Hans, With regards to the "foamy head" when pumping down. If the material is pumped for a longer time you will see the foamy head drop by itself. When this happens you have removed the largest portion of trapped air. It will continue to give off small bubbles for a while but with your 20 set time you will have a problem waiting that long. In our vintage bell jar we have a vent valve that we can crack open ever so gently to keep the vacuum level from getting too good which in turn keeps the volcano from over flowing the container. Another solution is to use a container that is about 3 times the size of the material mixed. Then you can (most of the time) walk away and it will collapse unattended. What a mess if it goes over the edge! Happy potting. Phil Nutting -----Original Message----- From: Hinners Hans Civ WRALC/LYPME [mailto:[log in to unmask]] Sent: Wednesday, September 13, 2000 4:47 PM To: [log in to unmask] Subject: Re: [TN] Potting Compounds Hi Phil N. Mary and Phil C., We mix in atmosphere and then placed it in a vintage bell jar vacuum system. (And everybody knows when I say vintage I mean vintage.) The thought has occurred to get a newer/smaller vacuum system - quicker, stronger pump, with say a calibrated pressure gauge. I've seen the "whipped cream" several times. The entire mixing cup gets quite a head of foam. You bring it back up to 1 ATM, the foam head collapses, and there are still lots of tiny bubbles. We've been using PR-1592 successfully but in much larger batches 1000+ grams versus 50 grams for this stuff. Desoto mentioned using much more than was required and discard the more bubbly sections. Thanks for the tips Mary, Phil C. - I'll check that site out tomorrow. Hans -----Original Message----- From: Phil Nutting [mailto:[log in to unmask]] Sent: Wednesday, September 13, 2000 3:42 PM To: 'TechNet E-Mail Forum.'; 'Hinners Hans Civ WRALC/LYPME' Subject: RE: [TN] Potting Compounds Hans, Are you mixing this material out on the bench or in a vacuum mixing system? When mixed on the bench, even without trying, you can whip the stuff up like whipped cream. With a 2 part potting epoxy we use we've had great results when we mix in a vacuum and then pour into the molds while still in the vacuum. But then we have a 3.5 hour cure cycle at 90°C. Just one man's opinion. Of course there could be something wild going on between the A & B materials... nah, that's two far out. Regards, Phil Nutting -----Original Message----- From: Hinners Hans Civ WRALC/LYPME [mailto:[log in to unmask]] Sent: Wednesday, September 13, 2000 3:27 PM To: [log in to unmask] Subject: [TN] Potting Compounds Hi All, I have a rare treat! - I get to recommend a substitute potting compound for a component we build. We pot several discrete components - it's not more than 2 cm long x 1 cm wide x 1.5 cm tall. The drawing called for a Courtaulds Aerospace (now PRC DeSoto) compound PR-1660, but that was replaced by PR-1664-D. Even with several cycles in a vacuum chamber we can't get the bubbles out of the mixed compound before it sets up (15 - 20 minutes). Part A pours like honey even before you start mixing with Part B. We plan to use an injection mold or a simpler pour mold. I plan to talk to PRC Desoto later today but I seek words of wisdom from the Group. So, does anyone know of a honey colored potting compound that doesn't generate bubbles as it cures? Oh yeah, something approved by an IPC or an old Mil Spec would be an added bonus. Thanks Gang! Hans ~~~~~~~~~~~~~~~~~~~ Hans M. Hinners Materials Engineer (Process & Manufacturing) Warner Robins Air Logistics Center Avionics Production Division Precision Attack/ Radar/Manufacturing Branch Engineering Section 380 Second Street, Suite 104 Building: 640, Mail Stop: LYPME Robins AFB, GA 31098-1638 Voice: (478) 926 - 1970 Fax: (478) 926 - 7164 mailto:[log in to unmask] http://www.robins.af.mil ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. 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