Segmental evolution of ultraviolet weathered polyurea

Blourchian, Aryan; Shaik, Atif Mohammed; Huynh, Nha Uyen; Youssef, George

doi:10.1007/s10965-021-02483-4

Cited by 16 publications

(5 citation statements)

References 27 publications

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“…[16,22,23] The desirable mechanical characteristics of polyurea are attributed to its segmental microstructure, consisting of interdispersed hard segments within a surrounding matrix of soft segments. [24,25] Over the past two decades, polyurea has been at the center of exhaustive academic and industrial research for its shock-resistant and impact-tolerant properties. [5,16,22,23,[26][27][28][29][30][31][32] The latter motivated researchers to convert bulk polyurea into elastomeric foams with attributes congruent to their base materials, resulting in improved impact mitigation properties due to the contributions of the cellular microstructure deformations to energy absorption efficacy.…”

Section: Doi: 101002/adem202200578mentioning

confidence: 99%

Density‐Dependent Impact Resilience and Auxeticity of Elastomeric Polyurea Foams

et al. 2022

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This research investigates the dynamic response of a novel polyurea foam with different densities by separately submitting samples to single and multiple impacts at different energies ranging from 1.77 to 7.09 J. The impact and transmitted force‐time histories are acquired during the impact events. Deformation of the samples is also recorded using high‐speed photography and analyzed using digital image correlation (DIC) to characterize density‐dependent strain rate and Poisson's ratio. The analyses of the force‐time histories highlight the interrelationship between the incoming impact energy and force characteristics, including amplitude and durations. The experimental results reveal that polyurea foams can absorb nearly 50% of the incoming impact energy irrespective of their density. The dynamic impact efficacy of the foam persists even after sequential impact events are imparted on the same samples, with only a 20% drop in the load‐bearing capacity after seven consecutive impacts. Furthermore, as verified via electron microscopy observations, the higher‐density foam does not exhibit any permanent damage. This high‐density polyurea foam shows reversible auxetic transition at all impact energies considered herein. The outcomes of this research indicate the suitability of polyurea foams for cushioning and impact mitigation applications, especially in repeated biomechanical impact scenarios.

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Section: Doi: 101002/adem202200578mentioning

confidence: 99%

Density‐Dependent Impact Resilience and Auxeticity of Elastomeric Polyurea Foams

et al. 2022

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“…In recent years, polyurea foams emerged in the scientific literature as a suitable material candidate for biomechanical impact mitigation applications. ,− Such emphasis was motivated by the contemporary work of Reed et al. , and Ramirez et al, − reporting viable approaches to foam bulk polyurea using spontaneous foaming and heat-activated/controlled foaming methods, respectively. Polyurea is a fascinating class of polymers with several formulations that span the spectrum from linear to cross-linked polymers. − Polyurea, with a specific mixture of diamine and diisocyanate, found favor in the scientific and technological communities for its superior mechanical and thermal properties, including hygrothermal stability, large extensibility, , a broad range of operating temperature, , adhesive properties, − chemical, moisture, and abrasion resistance, and toughness based on its tailored segmental microstructure. − This polyurea formulation was also found to be mildly affected by extended exposure to ultraviolet radiation . Research on bulk polyurea for impact mitigation applications, with an emphasis on military infrastructures and assets, i.e., response to ultrahigh ballistic strain rate, was recently collated by Barsoum. , The latter research culmination showed the momentous promise of this material while signifying polyurea as an interesting scientific testbed.…”

Section: Introductionmentioning

confidence: 99%

Quasi-Static Mechanical Response of Density-Graded Polyurea Elastomeric Foams

Smeets

Koohbor

Youssef

2023

ACS Appl. Polym. Mater.

