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Old 16th Nov 2019, 3:52 pm   #12
GrimJosef
Dekatron
 
Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: Dyeing colourless heatshrink blue to match small vintage electrolytics

In my limited experience of slitting heatshrink Symon (confined mostly to making a small hole in the stuff as a 'breakout' to feed a wire through) any cut opens up enormously when you start the shrinking. I'd struggle to believe that a tube which is still too large when fully shrunk could be modded to an even smaller size.

As a follow-up to my earlier posts I thought I would try a thinner, shinier, less scattery/milky heatshrink material. There is a family of these based on 'modified fluoropolymer' (a form of PVDF - polyvinylidene fluoride - I believe). What put me off them originally was a) that I know PVDF to be chemically very unreactive, so perhaps unusually difficult to dye and b) that the shrink temperature is much higher than the polyolefins. As it was, though, neither of these factors turned out to be a showstopper.

The attached picture shows the result. The lower capacitor is the one whose cladding I dyed a couple of weeks ago. The upper one is the latest result with the fluoropolymer. The colour is just as good but the upper film is indeed a lot thinner, shinier and clearer than the lower one. The picture clouds the distinction slightly because there is a little bit of camera defocus in the foreground. But that's certainly not the only reason for the clearer typescript visible on the upper capacitor (you can judge the defocus by looking at the leadout wires at the ends of the two caps).

The actual tubing I cose was Raychem RT-375-3/8-X-STK, available from Farnell, at least while stock lasts (their UK order code 1210450). This hardly needed to be shrunk at all to fit onto my caps, so heating wasn't as much of an issue as it might have been. But the thinner material and the lack of dye concentration during shrinkage meant I did need to load a lot of dye into the plastic. To do this I extended the soaking time to 10 minutes and raised the dye temperature to ~92C (94C at the start of the soak, 90C by the end). The tube didn't shrink detectably during the soak.

I think this is probably as close as I am going to get to the look of the original film. I really struggle to tell the difference fom old stock caps. I now need to set to work soaking a fair number of sleeves !

Cheers,

GJ
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