Does plastruct go brittle over time?

[Izzy]

I built some structures a while ago, a few years now I think, using a mix of materials, with plastruct to represent H section beams and struts. They were meant to be fixed into place on a small layout being built but this never happened and so they have sat in a cardboard box awaiting use at some point in time. That time has now arrived but when they were retrieved it was discovered that they were 'poorly'. Several of the plastruct sections have fallen off, sometimes breaking at butt joints which had been overlaid with plasticard, or at others where they seem to have cracked for no apparent reason. I am trying to repair the damage as best I can, but begin to wish I had used soldered brass bits instead.

 

Has anybody else encountered this?

 

Izzy

[Rowsley17D]

A building I made with Plastikard some time ago suffered from going very brittle. I put it down to the sun but it could just a well have been its age too. I used to keep shed bits and bobs in plastic containers from the boxes moist toilet wipes came in and they too suffer from going brittle with age. I guess that how we get the dreaded micro plastic.

Edited July 28, 2019 by Rowsley17D

[russ p]

Plastic certainly suffers as we found out this weekend,  we tend to use the bath rather than the shower but we have had company for the last few days.

I noticed a water mark on the kitchen ceiling so checked shower waste was putting some fresh sealent around it as it did that before then noticed some cracking when I touched it it just fell out the bottom 

Tried stripping it down to remove tray but tiles now also need to come off so getting a specialist 

But in answer to the original question plastic does go brittle over time 

[PaulCheffus]

Hi

 

I have things made from plasticard that are over twenty five years old without any sign of deterioration, however they are all painted.

 

Were your items bare plastic or painted?

 

Cheers

 

Paul

[Foulounoux]

Environmental Stress Cracking is a known issue with certain polymers 

UV degradation is also known 

Plasticised materials eg PVC faux leather will suffer from the loss of volatile additives 

All sorts of factors can apply there was a lot of work on why blue milk/beer crates didn't survives as long as red...turned out the pigments allowed crack propagation 

 

I'll need to go back and try and find my 40yr old text books to get the details for styrene polymers ....I think plastruct is styrene based 

 

 

Colin 

 

[sharris]

On the micro-scale I've had to replace brake gear from my earlier wagons which snapped off with the lightest touch- either part of plastic kits or fabricated from microstrip (I usually use Evergreen rather that Plastruct) - these days I mostly use brass (Ambis and Bill Bedford) for those structures instead.

 

On the macro-scale I've had a set of plastic Venetian blinds spontaneously self-destruct through old age (replaced with a wood and metal version)

 

The blinds may be down to UV degradation, but the models were painted and not stored in the light - in addition I've had fine structures in old boxed Ratio kits fracture when removing them from the sprue which must be non-UV aging.

[cypherman]

Hi all,

I have found with some of my wagons that have been stored away for several years that the plastic went very brittle. Now they were stored in sealed boxes and kept in a wardrobe. So the only reason I can think for them going brittle was variation of temperature over time. In this case about 10 years

[TheSignalEngineer]

Plastics will change over time, especially through atmospheric factors, such as early grey plastic drainpipes turning to dust through UV exposure. 

Different plastics in close proximity will also suffer from polymer migration. the result of this is usually one going brittle and the other soft and gooey. We had a number of serious problems with this where synthetic rubber and PVC cables has been run in the same trunking.  I've even seen cable sheathing go soft when in close proximity to some types of emulsion paint.

[melmerby]

16 minutes ago, cypherman said:

Hi all,

I have found with some of my wagons that have been stored away for several years that the plastic went very brittle. Now they were stored in sealed boxes and kept in a wardrobe. So the only reason I can think for them going brittle was variation of temperature over time. In this case about 10 years

I think you will find it is just slow degradation of plastic over time. Some types are worse than others.

I posted sometime ago about a plastic wagon I had made some years ago but couldn't remember the make (nothing on it)

Between posting a query and picture and getting a reply, handling of the said wagon had reduced it to a load of bits, however a load of other wagons made at the same time and stored together had not deteriorated at all but were a different make and presumably a different plastic mix.

[Foulounoux]

7 hours ago, TheSignalEngineer said:

Plastics will change over time, especially through atmospheric factors, such as early grey plastic drainpipes turning to dust through UV exposure. 

Different plastics in close proximity will also suffer from polymer migration. the result of this is usually one going brittle and the other soft and gooey. We had a number of serious problems with this where synthetic rubber and PVC cables has been run in the same trunking.  I've even seen cable sheathing go soft when in close proximity to some types of emulsion paint.

