3M clear transfer tape adhesion strength for various cuben applications

[TinCanFury]

I've been playing around with cuben lately, I've made a tarp and a few stuff sacks. I've also been doing some tests as to adhesion strength and use as well as doing some thinking and research.

I'm wondering what people's thoughts are on the following idea...

Not all taped junctions of cuben require the strength of adhesion that the popular 9485 tape provides, which is roughly rated at 150oz/in, for some applications 25oz/in, which many of the cheaper 2mil tape provides. Has anyone already played with using these different tapes for applications in their cuben projects where the stronger adhesion is not required, and if so, what has been your success?

My thoughts are that for things like edge folds, "straps" (I don't know if there is a more commonly used term for creating grosgrain replacements by taping a couple 1/2" strips of cuben together), stuff sack edges, etc. that the cheaper lower strength tapes would be more than strong enough since these parts of the gear see little, if any, shear stress on the tape.
I'd even go so far as to conjecture that "patches" that do not see much shear stress on the tape could also use a weaker tape, if not as low as 25oz/in, perhaps 60oz/in might be enough.

Thoughts?

[nuttysquirrel]

if your investing in cuben, id just go all the way and use 9485.

[TinCanFury]

I'd rather spend the money on the cuben than on the tape, but I'll gladly accept any spare money you have to cover my costs ;-)

[WV]

if your investing in cuben, id just go all the way and use 9485.

Or use 9460 with Primer 94, which is quite a bit better. However, I did tests on a number of 3M VHB Adhesive Transfer tapes when I first started working with cuben, and I believe that there are quite a few different tapes that are plenty strong enough for most applications where shear forces are concerned. Therefore, I think the OP is on the right track, both because he did some tests to find out for himself, and because he's correct that not every problem requires a top-of-the-line expensive solution. (Nonetheless, I am guilty of using 9460 + primer alsmost exclusively.)

[TinCanFury]

Or use 9460 with Primer 94, which is quite a bit better. However, I did tests on a number of 3M VHB Adhesive Transfer tapes when I first started working with cuben, and I believe that there are quite a few different tapes that are plenty strong enough for most applications where shear forces are concerned. Therefore, I think the OP is on the right track, both because he did some tests to find out for himself, and because he's correct that not every problem requires a top-of-the-line expensive solution. (Nonetheless, I am guilty of using 9460 + primer alsmost exclusively.)

thanks for the response WV!
9460 is one of the tapes I was looking at, and I have been using the 94 primer along with the 9485 tape so far. From what I understand, the 9460 has roughly 2/3 the bond strength of 9485. I was also looking at 463/465, 976, and 987, which have much lower bond strengths at ~< 1/4 the cost. I'm not sure about their weight per square-in, but for things like stuff sacks definitely, and maybe other things, they would be a much cheaper alternative.

I'll probably buy a roll of some of them to run some tests with scrap cuben and see how they fare.

Thanks!

[WV]

Both 9460 and 9485 will certainly do the job. I got my info talking with 3M techies and then tested both myself. One thing I learned is that when not using Primer 94 on a medium surface energy substance like polyester (e.g. cuben) the adhesive used for 9485 is slightly better, but the use of primer improves both (and the 9460 improves much more, so it comes out on top). Another interesting fact is that 3M makes these tapes in two thicknesses for different applications. They suggest formulations with 5 mil thick adhesive for rigid items, like aluminum signs fastened to walls or doors, and tapes with a 2 mil layer of adhesive for light, flexible materials, which cuben certainly is. Now here's the interesting part: 9485 is 5 mils thick. (It has a cousin with the same adhesive, 9482, that's 2 mils thick.) 9460 is one of the 2 mil tapes, and it's available in a 5 mil formulation, too, under the name of 9469. I tested all four of these tapes with cuben and found the 2 mil formulations just as strong as the 5 mil. I doubt that there is a measurable weight difference for our purposes. There was a slight tendency for the 5 mil tapes to be a bit gummy along the edges, but that's really splitting hairs.

What's the takeaway here? Both are good; use whatever you have on hand. I'd even go so far as to say that someone experimenting with cuben could use 9485 without primer and be perfectly okay. I haven't heard any reports of bonds breaking with anything.

[TinCanFury]

AHA!

