Determination of the crystallinity in polymer samples using ARL EQUINOX 100 benchtop X-ray diffractometer

Significance of the Topic

The structural arrangement of polymers, especially the degree of crystallinity, governs key mechanical and thermal properties. Reliable and rapid crystallinity assessment is essential for both material developers and manufacturers to ensure product performance across applications from everyday packaging to high‐performance aerospace components.

Study Objectives and Overview

This work evaluates the Thermo Scientific ARL EQUINOX 100 benchtop X-ray diffractometer combined with whole‐pattern Rietveld refinement for determining crystallinity in polyethylene (PE) and polypropylene (PP). The goal is to demonstrate a fast, user‐friendly workflow that matches the performance of larger floor‐standing systems and delivers results suitable for quality control and research.

Methodology and Instrumentation

• Sample preparation: Sheet specimens of PE and PP analyzed in transmission geometry under Cu-Kα radiation for five minutes per scan.
• Diffractometer: ARL EQUINOX 100 equipped with a curved position sensitive detector (CPS) and a low‐wattage Cu micro-focus tube (50 W) enabling rapid, simultaneous peak collection without external chiller requirements.
• Data analysis: Whole‐pattern Rietveld refinements performed in MDI JADE 2010 using the ICDD PDF4+ Organic database; amorphous fraction quantified by deconvolution of crystalline and amorphous contributions (density 0.85 g/cm³).

Key Results and Discussion

Qualitative phase identification confirmed PE and PP phases in all samples. Rietveld refinement yielded crystallinity values consistent with expected high‐density (PE 1: ~54 %) and low‐density PE (PE 2: ~23 %), and isotactic PP (PP 1: ~58 %, PP 2: ~40 %). Amorphous content inversely correlated with crystalline fraction. The benchtop instrument delivered data quality comparable to high‐power diffractometers within a five-minute acquisition time.

Benefits and Practical Applications

The compact ARL EQUINOX 100 system simplifies polymer crystallinity screening by eliminating extensive infrastructure and lengthy setup. Its rapid measurement cycle (<10 minutes total including preparation) and intuitive software enable even users with limited XRD experience to perform quantitative phase analysis, supporting on‐line quality control in production environments and routine laboratory testing.

Future Trends and Applications

Advances in detector technology and portable X-ray sources may further enhance field applicability of benchtop diffractometers. Integration with automated sampling systems and coupling with complementary techniques (e.g., DSC, FTIR) could provide more comprehensive polymer characterization. Expansion of database libraries will improve analysis of diverse polymer blends and novel biopolymers.

Conclusion

The ARL EQUINOX 100 benchtop XRD system, combined with Rietveld refinement in MDI JADE 2010, offers an efficient and reliable approach for quantifying polymer crystallinity. Its portability, speed, and ease of use make it a valuable tool for both industrial quality assurance and academic research.

Reference

• Simon Welzmiller and Ju Weicai, Determination of the crystallinity in polymer samples using ARL EQUINOX 100 benchtop X-ray diffractometer, Thermo Scientific Application Note AN41117, 2018.