Bending sheet plastic & transfering developments onto plastic

[kitnut617]

These might be a couple of useful tips for someone.

1.  I found another medium for applying my developments (layouts) onto plastic for cutting.  Previously, I had made a clear decal of my layouts (cones, barrel shapes etc.) so that I could follow the lines when cutting, but it didn't work out very well, the decal would separate from the plastic before I was done, or it got scratched off.  This time for my Atlantic project I used 'Multipurpose Labels', it comes in 8 1/2" x 11" size, has a sticky back and so far haven't had a problem with it lifting off the styrene (make sure it is totally dust free otherwise it will)



2. Again for my Atlantic project, I had to make a section of fuselage the same as the B-36 fuselage, a straight parallel piece but half round in shape.  I tried bending it with some long pliers which was half successful but it still wouldn't hold it's shape, and then I went onto boiling it for sometime in water, and that improved it somewhat.  But then I tried boiling it in the microwave -- now this did something almost instantaneous.  Not only did it maintain it's shape that I wanted, but all the crimp marks left by the pliers disappeared.  What I did was to wrap the styrene around something close to the diameter I wanted, put it into a bowl of water and then microwavd it on high for a few minutes, kept the water bubbling for about half a minute then took it out quickly and cooled it under cold water.  WARNING::: be very careful when you do this ----- VERY HOT!!!!!!!!  It would seem that with all the molecules being agitated by the microwave, it reset the plastics memory better.  Another WARNING: Don't microwave the styrene by itself ---- can you say  ---FIRE!!!!  (and no, I didn't find out the hard way     )
EDIT: Another WARNING: DO NOT USE ANYTHING METAL AS A SHAPE FORMER IN THE MICROWAVE. Use glass, plastic or wood

[PR19_Kit]

Mrs. PR19 will NEVER believe it when I ask her if I can use the microwave to build a model...... 

[Hobbes]

Thanks for the tip. I've been having trouble bending styrene, and this confirms that the temperature I've been using was too low.

[kitnut617]

When I've bent plastic before, I've always bent it, rolled it, formed it, a bit smaller than what I needed because the plastic would always try to open up again (the in-grained memory).  What I've found with this method is you don't have to pre-roll it around something that is too small, because I've been trying to open up the formed part again and it just won't, I mean it's holding the shape I had bent it to and the 'new' in-grained memory is holding it to that shape.

Here's something else I've found out, depending what altitude you live at, it will effect the boiling point of water.  Where I am at roughly 3000 ft, water boils at 90 degrees --  so boiling the water in the microwave seems to get the boiling water up a level or two.

[NARSES2]

Here's something else I've found out, depending what altitude you live at, it will effect the boiling point of water.  Where I am at roughly 3000 ft, water boils at 90 degrees --   so boiling the water in the microwave seems to get the boiling water up a level or two.

I forget what the drop in degrees C per metre of altitude is (someone will know) but unless I'm being thick at 3,000ft if water boils at 90C in the open air it will still boil at 90C in a microwave, unless of course you could pressurise the microwave ?

Edit : Just had a thought. The microwave may be bringing the plastic up to a higher temperature while the water is acting as a coolant thus preventing it reaching flamability. So although the water is boiling the actual plastic is above 90C ?

[Thorvic]

What I did was to wrap the styrene around something close to the diameter I wanted, put it into a bowl of water and then microwavd it

Might be wise to remind people NOT to use a metal former for this roll !

[kitnut617]

I forget what the drop in degrees C per metre of altitude is (someone will know) but unless I'm being thick at 3,000ft if water boils at 90C in the open air it will still boil at 90C in a microwave, unless of course you could pressurise the microwave ?

Me and the missus have had quite a discussion about that recently, she's been using her 'English' cookbook to do some recipes and they're not turning out right.  I said it has to do with the altitude and doing a google using the words 'cooking at altitude' was how I found that the water boils at a lower temperature.  So the question was, if some food stuff says it has to be cooked at boiling point (100C) on the box, is it being cooked correctly even though the water is boiling at 90C.  To me it isn't --

But you could be right with your comment about the plastic being heated to a higher temperature though --- but I think the molecules being agitated has also something to do with it.

Here's a little experiment that I found interesting, boil some water in a bowl on the stove, get it boiling for a short time then quickly take it off the ring and pour a teaspoon of sugar into it and then watch what it does.  Next do the same thing but boil the water in a microwave, then see what happens ---

[kitnut617]

What I did was to wrap the styrene around something close to the diameter I wanted, put it into a bowl of water and then microwavd it

Might be wise to remind people NOT to use a metal former for this roll !

Right on Geoff, I'll edit the original post   

[ysi_maniac]

I do not understand your discussion about boiling water at altitude, but if this serves to clarify ...
Water boiling at lower temperature is related with atmospheric pressure. Agitation of molecules is related with temperature (in fact, temperature can be defined as average kinetic energy of molecules) not with atmosphere pressure.

[ysi_maniac]

Anyway, you can also try to work with thinner plastic (2 layers of half thickness, for instance). Bend them as desired. glue them with liquid cement and leave them to cure but forced to the desired shape.

[kitnut617]

I do not understand your discussion about boiling water at altitude, but if this serves to clarify ...
Water boiling at lower temperature is related with atmospheric pressure. Agitation of molecules is related with temperature (in fact, temperature can be defined as average kinetic energy of molecules) not with atmosphere pressure.

I'll try to explain Carlos, me and the wife are originally from the UK many moons ago, my wife had bought a lot of recipe books and such when we were there.  These are what we call our 'English' recipe books and as such all the recipes are for cooking at sea level.   I don't think there are very many people in the UK that live over a 1000 ft above sea level let alone 3000 ft above (or more as we get into the Rockys, Calgary is almost 4000 ft above, also we're at what is called the flat lands because we're out on the Prairies)

So if we were in England and using the cook book, and it says to cook at boiling point, that would mean at 100C.  But if we use the same book here (at 3000 ft) and cook to boiling point, it's only cooking at 90C.  So is it cooking right It's still boiling but 10 degrees lower.

And your interpretation of the molecule agitation is exactly what I was trying to say, it's not dependant on heating through the water.

Robert

[Hobbes]

styrene doesn't contain water molecules so it won't be heated directly by a microwave, and won't end up with a higher temperature than the surrounding water.

[Brian da Basher]

That's an excellent tip, Robert! Many thanks! I'm sure I'll have the need to nuke some sheet into shapes someday.

Brian da Basher

[GTX]

Mrs. PR19 will NEVER believe it when I ask her if I can use the microwave to build a model...... 

Something about a 'shake and bake' kit...leaving now

[NARSES2]

So if we were in England and using the cook book, and it says to cook at boiling point, that would mean at 100C.  But if we use the same book here (at 3000 ft) and cook to boiling point, it's only cooking at 90C.  So is it cooking right It's still boiling but 10 degrees lower.

Robert

My first answer is no, it should reach 100C, but then I think again and don't really know