Dextrin with Acetone

[rellim]

I sometimes see compositions that contain dextrin but are supposed to be bound with acetone as the solvent. What is the purpose of the dextrin? An example:

 

Independence Red

 

50 Strontium Nitrate

18 Magnalium

16 Parlon

10 Red Gum

5 Dextrin

 

Description

Great formula, very bright, very red and slow burning. Sizzles a bit as it burns. Bind with Acetone (Alcohol will not work) and prime with 'Hot Changing Relay' then BP.

Source:

Independence Fireworks

 

 

[Mumbles]

When binding with acetone is serves very little purpose. Dextrin has a small fuel value but with how much you use, it's not very significant. What this likely really means is that the formula was likely originally designed to be bound with water. The acetone comment was added later by someone else. Acetone has several economic and safety draw backs to be used commercially all that often.

[Baldor]

Acetone will dissolve the parlon and red gum as binders in this formula, right?

[stix]

@ rellim,

 

I came across a similar composition a while back and posted a very similar question.

 

The upshot is as Mumbles points out, that the dextrin is there with the intention of using water as the binder. I tested a version using dextrin and it burned well. The disadvantage is that it took longer to dry, and through the air, left a bit of orange dross - but I was probably too close to it.

 

I ended up dropping the dextrin and adjusting the formula:

 

53 Strontium Nitrate

19 Magnalium

17 Parlon

11 Red Gum

 

I used Acetone as the solvent and also tried MEK (Methyl Ethyl Ketone) which left less dross and also made it easier to cut as it was less sticky.

 

Acetone will dissolve the parlon and red gum as binders in this formula, right?

 

Yes, that's correct.

[Arthur]

For commercial operations water is the preferred solvent on a price basis a gallon of water costs less than a gallon of ethanol or acetone, also in bulk acetone and alcohol vapours are highly flammable adding extra hazards to a large scale factory.

 

For home use in small quantities the hazards may be acceptable. some comps have red gum, parlon and dextrin so that any solvent can be used, it's probably less that optimal but suits whatever various makers have to hand, not all hobbyists have all the possible chemicals.

[rellim]

Strontium nitrate is hydroscopic. If bound with dextrin/water will it ever dry out? Will it stay dry?

[Mumbles]

It can be made to dry, yes. Reabsorbing water will depend on your ambient humidity. Pure strontium nitrate will absorb water if the relative humidity is above around 82-85%.

 

Red gum and phenolic don't really waterproof anything, so binding with it doesn't really solve any problems in this regard. Parlon is better, but still not perfect. The stars may feel harder since the binder is not reactivated by the absorbed water, but they'll be every bit as wet eventually.