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

Abstract

Roofing membranes of single ply heat seamable thermoplastic polyolefin (TPO) sheets are made with a metallocene-catalyzed polyethylene (MPO) blend. The membranes exhibit superior heat seam peel strengths and low temperature flexibility.

What is claimed is:  
     
         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 polyolefin, and about 10-50% of additives, 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 said polyolefin is a copolymer of ethylene and butene.  
     
     
         4 . A roofing membrane according to  claim 1  in which said layers include a crystallinity enhancing polymer.  
     
     
         5 . A roofing membrane according to  claim 1  wherein the molecular weight distribution (MWD) of said polyolefin is about 2 to 2.5.