Polymers

11 pages, 1808 KiB

Open AccessArticle

Chromatographic Method for Evaluation of Polymeric GC Stationary Phases Ageing Using the Novel Non-Cross-Linked Poly(3-(Tributoxysilyl)Tricyclononene-7) as the Model Stationary Phase

by Anastasiia Kanateva, Maxim Bermeshev, Dmitrii Alentiev, Alexander A. Korolev and Alexander Kurganov

Polymers 2021, 13(11), 1899; https://doi.org/10.3390/polym13111899 - 7 Jun 2021

Cited by 1 | Viewed by 2198

Abstract

The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable [...] Read more.

The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable than previously studied trimethylsilyl- and trimethoxysilyl- derivatives. The long-term heating at 170 °C resulted in an increase of mass transfer rate between stationary and mobile phases which could be observed as a decrease of parameter C of Van Deemter equation. This effect is rather unusual, as the polymeric stationary phases tend in decrease of the layer volume and porosity while ageing. Additionally, the values of thermodynamic parameters of sorption are calculated for the polymeric stationary phase: enthalpy of sorption varied −28 to −37 kJ/mol, entropy change was −41 to −51 J/mol K. The compensation curves were plotted for the alkanes, arenes, and alcohols, and the parameters of compensation plot were calculated, demonstrating the different sorption mechanisms both for hydrocarbons and oxygen-containing compounds, and different classes of organic compounds. Full article

(This article belongs to the Section Polymer Membranes and Films)

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14 pages, 1466 KiB

Open AccessArticle

Predicting Polymers’ Glass Transition Temperature by a Chemical Language Processing Model

by Guang Chen, Lei Tao and Ying Li

Polymers 2021, 13(11), 1898; https://doi.org/10.3390/polym13111898 - 7 Jun 2021

Cited by 46 | Viewed by 9363

Abstract

We propose a chemical language processing model to predict polymers’ glass transition temperature (

T_{g}

) through a polymer language (SMILES, Simplified Molecular Input Line Entry System) embedding and recurrent neural network. This model only receives the SMILES strings of a polymer’s [...] Read more.

We propose a chemical language processing model to predict polymers’ glass transition temperature (

T_{g}

) through a polymer language (SMILES, Simplified Molecular Input Line Entry System) embedding and recurrent neural network. This model only receives the SMILES strings of a polymer’s repeat units as inputs and considers the SMILES strings as sequential data at the character level. Using this method, there is no need to calculate any additional molecular descriptors or fingerprints of polymers, and thereby, being very computationally efficient. More importantly, it avoids the difficulties to generate molecular descriptors for repeat units containing polymerization point ‘*’. Results show that the trained model demonstrates reasonable prediction performance on unseen polymer’s

T_{g}

. Besides, this model is further applied for high-throughput screening on an unlabeled polymer database to identify high-temperature polymers that are desired for applications in extreme environments. Our work demonstrates that the SMILES strings of polymer repeat units can be used as an effective feature representation to develop a chemical language processing model for predictions of polymer

T_{g}

. The framework of this model is general and can be used to construct structure–property relationships for other polymer properties. Full article

(This article belongs to the Special Issue Artificial Intelligence in Polymer Science and Chemistry)

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10 pages, 2750 KiB

Open AccessBrief Report

Dynamic Mechanical Behavior of Graphene Oxide Functionalized Curaua Fiber-Reinforced Epoxy Composites: A Brief Report

by Ulisses Oliveira Costa, Lucio Fabio Cassiano Nascimento, Wendell Bruno Almeida Bezerra, Vinícius de Oliveira Aguiar, Artur Camposo Pereira, Sergio Neves Monteiro and Wagner Anacleto Pinheiro

Polymers 2021, 13(11), 1897; https://doi.org/10.3390/polym13111897 - 7 Jun 2021

Cited by 16 | Viewed by 2972

Abstract

The coating of natural fiber by graphene oxide (GO) has, over, this past decade, attracted increasing attention as an effective way to improve the adhesion to polymer matrices and enhance the composite properties. In particular, the GO-functionalized 30 vol% curaua fiber (Ananas [...] Read more.

The coating of natural fiber by graphene oxide (GO) has, over, this past decade, attracted increasing attention as an effective way to improve the adhesion to polymer matrices and enhance the composite properties. In particular, the GO-functionalized 30 vol% curaua fiber (Ananas Erectifolius) reinforcing epoxy composite was found to display superior tensile and thermogravimetric properties as well as higher fiber/matrix interfacial shear strength. In this brief report, dynamic mechanical analysis (DMA) was conducted in up to 50 vol% GO-functionalized curaua fiber reinforced epoxy matrix (EM) composites. The objective was not only to extend the amount incorporated but also for the first time investigate the composite viscoelastic behavior. The GO functionalization of curaua fibers (GOCF) improved the DMA storage (E′) and loss (E″) modulus compared to the non-functionalized fiber composites. Values at 30 °C of both E′ (13.44 GPa) and E″ (0.67 GPa) for 50 vol% GO-functionalized curaua fiber reinforced epoxy matrix composites (50GOCF/EM) were substantially higher than those of 20 GOCF/EM with E′ (7.08 GPa) and E″ (0.22 GPa) as well as non-functionalized 50CF/EM with E′ (11.04 GPa) and E″ (0.45 GPa). All these results are above the neat epoxy previously reported values of E′ (3.86 GPa) and E″ (0.09 GPa). As for the tangent delta, the parameters associated with damping factor and glass transition temperature were not found to be significantly changed by GO functionalization, but decreased with respect to the neat epoxy due to chain mobility restriction. Full article

(This article belongs to the Section Polymer Applications)

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26 pages, 2180 KiB

Open AccessEditor’s ChoiceReview

Closing the Loop with Keratin-Rich Fibrous Materials

by Simona Perța-Crișan, Claudiu Ștefan Ursachi, Simona Gavrilaș, Florin Oancea and Florentina-Daniela Munteanu

Polymers 2021, 13(11), 1896; https://doi.org/10.3390/polym13111896 - 7 Jun 2021

Cited by 25 | Viewed by 8129

Abstract

One of the agro-industry’s side streams that is widely met is the-keratin rich fibrous material that is becoming a waste product without valorization. Its management as a waste is costly, as the incineration of this type of waste constitutes high environmental concern. Considering [...] Read more.

One of the agro-industry’s side streams that is widely met is the-keratin rich fibrous material that is becoming a waste product without valorization. Its management as a waste is costly, as the incineration of this type of waste constitutes high environmental concern. Considering these facts, the keratin-rich waste can be considered as a treasure for the producers interested in the valorization of such slowly-biodegradable by-products. As keratin is a protein that needs harsh conditions for its degradation, and that in most of the cases its constitutive amino acids are destroyed, we review new extraction methods that are eco-friendly and cost-effective. The chemical and enzymatic extractions of keratin are compared and the optimization of the extraction conditions at the lab scale is considered. In this study, there are also considered the potential applications of the extracted keratin as well as the reuse of the by-products obtained during the extraction processes. Full article

(This article belongs to the Special Issue Renaissance of Fibers and Fibrous Materials)

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15 pages, 690 KiB

Open AccessArticle

Viscoelastic Properties of Cell Structures Manufactured Using a Photo-Curable Additive Technology—PJM

by Tomasz Kozior and Czesław Kundera

Polymers 2021, 13(11), 1895; https://doi.org/10.3390/polym13111895 - 7 Jun 2021

Cited by 18 | Viewed by 2685

Abstract

This research paper reviews the test results involving viscoelastic properties of cellular structure models made with the PolyJet Matrix—PJM additive technology. The designed test specimens were of complex cellular structure and made of three various photo-curable polymer resin types. Materials were selected taking [...] Read more.

