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ecos
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Quote: Originally posted by kecskesajt  | | Can I make a propellant using AN+Polystyrene?I know it is used in BLU - 82 with Al but that an explosive not a propellant. |
I would give you my point of view but it might not be correct.
the molcular formula for Polystyrene (C8H8)n , the ratio of H/C is not high also it would still need oxygen for its burning , this would mean extra
oxidizer.
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Fulmen
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In theory: Sure. In reality? Probably not. Formulating a working propellant involves much more than simply combining an oxidizer with a fuel. For the
novice the only realistic approach is to follow the work of others.
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PHILOU Zrealone
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| Quote: Originally posted by kecskesajt | | Can I make a propellant using AN+Polystyrene?I know it is used in BLU - 82 with Al but that an explosive not a propellant. |
NH4NO3 (= AN)
MM= 80.04
d= 1.72
(-CH2-CH(-C6H5)-)n (=(C8H8)n = PS)
MM/unit= 104.15
d= 1.06
NH4NO3 --> N2 + 2 H2O + 1/2 O2
So each mole of NH4NO3 gives 1/2 mole O2 (or 1 mole O).
You would need 20 moles of O to burn completely C8H8 into CO2 and H2O, and 12 moles O to burn it uncompletely to CO and H2O.
Partial combustion case
So 12*80.04g of NH4NO3 are needed for the of 104.15g of PS.
Weight ratio: 960.48/104.15
or 9.783% PS and 90.217% AN
Density of the mix = 1.65543
Complete combustion case
So 20*80.04g of NH4NO3 are needed for the of 104.15g of PS.
Weight ratio: 1600.8/104.15
or 6.109% PS and 93.891% AN
Density of the mix = 1.67968
From my experience with PS and NaClO3 (MM=106.44) what is a much better oxydant (3 O / mole) than NH4NO3 (so you need less oxydizer material% and it
allows to increase the PS binder%); NaClO3 is also denser (so the volume to coat by the binder is also less):
The stoechiometric mix with PS is very brittle and doesn't burn well (while NaClO3/fuel is usually easily set in fire and burns fiercely).
There are big chances AN/PS will be even more brittle and doesn't hold well together...also the flamability might be low and the burn propagation
might be ineffective (especially if AN not wel anhydrous).
To help a bit one may find interest in investigating polynitrostyrene ((C8H7NO2)n MM/U= 149.16) and polydinitrostyrene ((C8H6N2O4)n MM/U= 194.17)!
PNS needs 9.5 mole O for uncomplete combustion and 17.5 for complete burning.
PDNS needs 7 mole O for uncomplete combustion and 15 for complete burning.
The increase of the Oxygen balance will increase the % of binder:
AN/PNS (uncompl) weight%: 16.400% PNS / 83.600% AN
AN/PNS (compl) weight%: 9.624% PNS / 90.376% AN
AN/PDNS (uncompl) weight%: 25.737% PDNS / 74.263% AN
AN/PDNS (compl) weight%: 13.921% PDNS / 86.079% AN
The use of polytrinitrostyrene (expected density in the vicinity of 1.83 vs 1.54 for the monomer (TNS)) is unadvisable for propellant applications
because of the risk of detonation.
But as a brisant explosive,the stoechiometric mix AN/PTNS would display a good density and VOD.
Note that the nitrogroups can be set on the aromatic ring but also on the alkanic chain...so nothing prevent the study of
poly-trinitrophenyl-nitroethylenes and poly-trinitrophenyl-dinitroethylenes. The later two would have very high density because polymers have always
(a few rare exceptions exists) much higher densities than the monomeric material.
Typical examples:
Ar-CH=O + CH3-NO2 --> Ar-CH=CH-NO2 + H2O
Ar-CH2-NO2 + CH2=O --> Ar-C(NO2)=CH2 + H2O
Ar-CH=O + CH2(NO2)2 --> Ar-CH=C(NO2)2 + H2O
First and last conformation are less prone to easy polymerisation because the aromatic ring is not on the same side as the nitro group(s) and there is
thus a competition for the polarization of the double linkage...a polymerization inducer might then be needed!
If you start from mononitro-, dinitro- or trinitroaromatic reactants...you get the desired monomers with high densities!
In the case of TNP-C(NO2)=CH2 it should display a density arround the 1.79g/ccm, polymerization will boost the density up to a density arround
2.0573g/ccm!
[Edited on 18-3-2015 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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ecos
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I am sorry but I don't understand what is the benefit of Polystyrene for BLU-82 ? is it used as binder ?
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ecos
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I am in the last steps of building my ball mill.
The problem now is to find a 1/2 HP motor that rotates at 80 RPM ! , most of motors in the market starts with 1000 RPM.
This means I need to have a control circuit for speed.
Any suggestions ?
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Fulmen
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What you need is a pair of pulleys to reduce the speed.
The classic design uses a jar driven by a roller, in that case the diameter of the roller and the jar also works as gearing.
