Acrylates Copolymer
Acrylates Copolymer is mostly used as a thickening and emulsifying agent, film former, and can make formulas more water resistent, which can be helpful in makeup (where it can entrap pigments) and especially sunscreens.
Concern: Acrylates Copolymer is a water soluble, liquid plastic, officially not classified as a microplastic (as in a microbead). However, it is not biodegradable and will take a long time to break down in the environment.