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Volume 16
Issue 14
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Polymers, Volume 16, Issue 14 (July-2 2024) – 140 articles

Cover Story (view full-size image): Liquid crystals are increasingly important in various industries due to their high glass transition temperature, stability, and mechanical properties after curing. Recent years have seen significant efforts in developing these materials. New techniques such as DSC-TOPEM® and WAXS are advancing our understanding. DSC-TOPEM®, introduced by Mettler Toledo, enhances conventional DSC by resolving overlapping thermal events with greater precision. WAXS (Wide-Angle X-ray Scattering) provides critical insights into the atomic and molecular structures of diverse materials, pushing the boundaries of materials science. View this paper
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22 pages, 8833 KiB  
Article
Stability of Conducting Polymer-Coated Carbon Microfibers for Long-Term Electrical Stimulation of Injured Neural Tissue
by Hugo Vara, Gabriel Raúl Hernández-Labrado, Alexandra Alves-Sampaio and Jorge E. Collazos-Castro
Polymers 2024, 16(14), 2093; https://doi.org/10.3390/polym16142093 - 22 Jul 2024
Viewed by 634
Abstract
Electroactive microfiber-based scaffolds aid neural tissue repair. Carbon microfibers (CMFs) coated with the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)] (PEDOT:PSS-co-MA) provide efficient support and guidance to regrowing axons across spinal cord lesions in rodents and pigs. We [...] Read more.
Electroactive microfiber-based scaffolds aid neural tissue repair. Carbon microfibers (CMFs) coated with the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)] (PEDOT:PSS-co-MA) provide efficient support and guidance to regrowing axons across spinal cord lesions in rodents and pigs. We investigated the electrical and structural performance of PEDOT:PSS-co-MA-coated carbon MFs (PCMFs) for long-term, biphasic electrical stimulation (ES). Chronopotentiometry and electrochemical impedance spectroscopy (EIS) allowed the characterization of charge transfer in PCMFs during ES in vitro, and morphological changes were assessed by scanning electron microscopy (SEM). PCMFs that were 4 mm long withstood two-million-biphasic pulses without reaching cytotoxic voltages, with a 6 mm length producing optimal results. Although EIS and SEM unveiled some polymer deterioration in the 6 mm PCMFs, no significant changes in voltage excursions appeared. For the preliminary testing of the electrical performance of PCMFs in vivo, we used 12 mm long, 20-microfiber assemblies interconnected by metallic microwires. PCMFs-assemblies were implanted in two spinal cord-injured pigs and submitted to ES for 10 days. A cobalt–alloy interconnected assembly showed safe voltages for about 1.5 million-pulses and was electrically functional at 1-month post-implantation, suggesting its suitability for sub-chronic ES, as likely required for spinal cord repair. However, improving polymer adhesion to the carbon substrate is still needed to use PCMFs for prolonged ES. Full article
(This article belongs to the Section Polymer Fibers)
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14 pages, 3273 KiB  
Article
Optical Characteristics of a New Molecular Complex: “Nafion–Colloidal CdSe/CdS/ZnS Nanocrystals”
by Svetlana L. Timchenko, Sergey A. Ambrozevich, Evgenii N. Zadorozhnyi, Nikolai A. Zadorozhnyi, Alexander V. Skrabatun and Evgenii A. Sharandin
Polymers 2024, 16(14), 2092; https://doi.org/10.3390/polym16142092 - 22 Jul 2024
Viewed by 511
Abstract
Here, the optical properties of the Nafion polymer membrane containing colloidal CdSe/CdS/ZnS nanocrystals embedded by diffusion have been studied. The CdSe/CdS/ZnS nanocrystals have a core/shell/shell appearance. All experiments were carried out at room temperature (22 ± 2) °C. A toluene solution was used [...] Read more.
Here, the optical properties of the Nafion polymer membrane containing colloidal CdSe/CdS/ZnS nanocrystals embedded by diffusion have been studied. The CdSe/CdS/ZnS nanocrystals have a core/shell/shell appearance. All experiments were carried out at room temperature (22 ± 2) °C. A toluene solution was used to provide mobility to the active sulfone groups of the Nafion membrane and to embed the nanocrystals inside the membrane. The diffusion process of colloidal CdSe/CdS/ZnS nanocrystals into Nafion proton exchange membrane has resulted in a new molecular complex “Nafion–colloidal CdSe/CdS/ZnS nanocrystals”. The kinetics of the nanocrystals embedding into the membrane matrix was investigated using luminescence analysis and absorption spectroscopy techniques. The embedding rate of CdSe/CdS/ZnS nanocrystals into the Nafion polymer membrane was approximately 4·10−3 min−1. The presence of new luminescence centers in the membrane was proved independently by laser emission spectroscopy. The luminescence spectrum of the resulting molecular complex contains intensity maxima at wavelengths of 538, 588, 643 and 700 nm. The additional luminescence maximum observed at the 643 nm wavelength was not recorded in the original membrane, solvent or in the spectrum of the semiconductor nanoparticles. The luminescence maximum of the colloidal CdSe/CdS/ZnS nanocrystals was registered at a wavelength of 634 nm. The intensity of the luminescence spectrum of the membrane with embedded nanocrystals was found to be higher than the intensity of the secondary emission peak of the initial nanocrystals, which is important for the practical use of the “Nafion–colloidal nanocrystals” complex in optical systems. The lines contained in the luminescence spectrum of the membrane, which has been in solution with colloidal nanocrystals for a long time, registered upon its drying, show the kinetics of the formation of the molecular complex “Nafion membrane–nanocrystals”. Colloidal nanocrystals located in the Nafion matrix represent an analog of a luminescent transducer. Full article
(This article belongs to the Special Issue Highly Permselective Nanofiltration Membrane)
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19 pages, 2485 KiB  
Article
Brown Algae as a Valuable Substrate for the Cost-Effective Production of Poly-γ-Glutamic Acid for Applications in Cream Formulations
by Mattia Parati, Catherine Philip, Sarah L. Allinson, Barbara Mendrek, Ibrahim Khalil, Fideline Tchuenbou-Magaia, Marek Kowalczuk, Grazyna Adamus and Iza Radecka
Polymers 2024, 16(14), 2091; https://doi.org/10.3390/polym16142091 - 22 Jul 2024
Viewed by 943
Abstract
Poly-γ-glutamic acid (γ-PGA) is a carboxylic-acid-rich, bio-derived, water-soluble, edible, hydrating, non-immunogenic polymer produced naturally by several microorganisms. Here, we re-emphasise the ability of Bacillus subtilis natto to naturally produce γ-PGA on whole seaweed, as well as for the yields and chemical properties of [...] Read more.