This research paper reviews the test results involving viscoelastic properties of cellular structure models made with the PolyJet Matrix—PJM additive technology. The designed test specimens were of complex cellular structure and made of three various photo-curable polymer resin types. Materials were selected taking into account the so-called “soft” and “tough” material groups. Compressive stress relaxation tests were conducted in accordance with the recommendations of standard ISO 3384, and the impact of the geometric structure shape and material selection on viscoelastic properties, as well as the most favorable geometric variants of the tested cellular structure models were determined. Mathematica and Origin software was used to conduct a statistical analysis of the test results and determine five-parameter functions approximating relaxation curves. The most favorable rheological was adopted and its mean parameters determined, which enables to match both printed model materials and their geometry in the future, to make a component with a specific rheological response. Furthermore, the test results indicated that there was a possibility of modelling cellular structures within the PJM technology, using support material as well. Full article

(This article belongs to the Special Issue 3D/4D Printing in Advanced Robotics Systems)

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12 pages, 5765 KiB

Open AccessArticle

Effect of Oxidation Time on the Properties of Cellulose Nanocrystals Prepared from Balsa and Kapok Fibers Using Ammonium Persulfate

by Marwanto Marwanto, Muhammad Iqbal Maulana, Fauzi Febrianto, Nyoman Jaya Wistara, Siti Nikmatin, Nanang Masruchin, Lukmanul Hakim Zaini, Seung-Hwan Lee and Nam-Hun Kim

Polymers 2021, 13(11), 1894; https://doi.org/10.3390/polym13111894 - 7 Jun 2021

Cited by 16 | Viewed by 3771

Abstract

This study aimed to evaluate the effect of ammonium persulfate’s (APS) oxidation time on the characteristics of the cellulose nanocrystals (CNCs) of balsa and kapok fibers after delignification pretreatment with sodium chlorite/acetic acid. This two-step method is important for increasing the zeta potential [...] Read more.

This study aimed to evaluate the effect of ammonium persulfate’s (APS) oxidation time on the characteristics of the cellulose nanocrystals (CNCs) of balsa and kapok fibers after delignification pretreatment with sodium chlorite/acetic acid. This two-step method is important for increasing the zeta potential value and achieving higher thermal stability. The fibers were partially delignified using acidified sodium chlorite for four cycles, followed by APS oxidation at 60 °C for 8, 12, and 16 h. The isolated CNCs with a rod-like structure showed an average diameter in the range of 5.5–12.6 nm and an aspect ratio of 14.7–28.2. Increasing the reaction time resulted in a gradual reduction in the CNC dimensions. The higher surface charge of the balsa and kapok CNCs was observed at a longer oxidation time. The CNCs prepared from kapok had the highest colloid stability after oxidation for 16 h (−62.27 mV). The CNCs with higher crystallinity had longer oxidation times. Thermogravimetric analysis revealed that the CNCs with a higher thermal stability had longer oxidation times. All of the parameters were influenced by the oxidation time. This study indicates that APS oxidation for 8–16 h can produce CNCs from delignified balsa and kapok with satisfactory zeta potential values and thermal stabilities. Full article

(This article belongs to the Special Issue Manufacturing and Testing of Polymer Composites)

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14 pages, 3483 KiB

Open AccessArticle

Isolation and Characterization of Alpha and Nanocrystalline Cellulose from Date Palm (Phoenix dactylifera L.) Trunk Mesh

by Hamid M. Shaikh, Arfat Anis, Anesh Manjaly Poulose, Saeed M. Al-Zahrani, Niyaz Ahamad Madhar, Abdullah Alhamidi and Mohammad Asif Alam

Polymers 2021, 13(11), 1893; https://doi.org/10.3390/polym13111893 - 7 Jun 2021

Cited by 49 | Viewed by 6111

Abstract

Highly pure cellulosic polymers obtained from waste lignocellulose offer great potential for designing novel materials in the concept of biorefinery. In this work, alpha-cellulose and nanocrystalline cellulose were isolated from the date palm trunk mesh (DPTM) through a series of physicochemical treatments. Supercritical [...] Read more.

Highly pure cellulosic polymers obtained from waste lignocellulose offer great potential for designing novel materials in the concept of biorefinery. In this work, alpha-cellulose and nanocrystalline cellulose were isolated from the date palm trunk mesh (DPTM) through a series of physicochemical treatments. Supercritical carbon dioxide treatment was used to remove soluble extractives, and concentrated alkali pretreatment was used to eliminate the lignin portion selectively to obtain alpha-cellulose in approximately 94% yield. Further treatments of this cellulose yielded nanocrystalline cellulose. The structure–property relationship studies were carried out by characterizing the obtained polymers by various standard methods and analytical techniques such as Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), energy dispersive X-ray diffraction (EDX-XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Almost 65% yield of pure cellulose was achieved, out of which 94% is the alpha-cellulose. This cellulose shows good thermal stability and crystallinity. The microscopic analysis of the nanocellulose showed a heterogeneous mix of irregular-shaped particles with a size range of 20–60 nm. The percentage crystallinity of alpha-cellulose and nanocellulose was found to be 68.9 and 71.8, respectively. Thus, this study shows that, this DPTM-based low-cost waste biomass can be a potential source to obtain cellulose and nano-cellulose. Full article

(This article belongs to the Special Issue Functional Natural-Based Polymers)

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19 pages, 4517 KiB

Open AccessArticle

Synthesis and Characterization of β-Cyclodextrin-Essential Oil Inclusion Complexes for Tick Repellent Development

by Jennifer Hogenbom, Alysson Jones, Haozhe Vincent Wang, Laura Jane Pickett and Nicoletta Faraone

Polymers 2021, 13(11), 1892; https://doi.org/10.3390/polym13111892 - 7 Jun 2021

Cited by 20 | Viewed by 4988

Abstract

Essential oils (EOs) are used in several pest management applications. Due to their volatility, EOs may experience bioactivity reduction, thus requiring protection to extend their properties. In the present study, we investigated the inclusion complex formation (IC) of β-cyclodextrin (β-CD) with selected EOs [...] Read more.

Essential oils (EOs) are used in several pest management applications. Due to their volatility, EOs may experience bioactivity reduction, thus requiring protection to extend their properties. In the present study, we investigated the inclusion complex formation (IC) of β-cyclodextrin (β-CD) with selected EOs with known tick repellent activity using two co-precipitation methods. ICs were characterized by evaluating EO mass concentration and inclusion efficiency (% IE) and other instrumental methods. Co-precipitation method 2 yielded the highest EO mass concentration (88 ± 6 μg/mg β-CD) for the 1:1 molar ratio geranium Egyptian EO IC. The EO volatile release over time from the ICs was investigated by headspace SPME/GC-MS analysis. ICs were also tested in tick repellency bioassays. ICs reported significant tick repellent activity, with lemongrass IC performing best overall. Method 1 showed the best combination of high mass concentration EO, controlled volatile release, and tick repellency with lemongrass EO. The results demonstrated that β-CD had selectively encapsulated different EOs. Moreover, the formation of ICs may improve EO tick repellent properties protecting the active ingredients and providing a better, long-lasting repellent action. These findings will allow the development of more effective naturally derived repellent products to protect individuals from tick bites and prevent tick-borne illnesses. Full article

(This article belongs to the Special Issue Biopolymers: Recent Progress and New Perspectives II)

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19 pages, 5349 KiB

Open AccessArticle

Preparation of Chitosan/Calcium Alginate/Bentonite Composite Hydrogel and Its Heavy Metal Ions Adsorption Properties

by Zongkun Lin, Yuru Yang, Zizhan Liang, Lei Zeng and Aiping Zhang

Polymers 2021, 13(11), 1891; https://doi.org/10.3390/polym13111891 - 7 Jun 2021

Cited by 73 | Viewed by 6214

Abstract

In order to avoid the secondary pollution of the toxic residue of chemical crosslinking agent accompanied by chemical hydrogel adsorbent and enhance the adsorption performance of physical hydrogel, chitosan/calcium alginate/bentonite (CTS/CA/BT) composite physical hydrogel was constructed. The formation mechanism and structure of the [...] Read more.

