Large Scale Central

Given most models are plastic, over time ...

General Discussion
#1

Given most models are plastic, over time decay will become an issue.

This came up on a Tyco/Mantua forum this weekend when talking old Varney models’ plastic parts and white growth on them.

I found the following on plastics, which was helped by my already knowing this,

http://www.navsea.navy.mil/Home/Warfare-Centers/NSWC-Carderock/Resources/Curator-of-Navy-Ship-Models/Lead-Corrosion-in-Exhibition-Ship-Models/

Lead has been a popular metal for fabricating fittings for exhibition ship models. It has been attractive because it is easy to obtain, soft and easy to fashion, and it melts at a relatively low temperature. However, lead fittings frequently corrode. (1) Corrosion may be so severe as to completely consume the piece, leaving behind a white or gray residue popularly, and aptly, called “lead disease”, “lead rot”, “lead cancer”, or “lead bloom”.

In the ship modeling community there has been considerable speculation about what causes lead to corrode severely, how to arrest the process in pieces already installed, and how to prevent corrosion in the future. This report compiles some of the technical literature on the subject and relates that literature, in practical terms, to ship modelers and to museum staff who are unable to obtain the advice and services of objects conservators.

And now, on with the plastics;
Chemical & Engineering News July 18, 2011
Volume 89, Number 29 pp. 29 - 31
Preserving Plastic Art
Chemistry of polymer-based creations presents unique problems for conservators
[Sarah Everts](http://pubs.acs.org/cen/staff/biose.html)

Since the invention of plastics in the late 1800s, artists and designers have been using them to make everything from high-fashion hair combs and intricate sculptures to moon-mission spacesuits. But “the number of plastics used by artists increased dramatically in the 1960s,” Shashoua explains, during that era’s love affair with all things plastic and the corresponding increased availability of polymers. Yet it took until the 1990s before the museum world got over what conservators refer to as “plastics denial syndrome”—denying that plastics in a museum’s collection have short lifetimes and degrade—and woke up to the fact that many pieces of plastic-containing art were in grave danger of being lost, van Oosten says.

…

Because any conservation or cleaning strategy is specific to a plastic type, museum staff need to know an object’s precise plastic makeup. But few plastic art objects come with a chemical ingredient list, and not all museums have laboratories with the tools—primarily infrared and other spectroscopic equipment—to help analyze them. Conservators sometimes have to rely on their sense of smell to guide their plastic diagnosis, Shashoua says. Leaching phthalate plasticizers give PVC the smell of a new car, she explains, while cellulose acetate smells like vinegar, and polyester has the odor of raspberry jam, cinnamon, and burning rubber.

#2

Gee I hope there is no test!

Wasn’t Varney’s white crud from Zamak or zinc?

#3

John Caughey said:

Wasn’t Varney’s white crud from Zamak or zinc?

White metals will do that but plastic parts were the issue on the cars involved.

Here, more material,

Problem plastics, types of deterioration & where you find it

https://mmics.files.wordpress.com/2008/04/problem-plastics-check-list.pdf

#4

I understand the latter part of the post, but the first reference is all about the decomposition of lead, caused mainly by acetic acid, caused by wood releasing the acetic acid.

I cannot see any connection to plastic in that first reference, and I don’t see how understanding the lead decomposition relates to plastic decomposition.

Greg

#5

Greg Elmassian said:

I understand the latter part of the post, but the first reference is all about the decomposition of lead, caused mainly by acetic acid, caused by wood releasing the acetic acid.

I cannot see any connection to plastic in that first reference, and I don’t see how understanding the lead decomposition relates to plastic decomposition.

Greg

Get off you lazy butt and expend some effort in to finding your glasses, I said it outright,
I found the following on plastics, which was helped by my already knowing this,

Here I go and tell what my whole thought process is and here you go putting it down and dismissing it as valueless, guess I now know everything I need to know about your general character. I appreciate that insight, thank you.

I’ve had my fill of this business of because I have autism, dyslexia, and a couple other things there fore my thoughts have no value - enough of that , it ends - now.

#6

But the chemistry of plastics has improved over time. So are our “modern” plastic models subject to the same types of degradation as older plastic models?

#7

David; in some cases, yes, and others, sadly, no. Case in point: the Aristo switch, throw bar, moulded from non-uv protected plastic.

In some cases, the plastic is protected, mostly by the paint applied after moulding, but other plastic has additives that protect it from UV rays.

I have plastic rolling stock, and track (Ties) that have been in service since 1982, with no problems. BUT; I don’t leave the rolling stock out in the sun all day long, every day. The track is out all year long, and has “Behaved” well.

The first sign of trouble is when the plastic becomes brittle, and is easily broken. Try leaving a piece of unpainted white Styrene out in the sun for a few months; especially if you live down closer to the equator…people in the Southern States, can attest to this…

Fred Mills

#8

UV rays from the sun are the biggest problem, they can age our track ties rolling stock and us.

I have a dozen Bachmann cars that stay out year round and I find that some of the hook and loops couplers and side frames have turned grey and are prone to breakage. The cars themselves are mostly painted but faded a bit. I think it will be many years before they become brittle.

#9

Fred, yes, white polystyrene can warp or degrade in direct sunlight. I even had the seam of a aircraft wing pop when it was displayed in a hobby shop window for a couple of months. I forgot about the Aristo throw-bar/tie issue. But most of our rolling stock is supposed to be made out of something other then polystyrene.

So I am wondering if our models will become dust in the foreseeable future.

#10

@Greg - You might ought to practice what you preach. Forrest clearly stated in the OP the relationship. And that the relationship was for background information.

