Troy,This is a little off topic so please forgive me. What did you use to bond
the epdm to the case wall? Did you use any special preparation to bond the
propellant to the epdm liner? Thanks! Barry Sent from my Sprint Tablet.
-------- Original message --------From: Troy Prideaux
<troy@xxxxxxxxxxxxxxxxxxxxx> Date: 7/7/20 20:36 (GMT-05:00) To:
arocket@xxxxxxxxxxxxx Subject: [AR] Re: Making composite APCP in Australia
Another alternative to PBAN/HTPB is PPG which is something I’ve used
extensively in the past. Pros:Cheap as chipsAvailable locallyHigher performance
than HTPBHigher Density than HTPBNo Bonding agent needed if using IPDI to
cure*negative* pressure exponents possible (yes, I’ve measured them)Non Toxic
(actually used as a food additive) Cons: Its active hydroxyl groups are
generally not primary like HTPB, but secondary. This means they aren’t as
active and as a consequence the diisocyanate curative will have a much stronger
affinity to react with any H2O present first. I’m assuming you’re familiar
enough with polyurethane chem to know that NCO<->H2O reactions produce urea and
CO2 as products (read: CO2 bubbles/voids) which are very undesirable within a
composite solid propellant. This is why PPG is a very good polyol for
polyurethane foam production. However, with the right processing equipment, one
can ensure there is no moisture contained within the mix to be processed by a
combination of vacuum mixing and casting and raising the temperature of the mix
to assist the removal of volatiles (re: moisture). I can vouch that 100%
density is achievable in castable grains with consistency if it’s processed
correctly. HTPB is also much more hydrophobic than PPG which also assists with
minimising moisture absorption (for HTPB). This is a further moisture issue for
PPG (again, dealt with the above processing) but also presents some benefits as
well. There appeared to be enough polarization or something within the PPG
molecule to assist with the bond to AP without needing an additional (very
export controlled) bonding agent. So, providing a high MW monomer is selected
to begin with (2000 Da or higher), the resulting curative requirements and
physical properties of the composite are close to par with HTPB ie. a rubbery
matrix of good toughness and strength with good temperature stability and shelf
life. Actually, I increase the MW of my monomer well beyond 2000 Da prior to
including it into the propellant mix to both thicken it up a bit and to also
help stabilize its interaction with both the AP and any included metals. A
strand of IPDI cured PPG stretched to its
limits:www.propulsionlabs.com.au/Misc_Video_And_Images/Tuff.wmv AP+PPG (non
metalized) composite in flight (note: no
smoke)http://www.propulsionlabs.com.au/Oct16_11_Launch/Solid3.JPG and a casting ;
for the above flight with EPDM
liner:http://www.propulsionlabs.com.au/epdm_liner/IMG_0272.JPG This is not a ;
recommendation! It’s purely an option. I still like Ken’s suggestion or at
least something in that direction. TP From: arocket-bounce@xxxxxxxxxxxxx
[mailto:arocket-bounce@xxxxxxxxxxxxx] On Behalf Of Joshua CarrSent: Tuesday, 7 ;
July 2020 4:30 PMTo: arocket <arocket@xxxxxxxxxxxxx>Subject: [AR] Re: Making
composite APCP in Australia RE: PBAN/HTPB Alternatives Thanks Ken and all
others who have chimed in.. Asphalt looks like a solid alternative, as does 2
part epoxy. Re: ASRI Australia A while ago at Adelaide Uni, I was lucky enough
to be involved with them launching a repurposed Zuni rocket. I do remember them
having some involvement in manufacturing, Will also contact them and see what
their movements are. Cheers! Joshua Carr ---- On Tue, 07 Jul 2020 02:47:26
+0930 roxanna Mason <rocketmaster.ken@xxxxxxxxx> wrote ---- Hello Joshua, I
encourage you to look at an alternative to HTPB and their toxic isocyanate
curing agents, that being modified asphalts. Yes roofing tar, road paving
asphalt with an ingredient to lower its processing temp so AP can be used
instead of KP, potassium perchlorate with its high burn rate exponent. See
attachments of work I conducted with Dr. John Rusek at the Rocket Lab at
