Polymers

Editorial

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4 pages, 177 KiB

Open AccessEditorial

Polymer Physics: From Theory to Experimental Applications

by Célio Fernandes, Luís L. Ferrás and Alexandre M. Afonso

Polymers 2024, 16(6), 768; https://doi.org/10.3390/polym16060768 - 11 Mar 2024

Viewed by 1552

Abstract

The significance of polymer processing techniques cannot be overstated in the production of polymer components [...] Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

Research

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22 pages, 4076 KiB

Open AccessArticle

Simulation and Analysis of the Loading, Relaxation, and Recovery Behavior of Polyethylene and Its Pipes

by Furui Shi and P.-Y. Ben Jar

Polymers 2024, 16(22), 3153; https://doi.org/10.3390/polym16223153 - 12 Nov 2024

Viewed by 700

Abstract

Spring–dashpot models have long been used to simulate the mechanical behavior of polymers, but their usefulness is limited because multiple model parameter values can reproduce the experimental data. In view of this limitation, this study explores the possibility of improving uniqueness of parameter [...] Read more.

Spring–dashpot models have long been used to simulate the mechanical behavior of polymers, but their usefulness is limited because multiple model parameter values can reproduce the experimental data. In view of this limitation, this study explores the possibility of improving uniqueness of parameter values so that the parameters can be used to establish the relationship between deformation and microstructural changes. An approach was developed based on stress during the loading, relaxation, and recovery of polyethylene. In total, 1000 sets of parameter values were determined for fitting the data from the relaxation stages with a discrepancy within 0.08 MPa. Despite a small discrepancy, the 1000 sets showed a wide range of variation, but one model parameter,

σ_{v, L} (0)

, followed two distinct paths rather than random distribution. The five selected sets of parameter values with discrepancies below 0.04 MPa were found to be highly consistent, except for the characteristic relaxation time. Therefore, this study concludes that the uniqueness of model parameter values can be improved to characterize the mechanical behavior of polyethylene. This approach then determined the quasi-static stress of four polyethylene pipes, which showed that these pipes had very close quasi-static stress. This indicates that the uniqueness of the parameter values can be improved for the spring–dashpot model, enabling further study using spring–dashpot models to characterize polyethylene’s microstructural changes during deformation. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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16 pages, 4616 KiB

Open AccessArticle

Analyzing Homogeneity of Highly Viscous Polymer Suspensions in Change Can Mixers

by Michael Roland Larsen, Erik Tomas Holmen Olofsson and Jon Spangenberg

Polymers 2024, 16(18), 2675; https://doi.org/10.3390/polym16182675 - 23 Sep 2024

Viewed by 553

Abstract

The mixing of highly viscous non-Newtonian suspensions is a critical process in various industrial applications. This computational fluid dynamics (CFD) study presents an in-depth analysis of non-isothermal mixing performance in change can mixers. The aim of the study was to identify parameters that [...] Read more.

The mixing of highly viscous non-Newtonian suspensions is a critical process in various industrial applications. This computational fluid dynamics (CFD) study presents an in-depth analysis of non-isothermal mixing performance in change can mixers. The aim of the study was to identify parameters that significantly influence both distributive and dispersive mixing in these mixers, which are essential for optimizing industrial mixing processes. The study employed a numerical design of experiments (DOE) approach to identify the parameters that most significantly influence both distributive and dispersive mixing, as measured by the Kramer mixing index (

M_{K r a m e r}

) and the Ica Manas-Zloczower mixing index

(\bar{λ_{M Z}})

. The investigated parameters included mixing time, number of arms, arm size ratio, revolutions per minute (RPM), z-axis rotation, z-axis movement, and initial and mixing temperatures. The methodology involved employing the bootstrap forest algorithm for predicting the mixing indices, achieving an

R^{2}

of 0.949 for

M_{K r a m e r}

and an

R^{2}

of 0.836 for

\bar{λ_{M Z}}

. The results indicate that the z-axis rotation has the greatest impact on both distributive and dispersive mixing. An increased number of arms negatively impacted

λ_{M Z}

, but had a small positive effect on

M_{K r a m e r}

. Surprisingly, in this study, neither the initial temperature of the material nor the mixing temperature significantly impacted the mixing performance. These findings highlight the relative importance of operational parameters over traditional temperature factors and provide a new perspective on mixing science. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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18 pages, 6477 KiB

Open AccessArticle

Development of a Cure Model for Unsaturated Polyester Resin Systems Based on Processing Conditions

by Abdallah Barakat, Marc Al Ghazal, Romeo Sephyrin Fono Tamo, Akash Phadatare, John Unser, Joshua Hagan and Uday Vaidya

Polymers 2024, 16(17), 2391; https://doi.org/10.3390/polym16172391 - 23 Aug 2024

Cited by 1 | Viewed by 1049

Abstract

Unsaturated polyester resin (UPR) systems are extensively used in composite materials for applications in the transportation, marine, and infrastructure sectors. There are continually evolving formulations of UPRs that need to be evaluated and optimized for processing. Differential Scanning Calorimetry (DSC) provides valuable insight [...] Read more.

