Thermoplastic roofing membranes for fully-adhered roofing systems

A thermoplastic roofing membrane comprising:

• a planar thermoplastic sheet having a plurality of layers, with one layer forming a top layer of the membrane,
• where at least one layer of the plurality other than the top layer includes at least 40% by weight of a copolymer component based on the total weight of an ethylene-based olefinic block copolymer and any other thermoplastic material present in the layer,
• where the copolymer component includes a first ethylene-based olefinic block copolymer having a melt index of less than 5 g/10 min and a second ethylene-based olefinic block copolymer having a melt flow rate of greater than 5 g/10 min,
• where the first and second ethylene-based olefinic block copolymers each include, in polymerized form, ethylene units and α-olefin units,
• where the first and second ethylene-based olefinic block copolymers include a first plurality of ethylene-α-olefin blocks including less than 5 wt % α-olefin units and a second plurality of ethylene-α-olefin blocks including greater than 5% wt α-olefin units,
• where the at least one layer including the ethylene-based olefinic block copolymer includes at least 5% by weight of the filler, and
• where the sheet is characterized by a storage modulus of less than 450 MPa at 0° C.