enanthate Posted January 16, 2015 Author Posted January 16, 2015 (edited) Hi Petroleum,I haven't experienced that before, so don't know whats the real reason. Im sure you will get a more reliable answer from someone else. One thing that comes to mind is your dextrin. Are they hard? Also, your solvent is quite strong with 50% alc. I dont know your rollingprocedures, but if you barely wet the stars enough to pick up comp, the 50\50 solvent might not contain enough water to properly activate the dextrin. If you overwet on purpose however, like I do with charcoalstars, this is not the problem.I would still try more water if i was you, to let the dextrin activate properly. Also, you want the pores of the charcoal to absorb kno3, giving better sparks in C8, C6, TT, etc. 75\25 water\alc is most commonly used. Edited January 16, 2015 by enanthate
petroleum Posted January 16, 2015 Posted January 16, 2015 Hi Petroleum,I haven't experienced that before, so don't know whats the real reason. Im sure you will get a more reliable answer from someone else. One thing that comes to mind is your dextrin. Are they hard?Also, your solvent is quite strong with 50% alc. I dont know your rollingprocedures, but if you barely wet the stars enough to pick up comp, the 50\50 solvent might not contain enough water to properly activate the dextrin. If you overwet on purpose however, like I do with charcoalstars, this is not the problem.I would still try more water if i was you, to let the dextrin activate properly. Also, you want the pores of the charcoal to absorb kno3, giving better sparks in C8, C6, TT, etc. 75\25 water\alc is most commonly used.Hi Enanthate,About the C8 I use for rolling: The comp is ball milled with further dampening with water and screened through 20 mesh screen in wet state. After drying I grind it in mortar, screen the fraction -180 mesh and use it for rolling. As most of amateur pyromans I observe some difficulties with rolling of ball milled comps like C8 due to the "strawberry" effect. Taking into account that mix was already moistened with water I believe that KNO3 was already soaked into C particles. I tested various mixes of EtOH/H2O and found that this combination works well in my conditions for rolling of charcoal based stars providing acceptable results in terms of star hardness and efficiency. I suppose that moisture became through the hot prime layer to red mix (containing Sr(NO3)2 through the pores of charcoal.
enanthate Posted January 17, 2015 Author Posted January 17, 2015 Sounds good, you know what you're doing.Cant help you im afraid, good luck though. I do suspect the strontium as well. Im currently rolling very fine TT myself. If you get raspberry, wet more. As you know, its OK for this comp to be quite wet. Rolling relatively dry will quickly build up a raspberry shape.Overwetting can happen and will give a strange, sort of "cracky" shape. Adding a bit more powder, a bit more slowly, will remove this and make them round again quite quickly.Just my 2 cents.
Niladmirari Posted January 17, 2015 Posted January 17, 2015 Hi Dzintars Try replacing Sr(NO3)2 to SrCO3. Red cores: potassium perchl / SrСО3 / MgAl / parlon / charcoal / phenolic resin. Slightly changing %
petroleum Posted January 17, 2015 Posted January 17, 2015 Hi Nil! =)Nice to see you. Yes, of course, it would be the option. But my idea is to get the core exactly on nitrate base. But it seems, that I will try carbonate based ones as well =)Hi Dzintars Try replacing Sr(NO3)2 to SrCO3. Red cores: potassium perchl / SrСО3 / MgAl / parlon / charcoal / phenolic resin. Slightly changing %
Zumber Posted January 17, 2015 Posted January 17, 2015 Petroleum you mentioned for your stars you used water/alcohol and for hot prime kp,c,phenolic resin you used acetone ( why acetone here in hot prime).I have water soluable commercial phenolic resin which makes stars rock hard.
FlaMtnBkr Posted January 17, 2015 Posted January 17, 2015 I suppose that the problem came from the gyroscopic properties of Sr(NO3)2. Does the gyroscopic nature of strontium nitrate help when rolling the stars? I kid, I kid 1
petroleum Posted January 17, 2015 Posted January 17, 2015 (edited) To swapnilsutar1988:The idea of rolling of the hot prime layer with acetone was that the core contains parlon, which is soluble in acetone and will additionally protect the metal particles from undesirable reactions. The rolling of the cores using acetone alone (parlon as a binder) is quite challenging task. My result was not good - the comp become too sticky.Regarding the water soluble phenolic resin - it is the first time I hear about such material. The resin I have it is synthetic material called iditol or novolak resin (polycondensation product of phenol with formaldehyde) and it is not soluble in water (at least this resin could not be used as a binder if water is used as solvent) To FlaMtnBkr:Its difficult to evaluate this aspect, I didn't feel the differences if I roll Sr(NO3)2 based comp or something other. Edited January 17, 2015 by petroleum
Mumbles Posted January 17, 2015 Posted January 17, 2015 I've read that using a mix of acetone and alcohol (9:1 or so), can really cut down on how tacky and stringy parlon gets. Can't really help you with much else. I'm at as much of a loss as everyone else.
Carbon796 Posted January 17, 2015 Posted January 17, 2015 (edited) The fact that you used such an over engineered method. To try to avoid a very unlikely problem that, you shouldn't have had any issue with. Is probably what most of the problem is. You shouldn't have needed try to protect that formula from any adverse reactions. As long as you ARE using Mg/Al, and NOT magnesium. That type of comp is water bound all the time without issue. I've left a very similar formula ( PGI Red ) wet for a couple of days, without any reaction. ( I was pressing a few pounds of 1/4" stars ) Being as your comp was alcohol/phenolic bound that by itself is extra protection. It seals the comp from water adsorption. Bill Ofca has stated, that he has stored sodium nitrate/magnesium comps, bound with Phenolic resin, for up to a year. With no signs of degradation, but does not recommend doing so. He believes that the phenolic coats the individual particles in the comp. Which protects the magnesium from being attacked by the nitrate. My guess is that the dichromate my have reacted with the Mg/Al ( trying to form a protective coating on it ) or the high alcohol percentage in the C-8 layer. Also if you dried them too fast/hot, or in the sun could also be an issue. Edited January 17, 2015 by Carbon796
petroleum Posted January 17, 2015 Posted January 17, 2015 Muml, Carbon,Thank you for your tips.I will try to use another batch of Sr(NO3)2, because I had no any problems with this combination of comps before. Regarding the bichromate - I agree, that there could be another issue and I think that better to eliminate this chemical from the comps containing Mg/Al. It was used because I already had some amount of this comp and bichromate was already in it - so I used what I had. Drying was controlled at 17-19 degrees - I have some experience with uncontrolled "fast" drying resulting to deterioration of the effect of metallic based comps =).Nevertheless, thank you....
gregh Posted January 18, 2015 Posted January 18, 2015 Does the gyroscopic nature of strontium nitrate help when rolling the stars? I kid, I kidI was wondering if anybody else caught that... I bet it helps them fly straighter though!
patsroom Posted January 18, 2015 Posted January 18, 2015 I was wondering if anybody else caught that... I bet it helps them fly straighter though! It is the spinning that keeps it in-line and from falling over in flight! .................Pat
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