Tape Creep

October 17, 2008 9:48 PM

Is the vinyl tape on my flashlight exhibiting anomalous rheology?

Recently I bought a new flashlight that I decided to keep in the side pocket of my Carhartt trousers. The flashlight was slightly too skinny and too long for the pocket, and kept falling out. Furthermore, the on-off button was not recessed particularly deeply, and would become actuated accidentally.

I decided to wrap a band of vinyl tape around the flashlight, just below the on-off button to help keep the flashlight in my pocket, and to possibly decrease the accidental discharges.

The vinyl tape was some I got from Boeing Surplus years ago, and seemed in every way ordinary, with normally sticky adhesive on one side. The tape was one inch wide, and I wrapped a one inch wide band to a thickness of about 4mm. As much as I could, I kept the wrapping tension constant.

I put the flashlight back in the pocket and went to bed. This morning this is what I found. The top layers of tape had remained annular, but the bottom layers had crept remarkably.

What I find interesting is that I was not wearing the trousers at the time, so as far as I know, the flashlight was more or less flat during the night. Temperature was normal indoor room temperature. Only the head of the flashlight is tapered, the rest of the flashlight is cylindrical.

Is this a commonplace behavior of vinyl tape, or is something more interesting going on? Could this be due to a unique brand of tape that Boeing used? Am I simply a rheology n00b?

posted by Tube to science & nature (5 comments total)

It's commonplace if it was in your pocket and the weight of the torch pushed the tape, else it's haunted!
posted by lee at 10:35 PM on October 17, 2008

Yes, it is normal. The adhesive on vinyl tape is not all that strong and is very much subject to temperature changes. Due to the weak adhesive, tension on the tape itself can cause enough pressure to squeeze the upper layers over when they're wrapped. You'll notice that it moves over pretty evenly, and that's because the pressure is equalized to the adhesive at that point. The pressure is greatest at the center, so the 2nd turn (and all above it) are the first to start moving. Out it goes until the stickiness and the tension find a happy medium. It may squeeze out more, it might not.

I'd rewrap it with no tension at all.
posted by rhizome at 10:39 PM on October 17, 2008 [1 favorite]

I've seen whole rolls of tape do this. Think of it like toothpaste. The upper layers are squeezing the lower layers out of the tube.
posted by Kid Charlemagne at 6:34 AM on October 18, 2008

I'd heard rumors of Boeing 'Geoduck' tape, but I never imagined there might be anything to them.

I can't tell if the adhesive on the tape is as unusually dark as it appears to be in your photos, but if it is, I'm guessing some unique property of this tape is actually involved, such as that it was designed to work in very low temps-- as most tape will not, for example.
posted by jamjam at 10:32 AM on October 18, 2008

I'd rewrap it with no tension at all.

I tried rhizome's suggested technique, and it seems to be working!
In fact, even with as little tension as I could impart, the annular ring has still moved, but just a tad, and it doesn't create a problem.

I had failed to notice the first time that I wrapped it that the taper of the flashlight head actually extends just slightly behind the on-off button, so indeed I was starting my wrap on an irregular surface; partly flat, partly inclined.

After a full day of testing, the flashlight stays secure in my pocket, the on-off button has not been accidentally discharged, and I now have another funky "conversation piece" for the guys at work!
posted by Tube at 6:04 PM on October 21, 2008