surface energetics and adhesion - spe...
TRANSCRIPT
The content of this presentation is proprietary and confidential information of BTG Labs. It is not intended to be distributed to any third party without written consent of BTG Labs.
UnderstaUnderstanding and Controlling the Bond Surface in
Manufacturing for Reliable Adhesive Bonding of Composites
Surface in Manufacturing for Reliable Adhesive Bonding of Composites
BTG Labs
Cincinnati, OH USA
© 2017 BTG Labs
Agenda
• Who is BTG Labs?
• What is a surface?
• Measuring Surface Energy – why does this matter?
• Contact Angles as a convenient way to measure Surface Energy
• The Four Fundamentals of Controlling your Surface
• Correlating contact angles to system performance
• The Surface Analyst™
© 2017 BTG Labs
BTG Labs is the inventor of the patented Surface Analyst™, a fast, easy, accurate, and nondestructive instrument that quantifies surface preparation from the lab to the manufacturing floor.Our customers include:
• Aerospace• Biomedical• Electronics• Automotive OEMs and suppliers
Whose products depend on their ability to:• Bond• Coat• Seal• Paint• Clean
In an effective and predictable manner.
The Surface Analyst, along with our material science expertise helps companies better understand and define reliable surface preparation processes.
Who is BTG Labs?
© 2017 BTG Labs
What Differentiates a Surface from the Bulk?
Newly created Seconds later Minutes to hours later
Brittle and/or glassy materials:
© 2017 BTG Labs
30
32
34
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40
42
44
0 2 4 6 8 10 12
Surf
ace
Ener
gy (
mJ/
M2
)
Elapsed Time From Surface Creation
Manifestation of Surface Energy
• Rate of surface energy decay depends on initial surface, surface energy and environment
Point of Failure
Oxidation/hydration
Contaminant adsorption
Pristine
© 2017 BTG Labs
Methods Utilized in Manufacturing
Dyne InksWater BreakContact Angle
© 2017 BTG Labs
Contact Angles and Surface Energy
• An isolated liquid drop in the absence of external forces assumes a spherical shape
• Upon contact with a surface, drop shape is determined by the balance of liquid-liquid vs liquid-solid forces
© 2017 BTG Labs
Contact Angles for Evaluation of WA
• Work of adhesion: energy released when an interface is created
WA = l +s - sl
• Combine with Young equation:
γs = γsl + γl cosθ
• Allows direct measurement
WA = l(1+cosq)
© 2017 BTG Labs
• Contact Angle of incoming material• Supplier quality check
• How does the material respond to processing?
• Plasma• Grit blast• Washing• Solvent cleaning• Etc.
• How long does the processing last?• What is the shelf life?
• What is the appropriate contact angle to guarantee performance?
• At what point is my surface no longer acceptable?
4 Surface Fundamentals for Manufacturing and Repair
© 2017 BTG Labs
θH2O for Determination of Optimum Cleaning Process
© 2017 BTG Labs
Surface Preparation Process: Composites
Sanding and Solvent Wiping: Composite Panel
-
10.0
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50.0
60.0
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100.0
S1: Tool Side S3: Bag Side
Wat
er C
on
tact
An
gle
(Deg
rees
)
As Rec'd Solvent Wipe Sand and Solvent Wipe
• Water contact angle determines the most effective preparation process for composites
© 2017 BTG Labs
Surface Preparation Process: Composites
Contact angle measurements provide rapid, quantitative feedback about the effect of
surface treatment parameters that affect adhesion, and provide control limits for
transferring these processes into manufacturing
0
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20 30 40 50 60 70 80
Load
at
Failu
re (
Lbs)
Water Contact Angle (Degrees)
Single Lap Shear vs Contact Angle
over sand
spec sand
under sand
solvent wipe, no sand
© 2017 BTG Labs
Detection of Siloxane on Bond Surface via Surface Analyst™
-5
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0 10 20 30 40 50
Ato
mic
% S
i
Wat
er
Co
nta
ct A
ngl
e, d
egr
ee
s
µg/cm2 Silicone (Frekote 44)
WCA XPS17% Interfacial Failure, unacceptable amount
© 2017 BTG Labs
θH2O as Quantitative Prediction of Adhesion
GIc vs drop diameter (3µl DMSO)
0
0.5
1
1.5
2
2.5
3
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0 10 20 30 40 50 60 70 80
Contact angle
GIc
, in
-lb
/in
2
Failure remains interlaminar after 14 days in DI H2O @ 122° F: no crack growth
Wedge test
• Adhesives are liquid when applied to a surface
• The way a simple liquid like water adheres to a surface predicts the way an adhesive will adhere
• A water contact angle can make this prediction in about 2 seconds
Adhesive failureCohesive failure
© 2017 BTG Labs
Surface Analyst and Quality Assurance
• Sensitive to contamination level well below that which affects adhesive joint performance
• Quantitatively correlates to adhesive joint strength, toughness, failure mode
• Operator receives immediate ‘pass/fail’ indicator for bonding operations
• QC engineer receives detailed information about process drifts due to operators, climate, materials
GIc vs drop diameter (3µl DMSO)
0
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1
1.5
2
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0 10 20 30 40 50 60 70 80
Contact angle
GIc
, in
-lb
/in
2
Pass Fail
© 2017 BTG Labs
Cleaning and Preparation Methods Need to be Quantified
• There are many methods available when engineering surfaces to improve adhesion
• These methods are only as effective as the processing parameters set with the Surface Analyst
• These can be accomplished quantitatively using Surface Analyst contact angle measurements
– Reveal uniformity of treatment
– Differentiate between different treatment levels
– Predict adhesion
– Well suited to manufacturing environments and statistical process control methods
© 2017 BTG Labs
What Parameters Control our System?
