Does fiberglass resin have a shelf life?

[i4Marc]

I bought a gallon can about 8 months ago. I tried to mix up a batch for Micarta tonight but the resin was full of lumps. I mixed with the hardener and built my stack and clamped it. It has been over an hour and no signs of hardening yet. Has this happened to anyone else here? Obviously I need to buy a new can but just wondering if anyone has had their Micarta fail to harden.

 

[wbeatty]

Growing up in S Fla around boats my whole life, I've mixed many a batch. Several factors will effect how it sets off. Humidity, and temp. Being the ones that are hardest to control, you can compensate with the amount of MEK (hardener ) you use. I wouldn't think twice about grabbing a dusty old can of resin off the shelf, if it's thickened any you can thin it with some acetone, but we're talking many years old stuff .

Always mix a small test batch, when you're adding MEK, drops count, I shoot for it to start setup in 10-15 minutes. To slow, add a couple of drops of MEK, to quick ,add less. Don't just dump it in. Drip it in while sturin, mix it well. Remember you won't have much time, so have everything ready.




.

 

[Bufford]

The stuff will almost last forever. Just don't let it freeze, once its been frozen it does not set properly.

 

[mjderstine]

i would say it absolutely does. i have worked with it for years and if it sits for a long time...6 months or more. it never really sets up correctly again. always leaves a sticky residue.

 

[i4Marc]

I mixed it in my basement where it is low humidity and not hot. It never set up. I think maybe I didn't calculate for enough hardener. Even so, the resin was way too lumpy. I'm getting a new can and start from scratch. Too bad I ruined that stack of fabric. It was going to be nice. 47 layers of jet black fabric with nice weave texture and a bit of sheen.....wasted. Live and learn.

 

[wbeatty]

Again test with an oz or so. If cut a small water bottle in half, it makes a good container to do this. Just get a feel for it, you'll feel it getting warm and then you'll feel it thicken as you are stirring. You have to know how much time you have to get it set up.

 

[gredpe3]

After the can has been opened the shelf life is decreased,because of the air in the can.
Eddie

 

[i4Marc]

I think I opened it for the first time a day ago. Must have been too old. I bought a new can today. the graphics on the can have changed so it must be a recent batch. I should have done a test first but it was late and I was eager to get it done. I'll plan a bit better this time. Although, no matter how I plan it is still going to be tough to saturate and stack 47 layers before the resin starts to harden.

Let me ask you this:

Do you think it might work if I pre-soaked, say, half the layers with straight resin with no hardener mixed in so I wouldn't be racing the clock? Then mix a batch with a good dose of hardener. When I build the stack I could alternate the pre saturated layers with the resin/hardener mix layers so it cuts my slathering time in half. Under pressure during clamping the resin/hardener treated layers would mix with the straight resin layers resulting in a fully treated stack. I guess a test is in order.

 

[HallHandmade]

I've worked with some specialty stuff that has pretty volatile hardener, that had a posted shelf life of 1yr, and you could almost see the stuff degrade before your eyes. It was so sensitive to atmosphere that we had to store/open it in an inert glove box, and even then it was hit or miss on still being good at the 1yr mark.

Most stuff though, I think gets a little bit more finicky as it ages, but isn't such a huge deal. I've used tubes of 3M potting epoxy that were pushing 10yrs old, and only noticed a slight overall thickening and some crystallization in areas that were exposed (basically anywhere that was in close proximity to atmosphere).

 

[wbeatty]

I think I opened it for the first time a day ago. Must have been too old. I bought a new can today. the graphics on the can have changed so it must be a recent batch. I should have done a test first but it was late and I was eager to get it done. I'll plan a bit better this time. Although, no matter how I plan it is still going to be tough to saturate and stack 47 layers before the resin starts to harden.

Let me ask you this:

Do you think it might work if I pre-soaked, say, half the layers with straight resin with no hardener mixed in so I wouldn't be racing the clock? Then mix a batch with a good dose of hardener. When I build the stack I could alternate the pre saturated layers with the resin/hardener mix layers so it cuts my slathering time in half. Under pressure during clamping the resin/hardener treated layers would mix with the straight resin layers resulting in a fully treated stack. I guess a test is in order.

If we're talking standard polyester resins, I had a project last year that I used a can from the. 1970's, it was stuffed in the back of the garage, I couldn't find the MEK so I had to buy new, so that's what 40 years? I never throw it away, I will use it until it's gone.

Now presoaking will not work, no where near enough mixing. Perhaps you didn't mix the first batch enough? You need to really mix it. For like a minute. The big boys use sprayers to cover large areas.
Start small, I used a paint roller tray liner and dipped and squiged it off on the incline. You have to be quick. How about dry runs using tee shirt pieces and pancake syrup, it won't be any less a mess than the real stuff and you get to lick your fingers.
Seriously, the hard part is getting done what you have to before it sets up. But you can't take any short cuts in the prep. If it were easy, everyone would be doing it.

 

[i4Marc]

wbeatty,

I'm not sure if it is standard polyester resin or not. It's the 3M stuff you can get at the home stores. I mixed the resin and MEK very well. I think I just didn't figure for enough hardener. You are right I should start smaller. I was building a 7" x 14" stack. That's not that big if I were using a heavy material like canvas that builds up a thick stack quickly. But the material I'm working with is rather lightweight. To build the stack takes a lot of time slathering pieces. With approximately 47-50 layers to make a 1/2" slab I doubt I'll have enough time to finish before the resin begins to set. I like the paint roller tray liner idea. I was thinking about keeping the lumpy stuff for repairing my race fairings but I will return it to recover some costs. This stuff isn't cheap.