Unsaturated polyester resin (UPR) systems are extensively used in composite materials for applications in the transportation, marine, and infrastructure sectors. There are continually evolving formulations of UPRs that need to be evaluated and optimized for processing. Differential Scanning Calorimetry (DSC) provides valuable insight into the non-isothermal and isothermal behavior of UPRs within a prescribed temperature range. In the present work, non-isothermal DSC tests were carried out between temperatures of 0.0 °C and 250 °C, through different heating and cooling ramp rates. The isothermal DSC tests were carried out between 0.0 and 170 °C. The instantaneous rate of cure of the tested temperatures were measured. The application of an autocatalytic model in a calculator was used to simulate curing behaviors under different processing conditions. As the temperature increased from 10 °C up to 170 °C, the rate of cure reduced, and the heat of reaction increased. The simulated cure behavior from the DSC data showed that the degree of cure (α) maximum value of 71.25% was achieved at the highest heating temperature of 85 °C. For the low heating temperature, i.e., 5 °C, the maximum degree of cure (α) did not exceed 12% because there was not enough heat to activate the catalyst to crosslink further. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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21 pages, 6156 KiB

Open AccessArticle

Investigations of the Laser Ablation Mechanism of PMMA Microchannels Using Single-Pass and Multi-Pass Laser Scans

by Xiao Li, Rujun Tang, Ding Li, Fengping Li, Leiqing Chen, Dehua Zhu, Guang Feng, Kunpeng Zhang and Bing Han

Polymers 2024, 16(16), 2361; https://doi.org/10.3390/polym16162361 - 21 Aug 2024

Viewed by 921

Abstract

CO₂ laser machining is a cost effective and time saving solution for fabricating microchannels on polymethylmethacrylate (PMMA). Due to the lack of research on the incubation effect and ablation behavior of PMMA under high-power laser irradiation, predictions of the microchannel profile are [...] Read more.

CO₂ laser machining is a cost effective and time saving solution for fabricating microchannels on polymethylmethacrylate (PMMA). Due to the lack of research on the incubation effect and ablation behavior of PMMA under high-power laser irradiation, predictions of the microchannel profile are limited. In this study, the ablation process and mechanism of a continuous CO₂ laser machining process on microchannel production in PMMA in single-pass and multi-pass laser scan modes are investigated. It is found that a higher laser energy density of a single pass causes a lower ablation threshold. The ablated surface can be divided into three regions: the ablation zone, the incubation zone, and the virgin zone. The PMMA ablation process is mainly attributed to the thermal decomposition reactions and the splashing of molten polymer. The depth, width, aspect ratio, volume ablation rate, and mass ablation rate of the channel increase as the laser scanning speed decreases and the number of laser scans increases. The differences in ablation results obtained under the same total laser energy density using different scan modes are attributed to the incubation effect, which is caused by the thermal deposition of laser energy in the polymer. Finally, an optimized simulation model that is used to solve the problem of a channel width greater than spot diameter is proposed. The error percentage between the experimental and simulation results varies from 0.44% to 5.9%. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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33 pages, 514 KiB

Open AccessArticle

General Relations between Stress Fluctuations and Viscoelasticity in Amorphous Polymer and Glass-Forming Systems

by Alexander Semenov and Jörg Baschnagel

Polymers 2024, 16(16), 2336; https://doi.org/10.3390/polym16162336 - 18 Aug 2024

Viewed by 851

Abstract

Mechanical stress governs the dynamics of viscoelastic polymer systems and supercooled glass-forming fluids. It was recently established that liquids with long terminal relaxation times are characterized by transiently frozen stress fields, which, moreover, exhibit long-range correlations contributing to the dynamically heterogeneous nature of [...] Read more.