In order to avoid the secondary pollution of the toxic residue of chemical crosslinking agent accompanied by chemical hydrogel adsorbent and enhance the adsorption performance of physical hydrogel, chitosan/calcium alginate/bentonite (CTS/CA/BT) composite physical hydrogel was constructed. The formation mechanism and structure of the composite hydrogel were determined by FTIR, XRD and SEM. Adsorption performances of the hydrogel toward Pb²⁺, Cu²⁺ and Cd²⁺ in water under different condition as well as multi-ion competitive sorption were investigated. The adsorption processes were described with the canonical adsorption kinetics and isotherms models. With the utilization of XPS analysis and adsorption thermodynamics analysis, it was found that the adsorptions were spontaneous physico-chemical adsorptions. The results showed that the maximum adsorption capacity of the hydrogel for Pb²⁺, Cu²⁺ and Cd²⁺ reached up to 434.89, 115.30 and 102.38 mg·g⁻¹, respectively, better than those of other physical hydrogels or chitosan/bentonite composite. Moreover, the composite hydrogel improved the collectability of bentonite and showed a good reusability. The modification of bentonite and the formation of hydrogel were completed simultaneously, which greatly simplifies the operation process compared with the prior similar works. These suggest that the CTS/CA/BT composite hydrogel has promising application prospects for removal of heavy metal ions from water. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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11 pages, 2854 KiB

Open AccessArticle

Polyethyleneimine-Oleic Acid Micelles-Stabilized Palladium Nanoparticles as Highly Efficient Catalyst to Treat Pollutants with Enhanced Performance

by Xiang Lai, Xuan Zhang, Shukai Li, Jie Zhang, Weifeng Lin and Longgang Wang

Polymers 2021, 13(11), 1890; https://doi.org/10.3390/polym13111890 - 6 Jun 2021

Cited by 4 | Viewed by 2704

Abstract

Water soluble organic molecular pollution endangers human life and health. It becomes necessary to develop highly stable noble metal nanoparticles without aggregation in solution to improve their catalytic performance in treating pollution. Polyethyleneimine (PEI)-based stable micelles have the potential to stabilize noble metal [...] Read more.

Water soluble organic molecular pollution endangers human life and health. It becomes necessary to develop highly stable noble metal nanoparticles without aggregation in solution to improve their catalytic performance in treating pollution. Polyethyleneimine (PEI)-based stable micelles have the potential to stabilize noble metal nanoparticles due to the positive charge of PEI. In this study, we synthesized the amphiphilic PEI-oleic acid molecule by acylation reaction. Amphiphilic PEI-oleic acid assembled into stable PEI-oleic acid micelles with a hydrodynamic diameter of about 196 nm and a zeta potential of about 34 mV. The PEI-oleic acid micelles-stabilized palladium nanoparticles (PO-PdNPs_n) were prepared by the reduction of sodium tetrachloropalladate using NaBH₄ and the palladium nanoparticles (PdNPs) were anchored in the hydrophilic layer of the micelles. The prepared PO-PdNPs_n had a small size for PdNPs and good stability in solution. Noteworthily, PO-PdNPs₁₅₀ had the highest catalytic activity in reducing 4-nitrophenol (4-NP) (K_nor = 18.53 s⁻¹mM⁻¹) and oxidizing morin (K_nor = 143.57 s⁻¹M⁻¹) in aqueous solution than other previous catalysts. The enhanced property was attributed to the improving the stability of PdNPs by PEI-oleic acid micelles. The method described in this report has great potential to prepare many kinds of stable noble metal nanoparticles for treating aqueous pollution. Full article

(This article belongs to the Special Issue Function of Polymers in Encapsulation Process)

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24 pages, 6777 KiB

Open AccessReview

Toward Application of Liquid Crystalline Elastomer for Smart Robotics: State of the Art and Challenges

by Dandan Sun, Juzhong Zhang, Hongpeng Li, Zhengya Shi, Qi Meng, Shuiren Liu, Jinzhou Chen and Xuying Liu

Polymers 2021, 13(11), 1889; https://doi.org/10.3390/polym13111889 - 6 Jun 2021

Cited by 42 | Viewed by 8059

Abstract

Liquid crystalline elastomers (LCEs) are lightly crosslinked polymers that combine liquid crystalline order and rubber elasticity. Owing to their unique anisotropic behavior and reversible shape responses to external stimulation (temperature, light, etc.), LCEs have emerged as preferred candidates for actuators, artificial muscles, sensors, [...] Read more.

Liquid crystalline elastomers (LCEs) are lightly crosslinked polymers that combine liquid crystalline order and rubber elasticity. Owing to their unique anisotropic behavior and reversible shape responses to external stimulation (temperature, light, etc.), LCEs have emerged as preferred candidates for actuators, artificial muscles, sensors, smart robots, or other intelligent devices. Herein, we discuss the basic action, control mechanisms, phase transitions, and the structure–property correlation of LCEs; this review provides a comprehensive overview of LCEs for applications in actuators and other smart devices. Furthermore, the synthesis and processing of liquid crystal elastomer are briefly discussed, and the current challenges and future opportunities are prospected. With all recent progress pertaining to material design, sophisticated manipulation, and advanced applications presented, a vision for the application of LCEs in the next generation smart robots or automatic action systems is outlined. Full article

(This article belongs to the Section Smart and Functional Polymers)

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13 pages, 5426 KiB

Open AccessArticle

Non-Woven Fabrics Based on Nanocomposite Nylon 6/ZnO Obtained by Ultrasound-Assisted Extrusion for Improved Antimicrobial and Adsorption Methylene Blue Dye Properties

by M. Andrade-Guel, C. A. Ávila-Orta, C. Cabello-Alvarado, G. Cadenas-Pliego, S. C. Esparza-González, M. Pérez-Alvarez and Z. V. Quiñones-Jurado

Polymers 2021, 13(11), 1888; https://doi.org/10.3390/polym13111888 - 6 Jun 2021

Cited by 10 | Viewed by 3979

Abstract

Approximately 200,000 tons of water contaminated with dyes are discharged into effluents annually, which in addition to infectious diseases constitute problems that afflict the population worldwide. This study evaluated the mechanical properties, surface structure, antimicrobial performance, and methylene blue dye-contaminant adsorption using the [...] Read more.

