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Many people who have used heat-shrink tubing have probably experienced this: you forgot to insert heat-shrink tubing before soldering, and now it's too late!

Indeed, once the soldering is done:

  • you can't pass thin tube because of the connectors on both ends (example with a Macbook charger connector):

    enter image description here

  • you can only pass a large-diameter tube (because of the large connectors), but then the shrinking factor doesn't allow the heat-shrink tube to "fit" on the wire!

Question: is there something available as a roll like adhesive/electrical tape (so that you can wrap some around the middle of a cable without having to "pass" it around the large connectors on both ends of the cable, see for example this video) that would shrink with heat and be like traditional heat-shrink tubing at the end, i.e. a bit solidified/glued by heat?

TL;DR: is there a mix between heat-shrink tubing and adhesive tape?

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    \$\begingroup\$ Shrinking with heat makes no sense if its not a closed shape since it would pull apart since the heat activates both the shrinking and the adhesive. \$\endgroup\$ – DKNguyen Oct 13 '19 at 20:24
  • \$\begingroup\$ @DKNguyen I already use electrical tape, but at the end it's not very hard. What I like with heat-shrink tubes is that it becomes hard / strong after heating it. This is not the case with traditional electrical tape. Also, if we wrap a lot of turns around the cable, heat-shrink could make sense. \$\endgroup\$ – Basj Oct 13 '19 at 20:27
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    \$\begingroup\$ If you are after hardness then silicone self adhesive tape will become hard. Do a test run on scrap and let it sit a day before you do it on the real piece so you know how it behaves while pliable and after it cures and how to best work with it. You do not want to have to go in and remove it if you mes up. \$\endgroup\$ – DKNguyen Oct 13 '19 at 20:27
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    \$\begingroup\$ Thats the stuff. Those comments complain it wont stick flat are not using it as intended. It is meant to be STRETCHED and wrapped. I dont know what makes it hard but it does which surprised me too. It might be the mas fusing together to be thicker. Try it. I would rather remove heatshrink than this stuff. I have never been successful in excising it whereas heatshrink is dead easy hence my warning of a practice run. \$\endgroup\$ – DKNguyen Oct 13 '19 at 20:32
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    \$\begingroup\$ @DKNguyen Thank you for your comment. Actually it is an answer, maybe you could post all these comments together as an answer? Also, maybe add a photo (just to be sure we don't confuse with other types of silicon tape). Under which exact name can we usually find it in stores? \$\endgroup\$ – Basj Oct 13 '19 at 20:37
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Shrinking with heat makes no sense if its not a closed shape since it would pull apart since the heat activates both the shrinking and the adhesive.

If you are after rigidity and toughness then "silicone self adhesive tape", "self amalgamating tape", "self-fusing tape" (or some other name along those lands) will become hard. It looks like a roll of silicone tape backed with a transparent separate plastic to stop it from sticking to itself. It somewhat resembles something halfway between electrical tape and the the white teflon thread sealing tape. You should just be able to find it in a hardware store.

Do a test run on scrap and let it sit a day before you do it on the real piece so you know how it behaves while pliable and after it cures and how to best work with it. You do not want to have to go in and remove it if you mes up.

People who complain it wont stick flat on a surface are not using it as intended. It is meant to be STRETCHED and wrapped. I dont know what makes it hard but it does which surprised me too. It might be the mass fusing together to be thicker. Try it. I would rather remove heatshrink than this stuff. I have never been successful in excising it whereas heatshrink is dead easy hence my warning of a practice run.

Also, you realize your problem can be fixed using heatshrink with higher shrink ratios right?

