Cotton pillowcases create friction that leads to breakage and morning frizz....

https://noon-wiki.win/index.php/Why_Does_Chemically_Treated_Hair_Get_Worse_with_Cotton_Pillowcases%3F

Cotton pillowcases create friction that leads to breakage and morning frizz. Swapping to silk helps, but a loose braid or silk scrunchie is just as effective. Protecting your hair overnight is a simple habit that makes styling much easier once you wake up