axehandle
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Feasibility of welding glassware using PVC.
Has anyone ever tried this?
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chemoleo
Biochemicus Energeticus
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I haven't tried it, but I saw people making it (In a laboratory equipment producing company). It is possible, but not easy.. You could certainly
use it for simple apparati, even simple destillation columns. DIY? Dont know.
In industrial processes, clear or coloured PVCs (or most other plastics) are melted, and running through a ring. With air pressure, this is blown into
a preexisting form, to which it aligns perfectly.
There are different PVCs IIRC, where some can be used to 'weld' different pieces together. I doubt you could easily do it at home, you would
need forms/moulds, proper temp. control, uniform density/thickness etc etc. Cheaper to get your glassware from Ebay!
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Mr. Wizard
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PVC can be reheated and reformed. It is common practice for a plumber to heat a length of it with a torch moved quickly over it's surface or to
put it on the exhaust pipe of a truck for a few minutes. Even a hair dryer will work. Some discussions have the PVC placed in hot vegetable oil. Too
much heat will brown or scorch it. It becomes very flexible and can be formed with air or with tools. The bad news is it is soluble in many solvents,
especially ketones.
[Edited on 20-1-2004 by Mr. Wizard]
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unionised
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Not brilliant heat resistance and poor solvent resistance don't bode well for making labware out of PVC (and it's definitely thermoplastic
btw).
A lot of the PVC you see, especially the flexible stuff, is largely plasticisers that leach out and contaminate your product too.
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Organikum
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this works:
For connecting two glasstubes for example one can wrap the gap with PE foil and put the assembling in the oven for some minutes (nominal temperature
of 150°C worked fine for me).
The PE foil is prestretched and will shrink and fix the pieces together quite fine.
If the gap is big or pieces of different diameter or forms are to be connected you have to make a removable piece to bridge the gap - I used cardboard
tubing with a slit cut in the length for easier removal. The procedure can be repeated with new layers of PE so a more solid connector is needed, this
works better than wrapping lots of layers at once what produces no good results. (At least it didnt for me).
This produces astonishing strong but thin tubes/connections already with two layers of simple wrapping foil - very thin glyss might shatter by the
shrinking also this never happened to me also when neontubes where (ab)used.
Overall this is a ultracheap and easy way to produce labware for the "not so high" temperatures range which is also disposable.
Hint: If connecting glassware it is not necessary to put the expensive and big and unhandy pieces in the oven, but two pieces of short glasstubing of
the same form/diameter or even cardboard will do it. If cardboard is used it should be oversized, it is much easier to shrink the PE by further
heating with a hot air gun or hairblower onto the glass then it would be to widen it again later.
have fun!
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Organikum
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more
Much better than using one big piece of PE is to cut a long stripe of about 3cm width and to wrap this overlapping/diagonal around the
glass/cardboard. Two layers at per "burn-in" - counterdiagonal wrapped give good results.
I also tried to include glassfibre and alufoil and other shit but this is nonsense as it leads to burned in holes or air bubbels - not good. Plain PE
or also PP foil works best after my experience, give it a try.
addon:
The cardboard must be covered with alufoil which is to be oiled with saladoil or vaseline for the PE not to stick. After the PE is wrapped around it
should to be wrapped in alufoil also - this is not a must be but makes it less probable to burn the shit - and keeps the oven clean.
The PE foil used should be of the thicker kind like used for heavy duty garbage sacks or similar. PP gives a more stiff product, so using PP for the
outer layers is a good idea.
[Edited on 21-1-2004 by Organikum]
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ElectroWin
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are there coatings that might protect the PVC?
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