A modifier for forming sub-ambient temperature use containers includes (a) from 10 wt % to 50 wt % of a block composite, a specified block composite, or a crystalline block composite, (b) from 20 wt % to 90 wt % of a first polyolefin copolymer, the first polyolefin copolymer being derived from ethylene and at least one of a C3 to C10 alpha-olefin, having a melt index from 0.5 g/10 min to 1500 g/10 min, and having a density from 0.850 g/cm3 to 0.910 g/cm3, and (c) optionally, from 30 wt % to 70 wt % of a second polyolefin copolymer, the second polyolefin copolymer being derived from ethylene and at least one of a C3 to C10 alpha-olefin, having a melt index from 100 g/10 min to 2000 g/10 min, and having a density from 0.860 g/cm3 to 0.900 g/cm3.