Approximately 200,000 tons of water contaminated with dyes are discharged into effluents annually, which in addition to infectious diseases constitute problems that afflict the population worldwide. This study evaluated the mechanical properties, surface structure, antimicrobial performance, and methylene blue dye-contaminant adsorption using the non-woven fabrics manufactured by melt-blowing. The non-woven fabrics are composed of nylon 6 (Ny 6) and zinc oxide nanoparticles (ZnO NPs). The polymer nanocomposites were previously fabricated using variable frequency ultrasound assisted-melt-extrusion to be used in melt-blowing. Energy dispersion spectroscopy (SEM-EDS) images showed a homogeneous dispersion of the ZnO nanoparticles in nylon 6. The mechanical properties of the composites increased by adding ZnO compared to the nylon 6 matrix, and sample Ny/ZnO 0.5 showed the best mechanical performance. All fabric samples exhibited antimicrobial activity against S. aureus and fungus C. albicans, and the incorporation of ZnO nanoparticles significantly improved this property compared to pure nylon 6. The absorption efficiency of methylene blue (MB), during 60 min, for the samples Ny/ZnO 0.05 and Ny/ZnO 0.25 wt%, were 93% and 65%, respectively. The adsorption equilibrium data obeyed the Langmuir isotherm. Full article

(This article belongs to the Special Issue Polymer Nanocomposites for the Removal of Pollutants from Contaminated Water)

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13 pages, 2441 KiB

Open AccessArticle

A Hybrid Methodology to Minimize Freshwater Consumption during Shrimp Shell Waste Valorization Combining Multi-Contaminant Pinch Analysis and Superstructure Optimization

by Viviana Quintero, Arturo Gonzalez-Quiroga and Angel Darío Gonzalez-Delgado

Polymers 2021, 13(11), 1887; https://doi.org/10.3390/polym13111887 - 6 Jun 2021

Cited by 2 | Viewed by 2376

Abstract

The conservation and proper management of natural resources constitute one of the main objectives of the 2030 Agenda for Sustainable Development designed by the Member States of the United Nations. In this work, a hybrid strategy based on process integration is proposed to [...] Read more.

The conservation and proper management of natural resources constitute one of the main objectives of the 2030 Agenda for Sustainable Development designed by the Member States of the United Nations. In this work, a hybrid strategy based on process integration is proposed to minimize freshwater consumption while reusing wastewater. As a novelty, the strategy included a heuristic approach for identifying the minimum consumption of freshwater with a preliminary design of the water network, considering the concept of reuse and multiple pollutants. Then, mathematical programming techniques were applied to evaluate the possibilities of regeneration of the source streams through the inclusion of intercept units and establish the optimal design of the network. This strategy was used in the shrimp shell waste process to obtain chitosan, where a minimum freshwater consumption of 277 t/h was identified, with a reuse strategy and an optimal value of US $5.5 million for the design of the water network. Full article

(This article belongs to the Special Issue Advance in Preparation and Application of Chitosan, Chitin and Their Composites)

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18 pages, 3617 KiB

Open AccessArticle

Plasma Supported Deposition of Amorphous Hydrogenated Carbon (a-C:H) on Polyamide 6: Determining Interlayer Completion and Dehydrogenation Effects during Layer Growth

by Torben Schlebrowski, Henriette Lüber, Lucas Beucher, Melanie Fritz, Youssef Benjillali, Mohammed Bentaouit, Barbara Hahn, Stefan Wehner and Christian B. Fischer

Polymers 2021, 13(11), 1886; https://doi.org/10.3390/polym13111886 - 6 Jun 2021

Cited by 5 | Viewed by 2453

Abstract

Polyamide 6 (PA6) is a commonly used material in many different sectors of modern industry. Herein, PA6 samples were coated with amorphous carbon layers (a-C:H) with increasing thickness up to 2 µm using radio frequency plasma enhanced chemical vapor deposition for surface adjustment. [...] Read more.

Polyamide 6 (PA6) is a commonly used material in many different sectors of modern industry. Herein, PA6 samples were coated with amorphous carbon layers (a-C:H) with increasing thickness up to 2 µm using radio frequency plasma enhanced chemical vapor deposition for surface adjustment. The morphology of the carbon coatings was inspected by ex situ atomic force microscopy and scanning electron microscopy. Surface wettability was checked by contact angle measurements. The chemical composition was analyzed using the surface sensitive synchrotron X-ray-based techniques near-edge X-ray absorption fine structure and X-ray photoelectron spectroscopy, supported by diffuse reflectance infrared Fourier transform spectroscopy. Particular attention was paid to the coating interval from 0 to 100 nm, to specify the interlayer thickness between the PA6 polymer and a-C:H coating, and the region between 1000 and 2000 nm, where dehydrogenation of the a-C:H layer occurs. The interlayer is decisive for the linkage of the deposited carbon layer on the polymer: the more pronounced it is, the better the adhesion. The thickness of the interlayer could be narrowed down to 40 nm in all used methods, and the dehydrogenation process takes place at a layer thickness of 1500 nm. Full article

(This article belongs to the Special Issue Polymer Dynamics: Bulk and Nanoconfined Polymers)

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23 pages, 2942 KiB

Open AccessReview

Engineering Performance of Concrete Incorporated with Recycled High-Density Polyethylene (HDPE)—A Systematic Review

by Sonali Abeysinghe, Chamila Gunasekara, Chaminda Bandara, Kate Nguyen, Ranjith Dissanayake and Priyan Mendis

Polymers 2021, 13(11), 1885; https://doi.org/10.3390/polym13111885 - 6 Jun 2021

Cited by 23 | Viewed by 6725

Abstract

Incorporating recycled plastic waste in concrete manufacturing is one of the most ecologically and economically sustainable solutions for the rapid trends of annual plastic disposal and natural resource depletion worldwide. This paper comprehensively reviews the literature on engineering performance of recycled high-density polyethylene [...] Read more.

Incorporating recycled plastic waste in concrete manufacturing is one of the most ecologically and economically sustainable solutions for the rapid trends of annual plastic disposal and natural resource depletion worldwide. This paper comprehensively reviews the literature on engineering performance of recycled high-density polyethylene (HDPE) incorporated in concrete in the forms of aggregates or fiber or cementitious material. Optimum 28-days’ compressive and flexural strength of HDPE fine aggregate concrete is observed at HDPE-10 and splitting tensile strength at HDPE-5 whereas for HDPE coarse aggregate concrete, within the range of 10% to 15% of HDPE incorporation and at HDPE-15, respectively. Similarly, 28-days’ flexural and splitting tensile strength of HDPE fiber reinforced concrete is increased to an optimum of 4.9 MPa at HDPE-3 and 4.4 MPa at HDPE-3.5, respectively, and higher than the standard/plain concrete matrix (HDPE-0) in all HDPE inclusion levels. Hydrophobicity, smooth surface texture and non-reactivity of HDPE has resulted in weaker bonds between concrete matrix and HDPE and thereby reducing both mechanical and durability performances of HDPE concrete with the increase of HDPE. Overall, this is the first ever review to present and analyze the current state of the mechanical and durability performance of recycled HDPE as a sustainable construction material, hence, advancing the research into better performance and successful applications of HDPE concrete. Full article

(This article belongs to the Special Issue Flame-Retardant Polymers and Hybrid Composites: Recycling and Circular Economy)

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23 pages, 4467 KiB

Open AccessArticle

Thermo-Mechanical and Delamination Properties in Drilling GFRP Composites by Various Drill Angles

by Usama A. Khashaba, Mohamed S. Abd-Elwahed, Mohamed A. Eltaher, Ismail Najjar, Ammar Melaibari and Khaled I. Ahmed

Polymers 2021, 13(11), 1884; https://doi.org/10.3390/polym13111884 - 6 Jun 2021

Cited by 31 | Viewed by 3709

Abstract

This manuscript aims to study the effects of drilling factors on the thermal-mechanical properties and delamination experimentally during the drilling of glass fiber reinforced polymer (GFRP). Drilling studies were carried out using a CNC machine under dry cutting conditions by 6 mm diameter [...] Read more.

