Microstructural evolution of polyurea under hydrostatic pressure

Rosenbloom, Stephanie I.; Yang, Steven J.; Tsakeredes, Nikolas J.; Fors, Brett P.; Silberstein, Meredith N.

doi:10.1016/j.polymer.2021.123845

Cited by 11 publications

(13 citation statements)

References 42 publications

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“…The 2D SAXS results show that, in uniaxial tensile deformation, the hard domains, after relaxation, maintain a significant orientation following their displacement by the applied strain [ 73 ]. Under compressive loading (hydrostatic compression), the SAXS peak’s loss indicates that polyurea rapidly changes from an ordered, phase-separated state to a disordered, intermixed one, as demonstrated by Rosenbloom et al [ 70 ]. Regardless of the deformation type applied, surpassing the yield stress results in unrecoverable strain and domain orientation.…”

Section: Polyurea Coatings For Ballistic Protection Applicationsmentioning

confidence: 96%

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications

Toader,

Diacon,

Axinte

et al. 2024

Polymers

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This review presents polyurea (PU) synthesis, the structure–properties relationship, and characterization aspects for ballistic protection applications. The synthesis of polyurea entails step-growth polymerization through the reaction of an isocyanate monomer/prepolymer and a polyamine, each component possessing a functionality of at least two. A wide range of excellent properties such as durability and high resistance against atmospheric, chemical, and biological factors has made this polymer an outstanding option for ballistic applications. Polyureas are an extraordinary case because they contain both rigid segments, which are due to the diisocyanates used and the hydrogen points formed, and a flexible zone, which is due to the chemical structure of the polyamines. These characteristics motivate their application in ballistic protection systems. Polyurea-based coatings have also demonstrated their abilities as candidates for impulsive loading applications, affording a better response of the nanocomposite-coated metal sheet at the action of a shock wave or at the impact of a projectile, by suffering lower deformations than neat metallic plates.

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Section: Polyurea Coatings For Ballistic Protection Applicationsmentioning

confidence: 96%

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications

Toader,

Diacon,

Axinte

et al. 2024

Polymers

View full text Add to dashboard Cite

show abstract

“…[5,6] These mechanisms include dynamic glass-transition shifting [7] (e.g., Vogel-Fulcher-Tammann law), reversible in-operando pseudo-plasticization, deformation localization at soft/hard segment boundaries, significant mobility of the soft segment (up to plastic flow), and increased shear coupling as a function of compressive loading. [8][9][10][11] However, probing these mechanisms remains experimentally challenging due to the dichotomy in the timescale at which they occur, the lack of viable approaches, or the deformation exaggeration based on the compliant properties of elastomers.…”

Section: Introductionmentioning

confidence: 99%

“…[ 7 ] Furthermore, the increased intermingling of the hard and soft segments was reported in polyurea when submitted to hydrostatic compression exceeding 1 GPa, irrespective of the stoichiometric composition of the segregated microstructure. [ 11 ] The increased hard/soft segment affiliation was associated with elastic contraction of the mean spacing of the interchain hydrogen‐bonded hard segments as observed by in situ X‐ray scattering. [ 11 ] Here, the length of the soft segment plays a crucial role in deformation and recovery processes.…”

Section: Introductionmentioning

confidence: 99%

“…[ 11 ] The increased hard/soft segment affiliation was associated with elastic contraction of the mean spacing of the interchain hydrogen‐bonded hard segments as observed by in situ X‐ray scattering. [ 11 ] Here, the length of the soft segment plays a crucial role in deformation and recovery processes. [ 11 ] This hierarchical architecture is also attributed to strengthening mechanisms at the nanoscale and is responsible for the scale‐dependent relaxation and dissipation contrivances associated with dynamic loading scenarios.…”

Section: Introductionmentioning

confidence: 99%

“…[ 11 ] Here, the length of the soft segment plays a crucial role in deformation and recovery processes. [ 11 ] This hierarchical architecture is also attributed to strengthening mechanisms at the nanoscale and is responsible for the scale‐dependent relaxation and dissipation contrivances associated with dynamic loading scenarios. [ 15 ] These nanoscale processes are also directly linked to the remarkable improvement in the dynamic toughness of polyurea [ 16 ] and are forecasted to apply to the broader class of elastomeric polymers.…”

Section: Introductionmentioning

confidence: 99%

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Light‐Matter Interactions Revealing Load‐Induced Phase Mobility in Elastomers

Huynh

Koohbor

Youssef

2023

Macromol. Rapid Commun.

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Elastomers with segmental microstructure are a fascinating class of shock‐tolerant and impact‐resistant materials. However, their technological potential remains untapped due to a vague understanding of the molecular contributions to their superior mechanical behavior. Herein, in situ light‐matter interactions, to reveal the extent of microstructural mobility by temporally exploiting molecular processes during creep response, are leveraged. The segmental microstructure comprises aromatic hard domains embedded within an aliphatic soft matrix. High‐resolution digital image correlation reveals the development of strain striations, mild anisotropy, and the mechanisms responsible for domain mobility, where the rate of hard segment mobility is found to be 60% slower than that of the soft segment. Terahertz spectral analyses pinpoint the contributions of interchain hydrogen bonding of the hard segments and their significant conformational changes by observing spectral features at ≈1.2THz and ≈1.67THz. Moreover, the domain mobility is examined using experimental and computational light scattering approaches, uncovering dynamic scattering and elucidating the difference in the complex refractive index of the soft and hard segments. The study unlocks the pathway for quantitative measurements of elusive molecular mobility and conformational changes during mechanical loading and sheds light on the origin of the shock tolerance in some elastomeric polymers with segmental microstructure.

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The development of high‐strength, anticorrosive, and strongly adhesive polyaspartate polyurea coating suitable for pipeline spray repairs

Wang,

Du,

Fang

et al. 2024

J of Applied Polymer Sci

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This study synthesized polydimethylsiloxane (PDMS)‐modified polyaspartate polyurea (PPPU) with different ratios, considering the practical performance requirements of underground water supply pipeline spray repair materials. The successful synthesis of PPPU was confirmed using Fourier transform infrared spectrometer (FTIR) spectroscopy. The influence of the ratio of the two components and the content of ‐aminopropyl terminated polydimethylsiloxane (APT‐PDMS) on the drying time and tensile performance of PPPU coatings was evaluated. Based on this evaluation, a superior ratio for PPPU coatings was proposed. Subsequently, the bonding performance, hydrophobicity, and corrosion resistance of PPPU coatings at the superior ratio were tested. The results indicate that as the mass ratio of polyaspartic acid ester to hexamethylene diisocyanate trimer increases, both the drying time and tensile strength of the coating decrease. The addition of APT‐PDMS results in a decrease in the tensile strength of PPPU, but an increase in its elongation at break. The peak value of elongation at break is achieved when the APT‐PDMS content is 5%, making the PPPU2‐1‐5 coating the superior ratio for spray application on water supply pipelines. Through experiments, it was determined that the bonding strength of the PPPU2‐1‐5 coating with cement mortar under dry and humid conditions, static water contact angle (93.4°), and corrosion resistance performance are superior to those of the unmodified polyurea coating, demonstrating its application advantages. The conclusions drawn in this study provide a theoretical foundation for the practical engineering application of PPPU.

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Microstructural evolution of polyurea under hydrostatic pressure

Cited by 11 publications

References 42 publications

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications

State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications

Light‐Matter Interactions Revealing Load‐Induced Phase Mobility in Elastomers

The development of high‐strength, anticorrosive, and strongly adhesive polyaspartate polyurea coating suitable for pipeline spray repairs

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