klachner Posted April 21, 2017 Posted April 21, 2017 hello, some compositions i want to try contain phenolic resin, which i dont have. Is this only acting as a binder or does it also affect the color/burning speed/etc? Can it be replaced with dextrin or redgum? Dextrin would be the best because i prefer working with a binder which binds with water
NeighborJ Posted April 21, 2017 Posted April 21, 2017 (edited) Usually people are asking if the red gum can be replaced with Phenolic but I suppose it can work both ways. The fuel value of red gum is around 83% of Phenolic and Dextrin has even less (around 50%). So it can be replaced with the appropriate amount but you'll find the resulting comp will burn slower than designed. This may or may not benefit you depending on what comp you are trying to tweak. Most Phenolic comps seem to be originally formulated for red gum or both RG and dex, which have been tweaked for Phenolic use. You may want to try a mix of both to achieve a fuel value equal to the phen so you can use the solvent of your choice. Edited April 21, 2017 by NeighborJ
OldMarine Posted April 21, 2017 Posted April 21, 2017 Poked around in a few older books to see if they contained phenolic in any formulae. Nope.The comps calling for phenolic, unless recently published, are adaptations of existing ones using phenolic's speed of drying/hardening.
Mumbles Posted April 21, 2017 Posted April 21, 2017 The only book I've really seen it mentioned in is Principles of Pyrotechnics by Shidlovskiy. He discusses Iditol, which is a brand or type of novolac resin (acid catalysis, excess of phenol), which is the same type as the stuff being imported by Jim Widmann. It's not to be confused with Iditol the sugar. It's pretty clearly described on pages 47-48. That's a minor point though. Shimizu, Hardt, Lancaster, basically the entire modern pyrotechnic literature library is based mostly on red gum and shellac as organic fuels and Dextrin or SGRS as aqueous binders. Very likely you're finding formulas that were derived from formulas containing them. Unfortunately, some people are not great at giving credit where credit is due. If they did a faithful conversion, you'll probably notice that formulas do not add to 100 due to the stated differences in fuel value. Most of the above sources give formulas in terms of percentages, and not commercial sized batched in Kg or lbs. If you compare the other components like oxidizer, colorant, chlorine donors you can probably find the original formula. If you have a couple we'd be happy to help and see if we recognize anything. Chances are you will need to use both red gum and dextrin to recreate the formulas. Red gum is primarily a fuel, and kind of a shitty binder in my opinion. Whereas dextrin is a good binder, but poor fuel. In escence you need both. To recreate red gum + dex formulas check and see if they add to 100. If so, it'd take 4 or 5 parts dextrin and use the rest in red gum. The red gum should probably come out to be 6-12 parts generally. If it doesn't add to 100, I'd do the same conversion but take into account the above 83% conversion to see if that gets you there If both of these methods fail, try using 1:1 or .83:1 phenolic to red gum conversions, and just add in some parts dextrin. Some formulas compute the dextrin binder as a +5%, so some will see this as extra or extraneous when doing conversions and just chop it off without consideration. 1
OldMarine Posted April 21, 2017 Posted April 21, 2017 (edited) Since fuel-wise phenolic substitutes at 86%+/- for red gum and dextrin has a negligible value, I wonder if you couldn't just up the red gum to that percentage and still omit the dextrin. Other than for binding I've found it very expendable so far. Edited April 21, 2017 by OldMarine
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