two part sealants adhesives
TRANSCRIPT
Two Part Sealants/Adhesives
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Silicone
Adhesives/Sealants
RTVRoom Temperature
Vulcanizing
Products
HTVHeat Cure
Materials
1-part RTVMoisture Cure
2-part RTVNo Moisture Cure
2-part Heat CureAdhesives
1-part Heat CureAdhesives
Acetoxy Cure Oxime Cure
Alkoxy CureSilicone Reactive
Hotmelt
Alkoxy Cure
Silicone FoamCompression Gaskets
2-part CIPGCured In
Place Gaskets
Silicone Adhesives/Sealants C
on
den
sati
on
Cu
re Ad
ditio
n C
ure
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2-part RTV: How do 2-part RTV‘s cure?
• 2-RTV Cure = Condensation Cure (=Cure By-Product)
• 2-part Alkoxy Cure materials do NOT require humidity to cure
• The Cure Speed of 2-part RTV‘s (Alkoxy Cure System) can be influenced by:
– Product • E.g. Q3-3636 is faster than Q3-3526
– Temperature• Cure speed can be accellerated by applying moderate temperatures
(typically < 65°C)
– Mix Ratio• Higher Catalyst Level deliver faster snap/tack free time values
Just applied Cure continues
(Tack Free Time)
Fully cured
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2-part RTV: Alkoxy Cure System
• Features/Advantages:– 2-part System (typically 100:10)
– Does not need humidity to cure
– Give off Methanol as by product(neutral)
– Non corrosive
– Low odor
– Service Temperature Range: typically - 50 to +180°C
– Fast Cure at Room Temperature (typically < 20 min to handle parts)
– Cure speed depends on
• Temperature
• Mix ratio
• Disadvantages/Limitations:
– Upper operating temperature limit at
about +180°C
– Requires 2-part
meter-/mix equipment
– Currently not commercially available
in small cartridges
• For sampling only !!!
Si-OH + Si-OMe Si-O-Si + MeOH
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The components must be stored separately, and mixed just before
Application:
Base Curing agent
Polymer
+ H20Cross-linker
+ catalyst
+ adhesion prom.
OR
Polymer
+ cross-
linker
+ H2O
+
+Catalyst
+ adhesion prom.
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2-part RTV’s (Alkoxy Cure)
Product Mix
Ratio
Working
time, min.
Hardness
(Shore A)
Elongation at
Break, %
Tensile
Strength,
MPa
Color(s)
Q3-3526 100:10
to
100:15
5-10 38-40 280 2.0 Grey
(RAL 7038)
Black
(RAL 7016)
Special Black
(RAL 9011)
EA 2626 100:10
to
100:15
4-10 40-43 280 2.0 Grey
Q3-3636 100:13
to
100:17
3-10 35-38 250 1.9 Grey
Black
Special Black
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What effect do the ingredients have on Speed of cure & Adhesion ?
on cure speed on adhesion
1. Amount & type of tin catalyst large effect small effect
2. Amount & type of cross-linker large effect medium
effect
3. Amount & type of adhesn. Prom. medium effect large effect
4. Temperature small effect medium
effect
Differences between Q3-3636 & Q3-3526 Adhesives : 3636 vs 3526Higher concentration of tin, cross-linker, and adhesion promoter
As a consequence, Q3-3636 cures faster, and also has a bit better
adhesion than Q3-3526. The adhesion under hot/humid conditions is
also better. In addition, the polymer type & and additives used reduce fogging
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FIPG Concept / 2 Part RTV
1. ApplicationRobotic application
of 2-part RTV
silicone
A B
2. Assembly of the
mating part3. Curing at RT
(optional at elevated
temp.)
4. Finished Part
Part can be tested
within 30 min.
