Sciencemadness Discussion Board - Forming nitrocellulose to solid block?

Forming nitrocellulose to solid block?

Student32 - 12-4-2015 at 03:01

I've been reading the forum for years, but never had the need to post anything. Thank you for all the useful information you've posted!

I have a question on forming nitrocellulose (NC) into a solid block for use as a propellant.

Background
I've been doing amateur rocketry since I was a kid. This is uncommon here because of all the restrictions (for example the most powerful engines availible are D-class), and the lack of useful open fields. The amount of information available was non existent until the internet became big, and in the early years of the internet most sites with information on pyrotechnics were neither accurate nor safe.

I now have access to a workshop which is licensed for manufacture and storage of certain pyrotechnic devices. I only mention this because through that connection I have done some work on applied pyrotechnics, and the staff there have taught me a lot about working with those materials and the science involved. The goal of this thread is NOT for me to actually make it, I'm interested in the theories and science of the subject. I am of course also interested in information and experiences by anyone who has hands on experience on working with NC as monolithic blocks.

Issue
There is little information available on casting NC for use as a monopropellant. Most other energetic materials I have dealt with have two issues with casting; uneven solidification and block deformation by shrinkage.

Regardless of casting with a solvent or by heating, most materials will shrink slightly when they solidify. When casting, the outer edges and top surface will usually solidify first. When the volume inside these walls solidify it shrinks, but the walls don't shrink with them. Shrinking inside an inflexible wall, cracks, defects and air pockets will form.

The other issue is shrinkage of the entire block. If cast as a cylinder, the block will shrink slightly resulting in a concave outer surface which is slightly smaller than the original cylinder. This is a problem when the block is a rocket propellant; upon ignition the outer surface could start deflagrating, resulting in a higher combustion rate than intended, causing a CATO. Or the pressure in the burning core could expand the fuel block, causing it to crack. Each crack would now expose a greater surface area also resulting in a CATO.

Previous Research
There are some materials available on the theories about getting a heat cast material solidify in a controlled way to prevent volume defects. Unfortunately these methods only work on melt-casting, not on solvent casting.

Most of the material I have on that subject is from classified sources, sharing that information by posting it on a forum (or via PM) could result in high treason charges, at the very least I'd loose my access. I like my access. I'll gladly share the knowledge I've learnt from open sources, but not what I've learnt from those sources. I don't mean to be rude by not sharing it.

Those information sources have almost no information on NC as a monolith, since rockets and flares used by gvt. authorities and agencies use other energy sources with a higher energy density than NC.

Information Requested
I would be very grateful for any information, experiences or if someone knows where to look for more information.

I'm interested in any experiences from anyone who has worked with NC as a monolithic block, for example as a rocket propellant.

Any information about working with NC as a monopropellant block or as an energy source in a monolithic block. (Example; there is a lecture on youtube by Lancaster [1] where he demonstrates a clean burning red flare consisting of NC and strontium carbonate. The only way to get a slow even burn like that with NC would be to make it into a monolithic block. There is almost no visible smoke indicating there were no plasticisers or binding agents added in the NC.

Does anyone know how to deal with or prevent the formation of internal cracks when it solidifies, and the shrinkage deformation?

Sources
[1]: Lecture "Chemistry of Fireworks - Reverend Ron Lancaster" Source YouTube Begin at 1:14:20

[Edited on 12-4-2015 by Student32]

[Edited on 12-4-2015 by Student32]

[Edited on 12-4-2015 by Student32]

NitratedKittens - 13-4-2015 at 00:45

http://youtu.be/f_AvqnMTJjg I don't know for sure but this might work with nc ??

If so then you could just make a solid blob of nc then test

ecos - 13-4-2015 at 12:28

for NC as propellant , please review : http://www.sciencemadness.org/talk/viewthread.php?tid=14608#...

I would also like to take ideas of other experts to use this method for confinement : https://www.youtube.com/watch?v=wqtdfb1dJ5I

Bert - 13-4-2015 at 15:04

If you wish to form pure NC into a solid block as a rocket fuel grain, I believe you may be better off using a hydraulic press than a solvent process. As you noted, solvent processes are often not dimensionally stable on drying- Most such small NC based devices I use or encounter are prepared by pressing, rather than casting.

Your situation seems quite curious. Access to sensitive, secret defense related information? And a licensed pyrotechnics/propellant lab? But you ask here? For general, (and not intended to be implemented) amateur rocketry theory?

Bovine ordure.

caterpillar - 29-4-2015 at 02:16

You may press NC as much as you wish, but its fibrous nature won't go away. If pressed NC is used in rocket engine, it will burn too quickly. There is no alternative to gelatinized NC.

PHILOU Zrealone - 29-4-2015 at 03:43

Add some % of CH3-NO2...it will gelify the NC and you will get a block...the fibers will stick to each other and interpenetrate.

I would be more concerned by D2D transition of the NC block if used as a propellant.

Spartan - 29-4-2015 at 03:58

Quote: Originally posted by Bert

If you wish to form pure NC into a solid block as a rocket fuel grain, I believe you may be better off using a hydraulic press than a solvent process. As you noted, solvent processes are often not dimensionally stable on drying- Most such small NC based devices I use or encounter are prepared by pressing, rather than casting.

