cosden 8670 polypropylene polymer melt flow index 4 average molecular weight by gpc 204 000 using a 11 4 in 3 2 cm brabender u2122 extruder with a 12 in 30 5 cm wide film die at a thickness of about 1 5 mil 0 04 mm under the following conditions ______________________________________melt temperature u00b0 c 206screw speed rpm 47polymer flow rate kg hr 4 7die temerature u00b0 c 204______________________________________ the films were extruded onto a chrome plated 3 in 7 6 cm diameter casting roll spaced one inch 2 5 cm from the die the film was in contact with the roll for about 2 5 seconds the roll was maintained at 44 u00b0 f 6 7 u00b0 c and 150 u00b0 f 65 5 u00b0 c to provide non crystalline mesomorphous film example 1 and crystalline film comparative example 1 respectively each film was coated with a solution containing 99 9 weight percent acrylic acid and 0 1 weight percent wetting agent fc 430 available from 3m company the films were irradiated using an electron beam at a dosage of 5 mrad in an inert nitrogen atmosphere to effect graft polymerization of the acrylic acid onto the polypropylene films control films without the acrylic acid coating were also exposed to 5 mrad electron beam irradiation non irradiated graft polymerized and control films were tested for yield stress and elongation at break after 4 months storage at 70 u00b0 f 21 u00b0 c the results are shown in table i table i______________________________________.