A two part silicone adhesive is dispensed onto a part, the mating
surface is assembled and adhesive is cured providing a sealed unit
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Benefits vs Limitations / 2 Part RTV
Benefits and Features• Provides an environmental seal against air, water, dust, moisture
• Excellent weathering, UV and heat resistance to 150-190C
• Excellent for adhering parts with different thermal expansion rates
• Fast cure at RT compared to 1 part RTVs
• Develops adhesion strength rapidly at RT
• Good durable unprimed adhesion to many plastics, metal and glass
• Nonslump when mixed - extruded on any part without flow issues
• Non-corrosive and low odor during cure
Limitations• Potential reversion in confined applications exposed to high heat
• Needs to be tested
• Not compatible with Pt catalyzed products: CIPG, DFG
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Properties / Q3-3636 Components
•Q3-3636 BaseColor White Paste
Viscosity (mPa.s) 200,000
Density (g/cc) 1.30
Shelf life (based on DOM) 12 months @ 23C
Recommended storage temp 0-32C
Q3-3636 CatalystGray Black Sp Black
Viscosity (mPa.s) 18,000-48,000 55,000-135,000 200,000
Density (g/cc) 0.99 1.01 1.03
Shelf life (based on DOM) 5 months at 23C
Recommended storage temp 10-25C
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Processing / Q3-3636
• Handling Information– Base: keep covered to prevent contamination
– Catalyst
• Moisture sensitive
• Flammable and corrosive
• Equipment information– Feed Base & Catalyst via follower plate : 250 kg drum, 25 kg pail
– Meter via piston or gear pumps (7:1 to 5.8:1 by volume)
– Teflon lined hoses for curing agent
– Mix via disposable static mixer : 3/8 to ½” diam, 24-36 elements
– Purge mixer after 60 secs. if in standstill.
– Replace mixer every 2-4 hours
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Typical Production Line Layout/ FIPG
A B
Metering via piston or gear pumps
Static mixer
Meter-/mix equipment
Part
Drum/pailpumps
Part loading Robotic Application
Conveyor
belt
Finished parts
Pressure
testing
I.R or convection heating
tunnel : 10-20 min / 40-65C
(optional, for faster speed)
Suggested EQUIPMENT MFGRS:
• Graco
• SEE
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Adhesion / Q3-3636
• Q3-3636 contains adhesion promoters for primerless adhesion to
many plastics, glass and metals.
• Cure will develop quickly but adhesion requires time.
• Adhesion speed depends on substrate: glass > metal > plastic
• Proven adhesion to plastics: PC, ABS, PBT, PET, Acrylics,
Polyamides, GE’s Ultem
• Low energy plastics (PP, PE) require surface treatment such as cold
plasma, corona, primer, or flame treatment
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Adhesion / Q3-3636
• For best adhesion results
– Clean substrates are essential
– Temp >15C and humidity >40%RH is recommended
– Substrate temperature >20C
• Adhesion can be accelerated with moderate heat
– Warm the substrate before adhesive application: 35-45C
– Apply heat after part is assembled: 10-15 mins at 50-65C
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Adhesion / 3-3636 vs 1 Part Sealants
Lap Shear Strength vs Time for DC Sealants
0.00
0.50
1.00
1.50
2.00
2.50
3 6 18 24 168
Time (Hrs)
Lap
Sh
ear
(MP
a)
DC 3-3636
DC 3-7062
DC3-7091
DC 3-0117
DC 9-1350
Polycarbonate to f lame treated Polypropylene
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Rate of Adhesion Development/Q3-3636
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
PC PA PP PBTP Steel
Substrate (glass / plastic)
Lap
shear
MPa
30 mins
60 mins
7 h
RT Cure
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Polymer Crosslinker 3-dimensional Network
“Pt”Si-CH=CH2 Si-H Si-CH2 - CH2-Si+
Cure In Place Gaskets – Heat Cure
• Heat Cure = Addition Cure
• Heat is typically required to start cure process (normally > 100°C)
• The higher the cure temperature the faster the cure speed
• Products do NOT require humidity to cure
