Structural Evolution of UHMWPE Fibers during Prestretching Far and Near Melting Temperature: An In Situ Synchrotron Radiation Small- and Wide-Angle X-Ray Scattering Study

         The structural evolutions of gel-spun ultra-high molecular weight polyethylene (UHMWPE) fibres during pre-stretching at temperatures of 25 °C and 100 °C are investigated by Tian Cao, and related work has been published on Macromolecular Materials and Engineering (2018, 303(2): 1700493).

Combining a homemade extension apparatus and the in-situ synchrotron radiation small- and wide-angle X-ray scattering (SR-SAXS and SR-WAXS) methods for measurement, the structural evolutions of gel-spun ultra-high molecular weight polyethylene (UHMWPE) fibres during pre-stretching at temperatures of 25 °C and 100 °C are investigated, respectively. Lamellar rotation towards the stretching direction occurred before strain hardening, while the folded-chain crystal destruction and extended-chain fibrils formation processes occurred in the strain hardening zone at 25 °C. While at 100 °C, stretching induced crystal melting before the stress plateau region and formation of fibrous crystals at the onset of the stress plateau are observed. Further stretching results in shear displacement of crystal blocks and, finally, destruction of the folded-chain crystals and formation of extended-chain fibrils. Pre-stretching UHMWPE fibres at 100 °C within a certain strain range can produce highly oriented fibrous crystals, which may provide an ideal precursor structure for the post-stretching process.

This work was supported by the Natural Science Foundation of China (51227801, 51325301, 51633009), the China Postdoctoral Science Foundation (No. 2017M612087), the Anhui Provincial Science and Technology Major Projects (No. 16030901044), the Open Research Fund of Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, and the Anhui Provincial University Natural Science Foundation (KJ2017JD13).