Mechanical stress governs the dynamics of viscoelastic polymer systems and supercooled glass-forming fluids. It was recently established that liquids with long terminal relaxation times are characterized by transiently frozen stress fields, which, moreover, exhibit long-range correlations contributing to the dynamically heterogeneous nature of such systems. Recent studies show that stress correlations and relaxation elastic moduli are intimately related in isotropic viscoelastic systems. However, the origin of these relations (involving spatially resolved material relaxation functions) is non-trivial: some relations are based on the fluctuation-dissipation theorem (FDT), while others involve approximations. Generalizing our recent results on 2D systems, we here rigorously derive three exact FDT relations (already established in our recent investigations and, partially, in classical studies) between spatio-temporal stress correlations and generalized relaxation moduli, and a couple of new exact relations. We also derive several new approximate relations valid in the hydrodynamic regime, taking into account the effects of thermal conductivity and composition fluctuations for arbitrary space dimension. One approximate relation was heuristically obtained in our previous studies and verified using our extended simulation data on two-dimensional (2D) glass-forming systems. As a result, we provide the means to obtain, in any spatial dimension, all stress-correlation functions in terms of relaxation moduli and vice versa. The new approximate relations are tested using simulation data on 2D systems of polydisperse Lennard–Jones particles. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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32 pages, 9182 KiB

Open AccessArticle

Improved Approach for ab Initio Calculations of Rate Coefficients for Secondary Reactions in Acrylate Free-Radical Polymerization

by Fernando A. Lugo, Mariya Edeleva, Paul H. M. Van Steenberge and Maarten K. Sabbe

Polymers 2024, 16(7), 872; https://doi.org/10.3390/polym16070872 - 22 Mar 2024

Cited by 1 | Viewed by 1200

Abstract

Secondary reactions in radical polymerization pose a challenge when creating kinetic models for predicting polymer structures. Despite the high impact of these reactions in the polymer structure, their effects are difficult to isolate and measure to produce kinetic data. To this end, we [...] Read more.

Secondary reactions in radical polymerization pose a challenge when creating kinetic models for predicting polymer structures. Despite the high impact of these reactions in the polymer structure, their effects are difficult to isolate and measure to produce kinetic data. To this end, we used solvation-corrected M06-2X/6-311+G(d,p) ab initio calculations to predict a complete and consistent data set of intrinsic rate coefficients of the secondary reactions in acrylate radical polymerization, including backbiting, β-scission, radical migration, macromonomer propagation, mid-chain radical propagation, chain transfer to monomer and chain transfer to polymer. Two new approaches towards computationally predicting rate coefficients for secondary reactions are proposed: (i) explicit accounting for all possible enantiomers for reactions involving optically active centers; (ii) imposing reduced flexibility if the reaction center is in the middle of the polymer chain. The accuracy and reliability of the ab initio predictions were benchmarked against experimental data via kinetic Monte Carlo simulations under three sufficiently different experimental conditions: a high-frequency modulated polymerization process in the transient regime, a low-frequency modulated process in the sliding regime at both low and high temperatures and a degradation process in the absence of free monomers. The complete and consistent ab initio data set compiled in this work predicts a good agreement when benchmarked via kMC simulations against experimental data, which is a technique never used before for computational chemistry. The simulation results show that these two newly proposed approaches are promising for bridging the gap between experimental and computational chemistry methods in polymer reaction engineering. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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16 pages, 373 KiB

Open AccessArticle

Analytical Solutions to the Unsteady Poiseuille Flow of a Second Grade Fluid with Slip Boundary Conditions

by Evgenii S. Baranovskii

Polymers 2024, 16(2), 179; https://doi.org/10.3390/polym16020179 - 7 Jan 2024

Cited by 5 | Viewed by 1546

Abstract

This paper deals with an initial-boundary value problem modeling the unidirectional pressure-driven flow of a second grade fluid in a plane channel with impermeable solid walls. On the channel walls, Navier-type slip boundary conditions are stated. Our aim is to investigate the well-posedness [...] Read more.

This paper deals with an initial-boundary value problem modeling the unidirectional pressure-driven flow of a second grade fluid in a plane channel with impermeable solid walls. On the channel walls, Navier-type slip boundary conditions are stated. Our aim is to investigate the well-posedness of this problem and obtain its analytical solution under weak regularity requirements on a function describing the velocity distribution at initial time. In order to overcome difficulties related to finding classical solutions, we propose the concept of a generalized solution that is defined as the limit of a uniformly convergent sequence of classical solutions with vanishing perturbations in the initial data. We prove the unique solvability of the problem under consideration in the class of generalized solutions. The main ingredients of our proof are a generalized Abel criterion for uniform convergence of function series and the use of an orthonormal basis consisting of eigenfunctions of the related Sturm–Liouville problem. As a result, explicit expressions for the flow velocity and the pressure in the channel are established. The constructed analytical solutions favor a better understanding of the qualitative features of time-dependent flows of polymer fluids and can be applied to the verification of relevant numerical, asymptotic, and approximate analytical methods. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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18 pages, 2345 KiB

Open AccessArticle

Knot Formation on DNA Pushed Inside Chiral Nanochannels

by Renáta Rusková and Dušan Račko

Polymers 2023, 15(20), 4185; https://doi.org/10.3390/polym15204185 - 22 Oct 2023

Cited by 3 | Viewed by 8898

Abstract

We performed coarse-grained molecular dynamics simulations of DNA polymers pushed inside infinite open chiral and achiral channels. We investigated the behavior of the polymer metrics in terms of span, monomer distributions and changes of topological state of the polymer in the channels. We [...] Read more.

