Is satin basically plastic?

Not always, but most of the satin you see in fast fashion and affordable bedding today is essentially plastic. This is because satin is not a fiber itself, it is a type of weave characterized by a glossy face and dull back created by long floats of yarn. That weave can be done with any fiber. Traditional and luxury satin is made from silk, which is a natural protein fiber, and is not plastic at all. However, the vast majority of modern satin, especially cheap satin sheets, dresses, bonnets, and linings, is made from 100% polyester, which is polyethylene terephthalate, a petroleum-based plastic. Sometimes it is made from nylon or acetate, which are also synthetic. So when people say satin feels like plastic, makes you sweaty, and causes static, they are usually referring to polyester satin. If the label says polyester satin, charmeuse satin, or satin de Paris without mentioning silk, it is plastic fabric designed to imitate the shine of real silk satin at a fraction of the cost.