Cups for mixing?

Newbee question for both Epoxy & Polyester resins.

Yesterday I measured (with plastic spoons) 1 part epoxy resin (Primer Paint) 1 part Hardener (Paint activator) in a red plastic cup from some we bought at the grocery store for drinks. I wiped the spoons down after measuring and that part went ok.

The red plastic cup held up almost until I was done applying the mixed primer to the bottom of a metal door and then the bottom of the plastic cup started to separate from the catalyst heat.

Today I used a spare small metal can to mix. But wondering is there a type of plastic cup (or any kind of cup) that are not terribly expensive and will hold up a moderate time to the catalyst heat?

 

The red plastic cups that I have in mind is not suitable for mixing paints, adhesives, or anything with a strong solvent such as lacquer thinner.

Suitable small quantity containers can be utilized by using the mini tubs that contained cottage cheese, butter, or some deli items. If your cup melted from heat you had allowed too much time in which to use it all. We have been having some pretty warm weather in Florida and that too plays into the way you must treat that type of chemistry.

In order to slow the process down you can use different type of container that has a bottom with a lot of area. For a given volume of paint or adhesive the depth will be less and the mixture will not "kick" as quickly. In desperate cases you can set the paint container inside a larger container that has ice in it. The idea is to delay the heat that causes the polymerization process to begin. Actually there are numerous tutorials on line that will explain all this more clearly. Dial up West Systems, or System Three for example.

 

The containers used for toppings at my local Bagel store work well.
I get the same things for condiments at the local Barbecue joint.

 

Thanks for the replies I will get some of those. I may have caused my meltdown by thinking I read somewhere to let my particular epoxy to rest 3 mins after the first mix and then re-mix. I think I will forego that and just mix it well the first time.

I'm wondering about some medicine cups on Amazon sold reasonably priced by the hundred. Is there any criteria to decipher the type of plastic that is more resistant to melt down? I've read paper is ok as long as it's not waxed but I don't see any specs on those either as to wax or no wax.
I surmise it's a trial & error thing ?

 

Polypropylene or Polyethylene will work well.

I don't know what drink cups are made from.

 

I've used epoxy primers and 2 part linear polyurethane paint extensively and have never noticed heat build up. There are some very aggressive solvents in those paints though and they will dissolve many plastics.
Epoxy resin is exothermic and does generate heat as it cures. There are usually different hardeners available that slow down the curing process when the ambient temperature is higher. For instance I might use a lot more "fast" hardener up here in New York and you might prefer "slow" hardeners in Florida. Our resin might cure in about the same time but I'm working in a much cooler environment.
As far as mixing cups are concerned I find Polypropylene medicine cups work great for measuring small quantities. Up to 5 ounces or so, I always use yogurt containers. Yep, right out of the dairy section. Don't laugh, yogurt's good for you and those containers have never let me down, even when I mixed up a batch of Interlux Perfection and let it induct for an hour before I even put it on the boat. For larger quantities, head for your nearest Chinese restaurant and order up some hot & sour or won-ton soup. You can reuse the pint or quart containers.
If you've never seen the medicine cups they look like this:

http://www.mertons.com/Tools/medicinecup.html

BTW, letting the resin sit in the cup as you describe is a sure fire way to make an expensive paperweight or hockey puck! I'm also thinking that you may be using the wrong hardener. Take a look at System Three's Epoxy Book. It will give you a lot of information that is useful no matter the brand of resin you choose.

https://cdn.shopify.com/s/files/1/1000/1906/files/The_Epoxy_Book.pdf?1285685231865784556

 

I use (for small quantities) polythene measuring jugs from wilkos or poundstore. The flexibility of the jug means you can crack the hardened resin residue out of the jug by flexing it, though the jug itself does eventually become brittle after a few mixes. I use disposable plastic measuring syringes to measure the catalyst accurately. Again each will do a few mixes as the plunger does a good job of clearing out all the catalyst. In our climate I've never had any issue with heat build up though.

 

I've never had a problem with epoxy in anything plastic but polyester can be problematic heat wise when catalyzed. It's good to spread the resin into a fairly wide open tray when laminating to prevent it setting off too quickly from exothermic heat.

 

You can get "unwaxed" paper cups from fiberglass supplier. It comes in quart sizes to half a gallon. If you want to save money, used jugs from motor oil or canisters that holds cooking oil will do. For large batches and one time use, I use tin cans. Very cheap. Just make sure it is clean and oil free.

 

Thanks for all the replies, I'm copying this thread to a folder for reference for cups/containers. I really like that idea of disposable plastic measuring syringes, but wondering if they'd work on thick resin too. It didn't take me long to realize that trying to scoop measured amounts of thick primer paint resin is not an exact science.
The resin (even when well stirred prior) is so thick that success in getting it all out of (or off) the scoop item can be less than accurate in getting the same amount of resin in the mix as hardener. Not so much in just one scoop each but multiple scoops adds to the measure error factor.
So I started using equal water amounts to mark my mixing container and then dry it thoroughly prior to use. This works better for me than rather than attempting to measure by equal scooping. I also noticed (at least with the liquid hardener) that it's forgiving somewhat with small differences of equal mix. It just sets faster or slower respectively. But I remember once years ago doing a clear table top that I got too little of the hardener (that hardner was a resin consistency) and it never did set up. It was a mess that I ended up trashing.
Of course with the help & links you all have given me I will be better able to maybe track down some calibrated containers that are not too expensive.

 

You can also measure up your resin amounts by weight in containers on a scale. I use two separate electronic scales with a tare function to zero the weight. Then you don't need to worry about graduations on the container, it makes it easy to mix even small amounts to the correct ratio. You could also get away with just using one scale it doesn't really matter I just like being able to do both sets at once without taking them off the scales.

 

I had read somewhere that you should not use waxed cups for mixing resins? However I found these sold by System 3 that are stated to be specifically waxed.
https://www.amazon.com/Mixing-Cups-Graduated-ounce-pieces/dp/B00AKJ6ML2/ref=cm_cd_al_qh_dp_t

Is the non waxed thing not relevant?

Actually I would think if one used a paper cup without wax then it would have to have some sort of other type of sealer or it would leak through permeation.

Appreciate any comments.

 

If you use waxed type, it will dissolve in the resin and float to the top to seal the laminate. Not a problem if you are using peel ply or do not intend to bond anything on top of the laminate. If you do without peel ply, you will need to dewax, then sand lightly before adding a second layer.

The unwaxed paper cups we used did not leak with epoxy or poly. we used to consume hundreds of them in a week.

Even the tin cans we use, we make sure it is not the coated type (shellac?). It rust easily but we buy them new.

 

I use kitchen measuring jugs from Walmart/Asda.
Never had a problem,two part paint,epoxy etc.
I use a rechargeable drill with a paint mixer paddle,pretty quick for mixing,
Quick clean off each time with Acetone,works a treat.
For the resin hardener I use a bulbed disposable dropper,if you leave it upright,it drains
the hardener out for next time.Of course,you don't let the two mix when you squirt the hardener in,or it sets on the end of the dropper.
The jugs I use are marked,and hold a litre.