Epoxy
07-20-2014, 08:14 AM
#8
Two most important keys to epoxy resins, correct mix ratio, keep above 70 degrees. An epoxy that gets soft in the sun tells quite a lot. First it may not have been mixed at the correct ratio, it may have cured at too low of a temp or being in FL the humidity could have played a part. No matter the cause the result was an incomplete crosslink. Getting soft in the sun would actually be performing a somewhat uncontrolled post cure and after a few cycles the epoxy would cure a bit better.
07-21-2014, 08:05 AM
#10
Senior Member
Try CJ Composites or US Composites. Both offer inexpensive laminating epoxies (not finishing, so they might need a thorough sanding and cleaning to hold paint). Working time is about 30 minutes.
07-22-2014, 04:41 AM
#12
Mix ratios are simplified with use of a digital scale and calculator.
For a 3.72:1 ratio just equate 100 divided by 3.72, this gives you a 100/26.882 Resin/Hardener mixing ratio, so as an example lets' say you have poured yourself a 185 gram mass of resin into a tarred cup sitting on the scale, just take 185 X 1. 26882 and you have 234.73, or simply 235, now pour your hardener in the cup with the resin until you get to a 235 total gram mass, resin and hardener combined, mix and use.
By adding the 1 in the front of the 26882 you have included the resin mass to the equation, it is that simple and works with any epoxy resin systems or mixing ratios and is as accurate as a ratio pump.
Bob
For a 3.72:1 ratio just equate 100 divided by 3.72, this gives you a 100/26.882 Resin/Hardener mixing ratio, so as an example lets' say you have poured yourself a 185 gram mass of resin into a tarred cup sitting on the scale, just take 185 X 1. 26882 and you have 234.73, or simply 235, now pour your hardener in the cup with the resin until you get to a 235 total gram mass, resin and hardener combined, mix and use.
By adding the 1 in the front of the 26882 you have included the resin mass to the equation, it is that simple and works with any epoxy resin systems or mixing ratios and is as accurate as a ratio pump.
Bob
07-23-2014, 02:31 AM
#13
WAY COOL. BUT MY COMMON MIX IS AROUND, 5 TO 15 GRAMS RESIN. CALLED- WEST.. SAID 3.5 TO 3.9 CLOSE ENOUGH.. I THINK THATS FOR MUCH LARGER BATCH MIXES.. THANKS FOR INFO.. I NEED GRAM SCALE THATS MEASURES LESS THAN 1 GRAM.. sorry for caps,, old habbit
07-23-2014, 03:09 AM
#14
The calculation for mixing mass ratios is the same for a 5 gram mass,15 gram mass, 5000 gram mass or whatever, it doesn't matter, what does matter is the smaller your mass is, the more accurate you must be in your shop practices to achieve a proper cure, and you are mixing the smallest mass I have ever heard of, so that makes me very interested and brings me to a question if I may ask; what are you applying a surfacing resin too that would use only 5 grams of resin? Just curious...
Bob
Bob
08-02-2014, 09:59 AM
#16
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After a LOT of research and experimentation I now use Adtech 820 resin and hardener.
Go here: http://www.adtechplastics.com/pc-64-...ng-system.aspx
It is VERY low viscosity, very good properties re: cure, hardness, etc. even without hot boxing it... performs even better at slightly elevated temperatures. I use the 824 slow hardener. And unlike Pro-set very slow hardners (and some others), the 824 does not incur Haz-Mat charges.
Nothing wrong with WEST and I have a bunch of it left over from full size boatbuilding. But the 820 handles SO much beter for small parts that I use it for all modeling stuff now with the exceptions of making molds.
Tom
PS: The price ordered directly from Adtech is actually lower than retail dealers prices. Shipping is not bad either.
Tom
Go here: http://www.adtechplastics.com/pc-64-...ng-system.aspx
It is VERY low viscosity, very good properties re: cure, hardness, etc. even without hot boxing it... performs even better at slightly elevated temperatures. I use the 824 slow hardener. And unlike Pro-set very slow hardners (and some others), the 824 does not incur Haz-Mat charges.
Nothing wrong with WEST and I have a bunch of it left over from full size boatbuilding. But the 820 handles SO much beter for small parts that I use it for all modeling stuff now with the exceptions of making molds.
Tom
PS: The price ordered directly from Adtech is actually lower than retail dealers prices. Shipping is not bad either.
Tom
08-03-2014, 04:23 PM
#18
My Feedback: (6)
Just my 2 pennies worth.
Good Gram scale can be had from Harbor Fright, and I might add that it makes 1/1 mixes easy, also keep a cheep hand calculator handy make the math easy for any ratio mix. Have never had problems with any epoxy except Z-Poxy seams humidity is a big factor.
Cheers
Good Gram scale can be had from Harbor Fright, and I might add that it makes 1/1 mixes easy, also keep a cheep hand calculator handy make the math easy for any ratio mix. Have never had problems with any epoxy except Z-Poxy seams humidity is a big factor.
Cheers
