Two part sealants adhesives

Two Part Sealants/Adhesives

Dow Corning INTERNAL

2

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


3

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


4

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


5

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.


6

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


7

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


8

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


9

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


10

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


11

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


12

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


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


14

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


15

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


16

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


17

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)


18

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


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


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


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)


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


Dow Corning® D94-30P

• Extrusion Rate

– Part A 75 g/min





• Mod. 100% 0.80 MPa



– on Al 0.80 MPa

– on PA 6.6 0.90 MPa


– 22 h 177 °C45 %

– 24 h 150 °C25 %

• Specifications

– GM 236M Type 2


Dow Corning® D94-45M

• Extrusion Rate

– Part A 120 g/min





• Mod. 100%, 1.45 MPa



– on Al 1.05 MPa

– on PA 6.6 1.35 MPa


– 22 h 177 °C30%

– 24 h 150 °C15%

• Specifications

– Chrysler MS-GF 42B

– BWM 54160-MVQ-50

– VW AMV 176 810


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.


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


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


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


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


30

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)


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....


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.


How to apply a CIPG gasket bead ?

Part

surface

Overlap

StopRobot movement

Stop of dispensing

Start of dispensing

Robot movement

Start

Part

surface


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


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


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


39

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Documents

Two part sealants adhesives