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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
i have to admit i never would have thought of 1,4 dichlorobenzene...
as for Adrenaline's idea of benzoic acid, it turns to a liquid at 252 F, then volatizes at 480 F, AndrewM needs a solid to vapor phase change skipping the liquid phase (sublimation)... if a solid liquifies close to its boiling point maybe he can make that work, notsure what Andrews goals/purpose is though...
Registered Member #235
Joined: Wed Feb 22 2006, 04:59PM
Location:
Posts: 80
Well provided it doesn't need to sublimate... Ethyl cyanoacrylate could work. Plain Superglue is pretty much 100% Ethyl cyanoacrylate. It boils at 56C and de-polymerizes with heat, not sure how hot though.
Wikipedia wrote ... Heating causes depolymerization of the cured polyECA, producing gaseous products strongly irritating to lungs and eyes.
Registered Member #49
Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362
Cyanoacrylate might be a winner; I had discounted it without any research but it could be perfect:
wrote ... However, a notorious problem ofcyanoacrylate polymers is their susceptibility to thermal degradation at only moderately high temperatures. As a consequence, the instant adhesive benefits of cyanoacrylate monomers have not been available in many applications where the bondedsubstrates may be subjected to intermittent temperatures in excess of 120.degree. C. or extended exposure to temperatures of about 80.degree. C.
... depending on exactly how it decomposes.
I looked into the 1,4 dichlorobenzene and it sublimated readily at STP which is actually a bit undesirable - I'd like the film to be stable at room temp and disappear only at elevated temperatures. So I'll put that on the back burning.
Benzoic acid could be a winner as well, depending on how well i can make a film. I'd considered pine rosins previously which seem to be similar to the Benzoin resin precursor of benzoic acid.
Registered Member #49
Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362
Although there is this about CAs:
wrote ... In addition, the thermal decomposition of cyanoacrylate was studied using simultaneous thermogravimetric and differential thermal analysis (TGA-DTA). It was determined that detectable and quantifiable amounts of HCN were generated from the thermal decomposition of cyanoacrylate monomer and polymer at temperatures as low as 200 °C. Using an optimised picrate-resorcinol method, it was shown that around 10 μg of HCN could be generated from the heating of 1g of cyanoacrylate monomer at 200 °C. For one of the adhesives tested, this increased to above 100 μg of HCN when 1g of cyanoacrylate monomer was heated at 280 °C.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
well HCN is always a problem with combustion products of plastics, its interesting that cyanoacrylates only need to be heated not burned.
in aircarft crashes, A large fraction of the surviors of the initial crash/incident are often killed in the next minutes from inhaltion of vapor...Sometimes without the aircraft ever leaving the ground.
i find it hard to believe CA would decompose/volatize cleanly, as you require AndrewM. I may need to try this myself...
I have some citric on hand... any idea what it decomposes into? I wish I still had an academic account, this would likely be enlightening: EDIT: er found it - it decomposes into lots of things... looks like it probably can't be relied upon to leave the premises. Same thing with the other two, decomposition is only half the battle, I need the products to leave, probably in gaseous form.
Patrick wrote ...
i find it hard to believe CA would decompose/volatize cleanly, as you require AndrewM. I may need to try this myself...
I'll let you know, have some CA in the oven as we speak.
Registered Member #49
Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362
CA experiment showed... Heat really does destroy CA.
I glued 15 sheets of paper together with a single drop of CA in the center of each. When the stack was firmly bonded it went into the oven at 400F with a ~50g weight on top of the stack over the CA.
The purpose of the weight was to prevent the stack from separating when the CA was merely softened, as opposed to evaporated.
After about an hour pages could be peeled away slowly; the CA was clearly molten/tacky.
After about 3 hours most of the sheets were completely "free" with only some slight browning where the CA used to be. The sheets which got bigger drops of CA (it was hard to control accurately) were still bonded by definitely less strongly; the paper generally tore away easily with only surface tears.
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Nontoxic room-temp solid that boils under 500F
