A polymer blend composition comprising:(a) from 0.5 to 99 percent by weight, based on the total weight of (a), (b), and (c), of an aliphatic .alpha.-olefin homopolymer or interpolymer, or an interpolymer of an .alpha.-olefin and a non-aromatic monomer interpolymerizable therewith;(b) from 0.5 to 99 percent by weight, based on the total weight of (a), (b), and (c), of a homopolymer or interpolymer of monovinylidene aromatic monomers, or an interpolymer of monovinylidene aromatic monomer and a monomer interpolymerizable therewith other than an aliphatic .alpha.-olefin; and(c) from 0.5 to 99 percent by weight, based on the total weight of (a), (b), and (c), of a substantially random interpolymer comprising an .alpha.-olefin and a vinylidene aromatic monomer. An expandable composition, comprising such polymer blend composition and an expanding agent; a foamed composition obtained by subjecting such an expandable composition to a foaming process; an article of manufacture molded from such a polymer blend composition; and a method of packaging using such a polymer blend composition.