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Author Topic: dose plastic dry out?  (Read 1733 times)

bigford

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dose plastic dry out?
« on: December 28, 2007, 04:47:26 AM »

my deck crane in the happy hunter seems to have gone brittle  and is now
broken into a half dozen parts. so my question is after i paint all the other
plastic parts will the go brittle too???

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Circlip

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Re: dose plastic dry out?
« Reply #1 on: December 28, 2007, 08:12:13 AM »

You need a chemist for this one bigford,and a list of what you've done to the crane surface from flat to finish painted, and all the "chemicals" used. If you keep PVC (wire covering, soft plastic sleeving etc.) in close contact with expanded polystyrene, they self bond together like the proverbial s**t to a blanket, and the EP seems to etch itself into the PVC. Look at the effect of cyano fumes on fingerprints. I know it's long term but my grey UPVC drain pipes are very "dusty" after 30years of exposure to the elements, and "chemically" treating the surface of our models must only accelerate the processes. It don't seem to do it to traditional materials.
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barryfoote

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Re: dose plastic dry out?
« Reply #2 on: December 28, 2007, 08:14:00 AM »

Bigford. Plastic of most types unless it contains some ingrediant I don't know will go brittle if exposed to a lot of sunlight. Down here in southern Spain it is quite a problem.

Barry
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RipSlider

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Re: dose plastic dry out?
« Reply #3 on: December 28, 2007, 10:22:41 AM »

Footski is correct, most plastics get damaged in UV light.

Styrene is especially easy to damage as it has more random chains, which are more easily attacked by free radicals generated by the UV than many other plastics.

However, this is still a fairly slow process. It is however possible to have a bad batch of plastic.

Steve
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malcolmfrary

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Re: dose plastic dry out?
« Reply #4 on: December 28, 2007, 11:34:04 AM »

I always assumed that any volatile components in the plastic in the kits would migrate away over time.  Old kit parts always seem a bit delicate and brittle, even if they have been left in the box.  UV or even just the bit of extra warmth from sunlight probably accellerates things.  I have always used Humbrol enamel, and the painted bits seem to last well.  I assume that keeping the styrene separate from air helps.
I have a Lindberg trawler that will be having its 21st next year. The deck is sprung into the hull, and the hull shows no signs of brittleness, but it is rather thick material.  Some of the finer details have suffered. 
I have never been in favour of using superglue on styrene, preferring MEK or polystyrene cement out of the tube.  I just cant bring myself to trust a joint that consists of styrene, a mechanical surface join to another type of plastic (the superglue) and another join back to styrene, when a styrene to styrene weld is possible.
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bigford

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Re: dose plastic dry out?
« Reply #5 on: December 28, 2007, 12:01:20 PM »

the pic above is the  crane in question (not mine) i just won the boat on e-bay
the crane must be 10 years old or so  and was yellowish in color.
all i used was testors tube glue. let it sit for about two days then i bumped it
off the table and boom it shattered  >:(
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BobF

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Re: dose plastic dry out?
« Reply #6 on: December 28, 2007, 12:35:28 PM »

Hi bigford,

Was the crane un painted when you got it. If so it will be the effect of sunlight etc. Painting should help solve the problem unless all the parts are already to far gone. 

If you clear epoxy finish a model, it should always have an extra coat of exterior varnish to protect it from the effects of UV

I'm not technical but thats why plastic windows are called Upvc. it stands for "unplasticised" well thats what I was told.

I have a Graupner kit "Marina", although I painted the hull, I left the topsides as supplied because the finish colour was what I wanted. The entire topsides went brittle like meringue, but the hull is still perfect.

Bob
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bigford

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Re: dose plastic dry out?
« Reply #7 on: December 30, 2007, 03:58:19 PM »

crane was unpainted
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footskijunior

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Re: dose plastic dry out?
« Reply #8 on: December 30, 2007, 07:47:52 PM »

Does plastic dry out, well, I have the problem at work with plastic fitting, mooring ropes atc, which are all made from crude oil based products. the term is actinic degrdedation, and unfortunatly there isn't a great deal you can do about it. try and keep out of direct sunlight for prolonged periods (days not hours), and dry off any excess salt water. Some materials do have an additive but it hs to be implanted at the production stage, and is expensive.
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