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    \$\begingroup\$ Thank you for your answer. Which is the biggest ratio you achieved with heatshrink tubes? Is something like 5:1 possible? \$\endgroup\$ – Basj Oct 13 '19 at 20:44
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    \$\begingroup\$ Just a comment to help people searching in future - some sellers use another name for that "silicone self-adhesive tape" which is "self amalgamating tape" (which describes what it does quite well). \$\endgroup\$ – SamGibson♦ Oct 13 '19 at 21:02
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    \$\begingroup\$ @Basj - "Is it the same than "Self-Fusing Silicon Tape"?" That sounds the same ("self-fusing = "self amalgamating") but that's not a description which I have personally bought. If that tape mentions needing to be stretched, this is a good indication that the same principle is being used. "do you like it for electrical cables for example?" A couple of hints: (a) As DKNguyen said, you don't want to try to remove it. So if unsure, add some & test the flexibility. You can add more, but can't easily remove only some thickness. (b) The outside remains slightly "tacky", so it collects dust. \$\endgroup\$ – SamGibson♦ Oct 13 '19 at 22:28
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    \$\begingroup\$ @Basj Digikey indicates that at least 6:1 exists. \$\endgroup\$ – DKNguyen Oct 13 '19 at 22:52
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    \$\begingroup\$ I have tried some 6:1 heatshrink once, I found it was very stiff before shrinking, very thick and even stiffer after shrinking and took a lot of heating to get it to shrink. \$\endgroup\$ – Peter Green Oct 14 '19 at 16:33
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"Heat shrink tape" absolutely does exist. Just do a search using that phrase, and you'll find many vendors.

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    \$\begingroup\$ Indeed, this video seems to be exactly what I'm after (but wow, 40$ for a small length of this tape, oops!)! Is it such kind of heat shrink tapes you were talking about or did you mean something slightly different? \$\endgroup\$ – Basj Oct 13 '19 at 21:17
  • \$\begingroup\$ That's just one product out of many. Amazon has several other choices, some much cheaper. \$\endgroup\$ – Dave Tweed Oct 13 '19 at 21:29
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    \$\begingroup\$ Interesting. How does it not come apart? Does it just use an pressure-sensitive adhesive that functions at higher temperatures than the shrink temperature? \$\endgroup\$ – DKNguyen Oct 13 '19 at 21:41
  • \$\begingroup\$ @DKNguyen It's kind of a welding process. And the glue is probably a mixture of cold adhesive and hot melting glue. \$\endgroup\$ – Ariser Oct 13 '19 at 21:48
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    \$\begingroup\$ I have some non-adhesive heatshrink tape and it has been in the bottom of the drawer for a long time. As other comments have mentioned it is not a closed shape and unless you wrap it very very carefully the shrink process undoes all your work - the end needs to be wrapped under itself as in whipping the end of a rope. Far easier to undo the soldered wire and use some regular heatshrink tube. \$\endgroup\$ – Adam Eberbach Oct 14 '19 at 5:04
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Regarding your question about shrink ratios, the highest I've seen is 8:1 I think. Most "high ratio" shrink tubes achieve that high number by being lined with hot melt glue, which gets squeezed down to a much smaller diameter than the actual tube's ID. It makes for a waterproof and very robust seal that is seriously difficult to remove.

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    \$\begingroup\$ Good to know, thanks @Ryan. Were they super expensive (8:1 ratios seem to be rare, I have never seen any)? \$\endgroup\$ – Basj Oct 14 '19 at 10:24
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I've found Sugru to be useful in cases like this. It's a silicone rubber that you can mold like putty. Once formed, it will cure and develop a texture similar to rubber. Mold some into a flat strip, wrap it tightly around where the joint where you'd apply heat shrink, and let it cure. You can use different thicknesses to adjust the stiffness, texture, etc.

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  • \$\begingroup\$ I used Sugru as stress relief on my R/A headphone jack that had to be re-soldered when it failed after only around 18 months, since applying this, the cable has lasted at least another three years of daily use. For a one-off, it's a perfect solution. \$\endgroup\$ – SiHa Oct 15 '19 at 10:39
  • \$\begingroup\$ This is one of the main things that Sugru advertises itself for, and I can highly recommend it. Only downside is the short shelf-life of unused sugru. \$\endgroup\$ – Mike Brockington Oct 15 '19 at 11:02
  • \$\begingroup\$ On the advertisement of the product, it looks perfectly polished like this whereas real buyers have more things like this which is much less refined ;) Is there a way to mold it perfectly? \$\endgroup\$ – Basj Oct 17 '19 at 6:57
  • \$\begingroup\$ @Basj - It's a bit like modeling clay, you can give it almost any texture you want. The user-generated pictures generally look matte and lumpy because they were formed by rough hands. You'll get a cleaner look if you smooth the surface with a tool before it cures. Make the surface rougher and the resulting object is easier to grip. "Perfect" will depend on what you're trying to accomplish. \$\endgroup\$ – bta Oct 17 '19 at 17:56

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