Mixing Bedding Compounds

[Rustystud]

Just a helpful recommendation, I save the little cups that pudding, jello, and fruit cocktail come in. I get pop cycle sticks at the Michael's craft store. I buy both polyester resin (fiberglass resin) polyester filler and, epoxy from West Marine. I buy color pigments on line. You can buy fast or slow setting epoxy catalyst. I find these products serve me better than JB Weld for bedding materials.
Nat Lambeth

 

[Fast14riot]

Careful with polyester resins, shrinkage rates can be as high as 10% but you can lower that by adding different fillers. Cabosil mixed with chopped strand glass will reduce shrinkage down to nearly 1-2%, also polyesters are generally air-inhibited resins and you may need surface curing agent or to buy wax added resin. Adhesion is not as good as epoxy though either.

But, with polyesters you do not affect the final product by varying the amount of catalyst in the mix. 10-15 drops MEKP per ounce of resin is pretty standard, but going to 5 to extend pot life and cure time will not make the cured product weak. Also going to 30 (cold weather) or more won't make it brittle, but can cause it to self ignite.

-X

 

[X Ring Accuracy]

West System micro balloons work well but after trial and error, we stick with epoxy. Good tips either way

 

[Fast14riot]

Microballoons are typically used as a sanding filler where cabosil (silica) is used as a thixotropic additive. Combining silica and chopped strand can create a very strong resin matrix in either polyester or epoxy.

 

[carlsbad]

I'd just like to say that this is an excellent thread. The OP took the time to share something that works for him. In return, it was pointed out that there may be a better product that what he is using so he may have gotten paid back in spades. This suggestion was made politely, professionally, and helpfully. Others then stepped in with suggestions including some new words. I like new words.

So often I see these types of conversations on the internet go negative, discouraging anyone from ever posting suggestions. This is a great forum.

--Jerry

 

[Alex Wheeler]

I use these and spread out the epoxy thin like Bondo. Helps remove the bubbles.
https://www.amazon.com/dp/B002Z34UKQ/?tag=accuratescom-20

 

[Fast14riot]

Those mixing boards are a nice product, but pricey. If you can get ahold of a sheet of HDPE (any polyethylene actually) it is extremely chemical resistant and your resin (epoxy or polyester) will not stick to it. I'm sure many of you have seen those thin, flexible cutting boards sold in the camping stores, well those are HDPE and make great mixing boards. Just let the resin cure on it and flex it to pop it off. They cost just a few bucks.

A nice benefit of spreading out your resin, it allows it to dissipate the heat and can give you a longer pot life.

I will state that I do work in the plastics industry and also with lots of "fiberglass" products, but I don't want to post links to things I sell through my company on here, but if anyone has any specific questions feel free to PM me.

On to the OP's point about saving those little cups, those are usually made from polyethylene, just like "Tupperware", milk jugs, plastic cutting boards, etc. Mylar films (yes, like the balloons) are also great for mixing stuff on as it has the same chemical resistance as PE. The cups are a great thing to keep around the shop.

-X

 

[ebb]

I generally have formica scraps around the shop and cut these up and use them as mixing boards. I just toss them went done. I like Marine Tex, but have wanted to try Devcon. I understand that some solvents and oils will damage some of the products we use for bedding. What product is best with regard to shrinkage and resistance to solvents and oils?

 

[Alex Wheeler]

Devcon works well, but its is hell on tooling and the dust is abrasive. I prefer to use Marine tex. I think any epoxy is plenty strong for the task and some testing has proven to me Marine tex shinks less than devcon or jb.

 

[Fast14riot]

Devcon contains steel particles. Marine tex is good too.

Basically, any high strength epoxy, with chopped strand fiberglass and cabosil added, plus pigment will give you a perfectly acceptable bedding compound.

As a general rule of thumb, the longer an epoxy (not polyester) takes to cure by design, the stronger it is. 5min, JB Kwikweld, etc will not be as strong as their traditional counterparts.