Low Detection Limit of Polymer Crystallinity

The crystallization kinetics of solid polymers affects their nanoscale structure and the degree of crystallinity, and in turn, plays a significant role in the specific mechanical and physical properties of the polymers.

While the crystallographic order can be identified from the characterization of the fine semi-crystalline state at short length scales, information about the morphology of the crystalline phase can be provided by analysis at long length scales.

In this article, a study using Wide Angle X-ray Scattering (WAXS) analysis to measure the crystalline fraction of an isotactic polypropylene (i-PP) as a function of temperature is described. The Xeuss 2.0 SAXS/WAXS system was combined with an integrated temperature control stage, the Linkam HFSX350, to establish the polyolefin crystallinity fraction during the kinetic experiment, down to the low detection limit of 0.3%.

Measurement and Results

The process made use of a pellet of i-PP sample encapsulated by thin aluminum foil, to prevent direct contact with air and develop good thermal contact. The i-PP sample was fixed and then mounted on the Linkam stage.

The WAXS configuration of the Xeuss 2.0 SAXS/WAXS system was used to measure the crystallization of i-PP in real time, by carrying out a quench from the full molten state at 148 °C. Repeated WAXS measurements were obtained after quenching at an exposure time of 200s.

Figure 1 depicts the WAXS measurements of the crystalline fraction as a function of the time elapsed after the quench, displaying the ability of the Xeuss 2.0 SAXS/WAXS system to carry out crystallization kinetics characterization. This article will help individuals obtain more information on the determination of polymer crystallinity using the Xeuss,. As seen in Figure 1, the low detection limit of the crystallinity level for this polymer system is 0.3%.

Figure 1. Evolution of the crystalline fraction as a function of time. Exposure time = 200s per point.

Simultaneous SAXS and WAXS Measurements

To obtain further insight into the underlying mechanisms taking place during the process of crystallization, it is useful to examine the material on a larger scale using WAXS, simultaneously with SAXS measurements of the nanostructure. These simultaneous SAXS/WAXS measurements, which have been performed earlier at synchrotron facilities¹, can now be executed by employing the Xeuss 2.0 SAXS/WAXS system.

References and Further Reading

1. Panine et al, Polymer, 2008, 49, 676-680.

This information has been sourced, reviewed and adapted from materials provided by Xenocs.

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