Edwards AFB in California back in the 80's. Performance equal even exceeds
HTPB/AP/Al with an increase in density as a bonus. Asphalt SG ~ 1 compared to
HTPB ~0.9. Kraton is the key additive with which you can formulate your own
modified asphalts otherwise there is a supplier right here in California that
supply the AC type asphalts mentioned in the Edwards report..I got a free 5
gallon sample by just asking nicely.THe finished propellant has another bonus,
it's reusable so any excess you make can be remelted. You can use a version
that's compatible with your hot Aussie summers. FYI, I also used to work with
the Rocket Research Institute back in the 70's with the original GALCITE
asphalt rockets that ran Pc at 3000 psi using surplus 5" steel HIVAR rocket
motor cases. We routinely launched rockets 20-100KFt all legally under FAA
waivers. But with these modified asphalts you can now use low exponent AP
Pc<1000 psi.Good luck with Blessings,Ken On Mon, Jul 6, 2020 at 6:47 AM Joshua
Carr <admin@xxxxxxxxxxxxxxxxx> wrote: Hi Terry, The next step I am about to
take is to purchase your book from aeroconsystems.com. Is this the best place
to buy it? Also, I would like to ask your opinion on something, I hope you
don't mind. Given your chemistry background, do you have any recommendations
for understanding ignition and chemical reactions? After a lot of reading (and
a uni course or two) I still haven't found a decent explanation of what is
happening at the fundamental level. The same is the case for binders and
diisocyanate or curing agents ect. I have learnt a bit about this process, such
as bond types, from expanding foam and rubber making. But it seems a lot of
books on rocketry leave these things out. Anyway just a thought of mine, if you
are reading thanks for your time and hope to speak again soon. Kind regards,
Joshua Carr ---- On Fri, 29 May 2020 00:19:56 +0930 Terry McCreary
<tmccreary@xxxxxxxxxxxxxxx> wrote ---- Hello Joshua and the rest of the list, I
was on the TRA BoD during most of the BATFE lawsuit. If memory serves
(sometimes it doesn't anymore...:-\) that suit consumed a bit more than
two-thirds of a million dollars over a 10+ year period. Initially Judge Reggie
Walton ruled that BATFE had deference to classify (as an explosive) virtually
any material they chose. TRA+NAR appealed, the appeals court didn't buy the
"due-deference" argument, and the suit went back to Walton.At some point BATFE
decided that the burn rate of safety fuse was a guide to classification;
anything that burned faster than that was to be classified as an explosive. A
1000+ page document was submitted, "proving" that APCP burned at tens of
meters/second and was therefore an explosive.**TRA+NAR provided just a couple
dozen pages which included citations from actual peer-reviewed publications by
actual rocket scientists. Within those publications were some ballistic
properties of a few hundred propellant mixtures, most having burn rates @1000
psi on the order of 1 cm/s, and none exceeding about 3 cm/s.Following Judge
Walton's ruling in favor of TRA+NAR, a request for recovery of fees was made.
The amount recovered was well under $100K... oh well, we
WON!!https://www.courtlistener.com/opinion/2400163/tripoli-rocketry-v-bureau-of-alcohol-tobacco/?Best
-- Terry**BATFE's legal team apparently went to the W.C. Field's School of Law
and Heavy Machinery Operation: "If you can't dazzle them with brilliance,
baffle them with bulls++t." And somewhere in their submitted document was
proof...that if a rocket motor was clamped tightly enough to a steel rod, upon
ignition the case would rupture and undergo RSD---rapid spontaneous
disassembly. ;-) On 5/27/2020 10:34 PM, Joshua Carr wrote:In Australia we need
a full on explosives license to do what you fellas in the USA take for
granted.Sure Tripoli and the rest of you guys went to fight for APCP a while
back, but it would be great to share some wisdom to us Aussies down under (the
industry ain't exactly booming here). Regards, Joshua Carr -- Dr. Terry
McCrearyProfessor EmeritusMurray State UniversityMurray KY 42071
