Phenolic resin as binder

[MadMat]

It has been said in the forums that phenolic resin can be used as a replacement for red gum on a 1:1 basis and that it can be used as a binder for star comps using alcohol as the solvent. What I am wondering is the binding strength of phenolic. I am planning on trying phenolic for the first time, but some of my star comps have a fairly low percentage of red gum. Will phenolic still work as a binder at percentages of 5% or maybe even slightly lower?

[OldMarine]

Actually it's around 83% phenolic to red gum. I've used it at 3% using hexamine and heat to cross link the comp and it worked well.

6% hex+94% resin.

[MadMat]

Does Phenolic have to be cross-linked with hexamine to work as a binder?

[Mumbles]

Nope. Crosslinking does make incredibly hard stars though. Phenolic on it's own is very hard, so probably entirely harder than necessary. It's really nice and more applicable for things like larger comets where they can be dried in a day vs. 3 months.

[braddsn]

MadMat, I make rather large amounts of stars each year, I would say on a somewhat large scale compared to 'most' hobby pyros. I usually have about 30-40 kilos of cores on hand at all times. For this whole year (starting shortly after last 4th of july, up until now) I have been binding with phenolic. I primarily use the spanish (Jopetes.PDF) star formulas. For me, I have been simply substituting phenolic for red gum at a 1:1 ratio. I don't use hexamine. I don't even keep red gum in my shop anymore. The benefits of binding with phenolic are plentiful. 1) It's cheaper than red gum. 2) When I bind with phenolic, I can throw 8mm cores into the dehydrator right out of the star roller, and in 3 hours I have rock-hard stars, ready to prime and use. 3) Phenolic lowers ignition temperature. 4) You get harder stars than dex bound stars. 5) I use monocapa as one of my primes, so I am able to sub the phenolic for red gum and that gives me a prime that dries in about 5 minutes. One thing to note: It just so happens that all of the spanish colors call for more than 6% red gum, so when I sub phenolic, there is enough to bind with. IF you are using formulas that use less than 6% red gum, then I am not sure what happens. I do know that phenolic is like red gum, in that you can't just use it like dex. You can add dex to any comp without affecting the fuel value, but this is NOT the case with phenolic. For example, I recently tried to bind some charcoal-based stars with phenolic instead of dex. It did NOT work... the stars burned waaaaaay too fast, flew all over the place like go-getters, and were un-usable. Bottom line, binding with phenolic and alcohol has made my star rolling process twice as easy. I could never go back to dex when rolling colors. One thing that I have noticed that is strange, but causes no problems: I can take a phenolic-bound star that is dry and rock hard, prime it with bp, then throw it in the dehydrator.... and within 30 minutes in the heat, the entire star becomes soft again, you can just smash it with your fingers... but then when you let them cool off back to room temp, they become rock hard again. It's strange... it's almost like the phenolic melts again when it gets hot, but hardens when cools.

[DavidF]

That was great information Braddsn, thanks! I've also seen people say that phenolic works great instead of dextrin for cutting stars. I don't know what percentage of phenolic resin would make for good cutting. More detail on using phenolic resin for cut stars would be nice to have, if anybody else wants to share too

[braddsn]

I roll most of my stars, but I do cut and pump some as well. I use the same formulas, same amount of phenolic. I cut and pump the same as I did with dex, and have awesome results. Be careful though, if you use too much alcohol and get the comp too wet, with phenolic it becomes a REAL mess.. very sticky, and the cleanup can be a pain. I would say dextrin is a little more forgiving... but now that I have mastered doing it with phenolic, I could never go back. 3/4" cut stars bound with phenolic will be dry and ready to use in a day or 2.. even faster if you use a dehydrator.

[DavidF]

Well then- I guess I used way too much alcohol. I got the sticky mess in spades. Would you say that 5% phenolic resin could bind cut stars if used instead of dextrin? OR, are you saying that using phenolic instead of red gum in a formula 'normally' bound with dextrin- without removing the dextrin- is what works? Sorry to be a pest, but my failure to understand this binder has been very discouraging!

[OldMarine]

I was told that if the comp had enough red gum to be used for a binder you could replace the gum with phenolic resin and eliminate the dextrin. Like Brad said, it doesn't work for charcoal/glitter stars.