Your situation seems quite curious. Access to sensitive, secret defense related information? And a licensed pyrotechnics/propellant lab? But you ask here? For general, (and not intended to be implemented) amateur rocketry theory?

Bovine ordure.

I am also interested to forming NC to solid block. I have try with acetone and smokeless powder but it doesn't work well. I will try with hydraulic press. i am thinking of using double base smokeless powder that contains ~50 nitroglycerin. Do you think it will be safe to use hydraulic press with dbsp??

PHILOU Zrealone - 29-4-2015 at 04:08

If one use a tiny amount of solvent like aceton or nitromethan...not enough to dissolve wel the NC...then the core of the fibers will remain dry and only superficial solvatation will occure.

With help of an hydraulic press the fibers (or grain) will glue to each other and interpenetrate like a patchwork/mozaic or puzzle forming a coherent block.

Since the amount of solvent is low the evaporation will be slow or will even not happen...most likely the solvent will penetrate deeper into the fibers/grains and upon time the distribution of the low solvent % will become homogenous.

The pressing must happen quite fast otherwise the superficial gel will evaporate its solvent in the open air.

Praxichys - 29-4-2015 at 06:44

What about making a thin solution of NC and dipping a core repeatedly with drying between coats, kind of like dipping a candle? You might then be able to (carefully) machine it into a proper core shape.

If you poured it into a closed pipe and quickly dumped it out, then let the shell inside the pipe harden, and repeat, you might be able to slowly fill the entire pipe with cast NC.

Didn't they used to make billiard balls from nitrocellulose? Billiard balls are hard, dense, and smooth. How did they do that? US patent 50359 has some info, but it appears this type has a cloth core.

On Celluloid, from Wikipedia - "A typical formulation of celluloid might contain 70 to 80 parts nitrocellulose, nitrated to 11% nitrogen, 30 parts camphor, 0 to 14 parts dye, 1 to 5 parts ethyl alcohol, plus stabilizers and other agents to increase stability and reduce flammability."

After nitrating the cellulose - "The product then must be rinsed to wash away any free acids that did not react with the fibers, dried, and kneaded. During this time, a solution of 50% camphor in alcohol is added, which then changes the macromolecule structure of nitrocellulose into a homogeneous gel of nitrocellulose and camphor. The chemical structure is not well understood, but it is determined that it is one molecule of camphor for each unit of glucose. After the mixing, the mass is pressed into blocks at a high pressure and then is fabricated for its specific use"

On loss of the camphor - "The most inherent flaw is as celluloid ages, the camphor molecules are ‘squeezed’ out of the mass due to the unsustainable pressure used in the production. In detail, that pressure causes the nitrocellulose molecules to bind back to each other or crystallize, and this results in the camphor molecules being shoved out of the material. Once exposed to the environment, camphor can undergo sublimation at room temperature, leaving the plastic as brittle nitrocellulose."

Just some thoughts.

goldenoranges - 2-5-2015 at 22:08

Quote: Originally posted by Bert

Why say you have access to classified information at all. Pretty sure the smart thing would be to just not mention it at all, it's not like we would have known he supposedly has clearance.

Fulmen - 3-5-2015 at 04:13

Pressing alone will not produce a grain suitable for use as a propellant although it can be used as an explosive. If I'm not completely mistaken artillery propellants can exceed 1" cross section and is extruded in a colloided state like most other NC propellants. So the science has been done, you just need to find it.
From the images I've seen there is significant shrinkage, producing a slight hour-glass shape, but I'm sure that can be controlled to some degree by careful control of solvent removal. Most propellants will have a perforated core, by restricting the evaporation to the core it should be possible to keep the external dimensions tighter.

Fantasma4500 - 3-5-2015 at 09:39

i have have a way to turn cellulose into a fine powder.. somehow i managed to create abit less than 500mL of very strong formaldehyde solution, dont ask me how.
i put this in a jar and put a sticky not ontop
the lid kept popping off for whatever reason, put a plastic bag over it, airtight. now a year later i take a second look at the jar, and as i touch the paper it crumbles into dust, i didnt do much more than throwing the paper in the trash can, pretty stupid of me.. but i guess if the cellulose havent been totally broken down this could be very interesting to nitrate? possibly it would crumble into dust even when nitrated, as you would prefer having large particles for the washing process

formaldehyde could possibly be made from ''melamine'' plastic, which is melamine*formaldehyde, 100 sponges cost 6 euro over ebay with free shipping
i would like to play abit around with this myself, but i dont feel like i should be doing such right in these times

Microtek - 3-5-2015 at 23:25

It is quite easy to produce microcrystalline cellulose via hydrolysis of cotton wool. Discussions can be found here on SM. Formaldehyde can be bought on ebay, if you need it.

ecos - 19-5-2015 at 01:08

hmm , I have an idea but not sure.

I think it is possible to make NC as powder. you can press it and use binder to make a grain.

any body have idea how to make NC powder?