We performed coarse-grained molecular dynamics simulations of DNA polymers pushed inside infinite open chiral and achiral channels. We investigated the behavior of the polymer metrics in terms of span, monomer distributions and changes of topological state of the polymer in the channels. We also compared the regime of pushing a polymer inside the infinite channel to the case of polymer compression in finite channels of knot factories investigated in earlier works. We observed that the compression in the open channels affects the polymer metrics to different extents in chiral and achiral channels. We also observed that the chiral channels give rise to the formation of equichiral knots with the same handedness as the handedness of the chiral channels. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Polymer metrics in terms of the molecule’s span during pushing of DNA molecule inside channels as a function of pushing speed and confinement strength expressed as D/P. (a) The panel compares the polymer span in units of σ/ℓ pushed with different velocities of the piston v in units of 1000 σ/τ. The black lines indicate the span of a polymer pushed in helical channels, and red lines correspond to the simulations in a cylindrical channel. The areas in shades of purple show differences with the respective cases and a given confinement strength. The inset shows the velocities of the piston obtained for the external force employed on the piston. (b) The panel shows the span of polymer pushed in open infinite helical channels and compares the data with a previously investigated case of a polymer compressed in a blinded channel [<a href="#B36-polymers-15-04185" class="html-bibr">36</a>]. (c) The panel shows a comparison of the polymer’s span in open infinite channels versus blinded channels with cylindrical geometry and as a function of force in the units of Fσ/ε0 and confinement strength expressed in terms of D/P. The insets show rendered snapshots obtained for D/P = 0.5 and F = 5ε0/σ, where the polymer is shown in a rainbow color scheme, with one end of the polymer shown in blue and the other in red. Full article ">Figure 2
Monomer distributions of DNA polymer pushed inside channels with cylindrical and helical geometry. The panels show the distributions obtained in cylindrical (a–c) and helical channels (d–f). The distributions are also shown for different confinement strengths in terms of the D/P ratio, equal to 0.5 (a,d); D/P = 1 (b,e); and D/P = 2 in panels (c,f). The very left of each panel shows heatmaps of the monomer distributions with a color gradient ranging from blue to red, where the distribution’s peak is indicated by red and zero occurrences are denoted by blue. The left graph in every panel shows monomer distribution along the channel from the position (in units of σ/ℓ) of the piston as a function of piston velocity, taking into regard also direction of pushing in the simulations. The insets of this graph also show index-to-bead projections of axial monomer distributions obtained for F = 0.1ε0/σ and F = 5ε0/σ. The graphs to the right in the pair in every panel show radial distribution functions of monomers from the geometric center of the channel in units of σ/ℓ, in simulations represented by the x = 0 axis. The arrows indicate the direction of increasing or decreasing velocity. Each panel also shows a snapshot obtained for the particular geometry of the channel, confinement strength D/P, and force = 1 ε0/σ. The polymer is depicted in rainbow coloring, with the first bead in blue and the last bead in the chain in red. Full article ">Figure 3
Knotting probabilities. (a) The first two columns compare knotting probabilities in terms of crossing numbers, distinguished by a thermometer scale, obtained for DNA polymer pushed inside infinite open channels with cylindrical and helical geometries. The rows correspond to different confinement strength in terms of D/P. In the case of helical channels, the knot types are evaluated in terms of the frequencies of amphichiral (Am.), torus (Tor.), twist knots (Tw.), unknots (Un.), and undefined knots (“?”). The last column shows a comparison of equichiral and antichiral knots, i.e., the knots with the same handedness as or the opposite handedness to that of the chiral helical channel. (b) Average writhe of the DNA chains in helical channels as a function of increasing pushing velocities and strength of confinement in terms of the D/P ratio. The ω+ and ω− indicate handedness of the channels (see <a href="#sec2dot2-polymers-15-04185" class="html-sec">Section 2.2</a>). The computed pushing velocities are shown in the inset of <a href="#polymers-15-04185-f001" class="html-fig">Figure 1</a>a. (c) A proposed mechanism for how the helical channels control handedness of compression–confinement-induced knotting. Full article ">

13 pages, 3238 KiB

Open AccessArticle

Effectiveness of the Use of Polymers in High-Performance Concrete Containing Silica Fume

by Alya Harichane, Nadhir Toubal Seghir, Paweł Niewiadomski, Łukasz Sadowski and Michał Cisiński

Polymers 2023, 15(18), 3730; https://doi.org/10.3390/polym15183730 - 11 Sep 2023

Cited by 2 | Viewed by 1377

Abstract

The incorporation of polycarboxylate ether superplasticizer (PCE)-type polymers and silica fume (SF) in high-performance concretes (HPC) leads to remarkable rheological and mechanical improvements. In the fresh state, PCEs are adsorbed on cement particles and dispersants, promoting the workability of the concrete. Silica fume [...] Read more.

