Powder burn rate over time

[Subwrx300]

I'm hoping someone here has good knowledge of chemistry of powders.

I know that ether (or similar organic solvent) is used as a carrying agent and moisture control measure for most smokeless powders. My question: how does burn rate change as the ether evaporates over time as bottle is used? For instance an 8lb jug is opened 40-50 times and some of the prefer has a chance to bleed/evaporate the carrier.

Does a lower "ether/solvent" content over time change the burn rate or gas production volume for a given lot of powder?

Asking to help understand why I see small changes in velocity from powder that's right from new can vs sat in hopper over a week vs bottom of an old 8lb jug.

 

[biffj]

Ether is not used for moisture control, it is one of the solvents used for dissolving the nitrocellulose and making it possible to extrude or otherwise shape the powder grains. Once the mechanical work of forming the powder is done the ether is removed. There are a number of other chemicals used to reduce hygroscopic tendencies, control burn rates and other properties of the powder. There should be no ether left in your powder on the shelf. Diphenylamine is a stabilizer used in smokeless powders and it does dissipate over time. It does take a long time though......

Frank

 

[Deleted member 113831]

I can't speak to chemistry or ether but I have noticed the same. I live in a very dry environment. If I leave powder out it speeds up. I have expieremented with a new lot of Varget that was very slow by leaving it out for 48 hours in two glass casserole dishes in 23% humidity. It sped up by 70fps. Prior to that I could not load the new lot to the same velocity as the old lot. Once I dried it, it performed just like my older lot.

Water content is a major factor in a powders burn rate. I live in the Pacific Northwest. All my powders burn slower here than when I lived in AZ.

 

[Subwrx300]

Ether is not used for moisture control, it is one of the solvents used for dissolving the nitrocellulose and making it possible to extrude or otherwise shape the powder grains. Once the mechanical work of forming the powder is done the ether is removed. There are a number of other chemicals used to reduce hygroscopic tendencies, control burn rates and other properties of the powder. There should be no ether left in your powder on the shelf. Diphenylamine is a stabilizer used in smokeless powders and it does dissipate over time. It does take a long time though......

Frank

Good clarification; I listened to podcast that discussed some of the technical details of powder manufacturing process and most have mixed up the part used for moisture. What I notice is that powder straight from new bottle smells faintly like acetone/ether and after it's been opened several times (towards middle/bottom of 8lb jug) the smell is very very faint if not gone. Powder that sits out in hope for a few days also has no noticable smell.

To ask in a more direct way, does the chemical that causes that smell impact burn rate (i.e. less smell ~ higher velocity or vice versa)... It seems like my lots of H4350 specifically seem to speed up considerably as that smell dissapates. Almost to the tune of 1gr lower to get same velocity.

For example 42.0gr early in bottle achieved 2730ish avg and late in the bottle it produced 2770 or more (especially if left out in hopper).

Does this seem possible?

I can't speak to chemistry or ether but I have noticed the same. I live in a very dry environment. If I leave powder out it speeds up. I have expieremented with a new lot of Varget that was very slow by leaving it out for 48 hours in two glass casserole dishes in 23% humidity. It sped up by 70fps. Prior to that I could not load the new lot to the same velocity as the old lot. Once I dried it, it performed just like my older lot.

Your experience matches mine almost perfectly. New jugs of H4350 seem to produce about 30-40fps less per a given charge range than powder that is either left in Chargemaster 1500 for a few days or towards the end of the can.

I'm going to run the experiment you did for myself to see if I can duplicate. If results are conclusive and significant beyond 1.5-2 standard deviations of the Average for each group it would definitely seem to point to being extra careful with putting extra powder back in can immediately after finishing loading.

 

[spife7980]

No eveidence collected but I only open my 8lber a handful of times. I keep a one pound can that I’ll fill up periodically and feed out of that so I can try and reduce the amount of... outgasing, I guess, in an attempt to regulate it.

 

[Deleted member 10043]

I do the same thing but only because one pound is lighter than eight pounds.