Poly-γ-glutamic acid (γ-PGA) is a carboxylic-acid-rich, bio-derived, water-soluble, edible, hydrating, non-immunogenic polymer produced naturally by several microorganisms. Here, we re-emphasise the ability of Bacillus subtilis natto to naturally produce γ-PGA on whole seaweed, as well as for the yields and chemical properties of the material to be affected by the presence of Mn(2+). Hyaluronic acid (HA) is an extracellular glycosaminoglycan which presents a high concentration of carboxylic acid and hydroxyl groups, being key in fulfilling numerous applications. Currently, there are strong environmental (solvent use), social (non-vegan extraction), and economic factors pushing for the biosynthesis of this material through prokaryotic microorganisms, which is not yet scalable or sustainable. Our study aimed to investigate an innovative raw material which can combine both superior hygroscopicity and UV protection to the cosmetic industry. Comparable hydration effect of commercially available γ-PGA to conventional moisturising agents (HA and glycerol) was observed; however, greater hydration capacity was observed from seaweed-derived γ-PGA. Herewith, successful incorporation of seaweed-derived γ-PGA (0.2–2 w/v%) was achieved for several model cream systems with absorbances reported at 300 and 400 nm. All γ-PGA-based creams displayed shear thinning behaviour as the viscosity decreased, following increasing shear rates. Although the use of commercial γ-PGA within creams did not suggest a significant effect in rheological behaviour, this was confirmed to be a result of the similar molecular weight. Seaweed-derived γ-PGA cream systems did not display any negative effect on model HaCaT keratinocytes by means of in vitro MTT analysis. Full article
(This article belongs to the Special Issue Eco-Friendly Polymers: Synthesis, Characterization and Applications II)
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19 pages, 4026 KiB  
Article
Effect of Viscosity and Air Gap within the Spinneret on the Morphology and Mechanical Properties of Hollow-Fiber Polymer Membranes for Separation Performance
by Sirisak Seansukato, Sathish Kumar Ramachandran, Sivamesh Lamlong, Wirach Taweepreda and Gangasalam Arthanareeswaran
Polymers 2024, 16(14), 2090; https://doi.org/10.3390/polym16142090 - 22 Jul 2024
Viewed by 615
Abstract
Hollow-fiber membranes for nanofiltration were prepared from the blending of Poly (ethylene glycol) (PEG) with Poly (vinyl chloride) (PVC) with different PEG molecular weights (400 and 4000 g/mol) and PVC via a dry/wet spinning process. In the spinning process, the effects of air [...] Read more.
Hollow-fiber membranes for nanofiltration were prepared from the blending of Poly (ethylene glycol) (PEG) with Poly (vinyl chloride) (PVC) with different PEG molecular weights (400 and 4000 g/mol) and PVC via a dry/wet spinning process. In the spinning process, the effects of air gap, wind-up speed, dope extrusion rate, and bore extrusion rate were examined. In addition, the different lengths of the center tube, which acted as the inner-side fiber diameter during the preparation of hollow-fiber membranes, were studied. This research was investigated in order to observe the morphological, dielectric, and dynamic mechanical thermal properties to identify a suitable preparation of a hollow-fiber membrane for feasible applications. The morphology of the PVC-580 blended PEG-400 5 weight percent hollow-fiber membrane was seen to have a dense skin on both the inner and outer fiber surface, along with a suitable dope viscosity. Moreover, it offered finger-like substructures that could provide a high applicable feed-stream permeability and selectivity. Finger-like substructures were present on the near inner fiber surface at the controlled center-tube length of 0.3 cm, more so than at the center tube of 1 cm. This was because the solvent and non-solvent in the lumen tube exchanged more quickly than they did in the coagulant bath. The effect of the wind-up speed during the spinning process was significantly influenced by an affordable hollow fiber that can be indicated by the drawing ratio (λ). It was found that the drawing ratio of 3.3 showed a thickness thinner than 2.6 and 2.0, respectively. In summary, a controlled wind-up speed, an acceptable dope viscosity, and—most importantly—an agglomerated time resulted in membrane preparation. Full article
(This article belongs to the Section Polymer Membranes and Films)
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14 pages, 11987 KiB  
Article
Comparative Evaluation of Mechanical Properties and Color Stability of Dental Resin Composites for Chairside Provisional Restorations
by Haikun Yu, Jiaqi Yao, Zhili Du, Jingmei Guo and Wenlong Lei
Polymers 2024, 16(14), 2089; https://doi.org/10.3390/polym16142089 - 22 Jul 2024
Viewed by 647
Abstract
Resin composites have become the preferred choice for chairside provisional dental restorations. However, these materials may undergo discoloration, changes in surface roughness, and mechanical properties with aging in the oral cavity, compromising the aesthetics, functionality, and success of dental restorations. To investigate the [...] Read more.
Resin composites have become the preferred choice for chairside provisional dental restorations. However, these materials may undergo discoloration, changes in surface roughness, and mechanical properties with aging in the oral cavity, compromising the aesthetics, functionality, and success of dental restorations. To investigate the color and mechanical stability of chairside provisional composite resins, this study evaluated the optical, surface, and mechanical properties of four temporary restoration resin materials before and after aging, stimulated by thermal cycling in double-distilled water. Measurements, including CIE LAB color analysis, three-point bending test, nanoindentation, scanning electron microscopy (SEM), and atomic force microscopy (AFM), were conducted (n = 15). Results showed significant differences among the materials in terms of optical, surface, and mechanical properties. Revotek LC (urethane dimethacrylate) demonstrated excellent color stability (ΔE00 = 0.53-Black/0.32-White), while Artificial Teeth Resin (polymethyl methacrylate) exhibited increased mechanical strength with aging (p < 0.05, FS = 68.40 MPa-non aging/87.21 MPa-aging). Structur 2 SC (Bis-acrylic) and Luxatemp automix plus (methyl methacrylate bis-acrylate) demonstrated moderate stability in optical and mechanical properties (Structur 2 SC: ΔE00 = 1.97-Black/1.38-White FS = 63.20 MPa-non aging/50.07 MPa-aging) (Luxatemp automix plus: ΔE00 = 2.49-Black/1.77-White FS = 87.72 MPa-non aging/83.93 MPa-aging). These results provide important practical guidance for clinical practitioners, as well as significant theoretical and experimental bases for the selection of restorative composite resins. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials for Dental Applications III)
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18 pages, 43378 KiB  
Article
Numerical and Experimental Study on Balanced Performance and Axial Stiffness of Fiber-Reinforced Rubber Pipe
by Jingyue You, Yinglong Zhao and Ben Zhang
Polymers 2024, 16(14), 2088; https://doi.org/10.3390/polym16142088 - 22 Jul 2024
Viewed by 483
Abstract
Balanced fiber-reinforced rubber (FRR) pipes not only provide displacement compensation when transporting pressurized media but also prevent additional forces and displacements from being exerted on the connected pipeline system. Investigating the balanced performance of FRR pipes and the axial stiffness of balanced pipes [...] Read more.
Balanced fiber-reinforced rubber (FRR) pipes not only provide displacement compensation when transporting pressurized media but also prevent additional forces and displacements from being exerted on the connected pipeline system. Investigating the balanced performance of FRR pipes and the axial stiffness of balanced pipes is crucial for optimizing pipeline design and improving the reliability of pipeline systems. This paper develops a numerical model of FRR pipes that considers the nonlinearity of the rubber material and the interaction between the rubber matrix and fiber-reinforced layers. Using this model, the balanced performance of the pipe is calculated, and its axial stiffness under combined internal pressure and axial load is analyzed. Numerical results are compared with experimental data for validation. The results indicate that the pipe’s balance is achieved through the combined effects of the elongation and rotation of the reinforcing fibers and the deformation of the rubber matrix, highlighting the significant impact of the rubber matrix on the mechanical performance of the FRR pipe. Furthermore, the pipe’s balanced performance and axial stiffness are highly sensitive to the winding angle of reinforcing fibers. The proposed numerical model fills the gap in using numerical methods to evaluate the balanced performance of FRR pipes and provides valuable insights for their design and optimization. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymer Materials: Structure and Properties Characterization)
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21 pages, 8929 KiB  
Article
Ecotoxicity Assessment of α-Amino Acid-Derived Polyamidoamines Using Zebrafish as a Vertebrate Model
by Sofia Treccani, Paolo Ferruti, Jenny Alongi, Eugenio Monti, Daniela Zizioli and Elisabetta Ranucci
Polymers 2024, 16(14), 2087; https://doi.org/10.3390/polym16142087 - 22 Jul 2024
Cited by 1 | Viewed by 587
Abstract
The aquatic ecotoxicity of three α-amino acid-derived polyamidoamines (PAAs) was studied using zebrafish embryos as a viable vertebrate model organism. The PAAs examined were water-soluble amphoteric polyelectrolytes with a primarily negative charge, which were efficient flame retardants for cotton. The fish embryo acute [...] Read more.
