Duct tape has a running gag of being the miracle fix-it tool, but with a fail point of around 30 psi, it doesn’t quite hold up to its industrial cousin – 3M VHB (Very High Bond) tape.
With a standard fail rate of 250-300 psi, could this tape be a possible alternative to welding and fastening techniques?
ENGINEERING.com recently spoke with 3M’s bonding project manager, Peter Rebstock who filled us in on just how strong and versatile VHB tape could be. The video above and Q&A below document interview highlights.
Jim Anderton (JA): Mechanical processes have been around for years; there’s been a bit of a resurgence of flow-drive screws in mechanical fastening and welding has been around forever. Are there other cost-effective ways of fastening materials together?
Peter Rebstock (PR): Absolutely. What we’re highlighting here today are various technologies that will replace mechanical fastening and welding for a variety of manufacturing processes.
One of the major technologies that we work with is 3M VHB Tape. It’s a through-and-through acrylic, closed-cell foam tape that does a great job of bonding dissimilar materials, provides quick handling strength, clean bonds and lack of post-process finishing.
If you think about welding a material or riveting a material together, you’ve got pre-process, which is drilling the holes or prepping the surface. Post-process is cleaning off the welds, grinding down or refinishing any type of rivet scratches or paint marks.
With 3M VHB Tape, you’ll eliminate all of that. You basically apply the tape to a material, take off a removable liner and apply the second material. Applying pressure along the bond line of about 15 psi, you have immediate handling strength.
We’re also highlighting the ability of the same tape to work in a pre- or post-powder coat process. For pre-powder coat, where you’re going to send it through a bake cycle after you apply the tape, we have the 3M VHB Tape 4611, which can survive up to 450 degrees Fahrenheit during a bake cycle. For post-powder coat, you look at the surface that you’re bonding to. You’re no longer bonding to metal in a post-powder coat, you’re bonding to plastic.
With that, we’re going with our 3M VHB Tape 5900 series, which does a phenomenal job of bonding low surface energy plastics like PC ABS, Delrin or Acetal. Allowing your customer to work around whether they weld or fasten the material is something we can work with.
JA: With bonding dissimilar materials, the immediate question that comes up is the mismatch in thermal co-efficient of expansion. In my experience, that has been a major problem in using adhesive products. How do you address that problem?
PR: With 3M VHB Tapes in particular, we address that with what we call visco-elasticity.
Basically what we’ve engineered into all of our 3M VHB Tapes is the ability to absorb dynamic loading, so you’ve got the ability to stretch and deform, but return back to your original form. So if you think about the thermal co-efficient of expansion between a plastic and a metal it’s obviously going to be different, depending on the thickness of the metal as well.
With a hot or cold situation, the ability to absorb that expansion in the bond line and not transfer that stress to the metal or the plastic is critical and that’s what 3M VHB Tapes allow you to do. We also integrate that technology into our flexible epoxies, flexible structure acrylics and our polyurethane adhesive sealants.
JA: What type of surface preparation would you need in a production application for auto parts, for example?
PR: It varies depending on the type of material. Surface prep can be as simple as cleaning for FOD, what we call foreign object debris or it can be a little more critical, using isopropyl alcohol, abrading or with some of the lower surface energy materials, like a primer. It’s nothing substantial and nothing that should be too hard for any major manufacturing customer to work with.
JA: Everyone wants to know this: Strength. Can we come close to a screw, riveted, welded joint in terms of strength?
PR: If you think of mechanical fastening, what you’re getting is a localized strength. You’ve got holes drilled along the bond line, which you fastened for a defined length with a mechanical fastener. When you submit that to stress, you’re getting a localized stress around that actual hole, which creates stress points and actually weakens the material. With a 3M VHB Tape bond, you’re distributing the stress of that bond along the whole bond line, so you actually get a much greater ability to absorb dynamic stresses with a 3M VHB Tape.
3M VHB Tapes typically have about 250 to 300 psi in overlap shear. With structural you can get much higher than that, with some getting about 4000 psi. Strength is something we are quite capable of developing.
For more information on 3M VHB Tapes, visit solutions.3m.com.