Hysteresis and energy loss in flexible polyurethane foams

Hilyard, N. C.

doi:10.1007/978-94-011-1256-7_8

Cited by 12 publications

(9 citation statements)

References 23 publications

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“…The dissipated energy ( U d ) is the area enclosed in the hysteresis loop. The hysteresis loss is defined as the ratio between U d and U a as shown in eq : hysteresis = U normald U normala = U normala − U normals U normala …”

Section: Resultsmentioning

confidence: 99%

“…We have previously devised a strategy for rapidly synthesizing non-bio-based PHU foams by decoupling the gelling reaction (cyclic carbonate aminolysis) from the foaming reaction (thiol-decarboxylation). Recording the progression of the gelling reaction at elevated T by monitoring the shear storage modulus, shear loss modulus, and tan δ allows us to determine a tan δ value prior to the gel point that sustains uniform bubble growth. , We initially performed a SAOS experiment at room temperature to determine tan δ as a function of time (Figure S7), and we observed that tan δ > 40 even after 24 h. This reflects an insufficient extent of reaction, cross-linking degree, and viscosity for optimal bubble development. Because of the compromised reactivity of the bio-based monomers, it is necessary to adapt our rheological strategy.…”

Section: Resultsmentioning

confidence: 99%

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Reprocessable, Bio-Based, Self-Blowing Non-Isocyanate Polyurethane Network Foams from Cashew Nutshell Liquid

Purwanto

Chen

Torkelson

2023

ACS Appl. Polym. Mater.

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Growing environmental concerns and the goal of a circular economy for polymers necessitate the development of biowaste-based materials and efficient recycling of polymer materials. Here, we developed a series of self-blowing network polyhydroxyurethane (PHU) foams by leveraging the aminolysis and decarboxylation of cashew nutshell liquid (CNSL)-based cyclic carbonate with thiols to release CO2 as a blowing agent; these foams contain up to 80 wt % bio-based content. By systematically varying the blowing agent concentrations, we demonstrated the tunability of the morphologies and mechanical properties of CNSL-based PHU foams. Using dynamic mechanical analysis (DMA), compression testing, and hysteresis testing, we showed that these foams fall into the category of flexible foams with potential as memory foams or resiliency foams. To address the recyclability challenges of thermoset foams, we repurposed these CNSL-based PHU foams into bulk materials and reprocessed them by exploiting the dynamic chemistries of the hydroxyurethane linkages. Notably, the reprocessed bulk networks exhibited full property retention. Moreover, the systematic inclusion of permanent linkages to substitute dynamic cross-links presents an avenue to study the interplay of permanent linkages and cross-link density toward the dynamic characteristics. We showed that average relaxation times and activation energies increase with increasing levels of permanent linkages in the system, demonstrating highly tunable dynamic behaviors in PHU network materials.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Reprocessable, Bio-Based, Self-Blowing Non-Isocyanate Polyurethane Network Foams from Cashew Nutshell Liquid

Purwanto

Chen

Torkelson

2023

ACS Appl. Polym. Mater.

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“…The net heat transfer in a foam is the superposition of the conduction and the radiation considered separately. 26 The thermal conductivity of a foam can thus be expressed as the sum of these different contributions: the conduction through the foam matrix (solid or liquid) which is analogous to the electrical conduction and therefore given by the eqn (1), and the two contributions that take place inside the bubbles, namely the conduction through air and the radiation. For the thermal conductivity of the gas phase, we will simply weight the conductivity of air λ air by the amount of air, 1 − ϕ l , neglecting the contribution of the films.…”

Section: Predicting the Freezing Dynamicsmentioning

confidence: 99%

“…As we use relatively wet foams (>5%) with small bubbles (∼100 μm), radiation can be neglected. 20,26…”

Section: Predicting the Freezing Dynamicsmentioning

confidence: 99%

Early freezing dynamics of an aqueous foam

Bumma,

Huerre,

Pierre

et al. 2023

Soft Matter

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“…In literature, the synthesis and mechanical properties of both metallic 1–8 and polymer foams 9–27 have been extensively studied; however, these studies fall short of thoroughly investigating how those materials respond to repeated high-strain deformations. In 1994, Zhang and Ashby published a paper detailing methods for the mechanical selection of foams for packaging.…”

Section: Introductionmentioning

confidence: 99%

Inductive quantification of energy absorption of high-density polyethylene foam for repeated blunt impact

Drane

Jesus-Vega

İnalpolat

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part L:

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Foams are used in a variety of impact energy absorption applications because of their ability to engage in large deformations under steady load transfer during the cell collapse. Quantification of the energy absorption capabilities of foams, including those resulting from repeated loading and unloading, is critical to both modeling and prototype development of systems utilizing these important materials. This paper details a novel process of characterizing a cross-linked high-density polyethylene foam for its applicability within helmet liners designed for low-velocity blunt impact. The foams are characterized using various forms of compression testing and physical measurements. The analyses include examination of the tangent modulus, strain hardness, energy absorption ideality, and energy absorption efficiency. Together, these analyses identify the regions of changing behavior of the nonlinear impact absorption material system. A case study for the materials is presented, which reveals that the examined high-density polyethylene foam exhibits some of the most efficient impact properties during the first impact. However, this case study also identifies that those impact properties can reduce significantly, e.g. a 55% increase in stress in the case of a 0.50 strain-level deformation in the first impact, for a subsequent impact after only a 120 s rest period. The novel combination of testing and analysis presented within this paper enables the developer of a foam energy absorption system to advance their interrogation of foams for repeated large strain deformations and temperature variations.

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Hysteresis and energy loss in flexible polyurethane foams

Cited by 12 publications

References 23 publications

Reprocessable, Bio-Based, Self-Blowing Non-Isocyanate Polyurethane Network Foams from Cashew Nutshell Liquid

Reprocessable, Bio-Based, Self-Blowing Non-Isocyanate Polyurethane Network Foams from Cashew Nutshell Liquid

Early freezing dynamics of an aqueous foam

Inductive quantification of energy absorption of high-density polyethylene foam for repeated blunt impact

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