A stretching apparatus with broad strain rate and temperature ranges for in-situ x-ray scattering measurements of polymers

Abstract

A stretching apparatus capable of conducting tensile tests over a broad strain rate range (10−3–250 s−1) and a wide temperature range (−75–250 °C) has been designed for polymeric materials, in particular the polymeric films. Specifically, this stretching apparatus can be combined with in situ ultrasmall-, small-, and wide-angle x-ray scattering (USAXS/SAXS/WAXS) measurements. The sample stretching is achieved through the synchronized rotation of rolls, powered by servo motors. The output electrical signal extracted from a torque sensor, when combined with the rotational speed of rolls and initial sample dimensions, enables the determination of the relationship between engineering stress (σ) and Hencky strain (ε). With the sample chamber and precise control loop, the prescribed temperature can be achieved using either hot airflow for heating or cold liquid nitrogen flow for cooling. By integrating this stretching apparatus with a high brilliance x-ray source at beamline BL10U1 in Shanghai Synchrotron Radiation Facility (SSRF) and detectors featuring ultrafast acquisition rates, it becomes possible to monitor multiscale structure evolutions of polymeric samples under harsh conditions involving high-speed loading combined with varying temperatures.