The aquatic ecotoxicity of three α-amino acid-derived polyamidoamines (PAAs) was studied using zebrafish embryos as a viable vertebrate model organism. The PAAs examined were water-soluble amphoteric polyelectrolytes with a primarily negative charge, which were efficient flame retardants for cotton. The fish embryo acute toxicity test performed with PAA water solutions using 1.5–500 mg L−1 concentrations showed that toxicity did not statistically differ from the control. The survival rates were indeed >90%, even at the highest concentration; the hatching rates were >80%; and the numbers of morphological defects were comparable to those of the control. Tests using transgenic zebrafish lines indicated that the numbers of microscopic vascular and musculoskeletal defects were comparable to the control, with one random concentration showing doubled alterations. Sensory–motor tests in response to visual and tactile stimuli were also performed. In the presence of PAAs, embryos exposed to alternating light/dark cycles showed an insignificant mobility reduction during the dark phase. Touch-evoked response tests revealed a mild effect of PAAs on the neuromotor system at concentrations > 10 mg L−1. The cystine/glycine copolymer at 100 mg L−1 exhibited the greatest effect. Overall, the studied PAAs showed a minimal impact on aquatic systems and should be further considered as promising ecofriendly materials. Full article
(This article belongs to the Section Polymer Physics and Theory)
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14 pages, 4252 KiB  
Article
The Use of a Natural Polysaccharide Extracted from the Prickly Pear Cactus (Opuntia ficus indica) as an Additive for Textile Dyeing
by Lucia Emanuele, Mateo Miguel Kodrič Kesovia, Tanja Dujaković and Simone Campanelli
Polymers 2024, 16(14), 2086; https://doi.org/10.3390/polym16142086 - 22 Jul 2024
Viewed by 514
Abstract
The art of dyeing fabrics is one of the oldest human activities. In order to improve the fastness properties of dyeing products, various additives are added to optimize the uniformity of fibers and surfaces and improve dye distribution. Unfortunately, these additives can be [...] Read more.
The art of dyeing fabrics is one of the oldest human activities. In order to improve the fastness properties of dyeing products, various additives are added to optimize the uniformity of fibers and surfaces and improve dye distribution. Unfortunately, these additives can be harmful and very often are not biodegradable. This article reports on the possibility of using a natural additive for dyeing textiles: a polysaccharide extracted from the prickly pear cactus (Opuntia ficus indica). One type of fabric was tested, silk, with different colors. Several samples were prepared and dyed for each color, adding the same additives but also a commercial chemical aid for one of them and the mucilage of Opuntia for another. The fastness of the applied dyes was evaluated by washing at different temperatures with a common liquid detergent. All samples were analyzed before and after washing with a colorimeter to evaluate the color changes. The results of the analyses reported and compared indicate the potential of prickly pear mucilage as an additive for dyeing silk, which is easily accessible, safe, and sustainable compared to other commonly used additives. Full article
(This article belongs to the Special Issue Polysaccharide and Lignocellulose Materials)
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16 pages, 1176 KiB  
Review
Advancements in Stone Object Restoration Using Polymer-Inorganic Phosphate Composites for Cultural Heritage Preservation
by Toma Fistos, Irina Fierascu, Doina Manaila-Maximean and Radu Claudiu Fierascu
Polymers 2024, 16(14), 2085; https://doi.org/10.3390/polym16142085 - 22 Jul 2024
Viewed by 570
Abstract
Recent advancements in cultural heritage preservation have increasingly focused on the development and application of new composites, harnessing the diverse properties of their components. This study reviews the current state of research and practical applications of these innovative materials, emphasizing the use of [...] Read more.
Recent advancements in cultural heritage preservation have increasingly focused on the development and application of new composites, harnessing the diverse properties of their components. This study reviews the current state of research and practical applications of these innovative materials, emphasizing the use of inorganic phosphatic materials (in particular the hydroxyapatite) and various polymers. The compatibility of phosphatic materials with calcareous stones and the protective properties of polymers present a synergistic approach to addressing common deterioration mechanisms, such as salt crystallization, biological colonization, and mechanical weathering. By examining recent case studies and experimental results, this paper highlights the effectiveness, challenges, and future directions for these composites in cultural heritage conservation. The findings underscore the potential of these materials to enhance the durability and aesthetic integrity of heritage stones, promoting sustainable and long-term preservation solutions. Full article
(This article belongs to the Section Polymer Applications)
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17 pages, 1629 KiB  
Article
Influence of Different Deep Eutectic Solvents and Plant Extracts on Antioxidant, Mechanical, and Color Properties of Alginate Film
by Jolanta Kowalonek, Malo Hamieau and Aleksandra Szydłowska-Czerniak
Polymers 2024, 16(14), 2084; https://doi.org/10.3390/polym16142084 - 22 Jul 2024
Viewed by 688
Abstract
Eco-friendly functional alginate films with plant extracts (chokeberry pomace (ChP) or lemon balm (LB) herb) were obtained. Moreover, deep eutectic solvents (DESs) based on choline chloride, glucose, and betaine were used to acquire the active substances from plant materials. The films were tested [...] Read more.
Eco-friendly functional alginate films with plant extracts (chokeberry pomace (ChP) or lemon balm (LB) herb) were obtained. Moreover, deep eutectic solvents (DESs) based on choline chloride, glucose, and betaine were used to acquire the active substances from plant materials. The films were tested regarding the antioxidant, mechanical, and color properties. The results revealed that the films’ antioxidant capacities (AC) depended on the extract type and DES used, namely AC values for alginate films with LB were higher than those with ChP. Moreover, the results of the films’ mechanical properties depended only on the DES, which acted as a plasticizer in most cases. Furthermore, the color analysis of the studied films showed a dependence on the type of extract and DES. The lightness (L*) was influenced only by the DES type, while the solvent and extract type affected the a* and b* values. Our results show that the films can be applied as active packaging for food products. Full article
(This article belongs to the Special Issue Functional Polymers: Interaction, Surface, Processing and Applications: 2nd Edition)
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16 pages, 4156 KiB  
Article
Development of a Zr-Based Metal-Organic Framework (UiO-66) for a Cooperative Flame Retardant in the PC/ABS
by Shaojun Chen, Zerui Chen, Weifeng Bi, Wei Du, Ling Lin, Dasong Hu and Haitao Zhuo
Polymers 2024, 16(14), 2083; https://doi.org/10.3390/polym16142083 - 21 Jul 2024
Viewed by 762
Abstract
Polycarbonate/acrylonitrile butadiene styrene (PC/ABS) blends are widely used as engineering plastic alloys; however, they have a low fire safety level. To improve the flame-retardant property of PC/ABS, a zirconium-based metal-organic framework material (UiO-66) was synthesized with zirconium chloride and terephthalic acid and used [...] Read more.