What you just said about the 2mil vs 5mil was a question I wanted to get answered with my tests!

the spec sheet adhesion strength shows lower for 2mil, but I liked the idea of a thinner tape for cuben use, not just for weight, but because the extra 3 mils provides more space for the materials to shift against each other, which conceivably could allow for more creep and possibly less real world adhesion strength. The fact that you've found it's just as strong, even though the adhesion strength listed is lower, is very interesting to me!

I think I'll be making my next tarp all with 2mil tape to see how it works out. Definitely any future stuff sacks, etc.

Also interesting about the primer not adding as much value to the process with 9485 tape vs 9460.

I can see why 9485 is preferred from a manufacturing point, no need to worry about the primer. Do you have any thoughts on cleaning the cuben before using the primer as noted in the spec sheet for the 94 primer?

Also, did you look at all at the ATG tapes? from what the spec sheets say, they should be equivalent to the ATT tapes, just designed for the hand-held dispensers. Pricing I've seen for the ATG is more expensive, so it's somewhat of a moot point, but it was something that popped in my head during my research.

Final question, what do you know of using heat and pressure after application to strengthen the bond? the spec sheets say to apply pressure, which I've done and seems intuitive. I'm wondering what you know about the application of heat (say via a blow dryer, or even a heat gun), and the difference in bond strength after one or more heat cycles?

thanks!!!!

[WV]

I asked about the heat factor. They said that the bond reaches immediate strength if it's done at 200° F., but if done at normal room temperature it gets just as strong within a week, and it starts out pretty strong anyway (maybe 85% - I forget). I used to wait a week before hanging a tarp very tight (talk about agony!). Now I don't bother. I think I may have used alcohol to clean the area I was going to prime in the beginning, too.

Keep experimenting with those other tapes. I'm glad you're adding to the knowledge here. My tests were hardly exhaustive. (I could be wrong!)

One thing I'd like to find - a really good tape to carry for field repairs. I made up pieces of cuben with adhesive transfer tape ready to peel and use, but I don't carry a little bottle of primer. One lesson I learned with Gorilla tape and packing tape: they're tough to remove without taking part of the tarp with them and/or leaving adhesive behind. It would be nice to do a lightweight repair that you could leave in place. I suspect that one of the tapes that the cottage vendors sell would fill the bill. I tried one for making stuff bags from Quest Outfitters years ago, but don't know exactly what it was. (They didn't either; I asked.)

[TinCanFury]

Will do. I'll probably have to "waste" some cuben to find out, but such is science!

928 has an extremely low adhesion rating, and the spec says it can be easily removed and reused a few times. It may be good for patching a hole in a cuben tarp where all you care about is water seepage, that you could remove later to put a more proper patch.

It's still a double sided though, so would require a cut of cuben on the other side.

5421 is a single sided Polyethylene tape with a very low adhesion like 463/465, it may be more difficult to release from cuben once in place though. 640 tape might be a better bet, it's a general packing tape, with a similar adhesion, but is more conforming than 5421, but probably a weaker substrate as well. The upside is you could easily roll a bit around a toothpick or whatever since it can stick to itself.

if 9485 has minimal gain in primer use, you could continue what you are doing and just use that tape. though it would definitely be a more permanent repair.

[WV]

Will do. I'll probably have to "waste" some cuben to find out, but such is science!

928 has an extremely low adhesion rating, and the spec says it can be easily removed and reused a few times. It may be good for patching a hole in a cuben tarp where all you care about is water seepage, that you could remove later to put a more proper patch.
I was thinking more of something light and transparent that I could leave in place, and then put a more permanent patch on the opposite side, but plain old scotch tape might do for that. A removable tape would be useful. I once had to repair a small rip in a down-insulated cuben hammock. I used the 9460 "band-aid" I'd brought with me.

It's still a double sided though, so would require a cut of cuben on the other side.

5421 is a single sided Polyethylene tape with a very low adhesion like 463/465, it may be more difficult to release from cuben once in place though. 640 tape might be a better bet, it's a general packing tape, with a similar adhesion, but is more conforming than 5421, but probably a weaker substrate as well. The upside is you could easily roll a bit around a toothpick or whatever since it can stick to itself.

if 9485 has minimal gain in primer use, you could continue what you are doing and just use that tape. though it would definitely be a more permanent repair.

Note: not minimal, just less than 9460. If you have the option of using primer, do so.