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Issue 44, 2018
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The evolution of crystalline structures during gel spinning of ultra-high molecular weight polyethylene fibers

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Abstract

Most studies are focused on the final mechanical properties of the fiber and the processing window required to achieve high moduli and tensile strength. Several studies have alluded to the fact that the crystalline morphologies developed during gel spinning and post-drawing are very important in determining the final mechanical properties. However, it is surprising to know that no clear correlation exists between the crystalline structure and initial, evolving, and final mechanical properties. In an attempt to define structure–property relationships, we have developed novel tools to quantify the effect of processing on crystalline structure evolution. We examine through controlled gel-spinning and SAXS analysis the effect of flow kinematics on the development of crystalline structures. Direct correlations are made between polymer solution relaxation time, extension rates, crystallization time and gel-spun crystalline morphologies. We report direct evidence of flow induced crystallization, which approaches an asymptotic crystallization rate at high Weissenberg numbers. For Wi < 1, the crystalline structure is only slightly affected by equilibrium. For Wi > 1, the crystalline structure is highly anisotropic due to chain orientation/stretch during spinning. Fibers spun at different Weissenberg numbers are drawn to low draw ratios at constant temperature to measure the initial structure evolution. A qualitative SAXS analysis clearly shows similar evolution of different starting structures with the formation of more straight chain crystals upon drawing. However, there remain quantitative differences between the length of straight chain crystals and the size and distribution of lamellar domains depending on the starting structure.

Graphical abstract: The evolution of crystalline structures during gel spinning of ultra-high molecular weight polyethylene fibers

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Publication details

The article was received on 03 Aug 2018, accepted on 04 Oct 2018 and first published on 11 Oct 2018


Article type: Paper
DOI: 10.1039/C8SM01597J
Citation: Soft Matter, 2018,14, 8974-8985
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    The evolution of crystalline structures during gel spinning of ultra-high molecular weight polyethylene fibers

    C. K. Henry, G. R. Palmese and N. J. Alvarez, Soft Matter, 2018, 14, 8974
    DOI: 10.1039/C8SM01597J

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