In-situ understanding of pore nucleation and growth in polyurethane foams by using real-time synchrotron X-ray tomography

Pérez-Tamarit, S.; Solórzano, E.; Rodríguez‐Pérez, Miguel Ángel

doi:10.1016/j.polymer.2019.01.049

Cited by 27 publications

(19 citation statements)

References 42 publications

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“…Moreover, the formation of an even greater amount of polyurea groups, for RPUF/ AP_HO 2 C, detected by FTIR-ATR, suggests an even higher reactivity compared to the material with the other IL. According to Pérez-Tamarit et al, 19 when treated fillers are used into RPUF, a high shape irregularity may increase nucleation capability, which also increases the system reactivity. Figure 4 presents some images of the obtained RPUF/ AP composites.…”

Section: Properties Of the Rpuf Compositesmentioning

confidence: 99%

“…On the other hand, perpendicular to the rise direction ( Figure 5(e)-(h)), there was an increased number of cells ascribed to the AP incorporation, regardless of the IL treatment. According to Pérez-Tamarit et al, 19 the presence of particles in the liquid polymer significantly affects the homogeneous bubble nucleation of the neat media due to a nucleation effect. This behavior also yields superior bubble densities, as observed in the SEM images for RPUF/AP 1.0 wt%.…”

Section: Properties Of the Rpuf Compositesmentioning

confidence: 99%

See 1 more Smart Citation

Aramid pulp treated with imidazolium ionic liquids as a filler in rigid polyurethane bio‐foams

Kerche

Silva

Jankee

et al. 2021

J of Applied Polymer Sci

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This article reports an aramid pulp (AP) treated with two ionic liquids (IL), namely 1-n-butyl-3-methylimidazolium chloride (C 4 .Cl) and 1-carboxymethyl-3-methylimidazolium chloride (HO 2 C), and its use as a filler in reinforced rigid polyurethane foams (RPUF). The RPUF were incorporated with the treated AP at three weight fractions (c.a. 0.1, 0.5, and 1.0 wt%) and were produced by the free rising method. The results showed that the studied IL promoted a better interaction between the AP and the RPUF system, which increased the overall reactivity, imparting a higher cell anisotropy. This also yielded a positive effect in mechanical properties and thermal stability of the RPUF. Compared to the neat RPUF, outstanding increases of approximately 50 and 20% were achieved in compressive modulus and strength, respectively. In all, the use of IL promoted increased compatibility between matrix and reinforcement, especially that HO 2 C IL.

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Section: Properties Of the Rpuf Compositesmentioning

confidence: 99%

Section: Properties Of the Rpuf Compositesmentioning

confidence: 99%

Aramid pulp treated with imidazolium ionic liquids as a filler in rigid polyurethane bio‐foams

Kerche

Silva

Jankee

et al. 2021

J of Applied Polymer Sci

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“…In all these reports, the production of the PU foams containing nanoclays was carried out using a high-shear mixing device that, as is well known, introduces air bubbles during the mixing process. In addition, it is also known that heterogeneous nucleation is also caused by the air bubbles introduced during the mixing of the urethane foam components [39][40][41]. Brondi et al [42] studied the influence of air bubble inclusion on rigid PU and PIR foams.…”

Section: Introductionmentioning

confidence: 99%

Nanoparticles Addition in PU Foams: The Dramatic Effect of Trapped-Air on Nucleation

2021

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To determine the effect of nanoclays and trapped air on the formation of rigid polyurethane foams, three different production procedures were used. To study the influence of mixing at atmospheric pressure, two approaches were carried out employing either an electric or a magnetic stirrer. The third approach was executed by mixing under vacuum conditions with magnetic stirring. The samples thus obtained were characterized, and the effect of trapped air into the reactive mixtures was evaluated by analyzing the cellular structures. Different levels of trapped air were achieved when employing each manufacturing method. A correlation between the trapped air and the increase in the nucleation density when nanoclays were added was found: the cell nucleation density increased by 1.54 and 1.25 times under atmospheric conditions with electric and magnetic stirring, respectively. Nevertheless, samples fabricated without the presence of air did not show any nucleating effect despite the nanoclay addition (ratio of 1.09). This result suggests that the inclusion of air into the components is key for improving nucleation and that this effect is more pronounced when the polyol viscosity increases due to nanoclay addition. This is the most important feature determining the nucleating effect and, therefore, the corresponding cell size decreases.

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“…Biological systems such as a blowfly can be investigated to study relatively slow processes such as pupation 5 as well as very fast processes such as wingbeat 6 , requiring gating to achieve the acquisition speed 7 . Already since the early days of high-resolution X-ray imaging, foam-like structures have frequently been the subject of imaging studies due to the relative simplicity of inducing the relevant processes 8 – 10 . With the development of advanced add-on equipment such laser furnaces 11 and flow cells 12 , it has become possible to investigate processes in-situ in natural materials, e.g.…”

Section: Introductionmentioning

confidence: 99%

Improving image quality in fast, time-resolved micro-CT by weighted back projection

Heyndrickx

Bultreys

Goethals

et al. 2020

Sci Rep

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Time-resolved micro-CT is an increasingly powerful technique for studying dynamic processes in materials and structures. However, it is still difficult to study very fast processes with this technique, since fast scanning is typically associated with high image noise levels. We present weighted back projection, a technique applicable in iterative reconstruction methods using two types of prior knowledge: (1) a virtual starting volume resembling the sample, for example obtained from a scan before the dynamic process was initiated, and (2) knowledge on which regions in the sample are more likely to undergo the dynamic process. Therefore, processes on which this technique is applicable are preferably occurring within a static grid. Weighted back projection has the ability to handle small errors in the prior knowledge, while similar 4D micro-CT techniques require the prior knowledge to be exactly correct. It incorporates the prior knowledge within the reconstruction by using a weight volume, representing for each voxel its probability of undergoing the dynamic process. Qualitative analysis on a sparse subset of projection data from a real micro-CT experiment indicates that this method requires significantly fewer projection angles to converge to a correct volume. This can lead to an improved temporal resolution.

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In-situ understanding of pore nucleation and growth in polyurethane foams by using real-time synchrotron X-ray tomography

Cited by 27 publications

References 42 publications

Aramid pulp treated with imidazolium ionic liquids as a filler in rigid polyurethane bio‐foams

Aramid pulp treated with imidazolium ionic liquids as a filler in rigid polyurethane bio‐foams

Nanoparticles Addition in PU Foams: The Dramatic Effect of Trapped-Air on Nucleation

Improving image quality in fast, time-resolved micro-CT by weighted back projection

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