Sciencemadness Discussion Board

hot glue sticks

KonkreteRocketry - 18-3-2013 at 10:58

can you possibly burn hot glue sticks ? is there any flexible rubber-plastic like material that can burn with relatively less residue ? thx for answers.

ScienceSquirrel - 18-3-2013 at 12:19

Hot glue sticks are a polymer mixture, see here;
http://en.wikipedia.org/wiki/Hot-melt_adhesive#Materials_use...
The common EVA based ones are often used by fishermen for running repairs on tackle in the field where they are melted with a cigarette lighter or miniature torch. They will catch fire and burn with a luminous flame and drip hot burning glue blobules if you let them.
They do not burn very well though and you can easily blow them out.

franklyn - 18-3-2013 at 12:52

Acrylic
www.youtube.com/watch?v=TLPWqCMb7DE
www.popsci.com/diy/article/2013-02/gray-matter-watch-hybrid-...
How to construct it
www.youtube.com/watch?v=p-iAyp88qb4&NR
http://blog.makezine.com/2012/10/11/homemade-hybrid-rocket-e...
http://hackaday.com/2012/09/26/hybrid-rocket-engine-uses-acr...

Polyethylene
www.youtube.com/watch?v=p-iAyp88qb4&NR
How to construct it
www.youtube.com/watch?v=RDkjsVUcxmw

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This is cute. Uses N2O cylinders
www.aeroconsystems.com/motors/Screamer_folder/screamer.htm
www.ebay.com/itm/170898489729
www.ebay.com/itm/170648854658
www.ebay.com/itm/261090614290

Just because material is available in a convenient form does not
make it ideal rocket fuel. PVC has been applied but it makes HCl
fumes. I recommend melt cast asphalt as the grain to use with
oxygen.

.

IrC - 18-3-2013 at 19:00

Quote: Originally posted by ScienceSquirrel  
Hot glue sticks are a polymer mixture, see here;
http://en.wikipedia.org/wiki/Hot-melt_adhesive#Materials_use...
The common EVA based ones are often used by fishermen for running repairs on tackle in the field where they are melted with a cigarette lighter or miniature torch. They will catch fire and burn with a luminous flame and drip hot burning glue blobules if you let them.
They do not burn very well though and you can easily blow them out.


Since you understand the chemistry behind them can you tell me why I cannot get the stuff to make an electret? I held it between plates in liquid state for hours with 20 KV applied to the plates, and allowed to cool to room temp. Even then shorting the plates and storing for months, makes no difference. I think a tenth of a volt is the most I see assuming it's not just stray fields messing with my meter. I have tried this a few dozen times with many varying brands of glue sticks. Total failure every time. I have long thought it was due to a structure re-arrangement during cooling which ignores the applied voltage (which I kept steady all the way down to room temp.).

MikeSomething - 21-3-2013 at 09:45

Just a guess, but I'd assume that any vinyl compound would be too electrically lossy. I know using a PVC form for a Tesla coil will drastically reduce its efficiency due to the PVC absorbing too much of the charge. IIRC, the loss is actually due to PVC having a lower impedance as the frequency gets higher.

Either way, PVC is not a good choice for high voltage insulation. Maybe the same is true for PVA?

ElectroWin - 21-3-2013 at 11:21

hot glue sticks do burn, often with lots of smoke; if you mix with an oxidizer in the molten state and cast that, it might work quite well as a solid rocket fuel.

but be very careful! this stuff is sticky and can give you pretty bad burns

i have mixed hot glue with paraffin to make a safer casting material, but i have not tried mixing with oxidizer, myself. you'll need one that is stable at hot-glue melt temperature

IrC - 21-3-2013 at 22:19

Quote: Originally posted by MikeSomething  
Just a guess, but I'd assume that any vinyl compound would be too electrically lossy. I know using a PVC form for a Tesla coil will drastically reduce its efficiency due to the PVC absorbing too much of the charge. IIRC, the loss is actually due to PVC having a lower impedance as the frequency gets higher.

Either way, PVC is not a good choice for high voltage insulation. Maybe the same is true for PVA?


Not so sure the reason is dissipation. The 2 mv Tesla coil I built on 24" diameter PVC pipe has very low damping. I was thinking it may more related to hydrogen bonding and crystal structure. Something I had not considered a few years ago when I was trying the material in electret building. From the wiki page mentioned above:

"Hot glue sticks are usually based on one or more base material, with various additives. The composition is usually formulated to have glass transition temperature (onset of brittleness) below the lowest service temperature and a suitably high melt temperature. The degree of crystallization should be as high as possible but within limits of allowed shrinkage. The melt viscosity and the crystallization rate (and corresponding open time) can be tailored for the application. Faster crystallization rate usually implies higher bond strength. To reach the properties of semicrystalline polymers, amorphous polymers would require too high molecular weights and therefore unreasonably high melt viscosity; the use of amorphous polymers in hot melt adhesives is therefore usually only as modifiers and additives. Some polymers can form hydrogen bonds between the chains, forming pseudo-cross-links strengthening the polymer."

Electrets are made from an amorphous material and require the charge separation to be 'frozen' in place upon cooling. I am thinking even at 20 KV applied on the outside, the force is low compared to neighboring molecules forming into a crystal structure. To me this sounds like the likely reason for failure.

Fantasma4500 - 23-3-2013 at 06:55

well when i use hot glue i just melt it with a lighter, if you keep it in the blue part of a normal lighter's flame then it will just melt and wont become black.. wont be a problem if it would start to burn anyways..