The incorporation of polycarboxylate ether superplasticizer (PCE)-type polymers and silica fume (SF) in high-performance concretes (HPC) leads to remarkable rheological and mechanical improvements. In the fresh state, PCEs are adsorbed on cement particles and dispersants, promoting the workability of the concrete. Silica fume enables very well-compacted concrete to be obtained, which is characterized by high mechanical parameters in its hardened state. Some PCEs are incompatible with silica fume, which can result in slump loss and poor rheological behavior. The main objective of this research is to study the influence of three types of PCEs, which all have different molecular architectures, on the rheological and mechanical behavior of high-performance concretes containing 10% SF as a partial replacement of cement. The results show that the carboxylic density of PCE has an influence on its compatibility with SF. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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Particle size distribution curves of the PC and SF. Full article ">Figure 2
Particle size distribution curves of the used aggregates. Full article ">Figure 3
Chromatogram of polymers: (a) PCE1, (b) PCE2, and (c) PCE3. Full article ">Figure 3 Cont.
Chromatogram of polymers: (a) PCE1, (b) PCE2, and (c) PCE3. Full article ">Figure 4
Slump values of the HPC. Full article ">Figure 5
Plastic viscosity as a function of the shear rate of the cement paste: (a) PCE1, (b) PCE2, (c) PCE3; w/b = 0.35. Full article ">Figure 5 Cont.
Plastic viscosity as a function of the shear rate of the cement paste: (a) PCE1, (b) PCE2, (c) PCE3; w/b = 0.35. Full article ">Figure 6
Shear stress as a function of the shear rate of the cement paste: (a) PCE1, (b) PCE2, (c) PCE3; w/b = 0.35. Full article ">Figure 6 Cont.
Shear stress as a function of the shear rate of the cement paste: (a) PCE1, (b) PCE2, (c) PCE3; w/b = 0.35. Full article ">Figure 7
Zeta potential of the cement paste as a function of the PCE type. Full article ">Figure 8
Compressive strengths of the HPC (containing superplasticizers PCE1, 2, and 3) after different times of hydration. Full article ">

19 pages, 1379 KiB

Open AccessArticle

Numerical Simulation of Three-Dimensional Free Surface Flows Using the K–BKZ–PSM Integral Constitutive Equation

by Juliana Bertoco, Antonio Castelo, Luís L. Ferrás and Célio Fernandes

Polymers 2023, 15(18), 3705; https://doi.org/10.3390/polym15183705 - 8 Sep 2023

Cited by 3 | Viewed by 1180

Abstract

This work introduces a novel numerical method designed to address three-dimensional unsteady free surface flows incorporating integral viscoelastic constitutive equations, specifically the K–BKZ–PSM (Kaye–Bernstein, Kearsley, Zapas–Papanastasiou, Scriven, Macosko) model. The new proposed methodology employs a second-order finite difference approach along with the deformation [...] Read more.

This work introduces a novel numerical method designed to address three-dimensional unsteady free surface flows incorporating integral viscoelastic constitutive equations, specifically the K–BKZ–PSM (Kaye–Bernstein, Kearsley, Zapas–Papanastasiou, Scriven, Macosko) model. The new proposed methodology employs a second-order finite difference approach along with the deformation fields method to solve the integral constitutive equation and the marker particle method (known as marker-and-cell) to accurately capture the evolution of the fluid’s free surface. The newly developed numerical method has proven its effectiveness in handling complex fluid flow scenarios, including confined flows and extrudate swell simulations of Boger fluids. Furthermore, a new semi-analytical solution for velocity and stress fields is derived, considering fully developed flows of a K–BKZ–PSM fluid in a pipe. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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16 pages, 2539 KiB

Open AccessArticle

Analysis of the Dynamic Cushioning Property of Expanded Polyethylene Based on the Stress–Energy Method

by Yueqing Xing, Deqiang Sun and Guoliang Chen

Polymers 2023, 15(17), 3603; https://doi.org/10.3390/polym15173603 - 30 Aug 2023

Cited by 2 | Viewed by 1363

Abstract

This paper aimed to experimentally clarify the dynamic crushing performance of expanded polyethylene (EPE) and analyze the influence of thickness and dropping height on its mechanical behavior based on the stress–energy method. Hence, a series of impact tests are carried out on EPE [...] Read more.

