Apply to a small spot and test the adhesion before you apply it to the entire floor. You can always contact Minwax for more information.

Thank you.. ceiling boards...but a test spot is a great idea!!

No, not safe to assume. Unfortunately testing will take a few months or more to know whether or not it's really adhered unless it's just a flat out failure. Since the products come from different companies neither is likely to offer you much help, but you can certainly ask. If you go ahead I'd at least be sure to scuff sand the boards to maximize chances of adhesion.

Make sure you like the way the polyacrylic looks before applying it to your entire project. Don't much care for it myself.

I agree that you can't assume and probably should test a small area. I will add that I have touched up hardwood floors in the past with a different water-based poly than the one I originally applied (for the same reason; original product was unavailable) with good results. I get the sense that water based poly cures to a non-reactive plastic-like finish, instead of the more volatile, solvent-based products of yore. I would just check the can of your Varathane to make sure it's fully cured before you apply the Polycrylic to improve your odds of compatibility.

Also, you do have a comfortable margin of error since you won't be walking on, or even handling the wood once the finish is applied, if that gives you any peace of mind.

You might be a litle safer by not changing resins from urethane to acrylic. Another WB polyurethane is very likely to be compatible. That said, if the first coats are well cured and then sanded it will almost certinaly work.

All water based urethanes are essentially different formulations of the same resin base. Minwax should be able to tell you if it will stick to a urethane resin. Professional finishers mix and match sealers, pigments, and clear coats all the time across brands.

On a side note: Minwax Polycrylic is garbage IMO. See if you can get your hands on some General Finishes High Performance. It's urethane based so almost certainly compatible with your previous coats and it is a WAY better product than the Minwax. It's not cheap though, runs $80-100/gallon. You can spray it or brush it or roll it and it will come out well either way.

Hello I was able to purchase 2gal of the same urethane I started with.. thank you everyone. Very informative thread!