This manuscript aims to study the effects of drilling factors on the thermal-mechanical properties and delamination experimentally during the drilling of glass fiber reinforced polymer (GFRP). Drilling studies were carried out using a CNC machine under dry cutting conditions by 6 mm diameter with different point angles of ∅ = 100°, 118°, and 140°. The drill spindle speed (400, 800, 1600 rpm), feed (0.025, 0.05, 0.1, 0.2 mm/r), and sample thickness (2.6, 5.3, and 7.7 mm) are considered in the analysis. Heat affected zone (HAZ) generated by drilling was measured using a thermal infrared camera and two K-thermocouples installed in the internal coolant holes of the drill. Therefore, two setups were used; the first is with a rotating drill and fixed specimen holder, and the second is with a rotating holder and fixed drill bit. To measure thrust force/torque through drilling, the Kistler dynamometer model 9272 was utilized. Pull-in and push-out delamination were evaluated based on the image analyzed by an AutoCAD technique. The regression models and multivariable regression analysis were developed to find relations between the drilling factors and responses. The results illustrate the significant relations between drilling factors and drilling responses such as thrust force, delamination, and heat affect zone. It was observed that the thrust force is more inspired by feed; however, the speed effect is more trivial and marginal on the thrust force. All machining parameters have a significant effect on the measured temperature, and the largest contribution is of the laminate thickness (33.14%), followed by speed and feed (29.00% and 15.10%, respectively), ended by the lowest contribution of the drill point angle (11.85%). Full article

(This article belongs to the Special Issue Advances in Polymer Composites)

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20 pages, 3568 KiB

Open AccessArticle

Magnetic Field Dynamic Strategies for the Improved Control of the Angiogenic Effect of Mesenchymal Stromal Cells

by Ana C. Manjua, Joaquim M. S. Cabral, Frederico Castelo Ferreira and Carla A. M. Portugal

Polymers 2021, 13(11), 1883; https://doi.org/10.3390/polym13111883 - 6 Jun 2021

Cited by 12 | Viewed by 2738

Abstract

This work shows the ability to remotely control the paracrine performance of mesenchymal stromal cells (MSCs) in producing an angiogenesis key molecule, vascular endothelial growth factor (VEGF-A), by modulation of an external magnetic field. This work compares for the first time the application [...] Read more.

This work shows the ability to remotely control the paracrine performance of mesenchymal stromal cells (MSCs) in producing an angiogenesis key molecule, vascular endothelial growth factor (VEGF-A), by modulation of an external magnetic field. This work compares for the first time the application of static and dynamic magnetic fields in angiogenesis in vitro model, exploring the effect of magnetic field intensity and dynamic regimes on the VEGF-A secretion potential of MSCs. Tissue scaffolds of gelatin doped with iron oxide nanoparticles (MNPs) were used as a platform for MSC proliferation. Dynamic magnetic field regimes were imposed by cyclic variation of the magnetic field intensity in different frequencies. The effect of the magnetic field intensity on cell behavior showed that higher intensity of 0.45 T was associated with increased cell death and a poor angiogenic effect. It was observed that static and dynamic magnetic stimulation with higher frequencies led to improved angiogenic performance on endothelial cells in comparison with a lower frequency regime. This work showed the possibility to control VEGF-A secretion by MSCs through modulation of the magnetic field, offering attractive perspectives of a non-invasive therapeutic option for several diseases by revascularizing damaged tissues or inhibiting metastasis formation during cancer progression. Full article

(This article belongs to the Special Issue Polymeric Materials as Scaffolds for Tissue Engineering)

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17 pages, 2171 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Impregnation Technique on the Release of Esomeprazole from Various Bioaerogels

by Milica Pantić, Katja Andrina Kravanja, Željko Knez and Zoran Novak

Polymers 2021, 13(11), 1882; https://doi.org/10.3390/polym13111882 - 6 Jun 2021

Cited by 12 | Viewed by 3234

Abstract

The presented study shows the possibility of using bioaerogels, namely neat alginate, pectin, chitosan aerogels, and alginate and pectin aerogels coated with chitosan, as drug delivery systems for esomeprazole. Two different techniques were used for the impregnation of esomeprazole: Supercritical impregnation, and diffusion [...] Read more.

The presented study shows the possibility of using bioaerogels, namely neat alginate, pectin, chitosan aerogels, and alginate and pectin aerogels coated with chitosan, as drug delivery systems for esomeprazole. Two different techniques were used for the impregnation of esomeprazole: Supercritical impregnation, and diffusion via ethanol during the sol-gel synthesis. The prepared samples were characterized by employing N₂ adsorption-desorption analysis, TGA/DSC, and FTIR. The achieved loadings were satisfactory for all the tested samples and showed to be dependent on the technique used for impregnation. In all cases, higher loadings were achieved when impregnation via diffusion from ethanol was used. Extensive release studies were performed for all impregnated samples. The in vitro dissolution profiles were found to be dependent on the carrier and impregnation method used. Most importantly, in all cases more controlled and delayed release was achieved with the bioaerogels compared to using pure esomeprazole. Full article

(This article belongs to the Special Issue Synthesis and Characterisation of Aerogels: Fundamentals and Applications)

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18 pages, 6474 KiB

Open AccessEditor’s ChoiceArticle

Displacement Rate Effects on the Mode II Shear Delamination Behavior of Carbon Fiber/Epoxy Composites

by Kean Ong Low, Mahzan Johar, Haris Ahmad Israr, Khong Wui Gan, Seyed Saeid Rahimian Koloor, Michal Petrů and King Jye Wong

Polymers 2021, 13(11), 1881; https://doi.org/10.3390/polym13111881 - 6 Jun 2021

Cited by 8 | Viewed by 3255

Abstract

This paper studies the influence of displacement rate on mode II delamination of unidirectional carbon/epoxy composites. End-notched flexure test is performed at displacement rates of 1, 10, 100 and 500 mm/min. Experimental results reveal that the mode II fracture toughness G_IIC increases [...] Read more.

This paper studies the influence of displacement rate on mode II delamination of unidirectional carbon/epoxy composites. End-notched flexure test is performed at displacement rates of 1, 10, 100 and 500 mm/min. Experimental results reveal that the mode II fracture toughness G_IIC increases with the displacement, with a maximum increment of 45% at 100 mm/min. In addition, scanning electron micrographs depict that fiber/matrix interface debonding is the major damage mechanism at 1 mm/min. At higher speeds, significant matrix-dominated shear cusps are observed contributing to higher G_IIC. Besides, it is demonstrated that the proposed rate-dependent model is able to fit the experimental data from the current study and the open literature generally well. The mode II fracture toughness measured from the experiment or deduced from the proposed model can be used in the cohesive element model to predict failure. Good agreement is found between the experimental and numerical results, with a maximum difference of 10%. The numerical analyses indicate crack jump occurs suddenly after the peak load is attained, which leads to the unstable crack propagation seen in the experiment. Full article

(This article belongs to the Special Issue Mechanics of Polymer and Polymer Composite Materials and Structures)

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25 pages, 7001 KiB

Open AccessArticle

Amorphous Carbon Coatings for Total Knee Replacements—Part II: Tribological Behavior

by Benedict Rothammer, Max Marian, Kevin Neusser, Marcel Bartz, Thomas Böhm, Sebastian Krauß, Stefan Schroeder, Maximilian Uhler, Simon Thiele, Benoit Merle, Jan Philippe Kretzer and Sandro Wartzack

Polymers 2021, 13(11), 1880; https://doi.org/10.3390/polym13111880 - 5 Jun 2021

Cited by 30 | Viewed by 9855

Abstract

Diamond-like carbon coatings may decrease implant wear, therefore, they are helping to reduce aseptic loosening and increase service life of total knee arthroplasties (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well [...] Read more.

