Subject:
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Re: A question of humidity...
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Newsgroups:
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lugnet.general
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Followup-To:
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lugnet.color
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Date:
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Fri, 16 Jul 2004 16:58:00 GMT
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Viewed:
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1206 times
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In lugnet.general, John Barnes wrote:
> In lugnet.general, David Koudys wrote:
>
> (major snip>
>
> > I didn't think that LEGO bricks could 'absorb' water moisture. Always had it in
> > my mind that ABS was 'waterproof'. Eh, live and learn.
> >
> > Dave K
>
> What an interesting post. It had never crossed my mind before, but the circuit
> board assembly places which use infra-red ovens to melt solder on circuit boards
> to allow the surface mount parts to float into place go to extreme lengths to
> avoid moisture getting into the resins which chips are made of.
>
> They use special climate controlled cabinets to store parts so they don't absorb
> moisture. Otherwise the parts are inclined to suffer from "the pop-corn effect"
> when they get heated up in the oven and damage themselves.
>
> Quite a lot of materials are "waterproof" while still able to absorb a small
> amount of water. I believe plastic molecules are quite large whereas water ones
> a quite tiny.
>
> The really interesting thing is the difference in behaviour of the green and
> blue baseplates. I wonder, since the blue has been phased out while the green is
> still current, if the stock of blue comes from some older technology plastic? I
> believe that TLG use many different plastics for different parts dependent upon
> application. The baseplate stuff seems different from the run of the mill 2x4
> brick ABS. Of course you wouldn't be likely to know that unless you used 48x48
> stud baseplates as raw material much like you use 4x8 sheets of plywood ;)
> Baseplate cuts very differently from bricks.
>
> JB
I think you're right, John - the grade of ABS in the baseplate is different than
that of the brick. I'd guess that the masterbatch colorant that LEGO uses for
blue requires a unique grade of ABS, and we see differences based on humidity
levels.
That's the great thing about ABS - it can be graded according to application.
Your lawn mower cover has a different grade than your telophone handset or your
car's dashboard. All are graded according to surface luster, colorfastness,
etc., I'd guess. Since the reaction to humidity by the blue baseplates, and the
baseplate grade as a whole, we can assume that that grade is different. I'd
guess its grade has the colorfastness quality that LEGO's looking for (or looked
for in the case of blue). Maybe there's an impact on the ABS's coefficient of
expansion for that grade and humidity level.
Interesting, anyhow. I've seen the same effects in my basement, and have a
humidifier in the LEGO area there as well.
By the way, I noticed a little while back that BASF is consolidating it's ABS
production facilities in Europe, so I wonder if that'll effect coloration and
availability for LEGO, if they use BASF as a supplier. It's all about the
plastic, man!
Check out:
https://www.plasticsportal.net/wa/EU/Catalog/ePlastics/doc/BASF/prodline/terluran_standard/processing.xdoc#N100A0
...for more. There is a statement there about the need for predrying the resin
pellets, since they can absorb moisture.
Ed
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Message is in Reply To:
 | | Re: A question of humidity...
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| In lugnet.general, David Koudys wrote: (major snip> (...) What an interesting post. It had never crossed my mind before, but the circuit board assembly places which use infra-red ovens to melt solder on circuit boards to allow the surface mount (...) (20 years ago, 16-Jul-04, to lugnet.general)
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