Perishing of vinyl components

The Modern AFV discussion group is hosted by Erik Gustavsson and covers the variety of AFVs used by all nations in the post WWII era.

Perishing of vinyl components

Joined: November 18th, 2005, 7:23 pm

August 29th, 2017, 10:03 pm #1

Hi, I posting this in the "modern" DG just because it pertains to a modern AFV but it could go anywhere.

I keep my finished kits in boxes as I don't have the display space. I opened a box today with two complete Takom Chieftains in it when I saw the front of the turret of one had developed a satin sheen. Removing the turret showed an oily substance on the turret rim that seems to come from the vinyl mantlet cover. This has so far only affected one kit but that was the first completed. What shocked me the most was the fact that this residue had covered the whole front of the turret, basically the Stilbrew area. It seemed to wipe off ok and looks better once I rubbed a tissue over it but I wasn't too keen on the idea of having to clean it off. Has anyone else experienced this?

Stuart
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Joined: August 12th, 2004, 3:14 pm

August 30th, 2017, 1:19 pm #2

If the material itself is degrading (like DS tracks, for example) then you can't save it. if it is actually "vinyl" that can not be painted with solvent based paints, which will react with the plastic and cause an oily sticky sufrace. That is why if you build vinyl figure models etc those must be painted with acrylic paints.

Sometimes you get similar reactions to poorly cast resin parts (cheap or poorly mixed resins) that leach out oils forever and will bleed through paint. That stuff will also melt plastic.
DAVID NICKELS
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Joined: May 18th, 2004, 2:57 pm

August 30th, 2017, 1:55 pm #3

Hi, I posting this in the "modern" DG just because it pertains to a modern AFV but it could go anywhere.

I keep my finished kits in boxes as I don't have the display space. I opened a box today with two complete Takom Chieftains in it when I saw the front of the turret of one had developed a satin sheen. Removing the turret showed an oily substance on the turret rim that seems to come from the vinyl mantlet cover. This has so far only affected one kit but that was the first completed. What shocked me the most was the fact that this residue had covered the whole front of the turret, basically the Stilbrew area. It seemed to wipe off ok and looks better once I rubbed a tissue over it but I wasn't too keen on the idea of having to clean it off. Has anyone else experienced this?

Stuart
on my BTR and BRDM kits I built in the early 90s. The next time I tackled an armor kit with vinyl parts, I dipped the parts in Future floor polish (yes, I know it isn't a polish). Then I weathered the tires, or more accurately, I weathered the acrylic coating. I haven't had an issue with the vinyl tires melting like I did previously.
RobG
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Joined: April 18th, 2005, 3:05 pm

August 30th, 2017, 7:07 pm #4

If the material itself is degrading (like DS tracks, for example) then you can't save it. if it is actually "vinyl" that can not be painted with solvent based paints, which will react with the plastic and cause an oily sticky sufrace. That is why if you build vinyl figure models etc those must be painted with acrylic paints.

Sometimes you get similar reactions to poorly cast resin parts (cheap or poorly mixed resins) that leach out oils forever and will bleed through paint. That stuff will also melt plastic.
I have DS tracks I painted with enamels 7 or 8 years ago. They have not degraded, broke, crumbled, whatever over that time. I think most the problems people have with DS type parts comes from what they weathered them with.
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Joined: October 10th, 2004, 8:44 am

August 30th, 2017, 9:43 pm #5

Sherman and StuG, some oozing, getting brittle and broke like glass with the slightest handling.

I'm not the only one, many modellers experienced this, there are several threads on Armorama, Missing Lynx, FaceBook groups...

Cheers,

Christophe
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Joined: April 18th, 2005, 3:05 pm

August 31st, 2017, 3:01 am #6

I've never had any problems with anything DS.
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Joined: October 5th, 2004, 3:07 pm

August 31st, 2017, 6:49 am #7

The DS material is not bad "by design". If manufactured correctly it should be as durable as styrene or vinyl (the real one, not the rubbery stuff some Chinese manufacturers were using in the past). And in majority of cases DS tracks really work well.

The problem is that DS seems to be difficult to manufacture correctly and the manufacturing QA in Dragon's Chinese factories apparently isn't particularly good... The end result is a noticeable percentage of bad quality products
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Joined: August 12th, 2004, 3:14 pm

August 31st, 2017, 11:33 am #8

I have DS tracks I painted with enamels 7 or 8 years ago. They have not degraded, broke, crumbled, whatever over that time. I think most the problems people have with DS type parts comes from what they weathered them with.
Maybe you haven't had the problem but many other people have. And its not just on this page or this forum but pretty much every armor forum.