Diamond-like carbon coatings may decrease implant wear, therefore, they are helping to reduce aseptic loosening and increase service life of total knee arthroplasties (TKAs). This two-part study addresses the development of such coatings for ultrahigh molecular weight polyethylene (UHMWPE) tibial inlays as well as cobalt-chromium-molybdenum (CoCr) and titanium (Ti64) alloy femoral components. While the deposition of a pure (a-C:H) and tungsten-doped hydrogen-containing amorphous carbon coating (a-C:H:W) as well as the detailed characterization of mechanical and adhesion properties were the subject of Part I, the tribological behavior is studied in Part II. Pin-on-disk tests are performed under artificial synovial fluid lubrication. Numerical elastohydrodynamic lubrication modeling is used to show the representability of contact conditions for TKAs and to assess the influence of coatings on lubrication conditions. The wear behavior is characterized by means of light and laser scanning microscopy, Raman spectroscopy, scanning electron microscopy and particle analyses. Although the coating leads to an increase in friction due to the considerably higher roughness, especially the UHMWPE wear is significantly reduced up to a factor of 49% (CoCr) and 77% (Ti64). Thereby, the coating shows continuous wear and no sudden failure or spallation of larger wear particles. This demonstrated the great potential of amorphous carbon coatings for knee replacements. Full article

(This article belongs to the Special Issue Polymer-Based Biocompatible System)

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17 pages, 11505 KiB

Open AccessArticle

Air Permeability, Shock Absorption Ability, and Flexural Strength of 3D-Printed Perforated ABS Polymer Sheets with 3D-Knitted Fabric Cushioning for Sports Face Guard Applications

by Thet Khaing Aung, Hiroshi Churei, Gen Tanabe, Rio Kinjo, Kaito Togawa, Chenyuan Li, Yumi Tsuchida, Phyu Sin Tun, Shwe Hlaing, Hidekazu Takahashi and Toshiaki Ueno

Polymers 2021, 13(11), 1879; https://doi.org/10.3390/polym13111879 - 5 Jun 2021

Cited by 5 | Viewed by 3730 | Correction

Abstract

Sports face guards (FGs) are devices that protect athletes from maxillofacial injury or ensure rapid return to play following orofacial damage. Conventional FGs are uncomfortable to wear owing to stuffiness caused by poor ventilation and often slip off due to increase in weight [...] Read more.

Sports face guards (FGs) are devices that protect athletes from maxillofacial injury or ensure rapid return to play following orofacial damage. Conventional FGs are uncomfortable to wear owing to stuffiness caused by poor ventilation and often slip off due to increase in weight due to absorption of moisture from perspiration, lowering players’ performance. Herein, combinations of 3D-printed perforated acrylonitrile butadiene styrene (ABS) polymer sheets and 3D-knitted fabrics with honeycomb structures as cushioning materials were investigated to balance better wearing feel and mechanical properties. The flexural strength, weight, and shock absorption ability of, and air flow rate through, the ABS sheets with five different perforation patterns were evaluated and compared with those of conventional FG materials comprising a combination of polycaprolactone sheets for the medical splint and polychloroprene rubber for the cushioning material. The ABS sheets having 10% open area and 2.52 mm round holes, combined with knitted fabric cushioning, exhibited the requisite shock absorbing, higher air permeability, and lower weight properties than the conventional materials. Our results suggest that FGs fabricated using combinations of 3D-printed perforated ABS polymer sheets and 3D-knitted fabrics with honeycomb structures may impart enhanced wearing comfort for athletes. Full article

(This article belongs to the Collection Progress in Polymer Applications)

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11 pages, 2267 KiB

Open AccessArticle

Impact and Tensile Properties of Polyester Nanocomposites Reinforced with Conifer Fiber Cellulose Nanocrystal: A Previous Study Extension

by Grazielle da Silva Maradini, Michel Picanço Oliveira, Lilian Gasparelli Carreira, Damaris Guimarães, Demetrius Profeti, Ananias Francisco Dias Júnior, Walter Torezani Neto Boschetti, Bárbara Ferreira de Oliveira, Artur Camposo Pereira and Sergio Neves Monteiro

Polymers 2021, 13(11), 1878; https://doi.org/10.3390/polym13111878 - 5 Jun 2021

Cited by 12 | Viewed by 3028

Abstract

In a recent paper, novel polyester nanocomposites reinforced with up to 3 wt% of cellulose nanocrystals (CNCs) extracted from conifer fiber were characterized for their crystallinity index, water absorption, and flexural and thermal resistance. The use of this novel class of nanocomposites as [...] Read more.

In a recent paper, novel polyester nanocomposites reinforced with up to 3 wt% of cellulose nanocrystals (CNCs) extracted from conifer fiber were characterized for their crystallinity index, water absorption, and flexural and thermal resistance. The use of this novel class of nanocomposites as a possible substitute for conventional glass fiber composites (fiberglass) was then suggested, especially for the 1 and 2 wt% CNC composites due to promising bending, density, and water absorption results. However, for effective engineering applications requiring impact and tensile performance, the corresponding properties need to be evaluated. Therefore, this extension of the previous work presents additional results on Izod and tensile tests of 1 and 2 wt% CNC-reinforced polyester composites, together with a comparative cost analysis with fiberglass. The chemical effect caused by incorporation of CNCs into polyester was also investigated by FTIR. In comparison to the neat polyester, the Izod impact energy increased 50% and 16% for the 1 and 2 wt% composites, respectively. On the other hand, the tensile strength and Young’s modulus remained constant within the ANOVA statistical analysis. FTIR analysis failed to reveal any chemical modification caused by up to 2 wt% CNC incorporation. The present impact and tensile results corroborate the promising substitution of a polyester composite reinforced with very low amount of CNCs for common fiberglass in engineering application. Full article

(This article belongs to the Section Polymer Applications)

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15 pages, 2080 KiB

Open AccessArticle

Effect of Photoinitiator on Precursory Stability and Curing Depth of Thiol-Ene Clickable Gelatin

by Kai-Hung Yang, Gabriella Lindberg, Bram Soliman, Khoon Lim, Tim Woodfield and Roger J. Narayan

Polymers 2021, 13(11), 1877; https://doi.org/10.3390/polym13111877 - 5 Jun 2021

Cited by 27 | Viewed by 5138

Abstract

Recent advances highlight the potential of photopolymerizable allylated gelatin (GelAGE) as a versatile hydrogel with highly tailorable properties. It is, however, unknown how different photoinitiating system affects the stability, gelation kinetics and curing depth of GelAGE. In this study, sol fraction, mass swelling [...] Read more.

Recent advances highlight the potential of photopolymerizable allylated gelatin (GelAGE) as a versatile hydrogel with highly tailorable properties. It is, however, unknown how different photoinitiating system affects the stability, gelation kinetics and curing depth of GelAGE. In this study, sol fraction, mass swelling ratio, mechanical properties, rheological properties, and curing depth were evaluated as a function of time with three photo-initiating systems: Irgacure 2959 (Ig2959; 320–500 nm), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP; 320–500 nm), and ruthenium/sodium persulfate (Ru/SPS; 400–500 nm). Results demonstrated that GelAGE precursory solutions mixed with either Ig2959 or LAP remained stable over time while the Ru/SPS system enabled the onset of controllable redox polymerization without irradiation during pre-incubation. Photo-polymerization using the Ru/SPS system was significantly faster (<5 s) compared to both Ig2959 (70 s) and LAP (50 s). Plus, The Ru/SPS system was capable of polymerizing a thick construct (8.88 ± 0.94 mm), while Ig2959 (1.62 ± 0.49 mm) initiated hydrogels displayed poor penetration depth with LAP (7.38 ± 2.13 mm) in between. These results thus support the use of the visible light based Ru/SPS photo-initiator for constructs requiring rapid gelation and a good curing depth while Ig2959 or LAP can be applied for photo-polymerization of GelAGE materials requiring long-term incubation prior to application if UV is not a concern. Full article

(This article belongs to the Special Issue Rheology of Bio-Based Polymeric Materials)

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10 pages, 4028 KiB

Open AccessArticle

An Experimental Investigation of Viscoelastic Flow in a Contraction Channel

by Wei Wang and Linlin Wang

Polymers 2021, 13(11), 1876; https://doi.org/10.3390/polym13111876 - 4 Jun 2021

Cited by 6 | Viewed by 2156

Abstract

In order to assess the predictive capability of the S–MDCPP model, which may describe the viscoelastic behavior of the low-density polyethylene melts, a planar contraction flow benchmark problem is calculated in this investigation. A pressure-stabilized iterative fractional step algorithm based on the finite [...] Read more.

