Why can the insulation of headphone wires or other rubber parts of plugs become “sticky” (as if “melting”) over time?

Question

Cables and wires

Why does the insulation of wires, for example, headphones and other rubber parts of plugs, in a humid subtropical climate and living close to the sea, become sticky over time (as if "melting")?
What is the process for them? For example, ear pads made of foam rubber generally crumble in the form of dust. Is there any way to extend their lifespan? Or at least get rid of the sticky state with something?
A similar problem has never been observed in other climates.

Answer 1

The reason is that the (cheap, low quality) materials that these parts are made of contain a lot of so-called. plasticizers , such as DEHP . This thing does not enter into chemical compounds with the material and over time just comes to the surface. (By the way, specifically DEHP, when "taken orally" is very harmful to the kidneys, liver and genitals and is banned in Europe, at least in children's toys and food packaging. But do not be alarmed - in a particular case, there may be others , more or less harmful chemicals.) The process of "melting" is accelerated primarily by exposure to sunlight (ultraviolet radiation), which causes photochemical reactions in elastomers .
What exactly can be done. "Soak" the sticky mass of WD-40 and remove mechanically from the surface, after which do not forget to wash your hands thoroughly.
With foam rubber, a slightly different story, but the same moral: only replacing materials with better ones will help.
PS Just in case - I have never been an expert in materials science, I just happened to encounter a problem at work and retell the experts' explanations "in my own words".

Answer 2

At your own risk , you can try to use alcohol and cotton wool to remove the "sticky" layer. In my case, this allowed me to carefully get rid of the “floated” soft-touch coating on top of the usual plastic.

Answer 3

I usually observed the destruction of the rubber insulation with constant contact with the hands. For example, many years ago, all electronic equipment controllers, radio installers, development engineers were given antistatic dielectric mats made of gray rubber, they retained their properties and appearance for many years, only slightly darkened under the influence of light (sun), but the cutting edge, where the rubber constantly touched hands, completely depolymerized, destruction occurred. Rubber has become sticky, fluid, can be torn off and sculpted, as if from plasticine. The same thing happened with rubber cables, such as telephone headsets and headphones, where they were touched by hands. Although rather high temperatures (above 150 degrees) are required for the depolymerization of rubber (rubber), various acids and alkalis can be catalysts for the process, plus moisture and ultraviolet radiation (sunlight). The pH of the skin surface is usually acidic (due to the production of acids by bacteria living on the skin), these acids, plus sweat (containing various salts excreted by the sweat glands) and fat, can lead to the breakdown of many materials. As for the influence of proximity to the sea, I didn’t notice, although I live in Leningrad - St. Petersburg, perhaps the freshness of the water flowing into the bay, the absence of sea salts and bacteria developing in sea water, as well as the northern position, less ultraviolet radiation during the year, matter .
Foam rubber - foamed elastic polyurethane, in itself is unstable and short-lived, hygroscopic and collapses at elevated temperatures, and in a longer period - at room temperature, especially under the action of ultraviolet radiation, as well as building foam.
Now many are using short-lived materials, this is one way to get the consumer to buy new products, as well as the addition of "advanced innovative technologies" that do not affect the basic qualities of the product.