Three films (thickness 0,11-0,24 mm) made of thermoplastic starch modified with glicerol, poly(vinyl alc.) or/and keratin were prepd. by extrusion with blowing and studied for impact strength at relative air humidity 50-99%. The poly(vinyl alc.)-contg. films exhibited the highest crit. force response and the lowest elongation. The addn. of keratin resulted in decrease of both the cut. force response and elongation. The film samples studied under high relative humidity showed a low crit. force.