Ultra-High Modulus Polyolefins from Single Crystals
Recently we have shown that single crystal aggregates of ultra-high molecular weight polyethylenes (UHMW-PE), and of polypropylene (UHMW-PP), grown from dilute solutions, exhibit a dramatically high extensibility compared to melt-crystallized forms. The mats of solution-grown crystals for these two polymers have been drawn up to a ratio of 250 for UHMW-PE and 66 for UHMW-PP. Such superdrawn films exhibit extremes of properties including a tensile modulus, up to 220 GPa for the former and 33 GPa for the latter polymer. These values approach the uncertain theoretical maximum modulus reported for the perfect crystal for each of the two polymers. For effective deformation, the first draw step is solid-state extrusion. The choice of original morphology for extrusion draw is of major consequence, with single crystals offering a significant advantage.
KeywordsDraw Ratio Tensile Modulus Perfect Crystal Drawing Technique Material Research Laboratory
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- 3.J. Southern and R. S. Porter, Chem. Eng. News, p. 45 (Sept. 22, 1969 ).Google Scholar