Extensional rheometer for in situ x-ray scattering study on flow-induced crystallization of polymer

Abstract

We designed and constructed an extensional rheometer for in situ small and wide angle x-ray study on flow-induced crystallization of polymer. Two rotating drums with an axis distance of 20 mm are employed to impose extensional deformation on the samples. With a constant angular velocity, the two drums generate a constant Henkcy strain rate as sample length for testing keeps constant during deformation. An ionic liquid is used as heating medium to prevent polymer melt from bending downward due to gravity, which is excellent in terms of high thermal stability, low viscosity, and relative low adsorption on x-ray. Flow-induced crystallization experiments are conducted with this apparatus on x-ray scattering station in Shanghai Synchrotron Radiation Facility (SSRF), which allows us to collect rheological and structural data simultaneously and may lead to a better understanding on flow-induced crystallization of polymer.

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

“…A homemade stretching apparatus was used to conduct the drawing test, and the schematic of the apparatus is shown in Figure a. Figure b shows the illustration of the stretching portion of the experiment, where stretch is imposed by two symmetrical drums, ensuring that the detection point remains unchanged during the stretching process.…”

“…Manufacturing of UHMWPE fibers requires high stretching speed in the order of ≈1000 m min −1 , which makes it difficult to carry out an in situ study on the structural evolution, since the stretching rate requires high time resolution of the structure detecting techniques . Benefiting from the time resolved synchrotron radiation of small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray scattering (WAXS) techniques, many works have investigated the structural evolution during postdrawing of prestretched and extracted UHMWPE fibers with shish‐kebab structures . During stretching, the 2D SAXS patterns transition from two maxima along the stretching direction on both sides of the beam stop and an equatorial streak to only streak signals in the equator.…”

A simple constrained uniaxial tensile apparatus for in situ investigation of film stretching processing

“…Among these techniques, X-ray scattering is a prominent one due to its large penetration thickness. 28 In addition, timeresolved X-ray scattering is appropriate for in situ study and combination small angle X-ray scattering (SAXS) with wide angle X-ray scattering (WAXS) can get direct structural information of polymer film with different length scales.…”

Polymer Crystallization Studied by Hyphenated Rheology Techniques: Rheo‐NMR, Rheo‐SAXS, and Rheo‐Microscopy

“…The latter set‐up was used in the experiments presented here, and furthermore by other researchers to study block copolymers, platelet dispersions, and colloidal systems . Recently, hyphenations of extensional rheometers and X‐ray scattering techniques were used by Yan et al., Liu et al., and Wingstrand et al . to reveal the interplay of structural buildup and elongation rheology during flow‐induced polymer crystallization.…”