PU coated - European Coatings

Transcription

Protective and Insulative Coatings
for e-Fibers
Sumedh Ganu1, Hélène Ritter1, Patrick Rupper1, Felix A. Reifler1, Markus Faller2,
Christian Roth3, Matthias Neisius1, Sabyasachi Gaan1
European Coatings Conference │Functional Coatings
05 – 06 June 2012 Berlin/Germany
1Advanced
2Corrosion
Fibers, Empa, Swiss Federal Laboratories for Materials Science and Technology, St. Gallen
and Materials Integrity, Empa, Swiss Federal Laboratories for Materials Science and Technology, Duebendorf
3Institute
of Process Engineering, ETH, Swiss Federal Institute of Technology, Zurich
2
Overview
EMPA at a glance
Background (Tec InTex Project), Objectives
Approach: Method of Coating, Choice of Polymer
Effect of Coating Parameters: Submicron-Micron Coatings
Efficacy of Coatings: Electrical Insulation, Reflectance
Measurements and Corrosion Protection
Wash Permanency and Strip-off
Conclusion
3
EMPA at a glance
Conclusion
4
Our Vision
Materials and Technologies
For a Sustainable Future
Mission of EMPA –
Bridging Research and Applications
5
 Use-inspired Materials Science & Technology Development
 Interdisciplinary Know-how
 Efficient Technology Transfer
 For the Benefit of Industry
 For the Welfare of Society
 Committed to Excellence in all our Activities
6
Empa Today
Swiss Federal Laboratories of Material Science and Technology
937 employees (513 scientists)
24 Professors
61 Postdocs
111 PhD students
204 Interns
39 Trainees
St. Gallen
Dübendorf
Thun
110 mill $ federal funds
57 mill $ third-party
Focal areas
nanotechnology
sustainable buildings
natural resources
energy technologies
health & performance
 Applied research together with and for the industry
St. Gallen
7
EMPA at a glance
Conclusion
8
Tec InTex (e-Fibers)
EMPA, ETHZ, CSEM, UniZH
Yarns
Flexibility
2009-2012
Electronics
Textile
Ag sputtering (Argon)
+
e-Fiber
500 nm
Monofilament / Multifilament
Plasma Metallized Fibers:
Silver layer 100-200 nm
Integrating textiles and electronics:
Wearable functional clothes
9
e-Fiber Development
Objectives





Thin flexible protective coating
Minimal effect on handle – textile character
Electrical insulation , corrosion-resistance
Transparent coatings – metallic appearance
Suitable striping technology for interconnection
Tarnishing of Silver
Solution Coatings of
monomer or polymers
Melt Coating of polymer
Layer by layer assembly*
Insulating/Protective Coating
* Ultrathin, Flexible, and Transparent Polymer Multilayer Composites for the Protection of Silver Surfaces
Jens Langecker, Helene Ritter, Audrey Fichini, Patrick Rupper, Markus Faller, and Barbara Hanselmann
ACS Applied Materials & Interfaces 2012 4 (2), 619-627
10
EMPA at a glance
Conclusion
11
Dip Coating Approach
 Simple, inexpensive and efficient dip-coating process
 UV-curable PU dispersion
The main advantages of these UV-curable PU coatings are:
 easy and fast application
 environmentally benign (no use of solvent)
 uncured portions can be washed off very easily while the cured coatings
have excellent washing fastness.
 possibilities of interconnections to other electronic components
12
Theory of Dip-Coating
 Landau-Levich-Derjaguin* (LLD) Theory
For Newtonian fluids:
Coating thickness dependant on Capillary number
h/r ~ (Ca)2/3
Capillary number is defined by:
Ca = (ηV/σ), where η = solution
viscosity, V = withdrawal velocity and
σ = surface tension of liquid
*FLUID COATING ON A FIBER, Annual Review of Fluid Mechanics,
Vol. 31: 347-384 , 1999
13
LLD Theory
For a given radius r,
Coating
speed
(V)
h ~ (Ca)2/3
Competetive Forces
Coating
thickness
(h)
Surface
Tension
(σ)
Liquid
Viscosity
(η)
Non-Newtonian fluids exhibit a considerable variation from the
LLD theory.
14
Dip-Coating Machine with UV-Curing Unit
Drying units
drying unit 1 = 120 °C
speed controller
coating solution
UV curing chamber
drying unit 2 = 120 °C
main rollers
(synchronised)
Reifler, F. A.; Sanchez, F. A. L.; Clemens, F. J.; Varga, K.; Hufenus, R., Composites
Science and Technology, 2010, 70 (8), 1207-1213
UV curing chamber
15
Coating Conditions