I have opened brand new, sealed, store bought, kits and found the "soft" tracks to be a dark orange color, hard as a rock, and brittle. So, any deterioration has nothing to do with what you weather something with if they can go bad in a sealed box.

Likewise I have some Tamiya Churchill tracks that have done the same thing. They crack and split if you try to bend them around the wheels. They haven't even been painted. It's the newer gluable material from a current kit. The old vinyl ones don't have this problem.
DAVID NICKELS
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Joined: August 12th, 2004, 3:14 pm

August 31st, 2017, 11:35 am #9

The DS material is not bad "by design". If manufactured correctly it should be as durable as styrene or vinyl (the real one, not the rubbery stuff some Chinese manufacturers were using in the past). And in majority of cases DS tracks really work well.

The problem is that DS seems to be difficult to manufacture correctly and the manufacturing QA in Dragon's Chinese factories apparently isn't particularly good... The end result is a noticeable percentage of bad quality products
I've said before I thought that since the problem seems random and not in every kit, that it may be a formulation/mixing problem and that different production runs may have different mixes of the ingredients and sometimes it isn't right. Sort of the way you can have a badly mixed batch of resin that doesn't cure properly.
DAVID NICKELS
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Joined: May 24th, 2003, 3:07 pm

August 31st, 2017, 3:54 pm #10

Hi, I posting this in the "modern" DG just because it pertains to a modern AFV but it could go anywhere.

I keep my finished kits in boxes as I don't have the display space. I opened a box today with two complete Takom Chieftains in it when I saw the front of the turret of one had developed a satin sheen. Removing the turret showed an oily substance on the turret rim that seems to come from the vinyl mantlet cover. This has so far only affected one kit but that was the first completed. What shocked me the most was the fact that this residue had covered the whole front of the turret, basically the Stilbrew area. It seemed to wipe off ok and looks better once I rubbed a tissue over it but I wasn't too keen on the idea of having to clean it off. Has anyone else experienced this?

Stuart
Issues like this with softer plastics aren't uncommon. They're not universal, just not uncommon.

The primary contributor to this are the additives mixed, or compounded, with the base polymer and then moulded into the parts of the kit.

For instance, raw, pure polystyrene is the brittle, clear plastic used for clear parts and canopies. All the colours in kits are additives. The varying hardness we all know exists between different manufacturers and kits are also a function of different additives compounded with the base polymer. Others are added to increase mouldability, decrease shrinkage, etc. etc.

When it comes to the flexible plastics like vinyl or DS this is achieved through additives called plasticizers, adding plasticity (flexibility) to the base polymer. These, like all of these additives, come in a bewildering and ever-changing number of types and effects.

Now this would all be much more manageable if this sort of thing was strictly controlled. But, outside stuff bought to aerospace/defense/nuclear specifications (and paid for on that basis) these things are not terribly well controlled at all. Lots of times the compounder changes the additives to suit themselves (it's a touch cheaper or allows other additives to be inserted, etc.) and other times the moulder wants something a bit cheaper or easier (=cheaper) and they both simply make the changes they want and as long as there isn't a gross effect on the product, no-one's the wiser.

But sometimes there is an effect and it takes time to show up. Plasticizers, especially, have a tendency to leach out of the moulded product over time sometimes on their own, and sometimes in response to environmental conditions like heat, light or the presence of other chemicals. Plasticizer leaching out can leave a film on the object or on objects it touches. It can leave a product stiff, brittle and prone to cracking/splitting. It can also leach out of one product and into another making it look like the other product is "melting" if it is susceptible to that plasticizer.

The softer a part is, the more plasticizer it generally contains. The more, or more aggressive, at any rate. The more plasticizer a part has, the more likely it may be unstable over time.

Commercial compounders don't really check for this sort of thing and make no guarantees. If it happens, it happens and you're stuck. They also don't generally guarantee that their particular compound recipe won't change over time so a part that was good, may be not good for a while and then may go back to being good again. And it's entirely possible that no-one in the chain knows or cares why. It's a good bet that the compound recipe will change on a reissued kit, especially if several years have passed.

All of this is to provide some perspective on why this sort of thing happens and yet doesn't happen to everyone or every time.

Personally, I tend to avoid the flexible products on my models. I've had good luck with old school vinyl track, but avoid the flexible mantlet covers or DS track or soft truck tires simply because I feel the risk of leaching plasticizer is too high and I don't want to take a chance. If a new kit comes with flexible parts I now bag them separately to prevent contact and frequently don't use them in the end.

Here endeth the epistle...

Paul



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