In order to assess the predictive capability of the S–MDCPP model, which may describe the viscoelastic behavior of the low-density polyethylene melts, a planar contraction flow benchmark problem is calculated in this investigation. A pressure-stabilized iterative fractional step algorithm based on the finite increment calculus (FIC) method is adopted to overcome oscillations of the pressure field due to the incompressibility of fluids. The discrete elastic viscous stress splitting (DEVSS) technique in combination with the streamline upwind Petrov-Galerkin (SUPG) method are employed to calculate the viscoelastic flow. The equal low-order finite elements interpolation approximations for velocity-pressure-stress variables can be applied to calculate the viscoelastic contraction flows for LDPE melts. The predicted velocities agree well with the experimental results of particle imagine velocity (PIV) method, and the pattern of principal stress difference calculated by the S-MDCPP model has good agreement with the results measured by the flow induced birefringence (FIB) device. Numerical and experimental results show that the S-MDCPP model is capable of accurately capturing the rheological behaviors of branched polymers in complex flow. Full article

(This article belongs to the Special Issue Structural Rheology of Polymer Melts, Solutions and Compositions on Their Base)

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17 pages, 25180 KiB

Open AccessArticle

Study of Polyvinyl Alcohol-SiO₂ Nanoparticles Polymeric Membrane in Wastewater Treatment Containing Zinc Ions

by Simona Căprărescu, Cristina Modrogan, Violeta Purcar, Annette Madelene Dăncilă and Oanamari Daniela Orbuleț

Polymers 2021, 13(11), 1875; https://doi.org/10.3390/polym13111875 - 4 Jun 2021

Cited by 29 | Viewed by 3821

Abstract

The main goal of the present paper was to synthesize the polyvinyl alcohol-SiO₂ nanoparticles polymeric membrane by wet-phase inversion method. The efficiency of prepared membranes (without and with SiO₂) was investigated using a versatile laboratory electrodialysis system filled with simulated [...] Read more.

The main goal of the present paper was to synthesize the polyvinyl alcohol-SiO₂ nanoparticles polymeric membrane by wet-phase inversion method. The efficiency of prepared membranes (without and with SiO₂) was investigated using a versatile laboratory electrodialysis system filled with simulated wastewaters that contain zinc ions. All experiments were performed at following conditions: the applied voltage at electrodes of 5, 10 and 15 V, a concentration of zinc ions solution of 2 g L⁻¹, time for each test of 1 h and at room temperature. The demineralization rate, extraction percentage of zinc ions, current efficiency and energy consumption were determined. The polymeric membranes were characterized by Fourier Transforms Infrared Spectroscopy-Attenuated Total Reflection (FTIR-ATR), Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). The higher value of percentage removal of zinc ions (over 65%) was obtained for the polymeric membrane with SiO₂ nanoparticles, at 15 V. The FTIR-ATR spectra show a characteristic peak located at ~1078 cm⁻¹ assigned to the Si-O-Si asymmetrical stretching. SEM images of the polymeric membrane with SiO₂ nanoparticles show that the nanoparticles and polymer matrix were well compatible. The impedance results indicated that the SiO₂ nanoparticles induced the higher proton conductivity. The final polymeric membranes can be used for the removal of various metallic ions, dyes, organic or inorganic colloids, bacteria or other microorganisms from different natural waters and wastewaters. Full article

(This article belongs to the Special Issue Advanced Polymer Membranes)

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21 pages, 3659 KiB

Open AccessReview

Silica Containing Composite Anion Exchange Membranes by Sol–Gel Synthesis: A Short Review

by Emanuela Sgreccia, Riccardo Narducci, Philippe Knauth and Maria Luisa Di Vona

Polymers 2021, 13(11), 1874; https://doi.org/10.3390/polym13111874 - 4 Jun 2021

Cited by 12 | Viewed by 4256

Abstract

This short review summarizes the literature on composite anion exchange membranes (AEM) containing an organo-silica network formed by sol–gel chemistry. The article covers AEM for diffusion dialysis (DD), for electrochemical energy technologies including fuel cells and redox flow batteries, and for electrodialysis. By [...] Read more.

This short review summarizes the literature on composite anion exchange membranes (AEM) containing an organo-silica network formed by sol–gel chemistry. The article covers AEM for diffusion dialysis (DD), for electrochemical energy technologies including fuel cells and redox flow batteries, and for electrodialysis. By applying a vast variety of organically modified silica compounds (ORMOSIL), many composite AEM reported in the last 15 years are based on poly (vinylalcohol) (PVA) or poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) used as polymer matrix. The most stringent requirements are high permselectivity and water flux for DD membranes, while high ionic conductivity is essential for electrochemical applications. Furthermore, the alkaline stability of AEM for fuel cell applications remains a challenging problem that is not yet solved. Possible future topics of investigation on composite AEM containing an organo-silica network are also discussed. Full article

(This article belongs to the Special Issue Polymeric Materials for Fuel Cell Applications)

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19 pages, 1973 KiB

Open AccessArticle

One-Year Clinical Performance of the Fast-Modelling Bulk Technique and Composite-Up Layering Technique in Class I Cavities

by Louis Hardan, Layla Sidawi, Murad Akhundov, Rim Bourgi, Maroun Ghaleb, Sarah Dabbagh, Krzysztof Sokolowski, Carlos Enrique Cuevas-Suárez and Monika Lukomska-Szymanska

Polymers 2021, 13(11), 1873; https://doi.org/10.3390/polym13111873 - 4 Jun 2021

Cited by 9 | Viewed by 4564

Abstract

The aim of this study was to assess the one year clinical performance of a new application method, the Fast-Modelling Bulk Technique (FMBT), in comparison to the Composite-Up Layering Technique (CULT) in posterior cavities. Thirty patients with two class I cavities on permanent [...] Read more.

