jrbmoto

If I mix 5 minute epoxy with 30 minute will I get 12.5 minute epoxy?

SDCrashmaster

Yes, go buy 20 min. epoxy

Mastertech

My Feedback: (31)

Mix some up and try it.

LANNYBOB

no, you'll get 35 minute epoxy

superflea

no no no you get 17.5 minute epoxy.
its the average of the two.
30 minute plus 5 minute = 35 minute divided by the two = 17.5 minute. 17.5 minutes is the length of time the glue joint will hold before structural failure.

AlphaWhisky

I mixed 30 min epoxy with 5 min hardener, or maybe the other way round, by mistake a few weeks ago. All I got was a gooey mess - it didn`t go off at all......

Alan W

da Rock

Different epoxies don't mix.

You don't get different times with different combinations. You get nothing but lumps of non-curing goo.

superflea

...and while we're mixing different products, I'd like to say that mixing fiberglass resin hardener and bondo doesn't work real well either. but on the bright side, after approx. 30 months my cub cowl is only a little tacky and might be ready for final sanding and paint in a year or so. [&o]

impalacustom

LMAO Flea, I am so glad I wasn't the only one that did that. I put the bondo hardner in with my resin, and made one heck of a red gooey mess. Thankfully it somewhat peeled off and just after about 2 weeks of drying and some heat gun work it did set up enough where I could do it properly.

John Sohm

My Feedback: (9)

They're both polyester based products but the fiberglass resin usually uses MEKP (methl ethyl ketone peroxide)as a catalyst and if you read the label on the cream hardener used with Bondo, you'll notice it uses benzoyl peroxide. So it doesn't surprise me that you ended up with a gooey mess.

j.duncker

My Feedback: (2)

Weeeeell you might, if you were lucky, but I would not do it.

Bit of theory on how epoxy resin works.

You start with a Resin to which you add a catalyst. This starts the reaction which causes the resin to cure [ harden ]. In one case that I investigated the time to the first stage of 'setting' was 16 hours. N.B. at this stage the epoxy is said to be green and is not yet at full strength.

It is possible to speed this up with an accelerator. There are different chemicals which will do this.

It is possible to slow it down with a retarder. Again different chemicals are available.

It is likely that both the 5 min and the 30 min contains accelerator. If it is the SAME accelerator then yes the 'setting time ' should be somewhere between the 5 and 30 mins. But if the accelerators are different then it could all go horribly wrong.

I am mostly Scottish and even I buy 5 min [field repair box], 12 min [general construction], and 30 min. epoxies.

I try to buy from suppliers with a high turnover and discard all epoxy after a year. Epoxy has a shelf life.

RCVFR

My Feedback: (7)

Read the label? C'mon.........

MinnFlyer

My Feedback: (4)

If you want 30-minute epoxy to set faster, mix it up and heat it

A microwave works GREAT for this BUT!!!!

1) only give it 5-7 seconds (It doesn't take much! )

2) make sure your wife's not home

Also be aware that heat will really make the epoxy thin.

digital_trucker

I've had epoxy become much more brittle when cured after heating it also...but it's great for using as a fuel-proofer.

John Sohm

My Feedback: (9)

There are several problems with using a microwave to accelerate epoxy curing: One is that there is no way to evenly heat the mixture and control the temperature of the cure and two the fumes that are emitted by the epoxy pose a distinct health problem when inhaled. People tend to build an intolerance to it over time much as they do with prolonged exposure to the fumes from CA glues, especially the thinner, more active types.

When I used to work at a major computer manufacturer in the mid-hudson valley that is known by three letters and associated with the color blue, we used an industrial type of epoxy for bonding the motherboards to the stiffener frames used to mount in the mainframe cages. These boards would be placed under pressure in an oven and stay there for several hours to accelerate the curing process. Those ovens were vented through exhaust filters and the temperature was controlled. We used to do oven profiles to ensure there were no excessively hot or cold spots in the ovens. The point is, the temperature we picked was not one we made up, it was specified by the epoxy manufacturer just for that one particular type of epoxy.

So if you don't know what the recommended temperature is to speed up the process, it's best to let it cure at the recommended room temperature specs so you don't get the brittleness or whatever. If you need it to set faster, use a faster setting epoxy. That's not to say that if the bottle is cold, you can't place it in a pot of warm water to bring it up a few degrees to where it should be (most are to be used at room temperature, 70 degrees fahrenheit or a bit more).

Capt. Bill

Epoxies get their strength from being highly cross linked. 5 minute is really only good for light service, 30 minute is best for firewalls, wing mounts, landing gear blocks. just let it sit overnight.

The polyester and polysytrene resins are simply long chain polymers of simple molecules. They are really only useful when reinforced with fiberglass since they are very brittle on their own. The organic peroxides used are correctly called initiators since they start the curing by breaking a double carbon bond in the monomer. Methyl ethyl ketone peroxide (MEKP) is the most common. Benzoyl peroxide was the first organic peroxide used in polymer reactions and is also used in acne medicines and for bleaching flour. I have seen MEKP in hobby stores priced at $2-$3 for a half ounce. I am retired from a company that makes MEKP and we sold it for about $2 a POUND. Of course our smallest package size was a 4 x 7lb case, guess the money is in the repackaging.

superflea

so its not 17.5 minute epoxy then. [&o] oh well who'd a fiqured.

jrbmoto

Never mind.....I just bought some 20 min....