• Surfaces have different properties from bulk materials
– Higher reactivity: surface energy
• This excess energy is why materials stick together when brought into contact
– Systems tend towards lower energy states
• Contact angle measurements can be a convenient probe of surface state
• Contact Angle of incoming material• How does the material respond to processing?• How long does the processing last?• What is the appropriate contact angle to guarantee
performance?
© 2017 BTG Labs
The Surface Analyst™
• Fast - 2 second inspection• Easy - anyone can use it• Accurate – clean to a number• Non-destructive – will not harm
part being inspected• Flexible – multi-directional
inspections, can be used in many industries and applications
• Repeatable – passes Gage R&R
© 2017 BTG Labs
Why Did We Build The Surface Analyst?
• Prior to development of the Surface Analyst™, practical tools for qualifying surface preparation in manufacturing and repair environments did not exist
• In response to this and in conjunction with the Aerospace industry leaders we built the Surface Analyst ™
© 2017 BTG Labs
Ballistic Deposition Video
© 2017 BTG Labs
Ballistic Deposition Video
© 2017 BTG Labs
• Small droplet (<2 μl) of probe fluid is created on the surface from a pulsed stream of micro drops
• Contact angle is calculated from drop volume and drop diameter• 2 sec measurement cycle
– Single button operation– No operator input
• Designed to be used on the factory floor
d
V
How Does the Surface Analyst Work?
© 2017 BTG Labs
Fast & Accurate
• Measurements in just 2 seconds• Instrument gives an immediate contact angle or pass/fail indication • Sensitive to the first 2-3 molecular layers
The content of this presentation is proprietary and confidential information of BTG Labs. It is not intended to be distributed to any third party without written consent of BTG Labs.
Surface Analyst Gage – Aluminum
A1007
Surface Analyst Gage – Composite
A1007
• Passes Gage R&R
• Quantitative and objective measurement
Repeatable
Aluminum Carbon Fiber Composite
Operator to operator correlation on prepared and unprepared:
© 2017 BTG Labs
Easy & Flexible
• The Android operating system makes it easy for anyone to operate
• Tethered head allows access into small or difficult areas and in multi-directional angles
• Single Button operation
Vertical inspection on engine block seal Convex inspection on medical catheter
© 2017 BTG Labs
The Surface Analyst™
• Fast - 2 second inspection• Easy - anyone can use it• Accurate – clean to a number• Non-destructive – will not harm
part being inspected• Flexible – multi-directional
inspections, can be used in many industries and applications
• Repeatable – passes Gage R&R
© 2017 BTG Labs
Surface Energy and Composition
Material Surface
Energy
(mJ/m2)
Relative
Interfacial
Toughness
(Gint)
PTFE 18 Lowest
Polyethylene (PE) 31
Epoxy 42
Plasma treated PE 50
Silica (SiO2) 287
Aluminum oxide 638 Highest
© 2017 BTG Labs
• WA of high l liquids are most sensitive to substrate surface
energy
• q 30° maximize WA for all adhesives
Contact Angle of a Liquid as a Function of Surface Energy
© 2017 BTG Labs
What matters when measuring Surface Energy?
-10.0
0.0
10.0
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50.0
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70.0
-0.2 0 0.2 0.4 0.6 0.8 1 1.2
Cos H2O contact angle
Su
rface
en
ergy (
mJ/m
2)
Total surface energy
Polar
Dispersive
cosθ = (γsl – γs)/ γl
Dillingham, Oakley et al. J. Adhesion Science and Technology V29 9 (2015).
© 2017 BTG Labs
θH2O Is what you need for Energy Indication
© 2017 BTG Labs
θH2O as a Surface Energy Probe
© 2017 BTG Labs
Surface Analyst™ Contact Angle vs WilhelmyBalance Corona Treated BOPP film
© 2017 BTG Labs
Contact Us
5129 Kieley Place
Cincinnati, OH 45217
513.469.1800
Lucas Dillingham
www.btglabs.com