plastic bags are made from linear ethylene homopolymer or linear low density copolymers blended with up to about 10 weight percent of an aromatic polymer , e . g ., polystyrene or poly , to improve the ease of opening the bags by reducing the blocking tendency of the film . although ease of opening is improved the aromatic polymer does not adversely affect the other physical properties of the bag , such as md tear strength and stiffness , but improves them .