WHY YOU SHOULD AVOID EPOXIES WITH A 'WIDE' MIX RATIO

WHY YOU SHOULD AVOID EPOXIES WITH A 'WIDE' MIX RATIO (I.E. 5:1 ETC.)

by Paul Oman

Progressive Epoxy Polymers, Inc.

2/2/03

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Let's assume you are going to make a 30 ounce batch of epoxy. That's just less then 1 quart (which is 32 ounces) and just a little bit more than one liter of epoxy.

With a 3:2 epoxy mix that's 18 oz. of part A and 12 oz. of part B

With a 2:1 epoxy mix that's 20 oz. of part A and 10 oz. of part B

With a 4:1 epoxy mix that's 25 oz. of part A and 5 oz. of part B

Now let's pretend you mis-measured the epoxy and got an extra oz. of either part A or Part B. Perhaps you goofed or, if using pumps, there was an air bubble or the an off calibration. Instead of making 30 oz. of epoxy you made 31 oz. - that's only a 3% error and should be no big deal. You wouldn't even notice your error.

3:2 Mix

With the 3:2 mix (that's equal to a 1.5:1 mix) an extra oz. of Part A means you actually used a mix ration of 1.58:1 - that's a 5% error. Result? The epoxy will still set up just fine.

With the 3:2 mix (that's equal to a 1.5:1 mix) an extra oz. of Part B means you actually used a mix ration of 1.38:1 - that's a 9% error. Result? The epoxy will still set up just fine.

2:1 Mix

With the 2:1 mix an extra oz. of Part A means you actually used a mix ration of 2.1:1 - that's a 5% error. Result? The epoxy will still set up just fine.

With the 2:1 mix an extra oz. of Part B means you actually used a mix ration of 1.8:1 - that's a 11% error. Result? The epoxy will still set up just fine.

5:1 Mix

With the 5:1 mix an extra oz. of Part A means you actually used a mix ration of 5.2:1 - that's a 4% error. Result? The epoxy will still set up just fine.

With the 5:1 mix an extra oz. of Part B means you actually used a mix ration of 4:1:1 - that's a 22% error. Result? THE EPOXY WILL PROBABLY NOT SET UP AND YOU'VE GOT AN AWFUL MESS TO CLEAN UP AND A MAJOR WASTE OF TIME AND MONEY. PLUS, YOU'LL NEVER KNOW WHAT WENT WRONG!

CONCLUSION: epoxies with a mix ratio of between 1:1 or 2:1 are more 'goof proof' as they can accept mixing errors much better than epoxies with a 'wide' mix ratio.

So... why do folks sell you epoxies formulated with large number mix ratios? The curing agent part of the epoxy mix is the expensive part. It is a lot more expensive than the resin half. The less curing agent used per volume of resin, the more profit for the epoxy manufacturer. Look at the mix ratio and you have a potential clue as to whether the manufacturer had your best interests, or his own, when he formulated the epoxy.

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