@Forrest - Take a chill pill dude, it’s only a model railroad forum. Having read, and re-read the post, I see nowhere that Greg attached you personally, only that he didn’t understand the relationship of the two subjects being discussed. As for your last sentence, I have 4 grandchildren with varying degrees of Autism, ADHD, Speach Apraxia, and Dyslexia. None of those were mentioned nor referred to in any way. Maybe my understanding of those makes me a more considerate member, but there are others on this forum with similar/same afflictions without the sensitivity you displayed. As I have told my grandchildren many times, if something you read sounds offensive, re-read it in a monotone. Remove the inflection of emotion and see if it doesn’t sound better.

Frankly, I had to do the double read to follow along. Thank you for the information and references, they are quite informative. Even though I work for a military sub-contractor, I was un-aware that that level of information was available to the general public. Great stuff.

#11

David Maynard said:

…

So I am wondering if our models will become dust in the foreseeable future.

Dust to dust, ashes to ashes, I’m just hoping the foreseeable future means my models turn to dust before I do.

Thanks for the fascinating information Forrest.

#12

It’s not just UV, all those gears that cracked on the axles, shrunk. De-gassing releases compounds… NIB, I believe.

Usually only when they saw the light of day did you know they were bad… (no, not; all ways nor always, for the contentious)

John

#13

Some plastics depending on how they are formulated, and how they are used, react differently. Some. when used as gears, are put under tension, when pressed onto a metal axle. If they are machined a certain way they may accept the tension, but when moulded, they don’t.

The moulded gears are far less expensive to make, so that is a great saving to the manufacturer, but fail/crack, over a short time.

The plastic used as part of the axle on the pony trucks of the B’mann Ten Wheeler, are another example of the wrong plastic used for the job. They crack, and fail after a rather short period. They can be easily replaced, but I don’t think B’mann even stocks them as replacement parts, so you have to find some plastic tubing that will do the job

As far as most of the USTrains, Aristo, and Bachmann rolling stock; it is mostly basically a common type of Polystyrene plastic. The trucks are slightly different Polystyrene.

One way to prove this is to notice that MEC or lacquer thinner, can be used to “Weld” the Polystyrene used for them. The trucks might not weld as easily.

LGB’s original formula for plastic, was quite a different type, but later American style, Chinese manufactured equipment often appeared to be a more basic type of Polystyrene.

I hope others with more knowledge about “Plastic”, and its many, many variants, can correct me, and add to our knowledge.

Fred Mills

#14

There are two basic types of degradation to plastics. one is the uv degradation where the long strands of the polymer break down to smaller entities. Often the graying we see is caused by the loss of important additives known as plasticizers. Many plastics(polymers) are very brittle and crystaline. plasticizers are added to give the polymer more flexibility and less brittle. These are usually a very low volatile liquid. given heat they slowly evaporate and uv can destroy them. The most common evidence of this evaporation is the thin film seen on interior windshields present after a hot day in the parking lot. In any case the loss of these causes the plastic to return to its brittle state and break easily.

#15

A second problem with plastics with unknown pedigree is that glues do not always work with them. Few glues hold “euromystery plastic” for long. I’ve started using a hot soldering iron to weld pieces together. Not pretty, yet. But on the inside in corners, they hold really well. Welding doesn’t seem to care about whether the plastics are identical or not.

#16

An interesting discussion. As you have said, not all plastics are created equal. and you have said sun degrades plastics…some faster than others. I would bet that NO plastic is totally immune to the effects of the sun.

I was interested in the lead discussion too, though not plastic, for two reasons.

One, I have seen some REALLY neat ship models basically ruined by old lead based detail parts going bad.

And two, because I have visited that Naval facility that wrote the article. they build some REALLY FIRST RATE ship models for customers such as admirals, members of congress and the President. It was a very interesting visit. “Museum Quality” pales in comparison! No lead or plastic parts! The were located in the basement of one of the Naval Tow Basins, used to test the hull shapes of future ships. They would tow large scale models which accurately modeled only the ships hull shape at accurately scaled speeds on a 1/4 mile long swimming pool. Those models were built in a different shop and were also interesting but totally lacking in detail.

#17

I am not to concerned, my Lionels in my collection are older than I am, and the plastic is just fine. Several of my LGB pieces are as old as I am, get regular exposure to UV and are also fine. I think most of the damage we see on vintage trains comes from improper storage. And as one who is on the spectrum, there are always those, even here, that get under my skin, I just step away from the topic or not pay attention to thier post. LGB’s plastic is hard to glue, that is why most lgb models either snap together or are screwed together. They used Luran S during the Lehmann years and very few glues will work with it, and those that do are nasty to work with. Mike

#18

ok now if someone can come up with a time frame: X number of UV exposure/time =Y degradation or something along those lines, we will have an idea of what to expect for working life of a model. I guess the clear UV should be liberally applied to all rolling stock as a safety measure

#19

Pete, but the variables are so many that it would be difficult to come up with an answer. What is the plastic involved? Does a manufacturers plastic vary a little bit from batch to batch? At what latitude and altitude is the model exposed to sunlight? How long is each exposure? Is the sunlight diffused in any way? What is the storage environment for the cars? Does the paint affect the plastic over time, and how?

I am sure a chemist would come up with other variables. Its an interesting question, but one I am not sure there can be a pat answer for.

#20

Well, despite a wavery start this thread has turned out most interesting. Thanks for starting it Forrest.

I guess every household and not just those with large scale railroads have ‘plastic’ items that are in need of repair. How often did our attempts at gluing come to nothing?

I have been experimenting with Bondic of late - some successes so far.