Glass microbeads and epoxy

[Ted P]

I plan to use 30 minute clear epoxy for a complex assembly, but would like to thicken it a bit to avoid runs. I read that glass microbeads can be used to thicken the epoxy, so I tried it out on a not so complex assembly. Mixed the beads with the resin before combining with the hardener as directed.
A long story shortened, the my experience is that the micro beads changed the 30 minute epoxy to about 6 minutes until no longer spreadable and the Dixie cup got warm from the reaction. Finished up the assembly with yellow glue.
Anyone with a positive experience thickening epoxy? The technique mentioned is supposedly used on RC plane construction but does not seem to work for me.

 

[JNCarr]

The glass beads should not impact cure time. When I worked in the epoxy business of a major chemical company, I saw all sorts of filler being added by customers (beads, fibers, inorganic powders, etc) and usually the result was the opposite - slowed the cure down a little because it spread the reaction sites out per unit volume. Maybe check to make sure the catalyst ratio was correct or that your total volume was not too large.

 

[Ted P]

I used a digital scale, as well as the graduations on the bottles to get pretty exacting mix. And made up only about an oz total of the mix.
I suppose I should try the 30 minute epoxy by itself to see if work time is really that long.

 

[Cuprousworks]

I've experimented with thickening epoxy resins for use as non-drip coatings, using both Diatomaceous earth (DE) and System 3 brand thickener. Neither seemed to impact cure time. Based on my use I can't speak to impacts on joint strength.

I now use only the DE - it's relatively inexpensive and available at hardware stores. System 3 is product-specific and more expensive.

You can have the rest of my System 3 - most of the quart remains. Or I can spare a couple cups of DE if you want to experiment. I'm in Chapel Hill.
Mike

 

[Sealeveler]

Cabosil is what I used building boats for thickening epoxy.

 

[Ted P]

Well, my Bob Smith Industries 30 minute epoxy thickens at 6 minutes and was unusable pretty much from that point on. No thickener added.
This epoxy is a little over a year old. I would not have thought it would become more reactive with age.
Anyway, when I open the new bottles, I’ll try a sample again. For thickener, I am using Fasco Epoxies white glass microspheres-which is purpose made and sold for this use.

 

[Kelly]

I use wood flour as a thickener. Works great and eliminated runs. I got it from the epoxy company.

 

[Gofor]

The short thickening time and increased temperatures is reminiscent of adding cobalt to fiberglass resin. (glass beads also used) Did those glass beads possibly have a catalytic agent added?

 

[tvrgeek]

I agree, should not change set time. You must have added a bit too much catalyst. Do you use a precision scale of cylinders for the mix? I used beads quite a bit in fiberglass car work. We also use talcum power. I see no reason fine sawdust won't work. I usually used WEST system epoxy, but there are many others. To slow it in the pot, you can always chill it.

 

[bowman]

It sounds like the 30 minutes is the cure time, not working time?

 

[AllanD]

I wonder how much this heat wave is affecting it. Are you keeping it in a climate controlled shop? I use a variety of thicknessers but add them after mixing with hardener, basically "to effect" I have used West in the past but now I prefer MAS and keep Fast, Medium, and Slow hardeners. Sounds like you need to use a product that makes a slow hardener.

 

[NCPAPAOF2]

According to BSI 30 minute epoxy has a work time of 30 minutes full cure in 24 hrs. I use it for fiberglass work on occasion and find I get 20 to 25 minutes. First, don't mix in a cup, I use a plastic cutting board or a plastic coffee can lid. Second, keep it cool. Epoxy produces heat while curing. Mixing in a cup or when hot accelerates curing. The lady bug in my avatar had a glass globe that got broken. I made a foam form and used BSI 30 minute epoxy and fiberglass to form a new one. Used large baking sheet with a lip filled with cold water and mixed epoxy in a cake pan inside the baking sheet. Had plenty of time to work the layup. Did it in August last year, early in the day. You can thin it with acetone if needed but I wouldn't.

 

[NCPAPAOF2]

Also to address your use of thickener, I have used wood flour and micro balloons as thickener when using as a filler on rc airplanes. I never add anything when used for structural uses. Bob Smith Industries, and West Systems have websites with more information than you can imagine, Also BSI is very prompt replying to email questions and will discuss their product with you by phone.

 

[Ted P]

I guess my bad was to assume one could mix in a cup and have a little time to coat all the pieces and assemble.
I mixed in my shop which is conditioned to 75 deg. With about an oz in a cup, the new product was unspreadable after ~6 minutes.
I guess mixing on a flat surface in a cold water bath would probably help increase cure time, but seems grossly inconvenient to do in a wood shop. My limited experience with JBWeld has a longer open time than this slow cure epoxy. Yellow glue is roughly the same work time for assembly.
So I suppose it works as stated, but nothing like what I hoped for.
I guess I’ll use Titebond hide glue and hope for the best.
In a practice run, I got this assembled in 7-8 minutes. I’ll wait for another set of hands for the spindle assembly

 

[cfield60]

West Systems offers a glass powder for thickening their products. I have used these before relining industrial feeder bowls at my day job. The glass works very well but you must be careful and use appropriate ppe for safety.