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| Plastic cases that go sticky |
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| AndyBeez:
Possibly my top technical peeve!!! Perfectly servicable and valuable devices end up as scrap as the soft touch seems to 'melt' over time. I have zero idea what the feck this stuff is, but the feel is very similar to the epoxy component in two part epoxy glue. It appears to be a clear coating applied over the plastic, but not bonded to the plastic. The break down seems to be time related. Even in cold dark store, the soft touch coating turns into a sticky mess. Proof, the case of a temperature sensor gauge inside a fridge went to glue too. The only effective method is to scrape off the cunk/funk, cut back to bare plastic with 800 grit paper and respray. Nothing chemical touches it. Acetone, IPA, bleach, mineral/white spirit, absolutely nothing. If you guys have a secret sauce, then please share. (Photos to follow) |
| amyk:
It's probably a polyurethane foam, one of the least stable plastics in common use. |
| tooki:
--- Quote from: Gyro on February 23, 2024, 07:55:16 pm ---I was just about to edit my post above. Yes, I found the datasheet for the cheap stuff on the DIY store site, attached. It's mostly Ethanol, <10% IPA, <10% MEK plus the colour and nasty smell/taste. P.S. No more IBM Selectrics, more's the pity, they were fun to watch! --- End quote --- #LFMF and NEVER use denatured alcohol with Bitrex (denatonium) for cleaning! The damned Bitrex not only gets on your hands, but also on whatever you cleaned, recontaminating your hands every time you touch the thing. The result is... you realizing how constantly we touch our fingers to our faces without thinking about it. |
| Nominal Animal:
--- Quote from: tooki on February 23, 2024, 06:00:24 pm ---Besides, plasticizer migration works the opposite of how you think: it migrates from soft plastics to hard ones and softens the hard ones. Plasticizer migration would result in the plastic going soft, not in the rubber going gooey. --- End quote --- Yup. The worst offenders (as in way too much plasticizer) in my experience are fake "silicone" leads, which are really just overly-plasticized PVA PVC. The result is that if you keep them in a plastic box, the lead can literally meld into the box, due to the plasticizers. I often want softer multi-strand wires, and don't usually need the high temperature capability of silicone leads, so I wouldn't mind them being PVA PVC or some other non-silicone plastic, but the migrating plasticizer makes them annoying to store; they need to be stored away from anything plastic, including cutting mats and such. The issues with plastic additives have existed for as long as plastics have been industrially manufactured. Back in the previous century, when reversal/slide films were still widely used (called "dia" or "diafilm" here), sometimes the pocket sheaths used to store them in books had additives that caused film destruction in a few years to a couple of decades. For soft overmoldings, I do believe butyl rubbers are the worst offenders, as they become sticky (especially so from human skin oils) in a few years. Some varieties become stinky (vomit smell), as they slowly decay, one of the byproducts being butyric acid. AvE has mentioned these butyl rubber overmoldings in his BOLTR videos on Youtube, including how oils speed up the decay of the overmolding; so that for industrial tools and tools used with oily hands (think mechanical repairs), they really don't last long. My own worst experience has been with bicycle handles, which became tacky, more tacky than 3M post-it notes, in a few years, with that recognizable butyric acid vomit smell. Eww. Oh, and hand cart wheels, which were some black plastic with plasticizers, that stained a plastic/vinyl floor mat with yellow blotches when they sat there for a couple of months. Dammit; should have waxed the mat better. |
| RoGeorge:
For sticky rubber in hand tools, a second cover might be the way in case nothing cleans good enough. Seen that done many ways, either by wrapping the handle with textile thread, or by covering the handle in huge diameter thermal shrinking tube, or even by covering with PET bottles heat-shrunk over the sticky handle. Water and soda PET plastic bottles will shrink a lot when heated, and will shrink in diameter only. When heated too much, the plastic will turn from transparent to milky white. |
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