 

Its not the polymers that migrate but the additives 

if the solubility parameters of the polymer and additive are aligned then the additive will preferentially migrate from one polymer to another 

 

 

this can cause the donor polymer to lose the additive and become brittle whilst the recipient is softened 

 

 

back  to styrene materials and photo oxidation will cause chain scission so in effect the long chain polymer breaks down into shorter chains . This then reduces the physical strength of the material and eventually they become weakened 

 

 

Colin

[34theletterbetweenB&D]

1 hour ago, Foulounoux said:

Its not the polymers that migrate but the additives 

if the solubility parameters of the polymer and additive are aligned then the additive will preferentially migrate from one polymer to another 

 

this can cause the donor polymer to lose the additive and become brittle whilst the recipient is softened ...

Vividly illustrated by 1/72 Airfix tracked vehicle kits. I built a great many of these for supply to hamfisted wargamers, in exchange for cash to spend on model railway product. They were not happy when the styrene track wheels went runny due to contact with the flexible track material; an effect that many here will probably recall.

[Shed Driver]

A good few years ago  I had an old Mainline Weltrol? dating from the late 70s.  When I picked it up a bogie and the end platform crumbled and separated from the rest of the wagon.  On examining the rest of the wagon there was no strength left in the rest of the moulding.   The wagon had not been exposed to daylight but was stored in an attic,  The warmer summer temperatures may have accelerated the disintigration.  Is this an indication that our models may only have a life of about 30 years?

 

Norman

[34theletterbetweenB&D]

1 hour ago, Shed Driver said:

...  Is this an indication that our models may only have a life of about 30 years?

Possibly only 15 years (Farish OO wagon bodies that went all runny. But they were the completest inaccurate crap so who cares?). I have 60+ year old plastic moulded model railway product that's fine, and a lot of it spent 20+ years under a concrete tiled roof getting seasonally baked and frozen. Some items may fail, all down to the polymer formulation used, but overall I don't think a huge problem.

 

[John Tomlinson]

2 hours ago, 34theletterbetweenB&D said:

Vividly illustrated by 1/72 Airfix tracked vehicle kits. I built a great many of these for supply to hamfisted wargamers, in exchange for cash to spend on model railway product. They were not happy when the styrene track wheels went runny due to contact with the flexible track material; an effect that many here will probably recall.

I've long wondered why this happened, and now I know - thanks!

 

So if we'd stored the vehicles with tracks off and in a separate box it would presumably never have happened.

 

John.

[sharris]

28 minutes ago, 34theletterbetweenB&D said:

Some items may fail, all down to the polymer formulation used.

 

For the same batch of styrene, is there any difference in model longevity depending on whether Mekpak (which has had more than one formulation), Butanone, d-Limonene or some other solvent was used during construction?

 

[wainwright1]

I know a modeller who used to scratch-build wagons in gauge 1 from polystyrene and he found that after a couple of years that these tended to fall apart generally where they had been stuck together using solvent. I think that it was the plasticiser in the styrene that had evaporated out of the material that caused the problem. I am not sure if the problem is the same with ABS type plastic as used in Plastruct or Evergreen. The type of solvent used may also have implications. He now builds his wagons with wood and metal.

 

I built many Airfix kits over the last 50 years and do not recall any of them falling apart, although they were mostly constructed using the old polystyrene cement rather than solvent. I suspect that once they were painted it substantially reduced the migration of the plasticiser. I also have many old Tri-ang and other brands of plastic bodied locos, coaches and wagons and do not remember any of then going crumbly or soft. Obviously prolonged exposure to direct sunlight would be likely to cause damage on more than one level, but perhaps storing models somewhere where there might be exposure to some kind of fumes or vapour which might otherwise be considered innocuous might cause damage over a prolonged period of time.

[Fat Controller]

After the oil crisis of the early 1970s, I had problems with a couple of plastic kits . They would have been manufactured at about this time, though I bought them from a model shop in Folkestone in 1992 or '93. When I tried separating parts from the sprues, a couple broke into large fragments. Fortunately, I was able to stick them back together, and I've seen no subsequent deterioration.

I had problems with some vinyl records in the 1970s; it took three attempts before I got a copy of 'I want to see the bright lights tonight' which would play without jumping. I thought I had a similar problem with a Velvet Underground record as well, but was assured it was meant to sound as it did.

[34theletterbetweenB&D]

1 hour ago, sharris said:

For the same batch of styrene, is there any difference in model longevity depending on whether Mekpak (which has had more than one formulation), Butanone, d-Limonene or some other solvent was used during construction?

