BIAXIALLY ORIENTED POLYSTYRENE FILM CONTAINING SMALL RUBBER PARTICLES AND LOW RUBBER PARTICLE GEL CONTENT

A biaxially oriented film has a machine direction-orientation (MDO) ratio of more than 1.2 and a transverse direction orientation (TDO) ratio of 2.0 or less, where the MDO ratio is greater than the TDO ratio; where the film contains a polymer composition containing a first high impact polystyrene (HIPS) component with a block copolymer grafted to polystyrene, a rubbery conjugated diene content of one to seven weight percent based on first HIPS weight, less than 10 weight-percent gel concentration, an average rubber particle size of between one and 0.01 micrometers, about 40 to about 90 volume percent of the rubber particles have diameters of less than about 0.4 microns and from about 10 to about 60 volume percent of the rubber particles have diameters between about 0.4 and about 2.5 microns, a majority of rubber particles with a core/shell morphology and a concentration that accounts for 30 to 100 weight-percent of the total polymer composition weight and one to five weight-percent rubbery diene based on total polymer composition weight. The film can also contain up to 70 weight percent of a general purpose polystyrene and up to 20 weight-percent of a second HIPS component that is different from the first HIPS component, both based on total polymer composition weight. The polymer composition accounts for at least 95 weight-percent of the film, with the balance of the film weight being additives.