My feet are melting

[mikeselectricstuff]

Noticed this wierd thing happenning to some very old stick-on PVC (I think)  feet - timescale maybe 10-15 years at room temp
 

[BravoV]

Bio degradable ? 

[Mint.]

Bio degradable ? 

Good guess, I agree. Perhaps it is.

[Mechatrommer]

Bio degradable ? 

a reason for "time to buy a new one"

[Balaur]

Yeah, I've seen that happening several times. The rubber feet from my old (8+ years) laptop (acting as a server) fused to the docking station at some point. When I've tried to unplug it, it was like a very stringy cheese sandwich.

Foam-based stuff is even worse: earphone foam pieces decide to spontaneously deconstruct themselves, various foam-backed trim elements from my car deconnect from their support and started exhaling a rather unpleasant dust and so on.

Cheers,
Dan

[BravoV]

Bio degradable ? 

a reason for "time to buy a new one"

In the future we might hear something that sounds like this ......."Kid, in the good ole days, you can collect a really good & reliable scope that will last very long, but now, god damn it, just look at that good dso, its working fine but its melting like an ice-cream." 

[Jad.z]

Natural rubber is made of polyisoprene chains that slip past each other when the material is stretched.
 
When raw, the substance is too sticky and soft to be of much use, so it is toughened with the addition of chemicals such as sulphur that create cross-links between the chains, making the rubber stiffer and less sticky.
 
This process is called vulcanization.
 
With time, ultraviolet light and oxygen in the air react with the rubber, creating reactive radicals that snip the polyisoprene chains into shorter segments.
 
This returns the rubber to something like its original state, soft and sticky.
 
Meanwhile, these radicals can also form new, short cross-links between chains. This hardens the rubber and eventually it turns brittle. Any vulcanization agents left in the rubber contribute to the process.
 
Whether a rubber band goes sticky or hard depends on the relative rates of these processes, and these rates in turn depend on the rubber’s quality such as what additives, fillers, and dyes it contains, and how it is stored.
 
Heat and light speed up the reactions, for example, an 18°F rise in temperature will roughly double reaction rates, and the presence of strong oxidizers such as ozone creates even more radicals.
 
The eventual fate of your rubber band depends on the temperature in the room, and on whether you have a desk by a window or near a machine such as a photocopier that creates ozone.
 
How much light and heat is required for these changes?
 
The polymer chemistry of rubber is fairly messy, and so this is difficult to answer precisely. Obviously, the chemical reactions run slowly if the rubber is in a refrigerator, more quickly if left on a sunny desktop.
 
A rule of thumb is that reaction rates roughly double for an 18°F rise in temperature, but this is complicated when you take oxygen and light into consideration.
 
The quality of the rubber is also important, such as whether it contains additives, fillers, or dyes that absorb light energy or help transfer radicals.
 
The final factors that influence the change are ozone concentration, UV light intensity, and whether the band is stretched or not, stretching brings chains closer together, allowing radicals to jump from one chain to another more easily, and to create new bonds between chains.

[G7PSK]

Chlorine also makes rubber decompose so if cleaned with a chlorine containing product it could start to decompose, I believe that they put bleach onto the tyres of drag racers or the track at the start as this softens the rubber to give more grip.

[wkb]

Chlorine also makes rubber decompose so if cleaned with a chlorine containing product it could start to decompose, I believe that they put bleach onto the tyres of drag racers or the track at the start as this softens the rubber to give more grip.

Bleach (sodiumhypochlorite (spelling?) solution in water) does not decompose rubber.  Otherwise rubber gloves would disolve quickly on the hands of your local cleaning lady

Vulcanised rubber is quite stable, things like UV light, oxygen etc can degrade it but only over time

[G7PSK]

Chlorine also makes rubber decompose so if cleaned with a chlorine containing product it could start to decompose, I believe that they put bleach onto the tyres of drag racers or the track at the start as this softens the rubber to give more grip.

Bleach (sodiumhypochlorite (spelling?) solution in water) does not decompose rubber.  Otherwise rubber gloves would disolve quickly on the hands of your local cleaning lady

Vulcanised rubber is quite stable, things like UV light, oxygen etc can degrade it but only over time

Rubber gloves are not made of rubber or at least not pure rubber. Pure latex breaks down fairly fast in strong chlorine compounds especially at elevated temperatures. Also when you use household bleach with your marigolds on the bleach will be diluted and you or your wife will rinse the gloves after use in clean water.   If you read your washing machine or dishwasher instructions it will tel you not to use chlorine bleach, this is due to the chlorine degrading the rubber seals and pipes.
I looked up what happens with rubber and chlorine, The chlorine replaces some of the polymer bonds.

[nessatse]

Rubber also does not like being in contact with lacquer paint (as found in spray cans).  I almost ruined a lacquered guitar by hanging it in a rubber hanger.  I have also seen this happening to old modems that had been standing on a painted metal shelf inside a cabinet for a few years.

[Mint.]

I had a similar "issue". I recently bought an old cassette tape player. It had foam bits inside which I assume were for vibration and shock dampening. Upon opening the player up the foam pads fell off and crumbled. 

[wkb]

Chlorine also makes rubber decompose so if cleaned with a chlorine containing product it could start to decompose, I believe that they put bleach onto the tyres of drag racers or the track at the start as this softens the rubber to give more grip.

Bleach (sodiumhypochlorite (spelling?) solution in water) does not decompose rubber.  Otherwise rubber gloves would disolve quickly on the hands of your local cleaning lady

Vulcanised rubber is quite stable, things like UV light, oxygen etc can degrade it but only over time

Rubber gloves are not made of rubber or at least not pure rubber. Pure latex breaks down fairly fast in strong chlorine compounds especially at elevated temperatures. Also when you use household bleach with your marigolds on the bleach will be diluted and you or your wife will rinse the gloves after use in clean water.   If you read your washing machine or dishwasher instructions it will tel you not to use chlorine bleach, this is due to the chlorine degrading the rubber seals and pipes.
I looked up what happens with rubber and chlorine, The chlorine replaces some of the polymer bonds.

Latex gloves are a verry different thing than proper rubber gloves.  Latex breaks down with other chemicals than chlorine, IIRC acetone and MEK for example.   Rubber is also a common name, covering both natural rubber as well as highly stable artificial rubbers.  When handling any chemical one should ensure gloves are used that are suitable for the chemicals bing handled AND suitable for the concentrations of said chenicals AND suitable for the contact times for those chemicals.  In some cases chemicals over a longer period penetrates a glove, while at the same time are OK for short term exposure.  Same goes for concentrations, good example being sulphuric acid.  Not too bad (still hazardous though!) in concentrations used in car batteries, but horrible stuff in concentrated form, let alone in its 'smoking' form.

So, normal household concentrations bleach are not a problem for sensible household gloves.  Latex is not sensible stuff for work like this, also for reasons of mechanical strength btw.

[amyk]

Possibly it was stored in an environment with gasses that attacked the material and caused depolymerisation.

[im_a_human]

My very old fluke multimeter probes kept making a sticky liquid whenever they were put into the probe clips on the holster. It was only this one set of probes that did this as i have another set of the same  probes. I figured it was due to the materials in the holster and the probes causing some kind of chemical reaction.

Another thing is whenever cables and wires of any type touch walls the paint always comes off on the wires, weird