Let's say you have a 1" roller and a 4" jar, this gives a gearing-ratio of 4, meaning the roller must rotate at 320rpm. So if your motor runs at
1000rpm you need a 1000/320=3,1-ratio for the pulleys.
In theory you could use a VFD to drop the motor speed, but they are not cheap. A DC-motor should not be used as they spark continuously from the
brushes.
[Edited on 25-3-15 by Fulmen]
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ecos
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Hi Fulmen, this idea is great and easy  . I will try to use pulleys.
regarding the media in the jar , I found this balls.
weight = 21 grams
diameter = 1 "
It seems it is strong glass.
I think if it was iron balls it would be 60 grams but I still couldn't find them.
I understood from the ball mill document that, the media density should be higher than the charge.
Aluminum 2.7 (103 kg/m3)
Glass 2.4 - 2.8 (103 kg/m3)
I don't know why we have the rule of density here ?! would the glass balls work ?
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Fulmen
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I don't recall anything about the media density being higher than the charge, but as a general rule the density should be as high as possible. This is
related to the energy of each impact, smaller, high density media will provide more impacts per time unit. For any charge and jar size there will be
an optimal ball weight (it should decrease with increasing jar diameter IIRC), lighter balls won't have the energy to grind efficiently while heavier
balls will simply waste energy causing increased media wear. Determining this will require experimentation, looking at others results should provide
some guidelines.
The media must also be harder than the charge, that is certainly the case with glass. However, glass does come with some drawbacks. It can produce
fine glass powder which is known to increase friction sensitivity of powders. I would recommend steel media if you can get it, ceramics are probably
also safer. Just don't grind black powder with hard media, lead or copper alloys are the safest alternatives.
We're not banging rocks together here. We know how to put a man back together.
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ecos
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| Quote: Originally posted by Fulmen | I don't recall anything about the media density being higher than the charge, but as a general rule the density should be as high as possible. This is
related to the energy of each impact, smaller, high density media will provide more impacts per time unit. For any charge and jar size there will be
an optimal ball weight (it should decrease with increasing jar diameter IIRC), lighter balls won't have the energy to grind efficiently while heavier
balls will simply waste energy causing increased media wear. Determining this will require experimentation, looking at others results should provide
some guidelines.
The media must also be harder than the charge, that is certainly the case with glass. However, glass does come with some drawbacks. It can produce
fine glass powder which is known to increase friction sensitivity of powders. I would recommend steel media if you can get it, ceramics are probably
also safer. Just don't grind black powder with hard media, lead or copper alloys are the safest alternatives. |
I remember I read the sentence regarding the densities in "pyrotechnics_ball_mill_theory_sponenburgh" but I don't recall the page
Anyway your statements are very logical.
regarding the Jar, the document stated this design , I don't know what is the aim of the reducer and the smaller pipe?
I think the author uses rubber cap to avoid any friction for the media , is my understanding correct ?
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hissingnoise
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| Quote: | I think the author uses rubber cap to avoid any friction for the media , is my understanding correct ?
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In a case of accidental ignition, a rubber cap easily pops off ─ could make a difference between a deflagration and an explosion . . . ?
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Fulmen
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The reducer is there to provide clearance for the rubber cap and hose clamp, remember that the jar will rest on rollers. The rubber cap is probably
the most convenient end cap available, it also reduces friction that in theory could ignite the powder when opening the jar. If the powder ignites
during milling no cap is going to save the mill, it will explode.
[Edited on 27-3-15 by Fulmen]
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kecskesajt
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Ok,thanks.I might give it a try with KNO3
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hissingnoise
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| Quote: | | If the powder ignites during milling no cap is going to save the mill, it will explode. |
I was referring to ordinary BP ─ you're talking about something other than BP, apparently!
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Fulmen
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An explosion doesn't automatically mean detonation if that's where you're going, the powder would still only deflagrate. The word "explode" can simply
mean "to increase rapidly", for instance a "population explosion" does not mean that people are exploding (although that happens sometimes as well)
If a BP mill ignites it will explode, shattering the jar into fragments and propel the media at potentially dangerous speeds pretty much regardlessly
of any rubber cap.
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hissingnoise
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| Quote: | | An explosion doesn't automatically mean detonation. |
Since you don't appear to know what a detonation actually entails; a detonation is a reaction which proceeds through a mass of material at a speed
which corresponds to the speed of sound in the material!
BP cannot be made to detonate and its deflagration proceeds at the speed of heat conductance in BP.
BP when confined can deflagrate at a high speed but which is below supersonic!
A detonation is generally taken to mean any reaction which proceeds at supersonic speed!
When you can mill your own powders you'll find yourself on a learning curve . . .
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Bert
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From the viewpoint of actually seeing the results of various amateur pyrotechnists and rocketey experimenters who DID manage to explode a ball mill-
Milling such things as black powder and perchlorate based rocket fuels:
Nope, they didn't detonate.