Quite likely. I had the great joy of knowing a man who was chief analyst of ICI plastic's division, and quondam president of the Analytical section of the Royal Society of Chemistry; which hopefully gives some idea of his professional standing.

 

On many an occasion I asked him questions of this sort - mostly relating to polymer materials issues in my own career - but also touching on hobby related topics: and in summary: it's complicated and there is a knowledge deficit. For sure the knowledge gap has decreased since his much lamented death, but beyond educated guesses of what might have been the outcomes from constituents of the  commercial solvent mixture acting on a polymer of not fully knowable formulation, (or in other words, an inadequately defined problem set) we are still in the 'shit happens' zone of knowhow.

 

47 minutes ago, Fat Controller said:

...I had problems with some vinyl records in the 1970s; it took three attempts before I got a copy of 'I want to see the bright lights tonight' which would play without jumping...

That was 'quality output' from the pressing plant! Sometimes they would have entire days when nothing saleable was made! Anything over a net 50% of the pressings saleable was a great day at the factory. It was the Japanese dedication to really understanding all the essential success factors in the entire process that was required. Outside Japan very few cared to  follow that approach. The suckers would always buy...

[Izzy]

Thank you all for your replies, which have been most interesting and informative. Here is a photo of the structures in question, for a 1960's-on cement area distribution yard (Blue Circle), placed where I hope they will finally sit on my current 2mm layout when the re-made and mended parts have been painted.

 

 

I have been confused by the apparent strength of most of the structures, built from such odd items as plastic denture tubes (!!!), plasticard rod etc as well as ordinary/plain plasticard, (Slaters/Javis/Evergreen), all melded together with either Slaters Mek-Pak or EMA Plastic-Weld - my two standard liquid glues - and the failure of the plastruct sections alone. Not just at joints but warping along their lengths as well where they are not constrained by being against other parts.

 

If I find them disintegrating again then I am sure a re-build with metal parts will be the long term answer. Hopefully it will not be needed.

 

Izzy

 

 

 

 

[Izzy]

Well, just to bring this up to date it became clear after a while that the structures as they stood were beyond saving. More warping and disintergration took place very quickly. Can't quite believe how fast this was with the Plastruct parts especially. They seemed to just go very soft or just crumble away.

 

In the end most of it was just binned, but the gravity silo, inspired by the article in the first MRJ compendium on that at Barnstaple, has been rebuilt. Brass shim and rod was used to make the structure on which it sits. Embossing foil squeezed between coffee jar lids gave the corrugated sheet. Hopefully it will last a bit longer this time.

 

 

Izzy

 

 

[sharris]

19 hours ago, Izzy said:

Embossing foil squeezed between coffee jar lids gave the corrugated sheet. Hopefully it will last a bit longer this time.  

 

It took me a minute to visualise this until I remembered that some coffee jar lids had ridges around the outside - if you don't have that sort of coffee (none of my coffee has that sort of lid!), 4D Models of Aldgate, London (just a happy customer) sell corrugated brass and aluminium sheet with 1mm corrugations (right for standard 3" corrugations in 4mm scale), along with 1.5mm (passable in 7mm scale?) and 3mm.

 

[Pylon King]

I’ve been building power grid structures  using Plastruct/Evergreen for over fifteen years and haven’t noticed any changes .

[TheQ]

Many years ago included in one of my open university courses, was reference to an all plastic house 304mm to the foot scale,   "The house of the future" when it was built. It didn't last long,  Sagging,  warping,  bonding problems, and migration of chemicals all led to the bulldozer. 

Edited October 13, 2019 by TheQ

[TheSignalEngineer]

On 29/07/2019 at 11:53, wainwright1 said:

 

I built many Airfix kits over the last 50 years and do not recall any of them falling apart,

I've recently rebuilt a couple of Airfix 16T Minerals I originally built in the 1960s. No problems there. Also still running on new wheels are at least three Ratio wagons, a Starfish (Cambrian?), two Airfix Meat Vans and a Cattle wagon built c1980, a GWR Open C, and an LMS Short Tube plus an Ian Kirk LMS 5-plank of unknown vintage but probably about 40 years old. To go with it I recently made a stable mate picked up at an exhibition. The original price of these was less than £1. None of these show any plastic problems. 

Conversely, a canal transhipment shed I built in 1980 from plastruct section and styrene sheet didn't survive.

Edited October 13, 2019 by TheSignalEngineer

[Right Away]

8 hours ago, Pylon King said:

I’ve been building power grid structures  using Plastruct/Evergreen for over fifteen years and haven’t noticed any changes .

These are absolutely superb.