Isotactic polypropylene blend with ethylene! propylene! copolymer - combining thermal stability with tensile and flexural strength and cold flexibility

摘要

Elastomer-modified thermoplastics consist of blends of uncrosslinked ethylene-propylene block copolymers (I) with isotactic polypropylene (II), pref. of density 0.90-0.92. The blends pref. contain 30-80 (35-65) (wt.)% (II) and 20-70 (35-70)% (I), which consists of 65-93 (72-85)% C2H4 and 7-35 (15-28)% C3H6 units. The blends combine high thermal stability with good tensile strength, flexural strength and cold flexibility. They can be compression moulded and extruded, e.g. to shock absorbers, seat sheels, facings, instrument panels, spoilers, switch panels, steering wheel covers and ski boots. In an example, 70:30 (30:70) blend of (I) (74% C2H4, 26% C3H6) and (II) (density 0.906) had a tensile strength of 13.03 (16.56) MPa and Vicat softening temp. of 58 (136) degrees C. In notched impact tests at -20, -30 and -40 degrees C the 70:30 blend was unbroken, whilst the 30:70 blend gave values of 8.56, 6.15 and 3.56 kJ/m2 respectively.