Determining the influence of temperature and pressure on the structural stability in a polyurea elastomer

• Published in: Polymer (Guilford) Vol. 286; p. 126372
• Main Authors: Eastmond, T., Hu, J., Alizadeh, V., Hrubiak, R., Oswald, J., Kim, K., Amirkhizi, A., Peralta, P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 03-11-2023; Elsevier
• Subjects: Amorphous polymers; Energy dispersive X-ray diffraction; ENGINEERING; High pressure; Material Science; Molecular dynamics; Pair distribution function; Polyurea; Structure factor; Synchrotron radiation; Temperature effects; Total scattering; Structure factor; Amorphous polymers; Temperature effects; Polyurea; Molecular dynamics; Energy dispersive X-ray diffraction; Total scattering; Pair distribution function; Synchrotron radiation; High pressure
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2023.126372

The structural response of amorphous elastomers to applied pressure and temperature is of significant interest given their potential for blast and impact protection applications. While understanding disordered structures is often challenging, this study focuses on the ordered correlations that are present at the atomic level even in amorphous materials. This local order was characterized in polyurea elastomers with two molecular weights up to 6 GPa and ∼280 °C using in situ energy dispersive X-ray diffraction at the Advanced Photon Source via total scattering techniques. The resulting structure factors and pair distribution functions indicate that the applied pressure reduced the free volume but had little effect on covalent bonds for both molecular weights. Temperature-induced order-disorder transitions that occur readily at ambient pressures within the temperature range studied here were not observed, their onset likely delayed by the limited chain mobility associated with the free volume reduction. This study demonstrates that total scattering offers insights into the high-pressure structure of disordered polymers that are otherwise inaccessible using more conventional X-ray scattering techniques.
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•Atomic structure of polyurea studied at 6 GPa, 280 °C via total X-ray scattering.•Structural response was identical for two different molecular weights.•Applied pressure reduced free volume with little impact on covalent bonding.•Restricted chain mobility prevented temperature-induced transitions at 6 GPa.•Molecular dynamics simulations used to analyze and interpret the experimental data.