• Heat is required to cure the product AND to develop adhesion
(To obtain good adhesion you require more energy than for the curing
only)
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Cured In Place Gaskets - Heat Cure
• Features/Advantages:– 1- or 2-part Systems available
– No cure by product, hence no shrink (very little shrink)
– Non corrosive
– Low odor
– Good deep section cure
– Good adhesion to many plastics and metals
– Service Temperature Range: typically - 50 to + 250°C
– Very fast cure when exposed to elevated temperatures
• Disadvantages/Limitations:
– Requires heat to cure and develop
adhesion
– Risk of Cure Inhibition
(Pt-Catalyst can easily be poisoned)
Si-CH=CH2 + Si-H Si-CH2-CH2-Si
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CIPG – CURED IN PLACE GASKETS
• 2-part heat cure products are directly dispensed and cured onto the
part surface to be sealed
• provides a high performance integrated compression seal
1. Application 2. Curing
with heat
3. Transport
Typically cured
Within 5-10 minRobotically Applied
4. Assembly
HEAT
Part ready for
Next Action
A B
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Benefits vs. Limitations / CIPGFeatures/Benefits:
• Seals via compression
• Fast cure at elevated temperature (8-10 min. at 150 °C)
• Cost effective compared to manual assembly
• Application at tiered supplier
• Gasket reusable
• Precise fit of the gasket (stay in place adhesion)
• Medium to high clamping forces
Limitations/Disadvantages:
• Heat cure process not applicable to some substrates
• Aspect ratio may not be sufficient to compensate tolerances on
narrow flanges
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Product Features / CIPG
• 2-part heat cure systems (no cure by-products)
• 1:1 mix ratio
• Controlled Rheology (Rheology is the science of deformation and flow)
• Self priming
• Fluid resistant
• Various hardness's available
• Safe processing (products do not require CFC’s or other
environmentally harmful materials for processing)
• Sold as A&B kits (specific properties are certified)
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Dow Corning® D94-20P
• Extrusion Rate
– Part A 140 g/min
– Part B 240 g/min
• Hardness, Shore A 21
• Specific Gravity 1.19
• Tensile Strength 5.3 MPa
• Mod. 100% 0.40 Pa
• Elongation 900 %
• Lap Shear Adhesion
– on Al 0.70 MPa
– on Vinyl Ester 0.90 MPa
• Compression Set, -25%
– 22 h 132 °C39 %
• Specifications
– GM 236M Type 1
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Dow Corning® D94-30P
• Extrusion Rate
– Part A 75 g/min
– Part B 180 g/min
• Hardness, Shore A 32
• Specific Gravity 1.20
• Tensile Strength 7.2 MPa
• Mod. 100% 0.80 MPa
• Elongation 820 %
• Lap Shear Adhesion
– on Al 0.80 MPa
– on PA 6.6 0.90 MPa
• Compression Set, -25%
– 22 h 177 °C45 %
– 24 h 150 °C25 %
• Specifications
– GM 236M Type 2
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Dow Corning® D94-45M
• Extrusion Rate
– Part A 120 g/min
– Part B 230 g/min
• Hardness, Shore A 42
• Specific Gravity 1.20
• Tensile Strength 7.3 MPa
• Mod. 100%, 1.45 MPa
• Elongation 600 %
• Lap Shear Adhesion
– on Al 1.05 MPa
– on PA 6.6 1.35 MPa
• Compression Set, -25%
– 22 h 177 °C30%
– 24 h 150 °C15%
• Specifications
– Chrysler MS-GF 42B
– BWM 54160-MVQ-50
– VW AMV 176 810
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Application equipment / CIPG
• Dow Corning CIPG products are being applied via commercial available 2-part
meter-/mix units direct onto the part to be sealed
• A typical application unit consists out of:
– Pneumatic Drum Pumps (Product Supply)
– Gear/Rod Metering Pumps ( Servo Metering)
– Static Mixer (Mixing)
– 6-axis Robot or xyz-Table (Application)
– Pallet Conveyor Belt with Part Fixturing
– Oven (Curing)
The only difference between a DFG (Dispensed Foam Gasketing) system and the CIPG System is the addition of a zero cavity dispense valve at the end of the dispense head on the DFG System.