Polycarbonate/acrylonitrile butadiene styrene (PC/ABS) blends are widely used as engineering plastic alloys; however, they have a low fire safety level. To improve the flame-retardant property of PC/ABS, a zirconium-based metal-organic framework material (UiO-66) was synthesized with zirconium chloride and terephthalic acid and used as a flame-retardant cooperative agent. Its flame-retardant performance and mode of action in the PC/ABS blends were carefully investigated. The results showed that UiO-66 had good thermal stability and delayed the pyrolysis of the materials, thus significantly enhancing the efficiency of intumescent flame retardants. By compounding 7.0 wt% hexaphenyloxy-cyclotri-phosphazene (HPCTP) with 3.0 wt% UiO-66, the PC/ABS blends reached a limiting oxygen index value of 27.0% and V0 rating in the UL-94 test, showing significantly improved resistance to combustion dripping. In addition, UiO-66 enhanced the smoke and heat suppression characteristics of the intumescent flame-retardant materials. Finally, the flame-retardant mode of action in the blends was indicative of UiO-66 having a cooperative effect on the flame-retardant performance of PC/ABS/HPCTP materials. This work provides good ideas for further development of the flame-retardant ABS/PC. Full article
(This article belongs to the Special Issue Advance in Polymer Composites: Fire Protection and Thermal Management)
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16 pages, 4411 KiB  
Article
Utilizing Edge-Oxidized Graphene Oxide to Enhance Cement Mortar’s Properties Containing Crumb Rubber: Toward Achieving Sustainable Materials
by Mohammed Alamri and Mohammad Khawaji
Polymers 2024, 16(14), 2082; https://doi.org/10.3390/polym16142082 - 21 Jul 2024
Viewed by 511
Abstract
Scrap tires have become one of the most serious environmental issues worldwide in recent years. Exploiting this scrap has caught the attention of researchers in their efforts to conserve the environment. From a structural engineering materials perspective, a partial fine aggregate in cement [...] Read more.
Scrap tires have become one of the most serious environmental issues worldwide in recent years. Exploiting this scrap has caught the attention of researchers in their efforts to conserve the environment. From a structural engineering materials perspective, a partial fine aggregate in cement mortar can be replaced by crumb rubber produced from scrap tires. This research mainly emphasizes the role of adding 0.1% edge-oxidized graphene oxide EOGO (by the weight of cement) in enhancing the properties of cement mortars containing 5%, 10%, and 15% of crumb rubber (by sand replacement). Cube and prism specimens were employed to investigate compressive and flexural strengths at 7- and 28-day curing ages. A porosity test was also conducted after 28 days of curing. In addition, a scanning electron microscopy (SEM) test was performed to investigate the effect of incorporating EOGO on the interfacial transition zone (ITZ). Results showed an enhancement of the mechanical properties of cement mortar, including compressive and flexural strengths, with the inclusion of EOGO in the mixes. The findings demonstrated that adding EOGO can improve the mechanical properties of mixes containing crumb rubber particles. Specifically, the mortar mix with 0.1% EOGO and 5% crumb rubber exhibited better performance compared with the virgin mix without rubber particles. Therefore, crumb rubber is viable for use as a sand replacement when EOGO is included. Full article
(This article belongs to the Section Polymer Applications)
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17 pages, 6802 KiB  
Article
Properties of a Dental Adhesive Containing Graphene and DOPA-Modified Graphene
by Renata Pereira, Rodrigo Barros Esteves Lins, Elton Faria de Souza Lima, Maria do Carmo Aguiar Jordão Mainardi, Stephani Stamboroski, Klaus Rischka and Flávio Henrique Baggio Aguiar
Polymers 2024, 16(14), 2081; https://doi.org/10.3390/polym16142081 - 21 Jul 2024
Viewed by 558
Abstract
Graphene is a promising biomaterial. However, its dispersion in aqueous medium is challenging. This study aimed to modify graphene nanoparticles with L-dopa to improve the properties of experimental dental adhesives. Adhesives were formulated with 0% (control), 0.25%, 0.5%, and 0.75% of graphene, modified [...] Read more.
Graphene is a promising biomaterial. However, its dispersion in aqueous medium is challenging. This study aimed to modify graphene nanoparticles with L-dopa to improve the properties of experimental dental adhesives. Adhesives were formulated with 0% (control), 0.25%, 0.5%, and 0.75% of graphene, modified or not. Particle modification and dispersion were microscopically assessed. Degree of conversion was tested by Fourier-transform infrared spectroscopy. Flexural strength and modulus of elasticity were evaluated by a 3-point flexural test. Bond strength was tested by shear. To test water sorption/solubility, samples were weighed during hydration and dehydration. Antibacterial activity was tested by Streptococcus mutans colony-forming units quantification. Cytotoxicity on fibroblasts was evaluated through a dentin barrier test. The modification of graphene improved the particle dispersion. Control presented the highest degree of conversion, flexural strength, and bond strength. In degree of conversion, 0.25% of groups were similar to control. In bond strength, groups of graphene modified by L-dopa were similar to Control. The modulus of elasticity was similar between groups. Cytotoxicity and water sorption/solubility decreased as particles increased. Compared to graphene, less graphene modified by L-dopa was needed to promote antibacterial activity. By modifying graphene with L-dopa, the properties of graphene and, therefore, the adhesives incorporated by it were enhanced. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials for Dental Applications III)
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16 pages, 4152 KiB  
Article
Multiple Traces of Families of Epoxy Derivatives as New Inhibitors of the Industrial Polymerization Reaction of Propylene
by Joaquin Hernandez Fernandez, Rodrigo Ortega-Toro and John R. Castro-Suarez
Polymers 2024, 16(14), 2080; https://doi.org/10.3390/polym16142080 - 21 Jul 2024
Viewed by 696
Abstract
In this study, the impact of ethylene oxide, propylene oxide, 1,2-butene oxide, and 1,2-pentene oxide on the polymerization of propylene at an industrial level was investigated, focusing on their influence on the catalytic efficiency and the properties of polypropylene (PP) without additives. The [...] Read more.
In this study, the impact of ethylene oxide, propylene oxide, 1,2-butene oxide, and 1,2-pentene oxide on the polymerization of propylene at an industrial level was investigated, focusing on their influence on the catalytic efficiency and the properties of polypropylene (PP) without additives. The results show that concentrations between 0 and 1.24 ppm of these epoxides negatively affect the reaction’s productivity, the PP’s mechanical properties, the polymer’s fluidity index, and the PP’s thermal properties. Fourier transform infrared spectroscopy (FTIR) revealed bands for the Ti-O bond and the Cl-Ti-O-CH2 bonds at 430 to 475 cm−1 and 957 to 1037 cm−1, respectively, indicating the interaction between the epoxides and the Ziegler–Natta catalyst. The thermal degradation of PP in the presence of these epoxides showed a similar trend, varying in magnitude depending on the concentration of the inhibitor. Sample M7, with 0.021 ppm propylene oxide, exhibited significant mass loss at both 540 °C and 600 °C, suggesting that even small concentrations of this epoxide can markedly increase the thermal degradation of PP. This pattern is repeated in samples with 1,2-butene oxide and 1,2-pentene oxide. These results highlight the need to strictly control the presence of impurities in PP production to optimize both the final product’s quality and the polymerization process’s efficiency. Full article
(This article belongs to the Section Polymer Chemistry)
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19 pages, 6699 KiB  
Article
Thermally Stabilised Poly(vinyl alcohol) Nanofibrous Materials Produced by Scalable Electrospinning: Applications in Tissue Engineering
by W. Joseph A. Homer, Maxim Lisnenko, Sarka Hauzerova, Bohdana Heczkova, Adrian C. Gardner, Eva K. Kostakova, Paul D. Topham, Vera Jencova and Eirini Theodosiou
Polymers 2024, 16(14), 2079; https://doi.org/10.3390/polym16142079 - 21 Jul 2024
Viewed by 715
Abstract
Electrospinning is a widely employed manufacturing platform for tissue engineering applications because it produces structures that closely mimic the extracellular matrix. Herein, we demonstrate the potential of poly(vinyl alcohol) (PVA) electrospun nanofibers as scaffolds for tissue engineering. Nanofibers were created by needleless direct [...] Read more.
