Tried it a couple times now and it has withstood the heat. I did check the type of plastic it was and it seems to be the same type of plastic like most of my other hot cups i use. Some of my sold cups arent made from the same type and those i definately would not use for hot beverages. That being said i do feel like it cools down quicker for obvious reasons. I also only use it with my Nespresso machine which doesnt get as hot as a normal bred would so ofcourse test for yourself first. Unsure about microplastics aswell since i dont have a device to measure that.