a film of biodegradable polylactic acid polymers and copolymers are produced by biaxially orienting single and multilayer extrusions . the film and sheets are stiff , have excellent optical properties and show excellent retained folding and creasing properties making them especially desirable for the production of folded box like containers . the surface layer of the film and sheet may be heat scalable or modified with a particle to give improved coefficient of friction , blocking resistance , reduced static generation , improved winding and improved package formation on packaging machines .