Anyone heard of 'plastic corrosion'?

[carlos marighela]

And there's the thing. The assumption that all batches of similar materials are the same doesn't hold up. Pigments, additives and the chemical compounds of different manufactuers or even the same ones may change and thus alter the equation in terms of lifespan.

Zamak a metal much used in the manufacture of diecast models from the 1930s through to the 1950s developed a horrible reputation for crumbling into dust with age. yet there have been different formulations of the material over the years, just as there have been a wide variety of manufacturers of products using it. Some have crumbled, some are still goin strong almost 100 years on.

[SteveBurt]

It is only the bendy plastic which seems to go brittle. Hard polystyrene doesn't (unless you leave it out in the sun; UV will destroy it).
However, the strange rubbery tracks on old airfix tanks go sticky and will weld themselves to plastic surfaces they have been standing on

[Patrice]

Some of my very old Airfix figures broke or crumbled many years later. 

I thought perhaps because they had stayed in an attic and didn't like the cold?
Plastic is not a natural molecule...

[Dubbya]

I've left some unassembled & unpainted resin in my garage with record level heat this summer, interesting to see if it's affected it.
(I remember people leaving GW's awful "finecast" models in the car during summer!).

The oldest 1/72 models I have are "only" 20-25 years, suffering similar mistreatment. I hope I never see them crumble

[moiterei_1984]

I‘ve only recently got a good batch of my uncles Esci, Airfix, Matchbox and what not planes and ships from the 60s. All lovingly slathered in Enamels. Only thing that went bad were the decals, which turned yellow and partly flaked off just by looking at them. The latter probably because they weren‘t varnished at all bitd.