This paper aimed to experimentally clarify the dynamic crushing performance of expanded polyethylene (EPE) and analyze the influence of thickness and dropping height on its mechanical behavior based on the stress–energy method. Hence, a series of impact tests are carried out on EPE foams with different thicknesses and dropping heights. The maximum acceleration, static stress, dynamic stress and dynamic energy of EPE specimens are obtained through a dynamic impact test. Then, according to the principle of the stress–energy method, the functional relationship between dynamic stress and dynamic energy is obtained through exponential fitting and polynomial fitting, and the cushion material constants a, b and c are determined. The maximum acceleration-static stress curves of any thickness and dropping height can be further fitted. By the equipartition energy domain method, the range of static stress can be expanded, which is very fast and convenient. When analyzing the influence of thickness and dropping height on the dynamic cushioning performance curves of EPE, it is found that at the same drop height, with the increase of thickness, the opening of the curve gradually becomes larger. The minimum point on the maximum acceleration-static stress curve also decreases with the increase of the thickness. When the dropping height is 400 mm, compared to foam with a thickness of 60 mm, the tested maximum acceleration value of the lowest point of the specimen with a thickness of 40 mm increased by 45.3%, and the static stress is both 5.5 kPa. When the thickness of the specimen is 50 mm, compared to the dropping height of 300 mm, the tested maximum acceleration value of the lowest point of the specimen with a dropping height of 600 mm increased by 93.3%. Therefore, the dynamic cushioning performance curve of EPE foams can be quickly obtained by the stress–energy method when the precision requirement is not high, which provides a theoretical basis for the design of cushion packaging. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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18 pages, 4473 KiB

Open AccessArticle

A Phenomenological Model for Enthalpy Recovery in Polystyrene Using Dynamic Mechanical Spectra

by Koh-hei Nitta, Kota Ito and Asae Ito

Polymers 2023, 15(17), 3590; https://doi.org/10.3390/polym15173590 - 29 Aug 2023

Cited by 3 | Viewed by 1550

Abstract

This paper studies the effects of annealing time on the specific heat enthalpy of polystyrene above the glass transition temperature. We extend the Tool–Narayanaswamy–Moynihan (TNM) model to describe the endothermic overshoot peaks through the dynamic mechanical spectra. In this work, we accept the [...] Read more.

This paper studies the effects of annealing time on the specific heat enthalpy of polystyrene above the glass transition temperature. We extend the Tool–Narayanaswamy–Moynihan (TNM) model to describe the endothermic overshoot peaks through the dynamic mechanical spectra. In this work, we accept the viewpoint that the enthalpy recovery behavior of glassy polystyrene (PS) has a common structural relaxation mode with linear viscoelastic behavior. As a consequence, the retardation spectrum evaluated from the dynamic mechanical spectra around the primary T_g peak is used as the recovery function of the endothermic overshoot of specific heat. In addition, the sub-T_g shoulder peak around the T_g peak is found to be related to the structural relaxation estimated from light scattering measurements. The enthalpy recovery of annealed PS is quantitatively described using retardation spectra of the primary T_g, as well as the kinetic process of the sub-T_g relaxation process. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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15 pages, 3228 KiB

Open AccessArticle

Cellulose Nanocrystal Embedded Composite Foam and Its Carbonization for Energy Application

by So Yeon Ahn, Chengbin Yu and Young Seok Song

Polymers 2023, 15(16), 3454; https://doi.org/10.3390/polym15163454 - 18 Aug 2023

Cited by 1 | Viewed by 1560

Abstract

In this study, we fabricated a cellulose nanocrystal (CNC)-embedded aerogel-like chitosan foam and carbonized the 3D foam for electrical energy harvesting. The nanocrystal-supported cellulose foam can demonstrate a high surface area and porosity, homogeneous size ranging from various microscales, and a high quality [...] Read more.