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Density gradation of foam structures has been investigated and found to be a practical approach to improve the mechanical efficacy of protective padding in several applications based on nature-based evidence of effectiveness. This research aims to disclose a discrete gradation approach without adhesives by relying on the properties of the frothed foam slurry to bond and penetrate through previously cured foam sheets naturally. As confirmed by electron microscopy observations, bilayer-and trilayergraded elastomeric polyurea foam sheets were fabricated, resulting in seamless interfaces. The mechanical performance of seamless, graded foam samples was compared with monolayer, mono-density benchmark foam, considered the industry standard for impact mitigation. All foam samples were submitted to compressive loading at a quasi-static rate, reporting key performance indicators (KPIs) such as specific energy absorption, efficiency, and ideality. Polyurea foams, irrespective of gradation and interface type, outperformed benchmark foam in several KPIs despite the drastic difference in the effective or average density. The average compressive stress−strain curves were fitted into empirical constitutive models to reveal critical insights into the elastic, plateau, and densification behaviors of the tested foam configuration. The novelty of these outcomes includes (1) a fabrication approach to adhesive-free density-graded foam structures, (2) implementation of a diverse set of KPIs to assess the mechanical efficacy of foams, and (3) elucidation of the superiority of polyurea foam-based lightweight protective paddings. Future research will focus on assessing the dynamic performance of these graded foam structures under impact loading conditions at a wide range of velocities.

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“…[ 7–12 ] Aromatic polyurea, synthesized based on the stochiometric mixture of oligomeric diamine and modified methylene diisocyanate, exhibits excellent impact‐resistant and shock‐tolerant responses in harsh environments despite its low acoustic impedance due to its chemical, moisture, and ultraviolet radiation resiliency. [ 12,13 ] For example, adding a thin layer of bulk aromatic polyurea was shown to alter the mechanical performance of transparent armors, [ 11 ] steel armor plates, [ 8,14–18 ] and marine composite joints. [ 7,8 ] Hence, the foamed version inherits the desirable mechanical properties of bulk polyurea, including the suitability for severe loading scenarios.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10][11][12] Aromatic polyurea, synthesized based on the stochiometric mixture of oligomeric diamine and modified methylene diisocyanate, exhibits excellent impact-resistant and shock-tolerant responses in harsh environments despite its low acoustic impedance due to its chemical, moisture, and ultraviolet radiation resiliency. [12,13] For example, adding a thin layer of bulk aromatic polyurea was shown to alter the mechanical…”

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confidence: 99%

Full‐Field Analyses of Density‐Graded Elastomeric Foams Under Quasistatic and Impact Loadings

Smeets,

Kauvaka,

Uddin

et al. 2023

Adv Eng Mater

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Density‐graded elastomeric foams are emerging as effective protective structures to guard humans against mechanical loading. This research investigates the deformation of ungraded and graded foams under quasi‐static and impact scenarios using digital image correlation (DIC). The graded samples were assembled using two interfacing strategies (seamless and adhered), leveraging the adhesiveness of the foam slurry and bulk polyurea, respectively. Deformation mechanisms, including the effect of the interface type on strain transduction and localization in density‐graded structures, are imperative for improving the impact efficacy of protective paddings. Cuboid foam plugs were subjected to quasi‐static and impact loading while recording the corresponding deformation for DIC analysis. The DIC results were separated into three case studies based on the number of layers (1, 2, and 3). The interface effect on the overall mechanical performance of polyurea foam was revealed from the bilayer, mono‐density samples, showing drastic differences between the deformations within each layer. Seamless interface samples exhibited greater compliance than their adhered counterparts in the bilayer density‐graded configurations. Trilayer‐graded foams broadened strain‐time history, extended the impact duration, and reduced strains. This research substantiates the importance of interfacing and gradation strategies on the mechanical response of elastomeric foams as a function of strain rate.This article is protected by copyright. All rights reserved.

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Segmental evolution of ultraviolet weathered polyurea

Cited by 16 publications

References 27 publications

Density‐Dependent Impact Resilience and Auxeticity of Elastomeric Polyurea Foams

Density‐Dependent Impact Resilience and Auxeticity of Elastomeric Polyurea Foams

Quasi-Static Mechanical Response of Density-Graded Polyurea Elastomeric Foams

Full‐Field Analyses of Density‐Graded Elastomeric Foams Under Quasistatic and Impact Loadings

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