Melting display feet

[Coloruser]

So, I am now the lucky (we will see) owner of a IIsi 5/80 with Nubus adapter and FPU - including a 14" Apple RGB Color Monitor. Strange thing is, the displays feet almost melted away. They feel like fresh sanitary silicon.

The "debris" could be removed with 99% iso and at least one foot melted away thru the ventilation holes of the IIsi`s top cover and dropped on the power supply's outer metal shell. I have never seen this before.

Has anyone else experienced this? Is this because of the storage (unit was in storage since 1998).

 

[The Salami Boss]

This is incredibly common in long term storage and doesn't just affect Apple gear. I visited Computer Reset and basically everything in the warehouse with a particular composition of foot would have some variation of this fault. It's just the way they degrade in these conditions.

 

[Paralel]

Yeah, this happens to all types of systems over time. The material that makes feet semi-rigid separates out and what is left behind just becomes goo. It happens to all items made from this type of material, it's just a matter of time. The chemistry from it is inherently unstable over time. It was never considered a problem because people didn't think what they made would still be around in 20-40 years. Bad guess on their part.

 

[Phipli]

It can be caused by contact with plastics that offgas... something or other. Some bubblewrap does it.

I discussed it with a chemist at my old work, but have a terrible memory.

 

[Coloruser]

No bubble wrap, just standing on top of the IIsi like in normal operation.

 

[Danamania]

I had the same happen on the same model display a few years ago. I'd had the display sitting on wooden fibreboard shelves for years, pulled it down and all feet were fine. Sat it on top of my 6360, and within hours the rubber had melted and ran down the front of the Mac.

*only* on one corner though! The shelf I'd just taken the display off had no evidence there was gooey rubber on it, only marks that something had sat there for years, perfectly normal rectangular feet made of solid rubber. If they'd been liquid at the time there'd have been residue there, but there was none.

I suspect that after some time the rubber feet change composition and are still rubber, but they become very sensitive to other materials, and then when exposed to them turn to goo. That, or exposure to some cleaning compound 15 years ago made that one foot sensitive to the 6360's plastic.

Similar with an almost decade-old spectrophotometer at work with a rubberised coating. Co-worker changed to a different hand cream, touched it with barely any still on his hands, and it melted while he was using it. Old rubber gets *weird*!

 

[3lectr1cPPC]

I really think it does have to do with the material it's in contact with. I have an old laptop that I got in a small lot at a garage sale, and they were all stored vertically in a box. Only some of the feet were in contact with the next laptop over, and those were the ones that melted. The only exposed to air feet didn't melt.

 

[Paralel]

I had the same happen on the same model display a few years ago. I'd had the display sitting on wooden fibreboard shelves for years, pulled it down and all feet were fine. Sat it on top of my 6360, and within hours the rubber had melted and ran down the front of the Mac.

*only* on one corner though! The shelf I'd just taken the display off had no evidence there was gooey rubber on it, only marks that something had sat there for years, perfectly normal rectangular feet made of solid rubber. If they'd been liquid at the time there'd have been residue there, but there was none.

I suspect that after some time the rubber feet change composition and are still rubber, but they become very sensitive to other materials, and then when exposed to them turn to goo. That, or exposure to some cleaning compound 15 years ago made that one foot sensitive to the 6360's plastic.

Similar with an almost decade-old spectrophotometer at work with a rubberised coating. Co-worker changed to a different hand cream, touched it with barely any still on his hands, and it melted while he was using it. Old rubber gets *weird*!

Now that is rather fascinating. I have a feeling that the fibreboard shelves acted like a preservative, as strange as that may sound. Its my understanding that most fibreboard is made in a process that leaves residual formaldehyde behind. Formaldehyde can act as a preservative and a stabilizer. I wonder if the trace concentrations from the fibreboard were enough to stabilize the feet.

As far as old rubber getting weird, it's true. Besides a chemical used to make it more rigid (when needed), rubber almost always contains another chemical, a stabilizer which protects the isoprene bonds in the rubber from being attacked by outside chemicals, oxidation, etc... But, it acts almost like an antioxidant, it gets used up over time without being regenerated. Once its all used up, the isoprene bonds become susceptible to attack, and these bonds are what keeps rubber together. That's why rubber that is newer can essentially be touched all you want with whatever on your hands (unless its something that really preferentially attacks isoprene bonds) it doesn't harm it, it just consumes some of the stabilizer. But, once its gone, something that would have been taken care of by the stabilizer can now attack the isoprene bonds directly, and then you get melty rubber.

The nature of the interfacing material having a hand in the process is interesting. I bet its possible. I'll have to look into it.

 

[3lectr1cPPC]

Isn't formaldehyde toxic?

 

[Paralel]

Isn't formaldehyde toxic?

At a high enough dose, but the trace gas that comes off of many things made with it are not a problem. It's like the old pressure treated lumber, loaded with arsenic, but it's not too much of a problem because most people aren't licking it.

 

[LaPorta]

I've never seen that happen on any of my machines, ever. Either I live in the Twilight Zone, or theres something with how I store them that prevents it.