[Milsurplus] Plastics turning to cheesecake

[Hue Miller]

The other day i unwrapped a power supply cable for a radio, manufactured and wrapped in
1945. The surface of the cable was very sticky. Altho i will indeed try to clean it, i suspect
it is in the process of becoming sticky black cheesecake, like equipment feet, handles,
some cabling, and shock-resistant padding in shipping trunks on other equipment older than
40 years or so.
I wonder: what is going on here. Is the "plasticizer" which lends flexibility or some softness
to plastics based materials, now migrating to the surface? Or?
Will all plastics based components meet this fate - the still solid ones just waiting their turn?
Or is there a reason some plastics  components will  "melt" while some others will not?
I think the "melt" syndrome is similar to the situation seen in collectible transistor radios
where a headphone cord stored in the same box "burns" lines into the radio's case.
-Hue Miller  KA7LXY / Newport, Oregon, USA, Oregon's scenic Pacific coast