Kapton: Miracle Material with a Tragic History
hackaday.com
hackaday.com
I recently bought the #1 result on Amazon for "kapton tape". A banner on the item's description proclaimed that the listing was "Amazon's Choice for Kapton tape". So I ordered it without doing any more due diligence. When the item arrives, it turns out that it isn't Kapton. It's a knockoff called "Koptan". In their defense, the actual vendor's description doesn't call it Kapton, just the "Amazon's Choice" banner. Kinda sneaky
The tape I got looks a lot like Kapton. But is actually the same thing? Who the fuck knows. At the very least, my house hasn't burned down yet
Checkout 3M 5413 AMBER. Larger rolls can cost upwards of $300, not cheap stuff.
https://www.digikey.com/short/zrz730
Also, even if you've not used them before or have no need of kapton tape, take a look because their parametric search is one of the greatest I've seen, and makes Amazon's Choice system seem awful in comparison.
I'm super curious where you live, approximately! I'm in Saskatchewan, and Digi-Key reliably gets me parts next-day, even when shipped DDP (they take care of all of the duty for me). For crossing a border, that's pretty incredible!
We have never seen a single issue with pricing not as advertised at small quantities, or a shipping mistake not directly attributable to the carrier.
Mouser has performed similarly well but is (and has always been) significantly worse with their cutoff. Again, they're nominally 8pm CT but 6 or 6:30 is more realistic if you're counting on it being here the very next day.
Both are amazing if you're used to crappier distributors, but you do pay for it....
Ah. No, we haven't either.
The issue is that we have caught DigiKey charging different prices based upon login status and cookie status on low volume order items.
This would be fine if they were charging the returning customer less, but we caught them charging more. That made us very unhappy.
Maybe it was a bug. Maybe it was an A/B test. However, if I have to scrutinize my order cart, we're done.
We still use DigiKey. But we have significantly reduced our volume through them and we watch them like a hawk.
1. UPS do not leave packages at door in all countries
2. Some people live in apartments with nowhere safe for packages to be left
3. In some cities/countries in-person delivery does not exist at all. Only "collect at post office"
Food for consideration: since 3M is a ECIA member manufacturer[1], if the source isn't direct from the cow's mouth or one of their authorized distributors, it's prima facie suspect in my eyes and cannot be trusted on anything with skin in the game.
But nobody knows the generic name (the acronym isn't even in the wikipedia article) so fly by night vendors use 'kapton' wherever they can get away with it.
(and as with teflon, iirc they sell other polymers under the name of kapton too)
Others adopted the tradition and pilfered more pieces of foil. They were fairly indiscriminate. And spread the fruits widely. You can buy your own from places like here, https://shop.minimuseum.com/products/apollo-11-command-modul...
Personally, I would have loved to own a piece of our robotic explorers. Kapton has been used in incredible ways in craft like New Horizons. It's possible to overheat instruments in an object millions of miles away from the sun! https://mattcbergman.com/2015/08/02/new-horizons-thermal-con...
It is an expensive polymer compared to BoPET (a.k.a. Mylar) but it doesn't have the complex production complex. Mylar films are stronger but Kapton holds up better in the space environment so it is still the #1 choice for solar sails.
These are claimed to reflect 90% of sunlight and the feeling on my skin and my camera's exposure meter agree with that.
I think each layer of 'space blanket' on the satellite has about the same transmission as the Wal-Mart space blanket, so with 10 layers you are decoupled from the Sun and resistant to micrometerioid scratches, spots of corrosion, etc. There is the UV-light problem but also atomic oxygen and other reactive species out of equilibrium that will eat some materials.
I wondered about the manufacturing life cycle dynamics of DuPont's Kapton, particularly after reading this in the article:
> Planes built since then generally use TKT, which is Kapton with two thin layers of Teflon to provide better resistance to mechanical abrasion and water intrusion.
Would a measurement of the complexity of the production complex include the part where they dump the untreated toxic manufacturing waste into virgin streams in West Virginia, or would that be an externality?
I recently saw a film produced by Mark Ruffalo that told the story of the West Virginia farmers whose stream was poisoned. They had to spend 7 years fighting DuPont's lawyers for justice, and then they died of cancer.
