High Modulus Polyolefin Fibers Exhibiting Unique Microstructural Features

Abstract

A new class of high modulus polypropylene multifilament fiber and/or yarn is provided. Such a multifilament fiber and/or yarn exhibits an exceptional combination of high strength and toughness with low weight and density. The inventive fibers thus permit replacement of expensive polymeric fibers within certain applications with lower cost alternatives, or replacement of high density components with such low density fibers, without sacrificing strength or durability. Such multifilament fibers are produced through melt-spinning processes and exhibit highly unique microstructures therein, including significant void volumes, interspersed and crossed voids, and nanofilament bridges within such voids. Such microstructural characteristics appear to impart the exceptional properties noted above.

1 . A polyolefin multifilament fiber exhibiting repeated multiple striations therein aligned substantially perpendicularly along the longitudinal axis of said fiber, wherein said striations extend from the surface of said fiber and wherein at least a portion of said striations extend within the internal regions of said fiber. 
     
     
         2 . The polyolefin fiber of  claim 1  wherein said polyolefin is selected from the group consisting of a polypropylene, a polyethylene, and any blends thereof. 
     
     
         3 . The polyolefin fiber of  claim 2  wherein said polyolefin is a polypropylene. 
     
     
         4 . The polyolefin fiber of  claim 1  wherein said fiber exhibits a modulus strength of at least 8 GPa. 
     
     
         5 . The polyolefin fiber of  claim 3  wherein said fiber exhibits a modulus strength of at least 8 GPa. 
     
     
         6 . A polyolefin multifilament fiber exhibiting a modulus strength of at least 8 GPa with a fiber diameter of at most 100 microns, said fiber internally comprising a plurality of microfibrils therein, wherein said fiber further exhibits a plurality of voids interspersed within said microfibrils, wherein both said microfibrils and said voids are aligned substantially parallel to the longitudinal axis of said fiber. 
     
     
         7 . The polyolefin fiber of  claim 6  wherein said polyolefin is selected from the group consisting of a polypropylene, a polyethylene, and any blends thereof. 
     
     
         8 . The polyolefin fiber of  claim 7  wherein said polyolefin is a polypropylene. 
     
     
         9 . A polyolefin multifilament fiber exhibiting a modulus strength of at least 8 GPa with a fiber diameter of at most 100 microns, said fiber further exhibiting voids therein, wherein said voids exhibit include a plurality of nanofilament bridges therein. 
     
     
         10 . The polyolefin fiber of  claim 9  wherein said polyolefin is selected from the group consisting of a polypropylene, a polyethylene, and any blends thereof. 
     
     
         11 . The polyolefin fiber of  claim 10  wherein said polyolefin is a polypropylene. 
     
     
         12 . A polyolefin multifilament fiber exhibiting a shear stress tensile failure mechanism at a level less than a ductile fracture tensile failure mechanism. 
     
     
         13 . The polyolefin fiber of  claim 12  wherein said polyolefin is selected from the group consisting of a polypropylene, a polyethylene, and any blends thereof. 
     
     
         14 . The polyolefin fiber of  claim 13  wherein said polyolefin is a polypropylene. 
     
     
         15 . The polyolefin fiber of  claim 12  wherein said fiber exhibits a modulus strength of at least 8 GPa. 
     
     
         16 . The polyolefin fiber of  claim 15  wherein said fiber exhibits a modulus strength of at least 8 GPa. 
     
     
         17 . A polyolefin multifilament fiber exhibiting a modulus strength of at least 8 GPa with a fiber diameter of at most 100 microns, where said fiber exhibits a hot air shrinkage of less than 5% at 150° C. 
     
     
         18 . The polyolefin fiber of  claim 17  wherein said polyolefin is selected from the group consisting of a polypropylene, a polyethylene, and any blends thereof. 
     
     
         19 . The polyolefin fiber of  claim 18  wherein said polyolefin is a polypropylene.