The aim of this study was to assess the one year clinical performance of a new application method, the Fast-Modelling Bulk Technique (FMBT), in comparison to the Composite-Up Layering Technique (CULT) in posterior cavities. Thirty patients with two class I cavities on permanent human molars were enrolled in the present study. A total of sixty class I cavities were prepared and randomly divided according to the restoration technique used: 30 cavities restored by incremental layering technique and modelling of the last layer with Composite-Up Technique (CUT) using the composite Filtek Z250XT (3M ESPE; St. Paul, MN, USA) and the other 30 restored by Bulk Filling technique and modelling of the last layer by Fast-Modelling Technique (FMT) using the composite Filtek Bulk Fill Posterior Restorative (3M ESPE; St. Paul, MN, USA). Restorations were evaluated for up to one year by two observers according to Federation Dentaire Internationale (FDI) criteria, through clinical and radiological exams. Exact Fisher tests were used for statistical analysis. (p ≤ 0.05). From a biological perspective, at baseline, teeth restored with both techniques did not reveal any postoperative sensitivity. However, with time, FMBT showed less postoperative sensitivity and therefore more desirable results than CULT with a nonsignificant difference after one year (p > 0.05). Concerning secondary caries, fracture of the material, and marginal adaptation, no significant difference was noted between both techniques (p > 0.05). Regarding marginal staining, CULT resulted in more staining with a significant difference, as compared to FMBT (p < 0.05). Upon radiological examination, FMBT showed a good marginal fit during the first year, whereas CULT showed small empty voids from baseline with a nonsignificant difference (p = 1.00). After one year of clinical function, both techniques showed promising results. The present study indicates that the new FMBT could have a positive effect on the marginal staining of resin composite. Full article

(This article belongs to the Special Issue Design of Monomers and Polymers with Dental Applications: Dental Composites and Adhesives)

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21 pages, 6673 KiB

Open AccessArticle

Biodegradable Polymeric Foams Based on Modified Castor Oil, Styrene, and Isobornyl Methacrylate

by James Anthony Dicks and Chris Woolard

Polymers 2021, 13(11), 1872; https://doi.org/10.3390/polym13111872 - 4 Jun 2021

Cited by 6 | Viewed by 3098

Abstract

The environmental issues of petroleum-derived polymeric foams have necessitated seeking renewable alternatives. This work aims to prepare renewable free-radically polymerized polymeric foams with the ability to biodegrade. Furthermore, this work attempted to incorporate a bio-based reactive diluent, which has not been reported in [...] Read more.

The environmental issues of petroleum-derived polymeric foams have necessitated seeking renewable alternatives. This work aims to prepare renewable free-radically polymerized polymeric foams with the ability to biodegrade. Furthermore, this work attempted to incorporate a bio-based reactive diluent, which has not been reported in the literature. The synthesis of maleated castor oil glycerides was performed with products analyzed by Fourier transform infrared spectrometry using attenuated total reflection (ATR-FTIR) and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. Polymeric foams were prepared using maleated castor oil glycerides via free radical copolymerization with styrene and isobornyl methacrylate as reactive diluents. Scanning electron microscopy (SEM) was used to determine anisotropic macrocellular morphology, with log-normal cell diameter distributions. The compressive mechanical and energy absorption properties were investigated; the polymeric foams displayed Young’s modulus up to 26.85 ± 1.07 MPa and strength up to 1.11 ± 0.021 MPa using styrene as the reactive diluent, and Young’s modulus up to 1.38 ± 0.055 MPa and strength up to 0.088 MPa when incorporating isobornyl methacrylate. Furthermore, a thorough analysis of the cellular structure–property relationships was performed, indicating relationships to cell diameter, cell wall thickness and apparent density. The polymeric foams displayed rapid mass loss in an aerobic soil environment with multiple erosion sites revealed by SEM. In conclusion, renewable polymeric foams with excellent compressive properties were achieved using styrene as reactive diluent, but the incorporation of isobornyl methacrylate decreased strength-related properties. Full article

(This article belongs to the Special Issue Polymeric Foams II)

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13 pages, 3801 KiB

Open AccessArticle

Magnetic Superporous Poly(2-hydroxyethyl methacrylate) Hydrogel Scaffolds for Bone Tissue Engineering

by Beata A. Zasońska, Antonín Brož, Miroslav Šlouf, Jiří Hodan, Eduard Petrovský, Helena Hlídková and Daniel Horák

Polymers 2021, 13(11), 1871; https://doi.org/10.3390/polym13111871 - 4 Jun 2021

Cited by 10 | Viewed by 2939

Abstract

Magnetic maghemite (γ-Fe₂O₃) nanoparticles obtained by a coprecipitation of iron chlorides were dispersed in superporous poly(2-hydroxyethyl methacrylate) scaffolds containing continuous pores prepared by the polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) in the presence of ammonium oxalate [...] Read more.

Magnetic maghemite (γ-Fe₂O₃) nanoparticles obtained by a coprecipitation of iron chlorides were dispersed in superporous poly(2-hydroxyethyl methacrylate) scaffolds containing continuous pores prepared by the polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) in the presence of ammonium oxalate porogen. The scaffolds were thoroughly characterized by scanning electron microscopy (SEM), vibrating sample magnetometry, FTIR spectroscopy, and mechanical testing in terms of chemical composition, magnetization, and mechanical properties. While the SEM microscopy confirmed that the hydrogels contained communicating pores with a length of ≤2 mm and thickness of ≤400 μm, the SEM/EDX microanalysis documented the presence of γ-Fe₂O₃ nanoparticles in the polymer matrix. The saturation magnetization of the magnetic hydrogel reached 2.04 Am²/kg, which corresponded to 3.7 wt.% of maghemite in the scaffold; the shape of the hysteresis loop and coercivity parameters suggested the superparamagnetic nature of the hydrogel. The highest toughness and compressive modulus were observed with γ-Fe₂O₃-loaded PHEMA hydrogels. Finally, the cell seeding experiments with the human SAOS-2 cell line showed a rather mediocre cell colonization on the PHEMA-based hydrogel scaffolds; however, the incorporation of γ-Fe₂O₃ nanoparticles into the hydrogel improved the cell adhesion significantly. This could make this composite a promising material for bone tissue engineering. Full article

(This article belongs to the Special Issue Advances in Porous Polymers)

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14 pages, 4738 KiB

Open AccessArticle

Isolation of Two Bacterial Species from Argan Soil in Morocco Associated with Polyhydroxybutyrate (PHB) Accumulation: Current Potential and Future Prospects for the Bio-Based Polymer Production

by Amina Aragosa, Valeria Specchia and Mariaenrica Frigione

Polymers 2021, 13(11), 1870; https://doi.org/10.3390/polym13111870 - 4 Jun 2021

Cited by 10 | Viewed by 4994

Abstract

The environmental issues caused by the impacts of synthetic plastics use and derived wastes are arising the attention to bio-based plastics, natural polymers produced from renewable resources, including agricultural, industrial, and domestic wastes. Bio-based plastics represent a potential alternative to petroleum-based materials, due [...] Read more.

The environmental issues caused by the impacts of synthetic plastics use and derived wastes are arising the attention to bio-based plastics, natural polymers produced from renewable resources, including agricultural, industrial, and domestic wastes. Bio-based plastics represent a potential alternative to petroleum-based materials, due to the insufficient availability of fossil resources in the future and the affordable low cost of renewable ones that might be consumed for the biopolymer synthesis. Among the polyhydroxyalkanoates (PHA), the polyhydroxybutyrate (PHB) biopolymer has been synthesized and characterized with great interest due to its wide range of industrial applications. Currently, a wide number of bacterial species from soil, activated sludge, wastewater, industrial wastes, and compost have been identified as PHB producers. This work has the purpose of isolating and characterizing PHB-producing bacteria from the agricultural soil samples of Argania spinosa in the south region of Morocco where the plant species is endemic and preserved. During this research, four heat-resistant bacterial strains have been isolated. Among them, two species have been identified as endospore forming bacteria following the Schaffer-Fulton staining method with Malachite green and the Methylene blue method. Black intracellular granules have been appreciated in microscopy at 100× for both strains after staining with Sudan black B. The morphological and biochemical analyses of the isolates, including sugar fermentation and antibiotic susceptibility tests, preliminarily identified the strains 1B and 2D1 belonging to the genus Serratia and Proteus, respectively. Full article

(This article belongs to the Special Issue Feature Papers of Green and Sustainable Chemistry in Polymer Science)

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