In this study, we fabricated a cellulose nanocrystal (CNC)-embedded aerogel-like chitosan foam and carbonized the 3D foam for electrical energy harvesting. The nanocrystal-supported cellulose foam can demonstrate a high surface area and porosity, homogeneous size ranging from various microscales, and a high quality of absorbing external additives. In order to prepare CNC, microcrystalline cellulose (MCC) was chemically treated with sulfuric acid. The CNC incorporates into chitosan, enhancing mechanical properties, crystallization, and generation of the aerogel-like porous structure. The weight percentage of the CNC was 2 wt% in the chitosan composite. The CNC/chitosan foam is produced using the freeze-drying method, and the CNC-embedded CNC/chitosan foam has been carbonized. We found that the degree of crystallization of carbon structure increased, including the CNCs. Both CNC and chitosan are degradable materials when CNC includes chitosan, which can form a high surface area with some typical surface-related morphology. The electrical cyclic voltammetric result shows that the vertical composite specimen had superior electrochemical properties compared to the horizontal composite specimen. In addition, the BET measurement indicated that the CNC/chitosan foam possessed a high porosity, especially mesopores with layer structures. At the same time, the carbonized CNC led to a significant increase in the portion of micropore. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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Schematic of fabrication of modified CNC/chitosan composite structure. Full article ">Figure 2
Morphological analysis of the samples: Optical microscopic images of (a) the CNC/chitosan foam and (b) the carbonized CNC/chitosan foam. (c) Cryo-SEM image of (c) the CNC/chitosan suspension and SEM images of (d) the carbonized chitosan foam, (e) the CNC/chitosan foam, and (f) the carbonized CNC/chitosan foam. Full article ">Figure 3
(a) FT-IR result of the raw and carbonized chitosan foam. (b) Scanning results of carbonized CNC/Chitosan foam. (c) Raman spectra of the carbonized chitosan foam and CNC/chitosan foam. (d) WAXS spectra of the carbonized chitosan foam and CNC/chitosan foam. Full article ">Figure 4
Cyclic voltammetry results of (a) the carbonized chitosan foam and (b) the carbonized CNC/chitosan foam. Full article ">Figure 5
Chronoamperometry analysis of the sample: (a) photograph (left) and schematic image (right) of the experimental setup and (b) current result to time for the carbonized chitosan foam and CNC/chitosan foam. Full article ">Figure 6
Gas physisorption result of the uncarbonized chitosan foam and CNC/chitosan foam: (a) hysteresis loops; (b) BET analysis of adsorption isotherm and pore size distributions obtained from (c) MP and (d) BJH analyses. Full article ">Figure 7
Gas physisorption result of the carbonized chitosan foam and CNC/chitosan foam: (a) hysteresis loops; (b) BET analysis of adsorption isotherm and pore size distributions obtained from (c) MP and (d) BJH analyses. Full article ">

9 pages, 2127 KiB

Open AccessCommunication

Key Factors in Enhancing Pseudocapacitive Properties of PANI-InO_x Hybrid Thin Films Prepared by Sequential Infiltration Synthesis

by Jiwoong Ham, Hyeong-U Kim and Nari Jeon

Polymers 2023, 15(12), 2616; https://doi.org/10.3390/polym15122616 - 8 Jun 2023

Cited by 1 | Viewed by 1488

Abstract

Sequential infiltration synthesis (SIS) is an emerging vapor-phase synthetic route for the preparation of organic–inorganic composites. Previously, we investigated the potential of polyaniline (PANI)-InO_x composite thin films prepared using SIS for application in electrochemical energy storage. In this study, we investigated the [...] Read more.

Sequential infiltration synthesis (SIS) is an emerging vapor-phase synthetic route for the preparation of organic–inorganic composites. Previously, we investigated the potential of polyaniline (PANI)-InO_x composite thin films prepared using SIS for application in electrochemical energy storage. In this study, we investigated the effects of the number of InO_x SIS cycles on the chemical and electrochemical properties of PANI-InO_x thin films via combined characterization using X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and cyclic voltammetry. The area-specific capacitance values of PANI-InO_x samples prepared with 10, 20, 50, and 100 SIS cycles were 1.1, 0.8, 1.4, and 0.96 mF/cm², respectively. Our result shows that the formation of an enlarged PANI-InO_x mixed region directly exposed to the electrolyte is key to enhancing the pseudocapacitive properties of the composite films. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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Full article ">Figure 1
(a) Schematic illustration of structure of PANI-InOx/SiO2/Si samples. InOx content shows graded concentration along film thickness direction. (b) XPS depth profiles showing C, In, N, O, and Si atomic concentrations for four SIS samples with different cycle numbers: 10, 20, 50, and 100 cy. (c) O 1s and N 1s HRXPS data obtained at different locations (i.e., InOx-rich region, PANI-InOx mixed region, and PANI-rich region) in four samples. Each location at which HRXPS data were captured are shown as arrows in (b). Full article ">Figure 2
(a) UV-vis transmittance spectra, (b) ATR-FTIR absorbance spectra, and (c) Raman spectra of PANI-InOx samples at different number of cycles (10, 20, 50, and 100 cy) and PANI-only sample. The PANI-only sample was annealed under the same conditions as the PANI-InOx samples. Inset of (a) shows Tauc plot of 100 cy PANI-InOx sample. The dashed lines in panel (c) mark the location of Raman bands observed in the PANI-InOx film, which are also summarized in <a href="#polymers-15-02616-t001" class="html-table">Table 1</a>. Full article ">Figure 3
CV curves of PANI-InOx films prepared with different SIS cycles (10, 20, 50, and 100 cy) and PANI-only film. The CVs were collected at a scan rate of 10 mV/s in an aqueous electrolyte of neutral pH. Full article ">

12 pages, 4595 KiB

Open AccessArticle

Numerical Modeling of the Mixing of Highly Viscous Polymer Suspensions in Partially Filled Sigma Blade Mixers

by Michael Roland Larsen, Tobias Ottsen, Erik Tomas Holmen Olofsson and Jon Spangenberg

Polymers 2023, 15(8), 1938; https://doi.org/10.3390/polym15081938 - 19 Apr 2023

Cited by 3 | Viewed by 2076

Abstract

This paper presents a non-isothermal, non-Newtonian Computational Fluid Dynamics (CFD) model for the mixing of a highly viscous polymer suspension in a partially filled sigma blade mixer. The model accounts for viscous heating and the free surface of the suspension. The rheological model [...] Read more.