Fiber: Polyamide 66 monofil (100-200 nm silver-layer), diameter ≈ 78 µm

Coating Solution :
- PU dispersion = Bayhydrol UV XP 2736 (40% solid content)
- Thickener = Carboxymethylcellulose (CMC)
- Surfactant = Triton X100
- Photo-initiators = Benzophenone, 1-hydroxycyclohexyl phenyl ketone, 1:1 ratio

Coating speed : from 0.67 to 8.76 m/min

UV Lamp Power : 60 to 120 W/cm

Viscosity : Varying CMC conc. = 0 to 10%, Dilution of PU Dispersion
UV-curable PU dispersion
Isophorone Diisocyanate (D)
Polypropylene Glycol (P)
2-hydroxyethyl Acrylate (A)
Benzophenone (B)
+
PU Dispersion





UV-curing
Flexible films
Bayhydrol - Urethane Acrylate dispersion in water
Before UV curing, the surface is soft and slightly tacky
After UV-curing, the surface is flexible with good chemical and mechanical
resistance
Free-radical Photo-initiators: Benzophenone, 1-hydroxy-cyclohexyl-phenylketone
UV wavelength region: 250-330 nm
17
Transparency of PU coatings
UV-curable Bayhydrol PU coatings on glass plates
Transmission ≈ 100%
111,00
109,00
% Transmission
107,00
105,00
Glass
PU 6.3 microns 1
PU 6.3 microns 2
PU 13 microns 1
PU 13 microns 2
103,00
101,00
99,00
97,00
95,00
400,00
500,00
600,00
Wavelength (nm)
700,00
800,00
18
Coating Recipes
HIGH VISCOSITY COATING SOLUTIONS
Name of the solution
Weight of CMC preparation
(3.5wt% stock paste in water)
Weight of Bayhydrol
PU
CMC1
CMC2.5
CMC5
CMC10
0
1
2.5
5
10
100
99
97.5
95
90
Weight of photoinitiators (Benzophenone
/ 1-hydroxycyclohexyl phenyl ketone =
1/1)
3
3
3
3
3
LOW VISCOSITY COATING SOLUTIONS
Name of the solution
Solid content
(wt %)
Weight of Bayhydrol
(40wt% solid content)
Weight of water
PU32
PU20
32
20
80
50
20
50
Weight
of
photoinitiators
(Benzophenone
/
1hydroxycyclohexyl
phenyl
ketone = 1/1)
3
3
19
Rheology of the Coating Solutions
•
•
•
Shear Thinning
Concentric-cylinder-type rotational rheometer
PU dispersion shows shear thinning behaviour
As CMC conc. increases, viscosity increases, shear-thinning behaviour also increases
0,5
CMC10
0,45
CMC5
0,4
CMC2.5
Viscosity Pa.s
0,35
CMC1
0,3
PU pure
0,25
0,2
PU32
0,15
PU20
0,1
0,05
Newtonian
0
100
Shear rate 1/s
1000
20
EMPA at a glance
Conclusion
21
PU Coatings of Metallized Fibres
Uncoated plasma-metallized silver fibres:
rough & irregular surface
PU coated silver fibres:
smooth, uniform and continuous
22
AFM Analysis
Original PA 66 fibres – striations
Plasma-metallized silver fibres
– silver nano-particles
23
AFM Analysis
surface roughness (nm)
500
450
Sa
400
Sq
350
300
250
200
150
100
50
0
PA66 fibre
PA/silver fibre
PU coated uncured
PU coated - uncured
PU coated - UVcured
PU coated – UV-cured
24
Cross-section SEM
• PU coatings cover original surface
irregularities of plasma-metallized fibres
• Coating thickness is uniform across the
diameter and length of the fibres
25
PU nano-Coatings
Obtained by dip-coating at very
low speeds and viscosities
•
•
Minimum coating thickness of
409 nm
Some breakages or faults in
nano-coating due to fibrediameter irregularities
26
Effect of Viscosity and Coating Speed on Coating
Thickness
Increased Viscosity
CMC10
16
CMC5
CMC2.5
14
CMC1
PU
coating thickness (microns)
12
PU32SC
High coating speeds and
viscosity – thick and stable
coatings
PU20SC
10
Very low coating
speed – surface
tension should
be optimised for
better coating
results
8
6
4
Thin & stable coatings
2
Very low viscosity and coating
speed - breakages
0
0
1
2
3
4
5
coating speed (m/min)
6
7
8
9
27
Effect of Surfactant on Coating Thickness
Measured Surface Tension
γ (mN/m)
PU with 1%
Triton X 100
47.1
PU
65.7
𝜌𝑔
𝜎=
𝑐
h ~ (ηV/σ)2/3
Where:
𝜎 is surface tension (N/m)
𝜌 is density of liquid (kg/m3)
𝑔 is acceleration due to gravity (9.8 m/s2)
𝑐 is capillary constant (m-2) calculated from the
software*
7,0
PU+ 1% Triton X100
Coating Thickness (h) [µm]
Solution
PU
6,0
5,0
4,0
3,0
2,0
1,0
0,0
0,0
2,0
*ImageJ Plugin – LB-ADSA (Low Bond Axisymmetric Drop Shape Analysis)
4,0
6,0
Coating Speed [m/min]
8,0
28
EMPA at a glance
Conclusion
29
Electrical Insulation of PU Coatings
*
Standard Test Method SEV TP 20B/3C
*Britton, L., Avoiding Static Ignition Hazards in Chemical Operations. Center for Chemical Process,
American Institute of Chemical Engineers, New York, USA, 1999
30
Transparency of PU coatings
Uncoated
1µm thickness
4µm thickness
Reflectance values at 555nm for subsequent experiments
31
Corrosion-Resistance of PU coatings



