I have wood flooring which is coated with a polyurethane finish. According to the marketing, aluminum oxide has been incorporated into the polyurethane to make it more durable, but that's all that is said about it.
I understand that aluminum oxide is a hard substance, but I don't understand how it could be incorporated into a polymer to improve wear resistance. If it occurs as microscopic beads or granules of alumina within a polymer matrix, how does that confer durability? I can understand how a coating of alumina on top of the polymer would provide durability, but how could that even work?
So, my question is: What form does the alumina take in the end product and how, in that form, does it improve durability?