Electrospinning is a widely employed manufacturing platform for tissue engineering applications because it produces structures that closely mimic the extracellular matrix. Herein, we demonstrate the potential of poly(vinyl alcohol) (PVA) electrospun nanofibers as scaffolds for tissue engineering. Nanofibers were created by needleless direct current electrospinning from PVA with two different degrees of hydrolysis (DH), namely 98% and 99% and subsequently heat treated at 180 °C for up to 16 h to render them insoluble in aqueous environments without the use of toxic cross-linking agents. Despite the small differences in the PVA chemical structure, the changes in the material properties were substantial. The higher degree of hydrolysis resulted in non-woven supports with thinner fibres (285 ± 81 nm c.f. 399 ± 153 nm) that were mechanically stronger by 62% (±11%) and almost twice as more crystalline than those from 98% hydrolysed PVA. Although prolonged heat treatment (16 h) did not influence fibre morphology, it reduced the crystallinity and tensile strength for both sets of materials. All samples demonstrated a lack or very low degree of haemolysis (<5%), and there were no notable changes in their anticoagulant activity (≤3%). Thrombus formation, on the other hand, increased by 82% (±18%) for the 98% hydrolysed samples and by 71% (±10%) for the 99% hydrolysed samples, with heat treatment up to 16 h, as a direct consequence of the preservation of the fibrous morphology. 3T3 mouse fibroblasts showed the best proliferation on scaffolds that were thermally stabilised for 4 and 8 h. Overall these scaffolds show potential as ‘greener’ alternatives to other electrospun tissue engineering materials, especially in cases where they may be used as delivery vectors for heat tolerant additives. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials and Composites: Structure-Property Relationships)
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19 pages, 6245 KiB  
Article
Thermal, Morphological, Mechanical, and Biodegradation Properties of Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide)/High-Density Polyethylene Blends
by Yodthong Baimark, Prasong Srihanam and Yaowalak Srisuwan
Polymers 2024, 16(14), 2078; https://doi.org/10.3390/polym16142078 - 21 Jul 2024
Viewed by 669
Abstract
Polymer blends of poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA) and high-density polyethylene (HDPE) with different blend ratios were prepared by a melt blending method. The thermal, morphological, mechanical, opacity, and biodegradation properties of the PLLA-PEG-PLLA/HDPE blends were investigated and compared to the [...] Read more.
Polymer blends of poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA) and high-density polyethylene (HDPE) with different blend ratios were prepared by a melt blending method. The thermal, morphological, mechanical, opacity, and biodegradation properties of the PLLA-PEG-PLLA/HDPE blends were investigated and compared to the PLLA/HDPE blends. The blending of HDPE improved the crystallization ability and thermal stability of the PLLA-PEG-PLLA; however, these properties were not improved for the PLLA. The morphology of the blended films showed that the PLLA-PEG-PLLA/HDPE blends had smaller dispersed phases compared to the PLLA/HDPE blends. The PLLA-PEG-PLLA/HDPE blends exhibited higher flexibility, lower opacity, and faster biodegradation and bioerosion in soil than the PLLA/HDPE blends. Therefore, these PLLA-PEG-PLLA/HDPE blends have a good potential for use as flexible and partially biodegradable materials. Full article
(This article belongs to the Special Issue Biobased and Biodegradable Polymer Blends and Composites II)
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17 pages, 3261 KiB  
Article
Study of Plugging Compositions Based on Synthetic Resins for Repair and Insulation Work in Wells
by Svetlana V. Aksenova, Lyubov A. Magadova, Sergey I. Kudryashov, Mikhail A. Silin, Aleksandr N. Kulikov, Artem V. Gevorkian and Denis D. Polyakov
Polymers 2024, 16(14), 2077; https://doi.org/10.3390/polym16142077 - 21 Jul 2024
Viewed by 600
Abstract
This research is aimed at analyzing existing plugging compositions and developing a new plugging composition based on phenol-formaldehyde resin. This paper presents the results of studies of a hardening composition based on phenol-formaldehyde resin for repair and insulation work in wells. The plugging [...] Read more.
This research is aimed at analyzing existing plugging compositions and developing a new plugging composition based on phenol-formaldehyde resin. This paper presents the results of studies of a hardening composition based on phenol-formaldehyde resin for repair and insulation work in wells. The plugging composition consists of two parts: Component “A” (resin and additives) and Component “B” (hardener). A resol-type water-soluble phenol-formaldehyde resin was selected for testing. The resin was additionally modified with special additives to improve performance properties. A mixture of acids was chosen as a hardener. Concentrations of resin and hardener were selected to ensure optimal loss of fluidity of the composition for different temperatures. The main physicochemical properties of the plugging composition were determined. The elastic-strength characteristics of the developed composition after curing at various temperatures (Poisson’s ratio, Young’s modulus, and compressive strength) were assessed. It has been experimentally proven that samples based on phenol-formaldehyde resin do not collapse completely under load but undergo longitudinal and transverse deformations. As the amount of hardener in the system increases, the compressive strength decreases. The presence of the elastic-strength properties of cementing compositions based on synthetic resins distinguishes them favorably from hardening compositions based on cement and microcement. Full article
(This article belongs to the Section Polymer Applications)
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13 pages, 6737 KiB  
Article
In Situ Formation of Compound Eye-like SAN-OSB Composite Microspheres by Melt-Blending Method: Enhancing Multiple-Scattering Effect
by Yuhan Li, Yitong Ding, Yuhao Duan, Fengying Yang, Ying Xiong and Shaoyun Guo
Polymers 2024, 16(14), 2076; https://doi.org/10.3390/polym16142076 - 20 Jul 2024
Viewed by 785
Abstract
The preparation of novel structures of light-diffusing particles is currently a research focus in the field of light-diffusing materials. This study, conducted by the common melt-blending process, controlled thermodynamic and kinetic factors to distribute smaller-sized organic silica bead (OSB) particles at the interface [...] Read more.
The preparation of novel structures of light-diffusing particles is currently a research focus in the field of light-diffusing materials. This study, conducted by the common melt-blending process, controlled thermodynamic and kinetic factors to distribute smaller-sized organic silica bead (OSB) particles at the interface between a polycarbonate (PC) matrix and spherical island-phase styrene–acrylonitrile copolymer (SAN) for the in situ formation of compound eye-like microspheres with SAN as “large eyes” and OSBs as “small eyes”. Through the multiple-scattering effects of these compound eye-like microspheres, these light-diffusing materials significantly improved the haze, scattering range, and light-shielding capabilities while maintaining high transmittance. Specifically, the PC/SAN-OSB light-scattering materials achieved a haze of 100% with an OSB content of only 0.17%, maintaining a transmittance of 88%. Compared with the PC/OSB system with the same level of haze, the addition of OSB was reduced by 88%. Therefore, this study achieved exceptionally effective light-diffusing materials through a simple, environmentally friendly, and low-cost preparation method, suitable for the scalable production of light-diffusing materials in new display and lighting fields. Full article
(This article belongs to the Special Issue Advanced Polymer Blends: From Processing to Characterisation and Application)
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13 pages, 5566 KiB  
Article
Protective Encapsulation of a Bioactive Compound in Starch–Polyethylene Glycol-Modified Microparticles: Degradation Analysis with Enzymes
by Karen Sofia Valenzuela Villela, Karen Valeria Alvarado Araujo, Perla Elvia Garcia Casillas and Christian Chapa González
Polymers 2024, 16(14), 2075; https://doi.org/10.3390/polym16142075 - 20 Jul 2024
Viewed by 564
Abstract
Starch is a promising polymer for creating novel microparticulate systems with superior biocompatibility and controlled drug delivery capabilities. In this study, we synthesized polyethylene glycol (PEG)-modified starch microparticles and encapsulated folic acid using a solvent-mediated acid-base precipitation method with magnetic stirring, which is [...] Read more.
