants with low yellowing potential.
0
5
10
15
20
25
30
35
None UV O2 UVH2OO2
None UV O2 UVH2OO2
None UV O2 UVH2OO2
None UV O2 UVH2OO2
Blank E 1 Silane E 2 Silane Hindered Silane
Yello
wn
ess
E31
3
21 days
Tim BiggsResource Efficiency
Head of Applied Technology
2 Turner Place
Piscataway, NJ 08876
phone: 732-718-1219
Chelsea StantonResource Efficiency
Marketing Adhesives & Sealants
299 Jefferson Road
Parsippany, NJ
phone: 973-929-8551
ASC October 2016 Page | 29
Evonik Contacts for Questions
ASC October 2016 Page | 30