Faster assemblies at room temperature with new, very fast cure DOWSIL™ EA-3838 Fast Adhesive
Global adhesive and sealant market growth
The global adhesives and sealants market size is expected to reach USD 82.4 billion by 2025. This corresponds to a CAGR of 5.6% during the forecast period.
High demand for adhesives and sealants comes from different industries:
- Construction
- Assembly
- Automotive
- Appliance
- Aviation
Major growth trends
Addressing the needs: Improving profitability and reducing carbon footprint
DOWSIL™ EA-3838 Fast Adhesive has been developed for manufacturers of appliances, automotive electronics, lighting, aerospace and beyond, willing to improve their profitability while reducing their costs and carbon footprint.
Silicone cure technologies
Silicones product technologies
Seadling and bonding: Room-Temperature Vulcanization
Package / Delivery / Storage
Typical storage conditions of 1-part RTV sealants: When stored at or below 30°C (86°F) in the original unopened containers, this product has a usable life of 12 months from the date of production.
Storage conditions of SILASTIC™ Q3-3636 Adhesive Catalysts, 2-part RTV: When stored at or below 25°C in the original unopened containers, SILASTIC™ Q3-3636 Adhesive Catalysts have a usable life of 5 months from date of production.
Dispensing / Application
1-Part RTV equipment is less complex as no mixing or heating tunnels are required. This is because short-term heat has no significant effect on cure speed.
BUT a storage area is needed for curing finished parts. Time in storage area depends on:
- Temperature and humidity
- Part design
- Follow-up processes
Mix ratio of current 2-part RTV sealants is 100:14 by weight (100:17 by volume). Uneven mix ratio:
- Requires different pumps to meter correctly
- Requires precise mix ratio control
- Means that no commercial cartridge system is available
Open-time / Tack-free time
1-Part RTV
Cure rate – skin-over / tack-free time by fingertip contact
Abstract: The skin-over time, a measure of cure rate, is defined as the time in minutes required for a curing material to form a non-tacky surface film.
2-Part RTV
Working time – snap technique
Abstract: This technique measures the length of time it takes for a room-temperature vulcanizing material to show the first sign of rubberiness after the material is completely formulated and exposed to normal curing conditions
Cure rate – skin-over / tack-free time by polyethylene contact
Abstract: The skin-over time (measure of cure rate) is defined as the time in minutes required for a curing material to form a non-tacky surface film. This method uses polyethylene film contact to determine the non-tacky characteristic and can report pass/fail if the skin-over time is specified as a minimum.
Inline pressure leak test
The inline pressure leak test can be done with Time Worker from TM Electronics, Inc., in combination with a metal jig according to ASTM F2523-13. The jig has a gap of 1 mm height and 8 mm width. A small bead of material was applied all around the flange of the metal jig. Right after application of the material, the jig was assembled and the test was started.
- Dow lab leak test parameter: Charge 6.5 kPa for 80s -► hold 6.5 kPa for 5s -► test
- Test time: Hold 6.5 kPa for 120s
- Pass criteria: Pressure decay max. 0.1 kPa
- Test parameters are application and customer specific.
Cure Profile
1 – Part RTV
2 – Part RTV
Adhesion development
Typical properties
Special properties
Heat Resistance at 200ºC
Heat Resistance by product
Dynamic mechanical thermal analysis (DMTA)
Recap
Technical introduction to DOWSIL™ EA-3838 Fast Adhesive
General product information
- A 2-part, alkoxy, RTV material that develops early primerless adhesion on various substrates, with a very fast cure speed
- This adhesive consists of a black base and a white catalyst
- It has a variable 2:1 to 4:1 volumetric mixing ratio, non-flammable components, and an up to 12-month shelf life for both components
- It will be commercially available in pail, drum and dual-cartridge kit packaging
Mechanical properties versus competition
Cure speed and early adhesion development
Dispensing / Application; 1- and 2-part RTV
- Eliminates the need for oven acceleration, but can be accelerated through heating tunnels – max 60°C
- Elimination of heat decreases energy consumption and improves sustainability
- Faster cure makes earlier inline pressure leak testing possible, reducing cycle time drastically
- Variable mixing ratio provides flexibility to meet a wide range of open times– cure speeds
Adhesion development after full cure
Typical break pattern on clean surfaces without any surface pretreatment is cohesive failure, but adhesion depends on the specific properties of the surface.
Potential Mixing Ratios / Version
Heat resistance
DOWSIL™ EA-3838 Fast Adhesive can withstand temperatures up to 180°C and even shorter peaks at above temperatures.
When larger adhesive surfaces are subject to atmospheric contact (O2), resistance at higher temperatures might be negatively affected.
Package / Delivery / Storage Conditions
When stored at or below 30°C in the original unopened containers DOWSIL™ EA-3838 Fast Adhesive Catalyst has a usable life of 12 months from date of production.
Final recap
Applications – Household appliances
Applications – Other markets
Packaging
Conclusions
DOWSIL™ EA-3838 Fast Adhesive is a 2-part, alkoxy RTV silicone adhesive aimed at applications where a strong bond is needed along with a fast cure speed and early primerless adhesion development.
Features and benefits:
- Fast curing time
- Early primerless adhesion development
- Improved adhesion to several substrates
- Improved shelf life to 12 months
- Easy & flexible mixing ratio (2:1, 3:1, 4:1)
- Also available in cartridges
Main market: Appliance
Secondary markets: Aviation, automotive, lighting and industria
Source: Dow fast adhesive presentation