Starch is a promising polymer for creating novel microparticulate systems with superior biocompatibility and controlled drug delivery capabilities. In this study, we synthesized polyethylene glycol (PEG)-modified starch microparticles and encapsulated folic acid using a solvent-mediated acid-base precipitation method with magnetic stirring, which is a simple and effective method. To evaluate particle degradation, we simulated physiological conditions by employing an enzymatic degradation approach. Our results with FTIR and SEM confirmed the successful synthesis of starch–PEG microparticles encapsulating folic acid. The average size of starch microparticles encapsulating folic acid was 4.97 μm and increased to 6.01 μm upon modification with PEG. The microparticles were first exposed to amylase at pH 6.7 and pepsin at pH 1.5 at different incubation times at physiological temperature with shaking. Post-degradation analysis revealed changes in particle size and morphology, indicating effective enzymatic degradation. FTIR spectroscopy was used to assess the chemical composition before and after degradation. The initial FTIR spectra displayed characteristic peaks of starch, PEG, and folic acid, which showed decreased intensities after enzymatic degradation, suggesting alterations in chemical composition. These findings demonstrate the ongoing development of starch–PEG microparticles for controlled drug delivery and other biomedical applications and provide the basis for further exploration of PEG–starch as a versatile biomaterial for encapsulating bioactive compounds. Full article
(This article belongs to the Special Issue Polymer Microspheres—Current Development, Application and Future Challenges)
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17 pages, 8750 KiB  
Article
A Multiscale Modeling and Experimental Study on the Tensile Strength of Plain-Woven Composites with Hybrid Bonded–Bolted Joints
by Jianwei Shi, Junwei Zhang, Kou Du, Qiming Guo, Yuliang Hou and Cheng Dong
Polymers 2024, 16(14), 2074; https://doi.org/10.3390/polym16142074 - 20 Jul 2024
Viewed by 555
Abstract
CFRP hybrid bonded–bolted (HBB) joints combine the advantages of traditional joining methods, namely adhesive bonding, and bolting, to achieve optimal connection performance, making them the most favored connection method. The structural parameters of CFRP HBB joints, including overlap length, bolt-hole spacing, and fit [...] Read more.
CFRP hybrid bonded–bolted (HBB) joints combine the advantages of traditional joining methods, namely adhesive bonding, and bolting, to achieve optimal connection performance, making them the most favored connection method. The structural parameters of CFRP HBB joints, including overlap length, bolt-hole spacing, and fit clearance relationships, have a complex impact on connection performance. To enhance the connectivity performance of joint structures, this paper develops a multiscale finite element analysis model to investigate the impact of structural parameters on the strength of CFRP HBB joint structures. Coupled with experimental validation, the study reveals how changes in structural parameters affect the unidirectional tensile failure force of the joints. Building on this, an analytical approach and inverse design methodology for the mechanical properties of CFRP HBB joints based on deep supervised learning algorithms are developed. Neural networks accurately and efficiently predict the performance of joints with unprecedented combinations of parameters, thus expediting the inverse design process. This research combines experimentation and multiscale finite element analysis to explore the unknown relationships between the mechanical properties of CFRP HBB joints and their structural parameters. Furthermore, leveraging DNN neural networks, a rapid calculation method for the mechanical properties of hybrid joints is proposed. The findings lay the groundwork for the broader application and more intricate design of composite materials and their connection structures. Full article
(This article belongs to the Special Issue Multiscale Modeling and Simulation of Polymer-Based Composites)
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16 pages, 4380 KiB  
Article
Atmospheric Plasma Treatment to Improve PHB Coatings on 316L Stainless Steel
by J. Radilla, H. Martínez, O. Vázquez and B. Campillo
Polymers 2024, 16(14), 2073; https://doi.org/10.3390/polym16142073 - 20 Jul 2024
Viewed by 903
Abstract
In the present study, biopolymeric coatings of polyhydroxybutyrate (PHB) were deposited on 316L stainless steel substrates. The PHB coatings were developed using the spin coating method. To improve the adhesion of the PHB coating on the substrate, this method uses an atmospheric plasma [...] Read more.
In the present study, biopolymeric coatings of polyhydroxybutyrate (PHB) were deposited on 316L stainless steel substrates. The PHB coatings were developed using the spin coating method. To improve the adhesion of the PHB coating on the substrate, this method uses an atmospheric plasma treatment. Adhesion tests show a 156% increase in adhesion after 5 s of surface treatment. Raman spectroscopy analysis of the polymer shows the incorporation of functional groups and the formation of new hydrogen bonds, which can help us bind drugs and promote osteogenesis after plasma treatment. Additionally, the electrochemical behaviors in artificial body fluids (Hanks’ solution) of the PHB coatings on the steel were evaluated with potentiodynamic tests, which revealed a decrease in the corrosion current and resistance to the transfer of the charge from the electrolyte to the 316L steel because of the PHB coating. All the PHB coatings were characterized using scanning electron microscopy and Raman spectroscopy after the electrochemical tests. This analysis confirmed the diffusion of electrolyte species toward the surface and the degradation of the polymer chain for the first 15 s of treatment with atmospheric plasma. These findings support the claim that plasma surface modification is a quick, environmentally friendly, and cost-effective method to enhance the performance of PHB coatings on 316L stainless steel for medical devices. Full article
(This article belongs to the Special Issue Plasma Processing of Polymers, 2nd Edition)
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14 pages, 3814 KiB  
Article
Degradation of Polymer Films of Sodium Alginate during Prolonged Irradiation with X-ray under Ultra-High Vacuum
by Eugene N. Kabachkov, Sergey A. Baskakov and Yury M. Shulga
Polymers 2024, 16(14), 2072; https://doi.org/10.3390/polym16142072 - 20 Jul 2024
Viewed by 574
Abstract
Sodium alginate (NaAlg) is widely used as a food additive. To study the effect of irradiation with X-ray quanta with energies of 1253.6 eV and 1486.6 eV on the composition of NaAlg, thick films with a smooth surface were prepared, which did not [...] Read more.
Sodium alginate (NaAlg) is widely used as a food additive. To study the effect of irradiation with X-ray quanta with energies of 1253.6 eV and 1486.6 eV on the composition of NaAlg, thick films with a smooth surface were prepared, which did not differ in IR spectra from the original powders. The films were irradiated in a high vacuum (3 × 10−10 mbar) in the chamber of a Specs PHOIBOS 150 MCD9 XPS spectrometer with an X-ray source power of 150 W and an irradiation duration of up to 300 min, which significantly exceeded the time required to obtain an XPS spectrum. This made it possible to use XPS to monitor changes in the composition of the NaAlg surface directly during irradiation. As a result of the research, it has been established that NaAlg degrades with prolonged irradiation, which is accompanied by a significant decrease in the O/C ratio. When analyzing the dependence of the intensities of individual peaks in the C1s spectrum on the irradiation time, it was found that after 100 min of irradiation, a peak due to the carbonate group appears in the spectrum. The decomposition was also accompanied by a change in the color of NaAlg from white to yellow-brown. In the IR spectrum of the NaAlg film irradiated for 300 min, an absorption band was detected at 1910 cm−1, which is usually associated with the presence of allene groups. Full article
(This article belongs to the Special Issue Carbon/Polymer Composite Materials)
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12 pages, 3661 KiB  
Article
Degradation of Bioderived Polyurethane Composites by Spectroscopy in ISO20200 Composting Conditions
by Alexander Caschera, Tristan Calayan, Nicola Piccolo, Adel Kakroodi, Jason James Robinson and Guerino Sacripante
Polymers 2024, 16(14), 2071; https://doi.org/10.3390/polym16142071 - 20 Jul 2024
Viewed by 629
Abstract
Polyurethane foam compositions derived from bioderived polyester polyols with various additives were evaluated for disintegration under composting conditions using the ISO 20200 standard and were characterized by thermogravimetric analysis, microscopy, infrared spectroscopy, and imaging to provide additional insight. Compared to polyether polyol-based polyurethanes, [...] Read more.
