Polymorphism and crystallite size in β-Polypropylene determined with ARL EQUINOX 100 X-ray diffractometer

Significance of the Topic

Polymorphism and crystallite domain size in polypropylene have a key influence on mechanical and chemical performance. The β-phase of polypropylene offers improved toughness and chemical resistance relative to the α-phase while maintaining comparable viscosity. Accurate and rapid characterization of these parameters supports quality control and material design in industrial polymer applications.

Objectives and Study Overview

This study demonstrates the use of the Thermo Scientific ARL EQUINOX 100 benchtop X-ray diffractometer in combination with MDI JADE 2010 software and ICDD PDF4+ Organic database to:

• Identify polymorphic phases (α and β) in polypropylene.
• Determine crystallite sizes for each polymorph.
• Showcase rapid screening capabilities for polymer quality assessment.

Methodology

An injection-molded sheet of polypropylene was measured in transmission mode under Cu Kα radiation for 5 minutes. Diffraction data were collected simultaneously across all angles using a curved position sensitive detector. Phase identification was performed through pattern matching against the ICDD PDF4+ Organic database in MDI JADE 2010. Crystallite size estimations employed Le Bail profile fitting and the Scherrer equation.

Used Instrumentation

• Thermo Scientific ARL EQUINOX 100 X-ray diffractometer with Cu micro-focus tube (50 W) and mirror optics.
• MDI JADE 2010 software.
• ICDD PDF4+ Organic database.

Main Results and Discussion

Diffraction analysis revealed a predominantly β-PP phase with minor α-PP traces. Crystallite size was estimated at approximately 33 nm for β-PP and 10 nm for α-PP. The ARL EQUINOX 100 delivered data quality comparable to high-power floor-standing systems in a fraction of the time, making it well-suited for routine polymer screening.

Benefits and Practical Applications

• Speed: Simultaneous detection of diffraction peaks reduces analysis time to minutes.
• Portability: Benchtop design requires minimal infrastructure and can be moved between labs or to the field.
• Performance: Accurate phase identification and crystallite size determination support QC processes in polymer manufacturing and research.

Future Trends and Opportunities

Advances in detector technology and software algorithms will further decrease measurement times and improve sensitivity for low-volume or highly scattering samples. Integration with automated sample handling and data analysis pipelines will enable high-throughput polymer characterization. Emerging XRD techniques, such as in situ reaction monitoring, can extend capabilities to real-time polymer processing studies.

Conclusion

The combination of the ARL EQUINOX 100 benchtop XRD system, MDI JADE 2010, and ICDD PDF4+ database provides a rapid, reliable method for assessing polymorphic composition and crystallite size in polypropylene. This approach supports improved material development and stringent quality control in industrial polymer applications.