Damn the difference anyhow, the explosions were substantial and easily would have killed someone who was close by. A couple of them partially
destroyed buildings the mills were being run inside of.
Rather than worry about the semantics, worry about locating your mill where it will do no harm to people and minimum damage to property.
Oh, and one other thing: After somehow avoiding arrest, even after explaining truthfully to police and fire department how your garage exploded? Do
NOT call your insurance company and file a claim. The provision of insurance policies that you not be covered in case of losses caused by illegal acts
WILL spur the insurer to make sure that you get properly arrested!
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Fulmen
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I know the difference between detonation and deflagration. I was only correcting you on this part:
| Quote: | | rubber cap easily pops off ─ could make a difference between a deflagration and an explosion |
Deflagration is a mode of combustion, nothing else. It can cause a slow burn or a violent explosion depending on the conditions, they're not
exclusive. So what you meant to say was "difference between a *poof* or a BOOOM" or something to that effect.
Now I could be wrong, as I've never tried to blow up a mill before, but my gut feeling tells me it probably won't do much difference if the lid is
made from rubber or solid PVC. Mill powder will burn extremely rapid if confined, a reasonable sturdy jar should provide ample confinement for an
explosion.
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hissingnoise
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| Quote: | | I was only correcting you on this part. |
(sigh!)Son, I've forgotten more on the subject than you'll ever know!
But seriously, in the unlikely event of ignition within a jar containing moist BP, a flexible cap which pops off at the initial increase in
pressure within the jar will be a few magnitudes safer than otherwise!
That said, I've dry-milled BP using AH lead many times without problems ─ not something I recommend, obviously ─ but lead shot is non-sparking and
when properly earthed the mill is relatively safe to run!
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Fulmen
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Do I look impressed? Rather than telling me how much you've forgotten, could you educate me on exactly where I am wrong?
As for your claim that a rubber lid will reduce the blast, can you document this? From what I've read over the years a BP mill will explode violently
if ignited. Perhaps a rubber lid will reduce the blast somewhat, but I seriously doubt if it will prevent it from exploding. Remember that much of the
powder will be in between the media, this alone should provide a significant amount of confinement.
If you think a rubber cap fixed with a hose clamp will simply slip off at the first sign of pressure you're flat out wrong. You need a fair amount of
clamping force to guarantee that the lid will stay on during the milling process, more than enough to provide a fair amount of confinement during an
explosion.
And while my memory is somewhat rusty after 20 years, I cannot for the life of me recall that Lloyd ever claimed that these rubber lids would prevent
an explosion. IIRC it was chosen as a cheap, readily available lid that provided perfect seal with a minimum of friction during assembly/disassembly.
We're not banging rocks together here. We know how to put a man back together.
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hissingnoise
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| Quote: | | From what I've read over the years a BP mill will explode violently if ignited. |
Jeeez! Anyone can parrott the various texts they've read but it's a poor substitute for hands-on experience . . .
Go make your own powder, FFS ─ then perhaps you'll have more idea of what it may or may not do?
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Fulmen
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Who said I haven't? I actually have a mill (6" mill jar) built after Lloyds design, complete with the rubber lid in question. What I haven't done (for
obvious reasons) is to blow it up, therefore I have to rely on the experience of others. Is that so unreasonable? As Bert also confirms, these mills
are known to blow up violently if they ignite. The risk is slim, I've never tried to claim otherwise, but believing that a rubber lid will reduce the
severity of the blast can be a dangerous assumption.
Now if you have first hand experience with blowing up mills, both with a hard and a rubber lid, that's another story and I would very much like to
hear of your experience.
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Bert
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Everyone calm down and discuss either engineering concepts, which suggests some theory be provided and math to back it up quoted-
Or relevant personal experiences, ideally a precise and dispassionate description, with photographic evidence if available.
[Edited on 29-3-2015 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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ecos
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Hi all ,
I am not experienced like most of you but i read a lot of articles that state that milling BP is dangerous operations. Some add alchol to BP to
decrease its sensitivity.
The last chapter of the ball mill that Bert shared has a real accident of the author while milling magnesium powder. Just have a look.
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PHILOU Zrealone
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I always use an electric coffee ginder, and grind separately oxydizers and fuels.
I think that in a ball milling you may do the same to get extra security. Eventually with a highly unbalanced ratio oxydizer/fuel.
That way even if something happens, the powder will not explode.
Afterwards you may mix two powders (fuel(s) and oxydizer(s) (or unbalanced Fuel (+) Oxydizer (-) and unbalanced Oxydizer (+) and Fuel (-)) by the
Rolling paper method.
[Edited on 29-3-2015 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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hissingnoise
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| Quote: | | Afterwards you may mix two powders (fuel(s) and oxydizer(s) (or unbalanced Fuel (+) Oxydizer (-) and unbalanced Oxydizer (+) and Fuel (-)) by the
Rolling paper method. |
Diapering PHILOU? Jeez, it's a propellant ─ not a fucking primary?
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