Polyurethane foam compositions derived from bioderived polyester polyols with various additives were evaluated for disintegration under composting conditions using the ISO 20200 standard and were characterized by thermogravimetric analysis, microscopy, infrared spectroscopy, and imaging to provide additional insight. Compared to polyether polyol-based polyurethanes, the bioderived polyurethanes were found to display increased disintegration with an average mass loss of 25.4 ± 3.6 weight percent when subjected to composting conditions for 45 days, suggesting that these materials are less likely to persist in the environment when compared to other types of commodity plastics. Additives such as carbon black and lignin added within the foam composition did not accelerate the disintegration. Full article
(This article belongs to the Section Polymer Chemistry)
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13 pages, 4270 KiB  
Article
Degradation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Reinforced with Regenerated Cellulose Fibers
by Michael Seitz, Rainer Rihm and Christian Bonten
Polymers 2024, 16(14), 2070; https://doi.org/10.3390/polym16142070 - 19 Jul 2024
Viewed by 563
Abstract
PHBV is a promising plastic for replacing conventional petroleum-based plastics in the future. However, the mechanical properties of PHBV are too low for use in high-stress applications and the degradation of the polymer limits possible applications. In this work, the mechanical properties were, [...] Read more.
PHBV is a promising plastic for replacing conventional petroleum-based plastics in the future. However, the mechanical properties of PHBV are too low for use in high-stress applications and the degradation of the polymer limits possible applications. In this work, the mechanical properties were, therefore, increased using bio-based regenerated cellulose fibers and degradation processes of the PHBV-RCF composites were detected in accelerated aging tests under various environmental conditions. Mechanical, optical, rheological and thermal analysis methods were used for this characterization. The fibers significantly increased the mechanical properties, in particular the impact strength. Different degradation mechanisms were identified. UV radiation caused the test specimens to fade significantly, but no reduction in mechanical properties was observed. After storage in water and in aqueous solutions, the mechanical properties of the compounds were significantly reduced. The reason for this was assumed to be hydrolytic degradation catalyzed by higher temperatures. The hydrolytic degradation of PHBV was mainly caused by erosion from the test specimen surface. By exposing the regenerated cellulose fibers, this effect could now also be visually verified. For the use of regenerated cellulose fiber-reinforced PHBV in more durable applications, the aging mechanisms that occur must be prevented in the future through the use of stabilizers. Full article
(This article belongs to the Special Issue Advanced Biopolymers and Biocomposites)
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16 pages, 3277 KiB  
Article
Laser-Induced Electrochemical Biosensor Modified with Graphene-Based Ink for Label-Free Detection of Alpha-Fetoprotein and 17β-Estradiol
by Ridma Tabassum, Pritu Parna Sarkar, Ahmed Hasnain Jalal, Ali Ashraf and Nazmul Islam
Polymers 2024, 16(14), 2069; https://doi.org/10.3390/polym16142069 - 19 Jul 2024
Viewed by 795
Abstract
In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance [...] Read more.
In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance the electrical signals. The laser-induced graphene (LIG) sensor was used to detect alpha-fetoprotein (AFP) and 17β-Estradiol (E2) in the phosphate buffer saline (PBS) buffer and human serum. The electrochemical performance of the biosensor in determining these biomarkers was investigated by differential pulse voltammetry (DPV) and chronoamperometry (CA). In a buffer environment, alpha-fetoprotein (AFP) and 17β-Estradiol detection range were 4–400 ng/mL and 20–400 pg/mL respectively. The experimental results showed a limit of detection (LOD) of 1.15 ng/mL and 0.96 pg/mL for AFP and estrogen, respectively, with an excellent linear range (R2 = 0.98 and 0.99). In addition, the designed sensor was able to detect these two types of biomarkers in human serum successfully. The proposed sensor exhibited excellent reproducibility, repeatability, and good stability (relative standard deviation, RSD = 0.96%, 1.12%, 2.92%, respectively). The electrochemical biosensor proposed herein is easy to prepare and can be successfully used for low-cost, rapid detection of AFP and E2. This approach provides a promising platform for clinical detection and is advantageous to healthcare applications. Full article
(This article belongs to the Special Issue Development and Application of Polymer-Based Materials for Printable Sensors)
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24 pages, 11838 KiB  
Article
Lagrangian Split-Step Method for Viscoelastic Flows
by Martina Bašić, Branko Blagojević, Branko Klarin, Chong Peng and Josip Bašić
Polymers 2024, 16(14), 2068; https://doi.org/10.3390/polym16142068 - 19 Jul 2024
Viewed by 466
Abstract
This research addresses and resolves current challenges in meshless Lagrangian methods for simulating viscoelastic materials. A split-step scheme, or pressure Poisson reformulation of the Navier–Stokes equations, is introduced for incompressible viscoelastic flows in a Lagrangian context. The Lagrangian differencing dynamics (LDD) method, which [...] Read more.
This research addresses and resolves current challenges in meshless Lagrangian methods for simulating viscoelastic materials. A split-step scheme, or pressure Poisson reformulation of the Navier–Stokes equations, is introduced for incompressible viscoelastic flows in a Lagrangian context. The Lagrangian differencing dynamics (LDD) method, which is a thoroughly validated Lagrangian method for Newtonian and non-Newtonian incompressible flows, is extended to solve the introduced split-step scheme to simulate viscoelastic flows based on the Oldroyd-B constitutive model. To validate and evaluate the new method’s capabilities, the following benchmarks were used: lid-driven cavity flow, droplet impact response, 4:1 planar sudden contraction, and die swelling. These findings highlight the LDD method’s effectiveness in accurately simulating viscoelastic flows and capturing large deformations and memory effects. Even though the extra stress was directly modeled without any regularization approach, the method produced stable simulations for high Weissenberg numbers. The stability and performance of the the Lagrangian numerics for complex temporal evolution of material properties and stress responses encourage its use for industrial problems dealing with polymers. Full article
(This article belongs to the Special Issue Computational Modeling and Simulations of Polymers)
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22 pages, 9358 KiB  
Article
Determination of Residual Stresses in 3D-Printed Polymer Parts
by Madina Issametova, Nikita V. Martyushev, Abilkaiyr Zhastalap, Layla B. Sabirova, Uderbayeva Assemgul, Arailym Tursynbayeva and Gazel Abilezova
Polymers 2024, 16(14), 2067; https://doi.org/10.3390/polym16142067 - 19 Jul 2024
Viewed by 595
Abstract
This paper presents the results of an investigation of the possibility of the reliable determination of the residual stress–strain state in polymers and composites using a combination of bridge curvature, optical scanning, and finite element methods. A three-factor experiment was conducted to determine [...] Read more.