Dark Waters trailer https://www.youtube.com/watch?v=RvAOuhyunhY
The PET in BoPet (Mylar) is one of the most environmentally favorable plastics in practice used to make plastic coke bottles that look like coke bottles also as "polyester" fabrics. The "Bo" is the part that looks complex to me in that mylar production involves a careful process of stressing it in two different directions while annealing it.
It is funny because I have been tracing out the path to manufacture large Kapton/Al films using asteroid materials. It is not hard at all to find an asteroid with the resources, but the trick is building a 'chemical factory factory' that can turn space hydrocarbons into plastic films, assembling that -- the Chinese think they could build a sunshade at L1 Sunward for $60 Trillion with Long March tech, maybe SpaceX can do $5 Trillion with Starship, but to make it cheaper than that you have to make it from minor planets and turn all the 'difficulties' such as 'working into zero gravity' into opportunities such as 'easily handle films larger than New Jersey'.
https://journals.sagepub.com/doi/full/10.1177/16878140177192...
The $60T is my number based on the guess that the Long March 5 costs about the same as similar western rockets.
When used as an insulator where it can rub or be exposed to moisture: you’re going to have a failure at some point. What’s alarming then, was the conclusion:
> Still, hundreds of planes take off and land every day with Kapton insulated wires routed through every nook and cranny, some almost impossible to reach for inspection. And even when wire bundles are accessible, inspection comes down to a flashlight and a Mark I eyeball, looking for that cracks that might be lurking.
Where is our reassurance that everything is OK now??
At least some gigabit ethernet interfaces have built in weaker TDR that measures the length of each twisted pair, but I've only ever had one computer that showed that info in the BIOS/UEFI.
So, maybe if TDR is used for inspection, we can rest assured.
I've seen this info in the Realtek NIC diagnostic tool for windows (on one machine, anyway), and I've got a couple of semi-managed switches that show a line length estimate which I assume is based on similar measurements.
This is what I was told by the person who saw the demo. I believe them, because it'd just be a matter of sending an impulse (or sweeping a tone) and looking at all of the spikes in the impulse response.
Unfortunately it is rather false-positive prone when applied to fences, significant wind loading can cause the chain-link to lash back and forth and repeatedly deflect the cable. The resulting alarm fatigue was implicated in the somewhat (in)famous case of the nuns as site Y-12. Nonetheless this application is very common at federal installations and also certain non-federal infrastructure installations, e.g. the legacy iron fences around Portland, Oregon's surface water reservoirs (where remote-controlled PTZ cameras appear to be used for rapid remote confirmation of FiberPatrol detections... you can give the fence a shake and watch a camera pan to you almost immediately).
> In the 1970s, the most common wire for aircraft was Kapton-insulated wire. Kapton is a DuPont trade name. Today, aircraft wiring is typically insulated with Teflon, Tefzel, Cross Link Tefzel or TKT (Teflon-Kapton-Teflon). Typically, the AVS for an aircraft lists the type of wire insulation that will be used throughout the aircraft. For example, the OEM might decide that TKT will be used, with some exceptions such as radio cables and Teflon-insulated wire in boxed assemblies.
I've worked with kapton tape (but never kapton insulted wire) and I can't imagine it being much good as insulation for wires.
I've also worked with lots of PTFE insulated wire and it was nice to work with, but only once you'd got used to its low friction.
Your reassurance is the fact that flying is the safest form of travel thanks to decades of diligent work by engineers, mechanics and accident investigators.
Also, I suspect that circuit checks could detect at least some shorts in wiring that can't be physically inspected.
Once the insulation is compromised, arcing can occur, which leads to charring of the Kapton. This changes the insulation’s dielectric properties, turning it into a conductor. In some cases, this led to overloaded circuits that were not detected by circuit breakers, since the insulation was carrying the excess current rather than the conductor."
[...]
>"Planes built since then generally use TKT, which is Kapton with two thin layers of Teflon to provide better resistance to mechanical abrasion and water intrusion."
PDS: TKT sounds like a much better material, from a material science perspective...
Gonna have to remember that one
(At a stretch, eyeballs might be Mark I, as they obviously haven't yet been patched to move that interconnect bundle out of the high-res region. Brains have enough legacy layers that they're probably Mark V at least...)