Top 10 Questions: Structural Adhesives

Shawn Collins, 3M Senior Technical Services Engineer, answers your top 10 adhesives questions.

1: How are 07333, 08115 and 08116 different? (00:28)
One’s a structural adhesive, two are panel bonding adhesives. Here’s how they’re similar. All three are epoxies that handle heat well. All contain glass beads to guarantees a minimum bond line thickness. And all have corrosion inhibitors.

But there are important differences. Structural adhesives should be used only where the manufacturer says to. Panel bonding adhesives are used for outer body panels, not on structural panels (except for the 08115 on the Ford F-150). Always follow the OEM recommendations.

2: When do I use 08115 vs. 08116? (04:15)

08116 was designed to meet General Motors and Chrysler specifications for mode of failure. They wanted cohesive failure for better corrosion protection. Follow the OEM recommendations for when to use, but know:

• Chrysler wants 08116 used for all its bonding operations.
• General Motors specifies 08116 only for door skin bonding operations — for all other bonding operations, GM recommends the structural adhesive.

3: Why do we need to equalize and purge the cartridge? (05:58)

To get a good flow of material, you need to remove air pockets from the plungers in the cartridges and pull out anything that’s dried up inside the ports on the cartridge. Then you have to purge some material out after you’ve equalized the cartridge so it mixes thoroughly and cures properly.

4: Do I have to remove the e-coat or galvanized coatings? (09:19)

Follow OEM recommendations. Many OEMs defer to the adhesive maker’s instructions. Always track down and follow the proper instructions.

5: Can I use heat to force cure? (11:25)

Yes. The epoxy chemistry handles heat very well. Always observe the max temperatures. We recommend about 150 degrees for 40 minutes for close to a full cure.

6: Can I refrigerate the product to slow down the cure? (12:23)

Yes, but we recommend something less aggressive like an air-conditioned room. Watch how cold it gets, it shouldn’t freeze. It will thicken as it cools, so be sure not to force it out too hard or it may not mix thoroughly.

7: What do I do when I see equivalence in a repair procedure? (13:11)

A procedure may list a product, then say “or equivalent.” This is tricky. It’s very difficult to know if another product is an exact equivalent. To avoid any liability issues, we recommend always using the product listed.

8: Why do we weld bond? (14:04)

There are lots of benefits:

• The adhesive prevents corrosion by completely sealing the joint
• With impact-resistant structural adhesives, the part will collapse more predictably and absorb energy as it collapses
• The adhesive gives a continuous bond for great lap shear strength
• The weld prevents the adhesive from peeling

9: Can I weld through cured adhesive? (15:16)

3M does not recommend welding through the adhesive after it’s cured. It’s important to finish welding within the work time on the adhesive cartridge. The liquid adhesive helps with conductivity, but once it cures, it acts as an insulator and inhibits conductivity.

10: How do I keep my bonded flanges from corroding? (16:03)

Sometimes during a panel replacement you might lose some of the corrosion-resistant adhesive. Insurance against this is to follow all bonding operations with Cavity Wax Plus, making sure to get into any areas that might be exposed.

Bonus: How long will a cartridge last after it’s opened? (17:25)

Sometimes people throw away a cartridge that’s only been used once, even if it’s half full or more, because they think it’s no good. Not true. If you leave the nozzle on and let it harden and seal the cartridge, it should last close to the stated shelf life.

A word from our lawyers:

There are many factors that can affect an individual repair, so the technician and repair facility need to evaluate each specific application and repair process and determine what’s appropriate. 3M recommends referring to relevant vehicle repair and OEM guidelines prior to starting all repairs.

Products used in this video:

3M™ Impact Resistant Structural Adhesive 07333

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Impact-Resistant-Structural-Adhesive-IRSA-/?N=5002385+3291264165&preselect=3293786499&rt=rud

3M™ Panel Bonding Adhesive 08115 & 08116

https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Panel-Bonding-Adhesive/?N=5002385+3293241847&preselect=3293786499&rt=rud

For more advanced tutorials, check out 3M Collision Repair Academy:

https://www.3m.com/3M/en_US/collision-repair-academy-us/

You’ll find courses that will expand your knowledge, deliver practical procedures you can use right away, and in many cases earn you I-CAR credits.

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