H2S test – 0.5 ppm for 72 hours
Silver is highly vulnerable to
sulphur compounds
PU coating protects corrosion of
silver
a
b
c
d
a – PU coated silver fibres
b – uncoated silver fibres exposed to H2S
c – PU coated (uncured) silver fibres exposed to H2S
d – PU coated (UV-cured) silver fibres exposed to H2S
(DIN IEC 50B 345)
32
H2S Corrosion Protection: Effect of Coating Thickness
100
90
Degree of Corrosion* (%)
80
70
60
50
Minimum thickness of 2 µm required for protection
40
30
20
10
0
0
2
4
6
8
10
12
14
16
Thickness of the PU coating (in µm)
0.5ppm of H2S, 48 h, 75% relative humidity and 25°C (DIN IEC 50B 345)
*=
𝑅𝑐𝑜𝑟𝑟𝑜𝑑𝑒𝑑 −𝑅𝑢𝑛𝑐𝑜𝑟𝑟𝑜𝑑𝑒𝑑 𝑐𝑜𝑎𝑡𝑒𝑑
𝑅𝑐𝑜𝑟𝑟𝑜𝑑𝑒𝑑 −𝑅𝑢𝑛𝑐𝑜𝑟𝑟𝑜𝑑𝑒𝑑 𝑢𝑛𝑐𝑜𝑎𝑡𝑒𝑑
18
33
Corrosion Kinetics
0.5ppm of H2S, 75% relative humidity and 25°C (DIN IEC 50B 345)
34
EMPA at a glance
Conclusion
35
Accelerated Washing Tests*
 Uncured = washed-off in 5 mins at 60°C with ECE surfactant
 UV cured = intact even after 24 hours at 60°C with ECE surfactant.
Also withstands 3 hours washing with 10 steel balls at 60°C with
ECE surfactant
cured
*ISO 105 C06 Accelerated Washing test
uncured
36
Selective UV-curing
Metallized Fiber
Input power: 2000W
for 10-15 secs
Weaving /
Knitting
UV
Exposure
UV Curable Coating/
Insulation
Exposed fiber surface for
connection to sensors/ICs
UV
Resist
Washing
37
Selective UV-curing
 Dip-coating at 5.35 m/min
with CMC2.5:
thickness = 3.6 microns
 Very apt for use in interconnection technologies
38
EMPA at a glance
Conclusion
39
Conclusion
Flexibility,
Elasticity
Submicron
to Micron
coatings
Electrical
insulation
Corrosion
resistance
H2 S
Water based
UV-curable
system
PU coatings on
Metallized
fibers
Simple
dip-coating
process
40
Acknowledgements
Sumedh Ganu
Helene Ritter
Dr. Sabyasachi Gaan
Scientifically evaluated by the SNSF” as well as
“Financed by the Swiss Confederation” and
“Funded by Nano-Tera.ch”

PU coated - European Coatings

Transcription

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