This paper presents the results of an investigation of the possibility of the reliable determination of the residual stress–strain state in polymers and composites using a combination of bridge curvature, optical scanning, and finite element methods. A three-factor experiment was conducted to determine the strength of printed PLA plastic products. The effect of the residual stresses on the strength of the printed products was evaluated. By comparing the values of the same strength stresses, a relationship between the nature of the stresses and the strength of the samples was found. A tendency of the negative influence of tensile stresses and the opposite strengthening effect of compressive stresses was obvious, so at the same values of tensile strength, the value of residual stress of 42.9 MPa is lower than that of the fibre compression at the value of 88.9 MPa. The proposed new methods of the residual stress determination allow obtaining a complete picture of the stressed state of the material in the investigated areas of the products. This may be necessary in confirming the calculated models of the residual stress–strain state, clarifying the strength criteria and assessing the quality of the selected technological modes of manufacturing the products. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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20 pages, 6644 KiB  
Article
Fabrication of Electrospun Double Layered Biomimetic Collagen–Chitosan Polymeric Membranes with Zinc-Doped Mesoporous Bioactive Glass Additives
by Dilan Altan, Ali Can Özarslan, Cem Özel, Kadriye Tuzlakoğlu, Yesim Muge Sahin and Sevil Yücel
Polymers 2024, 16(14), 2066; https://doi.org/10.3390/polym16142066 - 19 Jul 2024
Viewed by 681
Abstract
Several therapeutic approaches have been developed to promote bone regeneration, including guided bone regeneration (GBR), where barrier membranes play a crucial role in segregating soft tissue and facilitating bone growth. This study emphasizes the importance of considering specific tissue requirements in the design [...] Read more.
Several therapeutic approaches have been developed to promote bone regeneration, including guided bone regeneration (GBR), where barrier membranes play a crucial role in segregating soft tissue and facilitating bone growth. This study emphasizes the importance of considering specific tissue requirements in the design of materials for tissue regeneration, with a focus on the development of a double-layered membrane to mimic both soft and hard tissues within the context of GBR. The hard tissue-facing layer comprises collagen and zinc-doped bioactive glass to support bone tissue regeneration, while the soft tissue-facing layer combines collagen and chitosan. The electrospinning technique was employed to achieve the production of nanofibers resembling extracellular matrix fibers. The production of nano-sized (~116 nm) bioactive glasses was achieved by microemulsion assisted sol-gel method. The bioactive glass-containing layers developed hydroxyapatite on their surfaces starting from the first week of simulated body fluid (SBF) immersion, demonstrating that the membranes possessed favorable bioactivity properties. Moreover, all membranes exhibited distinct degradation behaviors in various mediums. However, weight loss exceeding 50% was observed in all tested samples after four weeks in both SBF and phosphate-buffered saline (PBS). The double-layered membranes were also subjected to mechanical testing, revealing a tensile strength of approximately 4 MPa. The double-layered membranes containing zinc-doped bioactive glass demonstrated cell viability of over 70% across all tested concentrations (0.2, 0.1, and 0.02 g/mL), confirming the excellent biocompatibility of the membranes. The fabricated polymer bioactive glass composite double-layered membranes are strong candidates with the potential to be utilized in tissue engineering applications. Full article
(This article belongs to the Special Issue Sustainable Biopolymer-Based Composites: Processing, Characterization, and Application II)
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20 pages, 5784 KiB  
Article
Alginate Extracted from Azotobacter chroococcum Loaded in Selenium Nanoparticles: Insight on Characterization, Antifungal and Anticancer Activities
by Hebah A. Sindi, Ragaa A. Hamouda, Marwa S. Abdel-Hamid and Nuha M. Alhazmi
Polymers 2024, 16(14), 2065; https://doi.org/10.3390/polym16142065 - 19 Jul 2024
Viewed by 718
Abstract
Cancer is a threatening disease that needs strong therapy with fewer side effects. A lot of different types of chemotherapy or chemo-drugs are used in cancer treatments but have many side effects. The increasing number of antibiotic-resistant microorganisms requires more study of new [...] Read more.
Cancer is a threatening disease that needs strong therapy with fewer side effects. A lot of different types of chemotherapy or chemo-drugs are used in cancer treatments but have many side effects. The increasing number of antibiotic-resistant microorganisms requires more study of new antimicrobial compounds and delivery and targeting strategies. This work aims to isolate and identify Azotobacter sp., and extract alginate from Azotobacter sp. As well as fabricating selenium nanoparticles using ascorbic acid as reducing agent (As/Se-NPs), and loading extracted alginate with selenium nanoparticles (Alg-Se-NCMs). The As/Se-NPs and Alg-Se-NCMs were categorized by TEM, EDX, UV–Vis spectrophotometry, FT-IR, and zeta potential. The antifungal activities of both As/Se-NPs and Alg-Se-NCMs were investigated against some human pathogen fungi that cause skin infection such as Aspergillus niger (RCMB 002005), Aspergillus fumigatus (RCMB 002008), Cryptococcus neoformans (RCMB 0049001), Candida albicans (RCMB 005003), and Penicillium marneffei (RCMB 001002). The anticancer activities were determined against HCT-116 colorectal cancer and Hep G2 human liver cancer cells. UV spectra of As/Se-NPs and Alg-Se-NCMs confirmed a surface plasmon resonance at 269 and 296 nm, and zeta potential has negative charges −37.2 and −38.7 mV,. Both As/Se-NPs and Alg-Se-NCMs were hexagonal, size ranging from 16.52 to 97.06 and 17.29 to 44.2. Alg-Se-NCMs had anticancer activities against HCT-116 and HepG2. The Alg-Se-NCMs possessed the highest antifungal activities against Cryptococcus neoformans, followed by Aspergillus niger, but did not possess any activities against Penicillium marneffei. Alginate-capped selenium nanoparticles can be used as antifungal and anticancer treatments. Full article
(This article belongs to the Special Issue Bioactive Polymer Materials with Antibacterial Properties, 2nd Edition)
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23 pages, 7185 KiB  
Review
Modifications of Furan-Based Polyesters with the Use of Rigid Diols
by Konrad Walkowiak and Sandra Paszkiewicz
Polymers 2024, 16(14), 2064; https://doi.org/10.3390/polym16142064 - 19 Jul 2024
Viewed by 598
Abstract
The replacement of polymers derived from petrochemical resources has been a prominent area of focus in recent decades. Polymers used in engineering materials must exhibit mechanical strength and stiffness while maintaining performance through a broad temperature range. Most of the polyesters used as [...] Read more.
The replacement of polymers derived from petrochemical resources has been a prominent area of focus in recent decades. Polymers used in engineering materials must exhibit mechanical strength and stiffness while maintaining performance through a broad temperature range. Most of the polyesters used as engineering materials are based on terephthalic acid (TPA) and its derivatives, which provide necessary rigidity to molecular chains due to an aromatic ring. Bio-based alternatives for TPA-based polyesters that are gaining popularity are the polyesters derived from 2,5-furandicarboxylic acid (FDCA). To broaden applicational possibilities, one effective way to achieve specific properties in targeted applications is to adjust the composition and structure of polymers using advanced polymer chemistry techniques. The incorporation of rigid diols such as isosorbide, 1,4-cyclohexanedimethanol (CHDM), and 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) should result in a greater stiffness of the molecular chains. This review extensively explores the effect of incorporating rigid diols on material properties through a review of research articles as well as patents. Moreover, this review mainly focuses on the polyesters and copolyesters synthesized via two-step melt polycondensation and its alterations due to the industrial importance of this method. Innovative synthesis strategies and the resulting material properties are presented. Full article
(This article belongs to the Special Issue Bioplastics to Replace Fossil-Based Plastics—Perspectives for a Circular Economy)
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