
Kapton: Miracle Material with a Tragic History - apsec112
https://hackaday.com/2018/04/04/kapton-miracle-material-with-a-tragic-history/
======
Rebelgecko
Kapton tape is also a great example of how Amazon algorithmically enables
knockoff and counterfeit goods.

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

~~~
dapids
I bought a roll direct from 3M a few weeks back. Was well over $40. It would
also appear they don't call it kapton, but instead thermosetting adhesive.

Checkout 3M 5413 AMBER. Larger rolls can cost upwards of $300, not cheap
stuff.

~~~
LeifCarrotson
Digikey is one of the primary vendors of 3M, and well known for reliability as
a counterfeit-free distributor.

[https://www.digikey.com/short/zrz730](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.

~~~
dapids
Yes, I regularly order from them, but shipping via DigiKey hasn't been great
lately where I live so I went with 3M. I also highly recommend digi-key for
anyone's kapton needs. Edit: spelling

~~~
bsder
I've been tending toward using Mouser lately. DigiKey seems to be playing
games with low-volume prices on me lately as well as screwing up shipping.

~~~
exmadscientist
The only trouble we've had with Digi-Key over the last six months, with dozens
of orders, has been coming too close to their end-of-day shipment cutoff. (It
seems to be closer in practice to 7:30pm than their advertised 8 CT, but I'm
not begrudging them that during this pandemic! This is avoiding restricted
materials such as lithium batteries, flux, etc., as well as avoiding value-
added items. Order those earlier in the day if you want them fast!) Most of
our orders are overnighted, for what that's worth; I know the big distributors
do treat overnights differently.

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....

~~~
bsder
> We have never seen a single issue with pricing not as advertised at small
> quantities

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.

~~~
exmadscientist
OK, now _that_ I wouldn't have expected! Thanks for the heads up! (Not that
I'd likely be able to observe it with our weird procurement flow....)

------
areoform
As PaulHoule has pointed out,
[https://news.ycombinator.com/item?id=24179043](https://news.ycombinator.com/item?id=24179043)
, Kapton is the final "gold foil" layer in a foil sandwich to insulate almost
all spacecraft, inclusive of the LEM. It was used extensively as insulation in
almost every Apollo subsystem, including the Command Module, and it became a
small tradition to take pieces of the foil with you after splashdown. A final
keepsake after a mission gone well.

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...](https://shop.minimuseum.com/products/apollo-11-command-module-foil)

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...](https://mattcbergman.com/2015/08/02/new-horizons-thermal-control-
system/)

------
numinary1
Kapton insulation was not shown to be the root cause of the crash of Swissair
111, nor was it entirely ruled out. [https://www.tsb.gc.ca/eng/rapports-
reports/aviation/1998/a98...](https://www.tsb.gc.ca/eng/rapports-
reports/aviation/1998/a98h0003/a98h0003.pdf)

~~~
TwoBit
I read the report and it seems to put most blame on all the flammable
materials present than the initial arcing event.

------
PaulHoule
If you see a picture a satellite wrapped up in what looks like gold foil it is
probably Kapton film with aluminum coating on the other side.

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.

~~~
wombatmobile
> it doesn't have the complex production complex

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](https://www.youtube.com/watch?v=RvAOuhyunhY)

~~~
PaulHoule
Teflon is bad enough in terms of persistent organic pollutants.

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'.

~~~
unchocked
I'm also working the planetary sunshade. Any source for the Chinese $60T price
point?

~~~
PaulHoule
This paper describes a sunshade launched from a large expendable rocket of
current technology

[https://journals.sagepub.com/doi/full/10.1177/16878140177192...](https://journals.sagepub.com/doi/full/10.1177/1687814017719227)

The $60T is my number based on the guess that the Long March 5 costs about the
same as similar western rockets.

------
tyingq
Kapton is something you've probably seen if you've opened up a laptop. It's
the most typical material used for flexible pcbs: [https://raypcb.com/wp-
content/uploads/2018/03/35e7d51a831f15...](https://raypcb.com/wp-
content/uploads/2018/03/35e7d51a831f153.jpg)

------
dfee
The article describes numerous crashes associated with Kapton, beginning with
a story about a passenger plane where hundreds perished. It also mentioned a
short circuit on the launch of the Columbia Space Shuttle, and military
planes.

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.

~~~
x3haloed
> 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??

~~~
nitrogen
I don't know if such things are used on passenger aircraft, but I've heard
that fighter jets use time domain reflectometry to detect potential faults in
wires, and how far along the wire the fault lies. Even a small nick in the
insulation is supposed to change the impedance enough to create a detectable
reflection.

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.

~~~
wiremaus
Unfortunately I don't think TDR would help here: the issue isn't gross damage
to the metal of the wires, it's subtle damage to the insulation.

~~~
nitrogen
From my prior comment: "Even a small nick in the insulation is supposed to
change the impedance enough to create a detectable reflection."

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.

------
SAI_Peregrinus
It's also used as a tape. Very, very handy to hold down parts & wires when
soldering, since you can get it right next to the iron and not have any
melting/burning issues (with most electronics solders).

------
peter_d_sherman
>"Studies showed that Kapton was far from the ideal insulator everyone had
hoped it would be — it tended to develop circumferential cracks from the
slightest of nicks, exposing the conductors within. Kapton is also easily
degraded by moisture, exacerbating the problem in humid environments or areas
of an aircraft subject to moisture, like galleys and lavatories.

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...

------
B5C8ECB24DB47D1
Also commonly used as vacuum window in X-ray facilities/setups. Probably one
of the best ratio mechanical resistance / low absorption over a large energy
range.

------
c54
> Mark 1 Eyeball

Gonna have to remember that one

~~~
mark-r
Good luck with your Mark 1 Brain.

~~~
082349872349872
Mark I brains suffice to make incised graffiti. Although the data density is
pitiful, the observed retention lifetimes beat tape storage.

(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...)

------
S_A_P
I was a huge car audio nerd in the late 1980s/early 1990s. One bullet point
you could expect to see on most subwoofer spec sheets was 'KAPTON' voice coil
former. I often wondered why that fell out of favor, but it seems that we know
the answer... Most kilowatt subwoofers now use aluminum or copper voice coil
forms for what I can only guess is that they are just better...

~~~
analog31
Kapton was an improvement over paper and phenolic, due to higher heat
resistance. It's still widely used, e.g., in musical instrument speakers. I
could see how aluminum and copper could be further steps along a similar
progression.

------
pfdietz
Perhaps the solution is to go to optical fibers, and just have a small number
of power cables with better insulation.

------
unsrsly
Kapton is an outstanding substrate material for flexible printed circuits. It
has one of the lower dielectric loss tangents available, and this becomes
important in RF and microwave applications. However, PTFE is better.

------
nickbauman
Kapton is also inside many nuke plants in the US, too. What could possibly go
wrong?