This paper presents a non-isothermal, non-Newtonian Computational Fluid Dynamics (CFD) model for the mixing of a highly viscous polymer suspension in a partially filled sigma blade mixer. The model accounts for viscous heating and the free surface of the suspension. The rheological model is found by calibration with experimental temperature measurements. Subsequently, the model is exploited to study the effect of applying heat both before and during mixing on the suspension’s mixing quality. Two mixing indexes are used to evaluate the mixing condition, namely, the Ica Manas-Zlaczower dispersive index and Kramer’s distributive index. Some fluctuations are observed in the predictions of the dispersive mixing index, which could be associated with the free surface of the suspension, thus indicating that this index might not be ideal for partially filled mixers. The Kramer index results are stable and indicate that the particles in the suspension can be well distributed. Interestingly, the results highlight that the speed at which the suspension becomes well distributed is almost independent of applying heat both before and during the process. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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18 pages, 8414 KiB

Open AccessArticle

Multiphase Flow Production Enhancement Using Drag Reducing Polymers

by Abdelsalam Alsarkhi and Mustafa Salah

Polymers 2023, 15(5), 1108; https://doi.org/10.3390/polym15051108 - 23 Feb 2023

Cited by 3 | Viewed by 1475

Abstract

This paper presents a comprehensive experimental investigation concerning the effect of drag reducing polymers (DRP) on enhancing the throughput and reducing the pressure drop for a horizontal pipe carrying two-phase flow of air and water mixture. Moreover, the ability of these polymer entanglements [...] Read more.

This paper presents a comprehensive experimental investigation concerning the effect of drag reducing polymers (DRP) on enhancing the throughput and reducing the pressure drop for a horizontal pipe carrying two-phase flow of air and water mixture. Moreover, the ability of these polymer entanglements to damp turbulence waves and changing the flow regime has been tested at various conditions, and a clear observation showed that the maximum drag reduction always occurs when the highly fluctuated waves were reduced effectively by DRP (and that, accordingly, phase transition (flow regime changed) appeared. This may also help in improving the separation process and enhancing the separator performance. The present experimental set-up has been constructed using a test section of 1.016-cm ID; an acrylic tube section was used to enable visual observations of the flow patterns. A new injection technique has been utilized and, with the use of different injection rates of DRP, the results have shown that the reduction in pressure drop occurred in all flow configurations. Furthermore, different empirical correlations have been developed which improve the ability to predict the pressure drop after the addition of DRP. The correlations showed low discrepancy for a wide range of water and air flow rates. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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Review

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26 pages, 5353 KiB

Open AccessReview

The Elasticity of Polymer Melts and Solutions in Shear and Extension Flows

by Andrey V. Subbotin, Alexander Ya. Malkin and Valery G. Kulichikhin

Polymers 2023, 15(4), 1051; https://doi.org/10.3390/polym15041051 - 20 Feb 2023

Cited by 4 | Viewed by 3599

Abstract

This review is devoted to understanding the role of elasticity in the main flow modes of polymeric viscoelastic liquids—shearing and extension. The flow through short capillaries is the central topic for discussing the input of elasticity to the effects, which are especially interesting [...] Read more.

This review is devoted to understanding the role of elasticity in the main flow modes of polymeric viscoelastic liquids—shearing and extension. The flow through short capillaries is the central topic for discussing the input of elasticity to the effects, which are especially interesting for shear. An analysis of the experimental data made it possible to show that the energy losses in such flows are determined by the Deborah and Weissenberg numbers. These criteria are responsible for abnormally high entrance effects, as well as for mechanical losses in short capillaries. In addition, the Weissenberg number determines the threshold of the flow instability due to the liquid-to-solid transition. In extension, this criterion shows whether deformation takes place as flow or as elastic strain. However, the stability of a free jet in extension depends not only on the viscoelastic properties of a polymeric substance but also on the driving forces: gravity, surface tension, etc. An analysis of the influence of different force combinations on the shape of the stretched jet is presented. The concept of the role of elasticity in the deformation of polymeric liquids is crucial for any kind of polymer processing. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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