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Polymers
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State-of-the-Art Polymer Science and Technology
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State-of-the-Art Polymer Science and Technology

A topical collection in Polymers (ISSN 2073-4360).

Editor

Prof. Dr. Ignazio Blanco

E-Mail Website
Collection Editor
Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria 6, 95125 Catania, Italy
Interests: materials; polymers; thermal properties; nanocomposites; composites
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

With the aim of presenting state-of-the-art research and reviews in the field of polymer science and technology in various countries and territories all over the world, the journal has launched this collection, details of which can be found at the website links below.

We welcome scholars to collaborate with us on the future collections in this collection!

Polymers Editorial Office
polymers@mdpi.com

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Published Papers (4 papers)

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2021

39 pages, 20364 KiB  
Review
Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art
by Mariya Edeleva, Paul H.M. Van Steenberge, Maarten K. Sabbe and Dagmar R. D’hooge
Polymers 2021, 13(18), 3027; https://doi.org/10.3390/polym13183027 - 07 Sep 2021
Cited by 18 | Viewed by 3342
Abstract
In recent decades, quantum chemical calculations (QCC) have increased in accuracy, not only providing the ranking of chemical reactivities and energy barriers (e.g., for optimal selectivities) but also delivering more reliable equilibrium and (intrinsic/chemical) rate coefficients. This increased reliability of kinetic parameters is [...] Read more.
In recent decades, quantum chemical calculations (QCC) have increased in accuracy, not only providing the ranking of chemical reactivities and energy barriers (e.g., for optimal selectivities) but also delivering more reliable equilibrium and (intrinsic/chemical) rate coefficients. This increased reliability of kinetic parameters is relevant to support the predictive character of kinetic modeling studies that are addressing actual concentration changes during chemical processes, taking into account competitive reactions and mixing heterogeneities. In the present contribution, guidelines are formulated on how to bridge the fields of computational chemistry and chemical kinetics. It is explained how condensed phase systems can be described based on conventional gas phase computational chemistry calculations. Case studies are included on polymerization kinetics, considering free and controlled radical polymerization, ionic polymerization, and polymer degradation. It is also illustrated how QCC can be directly linked to material properties. Full article
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11 pages, 2705 KiB  
Article
Nanoparticles Addition in PU Foams: The Dramatic Effect of Trapped-Air on Nucleation
by Beatriz Merillas, Fernando Villafañe and Miguel Ángel Rodríguez-Pérez
Polymers 2021, 13(17), 2952; https://doi.org/10.3390/polym13172952 - 31 Aug 2021
Cited by 14 | Viewed by 2314
Abstract
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 [...] Read more.
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. Full article
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23 pages, 1430 KiB  
Review
Latest Advances on the Synthesis of Linear ABC-Type Triblock Terpolymers and Star-Shaped Polymers by RAFT Polymerization
by Athanasios Skandalis, Theodore Sentoukas, Despoina Giaouzi, Martha Kafetzi and Stergios Pispas
Polymers 2021, 13(11), 1698; https://doi.org/10.3390/polym13111698 - 22 May 2021
Cited by 17 | Viewed by 4111
Abstract
This review article aims to cover the most recent advances regarding the synthesis of linear ABC-type triblock terpolymers and star-shaped polymers by RAFT polymerization, as well as their self-assembly properties in aqueous solutions. RAFT polymerization has received extensive attention, as it is a [...] Read more.
This review article aims to cover the most recent advances regarding the synthesis of linear ABC-type triblock terpolymers and star-shaped polymers by RAFT polymerization, as well as their self-assembly properties in aqueous solutions. RAFT polymerization has received extensive attention, as it is a versatile technique, compatible with a great variety of functional monomers and reaction conditions, while providing exceptional and precise control over the final structure, with well-defined side-groups and post-polymerization engineering potential. Linear triblock terpolymers synthesis can lead to very interesting novel ideas, since there are countless combinations of stimuli/non-stimuli and hydrophilic/hydrophobic monomers that someone can use. One of their most interesting features is their ubiquitous ability to self-assemble in different nanostructures depending on their degree of polymerization (DP), block composition, solubilization protocol, internal and external stimuli. On the other hand, star-shaped polymers exhibit a more stable nanostructure, with a distinct crosslinked core and arm blocks that can also incorporate stimuli-responsive blocks for “smart” applications. Full article
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Graphical abstract

15 pages, 5851 KiB  
Article
Study of an Online Monitoring Adaptive System for an Injection Molding Process Based on a Nozzle Pressure Curve
by Jia-Chen Fan-Jiang, Chi-Wei Su, Guan-Yan Liou, Sheng-Jye Hwang, Huei-Huang Lee, Hsin-Shu Peng and Hsiao-Yeh Chu
Polymers 2021, 13(4), 555; https://doi.org/10.3390/polym13040555 - 13 Feb 2021
Cited by 8 | Viewed by 2044
Abstract
Injection molding is a popular process for the mass production of polymer products, but due to the characteristics of the injection process, there are many factors that will affect the product quality during the long fabrication processes. In this study, an adaptive adjustment [...] Read more.
Injection molding is a popular process for the mass production of polymer products, but due to the characteristics of the injection process, there are many factors that will affect the product quality during the long fabrication processes. In this study, an adaptive adjustment system was developed by C++ programming to adjust the V/P switchover point and injection speed during the injection molding process in order to minimize the variation of the product weight. Based on a series of preliminary experiments, it was found that the viscosity index and peak pressure had a strong correlation with the weight of the injection-molded parts. Therefore, the viscosity index and peak pressure are used to guide the adjustment in the presented control system, and only one nozzle pressure sensor is used in the system. The results of the preliminary experiments indicate that the reduction of the packing time and setting enough clamping force can decrease the variation of the injected weight without turning on the adaptive control system; meanwhile, the master pressure curve obtained from the preliminary experiment was used as the control target of the system. With this system, the variation of the product weight and coefficient of variation (CV) of the product weight can be decreased to 0.21 and 0.05%, respectively. Full article
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