Single ply thermoplastic (TPO) roofing membranes having superior heat seam peel strengths and low temperature flexibility

1. A thermoplastic polyolefin (TPO) roofing membrane comprising a reinforcement scrim sandwiched between cap and base layers which are pressed into a single ply membrane having a thickness of about 35-90 mils, characterized in that both of said layers are made of, by weight, 50-90% of metallocene-catalyzed polyethylene and about 10-50% of additives including a crystallinity enhancing polymer comprising high density polyethylene (HDPE), said membrane exhibiting a 90° heat seam peel strength of ≧60 lbs/linear inch (ASTM D-413) and a cold brittleness point of ≦50 °C. (ASTM D-413).

2. A roofing membrane according to claim 1 wherein said 90° heat seam peel strength is about 66-69 lbs/linear inch over a 4 day period, and said cold brittleness point is about −58 to −70° C.

3. A roofing membrane according to claim 1 wherein the molecular weight distribution (MWD) of said polyolefin is about 2 to 2.5.

4. A thermoplastic polyolefin (TPO) roofing membrane comprising a reinforcement scrim sandwiched between cap and base layers which are pressed into a single ply membrane having a thickness of about 40-90 mils,

wherein both of said cap and base layers are produced by a process comprising combining, by weight:

(a) 50-90% of the polymeric components of the cap and base layers of metallocene-catalyzed polyethylene;

(b) an ethylene-propylene rubber (EPR); and

(c) a crystallinity enhancing polymer comprising one of the following:

(i) high density polyethylene (HDPE) having a crystallinity of 67 wt. %; and

(ii) polypropylene (PP) having a crystallinity of 50 wt. %.