[Carbon796]

In some of the early experimental testing by Bill Ofca. He was advocating a minimum of 6% phenolic for binding, and activated by 6% alcohol. If a comp didn't have enough red gum in it, he just added extra phenolic to get to 6%.

 

Dextin does have a fuel value, it is ruffly, about half the value of red gum. While adding additional dex ( with in reason ) to BP type comps won't affect them to adversely. The higher percentages of dex will lead to a excess of smoke output. So a star bound with an excess of phenolic, will likely still burn cleaner, than one with a excess or dex.

[braddsn]

David, what I do is simply replace the red gum in my formulas with Phenolic, 1:1. Then leave the dex out. The formulas that I do this with call for at least 5-6% (or more) red gum... I am sure that 5% would be plenty. 4% and under, I am not sure. I don't know what the minimum would be. Also, yes you have to be very conservative with the alcohol when you are cutting. It is non-forgiving. If you add just a little too much alcohol, you are in trouble... sticky mess!! But if you do it right, the results are AWESOME!

[MadMat]

Thanks for the tips and info guys. My stars are only 3/16-1/4", so I'm not really in need of the accelerated drying time, but I am looking for the other advantages of phenolic namely; lower ignition temperatures. Lloyd once mentioned to me that the general consensus is cutting stars with phenolic is easier than with dextrin. So, with that in mind, I'm glad you guys mentioned the problems associated with using too much solvent. So, 6% max. alcohol? I know that the density of alcohol is less than water (1g/ml), but I am using a T.C. graduated cylinder which isn't exactly the most accurate. If the 6% max. number is correct, I am assuming 6ml of alcohol/100 g. of comp would be a little less than 6% and would put me in the ball park.

Edited June 11, 2017 by MadMat

[Carbon796]

The 6% alcohol that I listed, was what Bill Ofca recommend for pressing. I generally found 6% a little wetter than I preferred . . . And that percent will vary from comp to comp, some. Edited June 11, 2017 by Carbon796

[Doloy]

While reading this I'm starting to wonder; is phenolic a good fuel as well?

Has anyone tried to use it in a composition which is normally fuelled with red gum like Ba(ClO3)2 green for example? (85/15 ratio)

Would it burn too fast/not at all?

[OldMarine]

Phenolic replaces red gum at around 83% since it has a slightly higher fuel value. I'm getting to the point I use it in almost all my metallic colors. I can't see a noticeable difference in burn speed.

[braddsn]

OldMarine, I was the same way.. and finally I replaced red gum completely. I bet you will too.

[redoxide]

It has been said in the forums that phenolic resin can be used as a replacement for red gum on a 1:1 basis and that it can be used as a binder for star comps using alcohol as the solvent. What I am wondering is the binding strength of phenolic. I am planning on trying phenolic for the first time, but some of my star comps have a fairly low percentage of red gum. Will phenolic still work as a binder at percentages of 5% or maybe even slightly lower?

You should decrease the ammount of phenolic resin by half , of that you have in Red Gum.

eg; if you have 100 grms of Red Gum in a pyro formula .you replace complete with 50 grms Phenolic,

[Arthur]

Two relevant questions!

Is there a resin that will make quick drying hard and dry charcoal stars (willows/slow gold etc)?

 

Is there a formula for resin bound rocket motors?

-In the UK we used to have UK made resin bound rockets which were know for their power, they are no longer made here can anyone shed light on a suitable formula and method?

[Mumbles]

You should decrease the ammount of phenolic resin by half , of that you have in Red Gum.

eg; if you have 100 grms of Red Gum in a pyro formula .you replace complete with 50 grms Phenolic,

 

 

I'm curious where this suggestion comes from? It's at odds with what most other people, including professional manufacturers and importers, suggest.

[OldMarine]

Two relevant questions!

Is there a resin that will make quick drying hard and dry charcoal stars (willows/slow gold etc)?

 

Is there a formula for resin bound rocket motors?

-In the UK we used to have UK made resin bound rockets which were know for their power, they are no longer made here can anyone shed light on a suitable formula and method?

Charcoal and glitters don't play well with phenolic resin. Buttered Popcorn and Winokur 39 are passable but I've found no others so far. The resin turns the charcoal stars into gravel.

Edited August 29, 2017 by OldMarine