Anyone heard of 'plastic corrosion'?

[Daeothar]

I just came across this clip and found it too relevant for us miniature collectors not to share.

I'm sure there's a more accurate term out there than Plastic Corrosion, but the phenomenon looks pretty serious nonetheless. Anyone heard about this? Could this become an issue with polystyrene given enough time?

video link (youtube)

[Westfalia Chris]

The loss of softening agent has been discussed in other modelling circles for some decades now. It mainly affects those soft plastics, notable examples being toy car tires and the vinyl covers of 1990s Patlabor model kits which were quite notorious for the issue.

The loss of softening agent makes the plastic more brittle, obviously. It is also commonly found in old plastic toys, although some types of plastics seem to be more susceptible than others. I don't recall exactly where I read it, but hard polystyrene seems to be more susceptible than, say, ABS, e.g. comparing plastic kits from 1970s manufacturing runs to Playmobil toys from the same era, which my nephew is now still playing with 40 years after my brother and I did.

Essentially, it will affect any type of plastic, be it a thermoplast, an elastomere or a duroplast, if it contains any softening agent, including polystyrenes and resins.

I experienced both myself, and I tend to replace vinyl and rubber accessories by more resilient materials, e.g. plastic, metal or resin components. Another variation is the direct contact of rubber or vinyl to other plastics, which may lead to the soft part deteriorating due to softening agent dissipating from the hard plastic and attacking the soft (had that on a Solido Panhard armoured car, where the quite rigid vinyl tires turned out almost as soft as bubblegum).

It's quite noticeable with those plastic soldier type figures made of soft plastic, which are turning quite brittle now.

[Harry Faversham]

I've got some of the very earliest Airfix figures. The British Infantry Group are still as bendy as ever, the Germans snap like dry twigs!
On a happier () note, all my fifty year old Napoleonics, bend like fook and shed paint from sword and bayonet...
as good now as the day they were born!
 

[Elbows]

Even if it does..I'm not overly concerned about plastics going brittle in 40-50 years time.  That's more than enough service.

[Cubs]

I had some Zvezda plastic Gauls that were maybe 15 or 20 years old and they crumbled under my fingers when I rediscovered the boxes of them and started to examine them before painting. But the Airfix Ancient Britons I had from around the same time were still pliable and in good shape.

[carlos marighela]

Ça plane pour moi. 

[Pattus Magnus]

Does anyone know whether acrylic paint (or enamel, for that matter) effectively seals in the softening agents that can be lost over time, or do the chemicals pass through it, too?

[Ultravanillasmurf]

Ça plane pour moi. 

You are really showing your age.

[2010sunburst]

Leaching of plasticisers is well known in plastics, as is UV degradation. 
In normal use I can’t see our figures suffering overmuch, especially if they are made from decent quality material and kept in ambient conditions.  Keeping them in warm areas such as lofts may speed up leaching as it is temperature dependent.  Leaving them in sunlight for extended periods of time may increase degradation as well. 
As to longevity, I recently disposed of a tranche of old Airfix and Matchbox kits I had from my youth, and despite being a good fifty years old they were as good as the day they were made.  The old Airfix PVA figures I disposed of at the same time were also fine, though a few, ACW grey jobs, had become brittle.  I think the brittleness may be influenced by the pigment used to colour them. 
Recycled material may well degrade faster due to the reprocessing conditions experienced by the vinyl, so perhaps the Zvesda figures are made from that. 

[Storm Wolf]

Interesting?

Whilst I cannot claim any deep knowledge of the injection molding of plastic models, I did do a fair stint working with high voltage cross-linked polyethylene and rubber type cable insulations as well as other types of injection moulding materials.

Yes plasticizers can leach out, and the plastic structure can degrade as antioxidants are used up over time and then a thing called chain scissions occurs, this breaks the cross-linked strands holding the plastics form together (which is what makes it a thermoset plastic).
But I don't know if the hard plastic and certain other PVC models are even thermoset plastic. The fact they can be heated and bent slightly (or a lot) argues against this.

From that mentioned above in this thread, I feel its a mixture of the anti-oxidants being used up simply by time/heat/UV for the brittle models and some plasticizers coming out for the slimy and paint damaged ones.
My guess this is going to be a much, much worse issue for the 3d printed stuff in the far future though?

My 2P from more of an alchemist than a chemist

[SteveBurt]

My old Airfix ancients all went brittle, as did my ESCI Zulus, but the even more antique ACW figures are fine, as are the WW2 and as were the Napoleonics. So seems to be a matter of chance.

[Khusru2]

I got out my Airfix British and Zulus to paint last year and they just crumbled.

[Cubs]

Do you mean Esci British and Zulus? Airfix never did Zulu War stuff.

[Khusru2]

Yes! Of course it was.

[carlos marighela]

My mother foisted a couple of mystery boxes on me last week. Upon opening them, there was a mixed collection of Airfix 54mm plastics (mostly Napoleonics and WW2), a few Britains plastic figures (the ones with a metal base) and a selection of Timpo swappit figures. As these all date to my childhood, so they are 40-50 years old.

All appear to be perfectly fine in fact apart from bits snapped off in childhood warfare, they are pretty much exactly as they were 40-50 years ago. Plastic seems to have aged gracefully, just as pliable as it was when they were new.