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Typical layout of a production line / CIPG
(optional)
A B
Metering pumps
Static mixer
Meter-/mix equipment
Part
Drum
pumps
Part loading Robotic Application
Pre-treating
Heating tunnelConveyor
belt
Finished parts
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Fixturing / CIPG
• Good fixturing is critical for repeatable / accurate dispensing
• Corrects for part to part variation
• Maintains part alignment
• Poor fixturing will lead to irregular gasket beads
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The Cure Process / CIPG
• Dow Corning CIPG products require heat and timefor complete curing and obtaining adhesion
• Typical part temperature during last 2-3 minutes of an 6 to 8 minute cure time: >138 °C
• Typical total time: 6 - 10 min.(Larger thermal masses take more time to reach temperature)
• Note: Heating time is not equal cycle timeThe cycle time is the dispensing time and, therefore, depending on the contour of the part (length of bead/robot speed + move to next part)
• Any method that heats the seal material is acceptable, heat is the important factor.
– Air ventilated oven
– Infrared
– Gas Fired
– Electric heated
– Microwave ?
• Pre heating is normally not required
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Typical CIPG Cure Schedule
0
40
80
120
160
0 3 6 9 12 15
130 °C
Time, min.
Tem
per
atu
re, °C
150 °C
TTop (Top of Gasket)Heat
Tint (Interphase)
TInside
t (TInt > 130°C) 3 min
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Capitol Concerns
How much do these things cost?
• Minimum Capitol cost for CIPG is approx. $100,000.00
– System would be small xyz robot with servo driven meter-mix, fixture
nest’s, small IR conveyor oven.
• Maximum could be from $750,000 to $1,000,000.00
– System could be large xyz or Articulated Arm with servo driven
meter-mix and integrated system monitoring and with data recording,
Automated part measuring and bead profile system, with bead
inspection and data collection, (Fully integrated cell)
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Cure Inhibition / CIPG
• Dow Corning CIPG materials are addition cure products containing Pt-
catalysts
• Certain chemicals, curing agents and plasticizers can inhibit cure. These
include:
– Organo-tin compounds
– Silicone rubber containing organo-tin catalysts
– Sulphur
– Polysulfides
– Polysulphones and other Sulphur containing Materials
– Amines
– Amides
– Urethanes
– Azides
– etc....
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Adhesion / CIPG
• All CIPG materials contain adhesion promoters for primerless
adhesion to many plastics and metals.
• Heat and time (3-4 mins > 138 °C, measured at the contact area
between gasket and part) is needed for adhesion promotion.
• Not all materials adhere equally. Naturally there are exceptions. Dow
Corning will perform adhesion testing on a customer’s substrate and
recommend materials.
• If higher degree of adhesion is required, surface treatments such as
cold plasma, corona, primer, or flame treatment are recommended.
• Part design considerations such as grooves and channels can also
improve adhesion (stay-in-place adhesion)
• Adhesion may be less successful on low energy plastics such as
polyethylene, polypropylene or PTFE.
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How to apply a CIPG gasket bead ?
Part
surface
Overlap
StopRobot movement
Stop of dispensing
Start of dispensing
Robot movement
Start
Part
surface
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Bead Profile Parameters / CIPG
• Program (how the robot moves the
nozzle relative to the part)
• Nozzle tip (diameter, shape)
• Throughput Rate (amount of material
that is dispensed per second)
• Robot Speed
• Distance Tip – Substrate
(recommended about .020“ to .03“ over
the height
of the final gasket)
• Fixturing
(to ensure the part has always the same
relative distance to the nozzle tip)
h
b
Typical Aspect Ratio:
0.7-0.85
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Bead/Groove Design Considerations / CIPG
• A groove is not essential for CIPG, but advantageous for some
applications.
Examples:
I flat surface
II shallow groove, recommended
for partially decoupled parts
III groove design for direct flange contact
(L-shaped)
IV groove design for direct flange contact
(U-shaped)
recommended for direct oil contact
I II
III IV
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Guidance to the gasket bead dimensions
wb
th
h b
1 1.3 0.1
1.5 2.0 0.2
2 2.6 0.3
2.5 3.3 0.3
3 3.9 0.4
3.5 4.6 0.4
w ~ 3 · t
t ~ 0,7 · h
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