Devcon Not Hardening
- Thread starter centershot
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Preacher
Gold $$ Contributor
So your thoughts are that a erectile dysfunction med will help clean it up ????
Wondering how that would help is all......
okie
Gold $$ Contributor
simply a joke, to "harden" the devcon...sorry didnt mean to ruffle any feathers...
Yes. Heat speeds up nearly every chemical reaction. However, heat will NOT change the ratio of resin to hardener. If the ratio is off by very much, the mechanical properties will NEVER be achieved no matter how hot you get it even if it does harden. Get the mix ratio really far off and it won't cure at all.
Keep in mind that too much heat will damage the epoxy. In fact, many epoxy products deteriorate at surprisingly low heat levels, so don't go crazy with your heat gun.
Preacher
Gold $$ Contributor
No problem, thought it was funny though !!!!
XTR
F-TR obssessed shooting junkie
His problem is that it won't set
centershot
Silver $$ Contributor
I had one job that wouldn't harden, even after days. The mix was incorrect. Actually had too much hardener. I went by volume. Now I go by weight.
Wisecracks welcome.
What do you put the Devcon in to weigh it? That stuff is very messy.
Preacher
Gold $$ Contributor
IF I was going to weigh it, I would use small sheets of waxed paper that had been weighed, and zeroed out....
Measuring spoons used, and scraped off flat with a mixing stick have never caused a problem setting up..
hogpatrol
Gold $$ Contributor
On a piece of 1/16" plastic, about five inches square. Weigh it on my RCBS Chargemaster. Mix it on it also.
timeout
Silver $$ Contributor
Exactly what I do. Weigh and mix on the same piece. Works slicker than pockets on a shirt.
Depart123
That is a damn good idea, hadn't heard that one before.
On the differences between epoxy and polyester, I offer this very fine explanation I learned many years ago in my aircraft building life.
Epoxies gain their superior strength by forming very long chain molecules. The analogy that sticks in my mind is this: Imagine a football field with 100 girls and 100 boys. They are told to form one continuous line by holding hands. Girls can only hold hands with boys and vice versa. Doing so they will form a continuous line, boy-girl, boy-girl etc.
Now imagine the same field with 128 girls and 72 boys and are told to join as before. There will be numerous and shorter unbroken lines, or in this case, a weaker epoxy (and of course, some very happy boys). This is why it is so important to proportion accurately and mix thoroughly.
Heat speeds up the action, just as it does when a catalyst releases heat in polyester resin. Too hot is not good, it can catch fire, but not hot enough is also not good, it can cold cure inhibit and never harden fully. 150 to 170 F is about perfect for room temperature curing epoxies, IME.
Epoxies gain their superior strength by forming very long chain molecules. The analogy that sticks in my mind is this: Imagine a football field with 100 girls and 100 boys. They are told to form one continuous line by holding hands. Girls can only hold hands with boys and vice versa. Doing so they will form a continuous line, boy-girl, boy-girl etc.
Now imagine the same field with 128 girls and 72 boys and are told to join as before. There will be numerous and shorter unbroken lines, or in this case, a weaker epoxy (and of course, some very happy boys). This is why it is so important to proportion accurately and mix thoroughly.
Heat speeds up the action, just as it does when a catalyst releases heat in polyester resin. Too hot is not good, it can catch fire, but not hot enough is also not good, it can cold cure inhibit and never harden fully. 150 to 170 F is about perfect for room temperature curing epoxies, IME.
I place a paper plate on a gram scale. Tare out the scale and typically place 18 grams of part A, and two grams of part B on the plate in separate piles. Mix thoroughly with a tongue depressor with the round end cut off straight with wire cutters. Keep the extra mix to verify the batch has hardened by attempting to press a sharp tool into the mix. When it doesn't yield, its ready. Pop the action out, and trim excess epoxy immediately with carbide burrs and drum sanders or sand paper. It will cut very easily in a green state, but wait a day or two and.....oh boy!
It is gooey which is why you don't want to put small quantities IN anything. You'll never get it all out and that will compromise your mix ratio.
As others have suggested, put it ON a piece of heavy paper, light cardboard, or thin plastic. Weigh the components on a postage scale (don't ruin your powder scale) and then (this is important) mix it thoroughly with a putty knife or a wide tongue depressor with the rounded end cut off square.
There is some leeway in the mix ratio but you should try to get it exact and then mix ALL the material by carefully scraping and stirring on a flat surface, especially with high viscosity products like Devcon 10110 and doubly so when you're dealing with small quantities.
KMart
Gold $$ Contributor
Epoxy is manufactured from the base product, Bisphenol-A (BPA). It is the same base product used in the manufacturing of polycarbonate plastic (trade names Makrolon and Lexan)
BPA is produced by feeding a mixture of phenol and acetone through a reactor and catalyst bed, then refining out the impurities.
Polyester resin is manufactured from maleic anhydride. Maleic is produced by feeding butane through a reactor and catalyst bed, then refining out the impurities. Maleic is also used in motor oil additives, baby diapers and the tart taste in Sweet Tarts.
centershot
Silver $$ Contributor
Success!! I re-did the rifle and it got rock hard. Used the weight method this time. Thanks for your help in understanding epoxy resins. I weighed the plastic measuring spoons. Filled the Tablespoon with resin and weighed it again. Subtracted the weight of the spoon. Took .9 of the net weight and used that much hardener.
Fast14riot
Gold $$ Contributor
Weight is a good way for thick epoxies, but I prefer volume for thinner laminating type resins and use a 3 cup mixing method.
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