Acetate is a plastic-like material formed from nylon, making it more durable, flexible, and stronger than conventional plastic. It is also more resistant to pressure and can bend further before breaking. Acetate is very flexible which helps your acetate sunglasses and eyeglasses frames last longer. Cellulose fibers bend fairly easily when force is applied to them, giving the acetate material great flexibility. The flexibility of acetate glasses allows them to mold to your face for maximum comfort.