High Temp resistant adhesives which withstand paint-bake processes
Often adhesives are not considered suitable candidates for joining structural assemblies that need to go through a paint-bake or stoving process due to the brief exposure to high temperature (around 200°C / 390°F for 10-15 minutes). However, there are many temperature resistant adhesives which can resist these conditions for this brief duration – providing the joint is not unduly stressed and upon returning to normal room temperature, the bonded joint will regain the vast majority of its original strength.
BENEFITS OF USING AN ADHESIVE
-No need to weld or braze = improved safety, less fire risk, no need to employ trained welders
-100% seal with adhesive, no leaks
-Better stress distribution and less damage to parts
-Improved appearance, cured adhesive can be painted or powder-coated, giving a great finished appearance
-Greater freedom joining dissimilar metals
TYPES OF ADHESIVE TO CONSIDER USING
Although two-part epoxies normally quote an upper service temperature limit of 80°C, this doesn’t mean that for brief periods they can’t go higher. We have seen excellent results with two part epoxies such as Permabond ET538, which has been used for structural bonding. The adhesive joint is easily powder coated, and then the joint is supported during the stoving process. Upon cooling the bond strength is regained and the parts can be put into normal action.
Single-part epoxy adhesives, on the whole, offer higher temperature resistance than regular two-part epoxies – so are ideal if greater loadbearing is required during the stoving process or where supporting a joint is not feasible.
Structural acrylic – recent testing suggests MMA-based structural acrylic, Permabond TA4210 is performing exceptionally well at temperatures in excess of 180 deg C, making it capable of withstanding a paint-bake cycle or powder coating process. MMA adhesives offer a fast room temperature cure – as well as a very high bond strength with good resistance to peel, impact and vibration stress.
The graph above shows lap shear strength retention of Permabond TA4210 MMA-based structural acrylic adhesive after high temperature exposure.
- Test pieces cured for 24 hours at room temperature
- 25 minutes exposure to the following temperatures: 120°C, 140°C, 160°C and 180°C
- Test pieces cooled and tested at room temperature
Conclusion: After paint baking at 180 deg C, a very high bond strength is recovered after return to normal room temperature, indicating minimal damage to the adhesive bond from the heat exposure. For customers in the US, the closest similar product would be Permabond TA4810.
For further help and advice selecting temperature resistant adhesives, please contact our Permabond technical team and we would be happy to assist.