Heterogeneous polymer blends and molded articles therefrom

This invention relates to a molded article comprising a heterogeneous blend comprising: 1) from 60 to 99 weight percent of one or more semi-crystalline polymers (based upon the weight of the semi-crystalline and semi-amorphous polymers), each semi-crystalline polymer comprising propylene and from 0 to 5 weight % alpha-olefin comonomer (based upon the weight of the polymer), said semi-crystalline polymers each having a melting point between 100 and 170° C. and a melt flow rate of 200 dg/min or less; and 2) from 1 to 40 weight % of one or more semi-amorphous polymers (based upon the weight of the semi-crystalline and semi-amorphous polymers), each semi-amorphous polymer comprising propylene and from 10 to 25 weight % of one or more C2 and/or C4 to C10 alpha-olefin comonomers, said semi-amorphous polymers each having: a) a heat of fusion of 4 to 70 J/g; and b) a melt flow rate of 0.1 to 200 dg/min; and c) an intermolecular compositional distribution as determined by thermal fractionation in hexane such that 85% by weight or more of the polymer is isolated as one or two adjacent, soluble fractions with the balance of the polymer in immediately preceding or succeeding fractions; and wherein each of these fractions has a wt % comonomer content with a difference of no greater than 20 wt % relative to the average wt % comonomer content of the copolymer; and d) an Mw/Mn of 1.5 to 4, and e) a propylene triad tacticity, as measured by 13C NMR, of 75% or greater; where the blend has: i) a melt flow rate of 0.5 to 200 dg/min; and ii) less than 5 weight % filler, based upon the weight of the polymers and the filler; and iii) a permanent set of greater than 65%; and iv) a haze of 20% or less on a 1 mm injection molded chip; and the molded part has: a) a thickness of 250 mum to 10 mm; and b) a notched Izod impact strength at 23° C. of 80 J/m or more; and c) a notched Izod impact strength at 0° C. of 27 J/m or more; and d) a 1% secant flexural modulus of 1035 MPa or lower; and e) an ultimate elongation where greater than 50% of 5 test specimens suffer no break through extension to 1000%; and f) a resistance to stress whitening of Hunter color DeltaL of 15 or lower.