DCF Seam Strength Test

Well, I went back and read through the above mentioned threads (topics 103910 and 89474) and the same arguments are coming up again here in this thread!  It’s cool that Lawson paid 3M to test their adhesive, but I’d like to know a little more about the testing.  The drop in peel strength from 90 Oz/in to 11 Oz/in @ 0°F seems like enough that 3M could not claim it would work at 0°F, yet in their spec sheet 9485PC is rated to -40°F (that’s negative 40)!!  These are well tested and presumably well understood industrial adhesives, and I would think that if they don’t retain their bond strength over the specified temperature range, industry would have pushed back by this point.  Maybe the min and max temperatures listed are extremes where you might expect the product to fail, but that’s not usually how specifications work.  Here’s a screen shot of their transfer tape brochure I found poking around their website:

So the tapes with the 350 series adhesive (like 9485PC) have the highest bonding strength with both high and low surface energy plastics.  DCF falls in the high surface energy category I believe, because of the Mylar (PET) sheet the the dyneema fibers are laminated to, but not by much.  Either way, the 9485PC or 9482PC SHOULD be the state of the art in transfer tape adhesives for DCF according to this spec sheet.  The tapes with 300LSE series adhesive should also be just as good.  I would definitely be curious to hear 3M’s response to their own test results (as reported by Lawson) and how that relates to their low temperature specification.

For me, I don’t think this will matter much since I will probably never be out in conditions that approach 0°F.  Maybe in temps that approach 20F, but my other gear will start to get questionable at that point anyway.

My goodness, this is a helpful thread!  Thank you, all.

Wow, it seems that this bonding vs. sewing is still a hot topic. I believe it has been discussed for many years.

I will start by commenting on the following picture.

The right one is a tape on top of a sewn french seam (or felled seam). The tape has two purposes:

1. waterproof the french seam that has needle holes.
2. give more strength

For the point 2, think about it carefully: only the upper 1/3 of the tape (the bottle neck) is supporting the connection of the two DCF pieces. correct? If the tape is one inch wide, 1/3 is 8 mm taping.

This 8 mm width bears any first-come force. In other words, the sewn french seam (the threads) contribute little or even none until the force is big enough and about to break thought the first layer of taping.

In this sense, the right picture is 2-3 times stronger than the left, because in the bonding mode, the total 1 inch width is fully supporting the seam for any first come force.

But as you already know, the bonding power drops when temperature drops under zero degrees. So, it’s safe to state that the right one outperforms the left in most situations, but theoretically may not be absolutely reliable when the weather is freezing.

In my opinion, the left one is not that cottage style. The factories that do traditional tents always do felled seam and apply a PU tape on top. They already have an expensive double needle machine, so why not using it also for DCF? But, it then make no difference between DCF and normal poly/nylon fabrics in terms of constructing techniques.

So what is good for DCF constructions? I’ll post next. :-)

An elegant DCF design should also incorporate the construction methods that are unique to DCF that cannot be re-produced with normal fabrics:

• In terms of an ideal DCF connection. Think about two aspects:
  1) typical loading capacity
  2) reliability
• Bonding/taping is very strong in most cases (perhaps 99%), but not absolutely reliable.
• Sewing is still the most reliable way to connect two pieces, but weak as for DCF.
• It’s good practice to try to combine bonding and sewing together in the construction.
• The adhesive needs to do 80% of the work to bear force in 80% of the cases.
• The threads do the remaining 20% of the work in the remaining 20% of the cases.
• Note the ratio is just a rough idea: bonding should take the major role over sewing.  Sewing is an addition or a safe guard. This is the proper “cottage/MYOG” approach in my opinion

Variations of over-bonding or over-sewing posted above generally do not hurt too much. But bear in mind:

• It will take much more time to make -> not a problem for MYOG though.
• Note the adhesive also has weight and is heavier than DCF; threads and DCF weight too. Over-bonding or over-sewing with more adhesive/threads/DCF adds grams to a UL master piece.
• Over-bonding or over-sewing makes the seam bulky and rigid, and somewhat losts its balance to the single thin DCF piece around the seam.
• Over-bonding or over-sewing makes the seam thicker. In some cases, I think even a slightly thicker seam will reduce the shearing capacity of the seam. This is not good but I do not have test to support my idea.

  Anyway, all you need is a simple (beautiful), strong, and reliable seam.

Claim: I am the owner of a small DCF cottage. and I would be happy to answer some DCF questions.

Here’s what I used on my tarp ridgeline. The seam was inspired by one used by Roger Caffin on his tents. The image below shows the seam 1) as it is sewn, 2) flattened and 3) taped. Of course, the tape is the primary connection, but this seam should be a good backup. I think think seam has some nice features:

• The seam is easy to sew, because it is sewn on the edge of the two layers (fig. 1) rather than in the middle of a large panel.
• Because it is sewn through a folded edge of the material, the seam allowance can be very small. The final width of the flattened seam on my tarp is about 8mm. This maximizes the area around the seam where the tape sticks directly to the fabrics.
• The first layer is backed up with a second layer of the folded edge that is not under tension. It should distribute the force from the thread better and reduce hole enlargement / ripping.

Jan,

How did it go ensuring the seam and edges were spread flat as you applied the tape?  In use, do you think the thread takes any load, or is it all on the tape, with thread just available as back up?

Taping as you have takes on some of the role of the secondary stitches I suggested, in preventing the edge from sliding through the ‘pulley’ (center) seam, elongating needle holes.  One caveat to this I forgot about is that if you don’t sew a straight line, you end up concentrating tension in some areas, leaving slack in others.

I looked up the specs for 3M 300LSE adhesive, available on adhesive strips or with a double sided substrate.  They are spec’d to function at -40C/F with no loss of adhesion.

https://technicaldatasheets.3m.com/en_US?pif=44

What I would like to find, and cannot find informaiton on anywhere, is a pressure/heat tape.  TarpTent references using such a tape on their tents and the Dyneema Project demonstrates a tape and press on the website, but what is the product name and manufacturer?  Does anyone know?