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Polymers, Volume 16, Issue 13 (July-1 2024) – 197 articles

Cover Story (view full-size image): Due to the presence of micro-nano hierarchical structures on superhydrophobic surfaces, light scattering behavior is affected, thereby significantly impacting surface transparency. The construction of surfaces with both excellent superhydrophobicity and high transparency has long been a crucial research challenge. Here, we have developed a transparent superhydrophobic coating using a combination of hydrophobic fumed silica and waterborne polyurethane through a facile spray-coating technique. The coating exhibited superior water-repellency, extremely low interfacial adhesion, self-cleaning, and high transparency, with the light transmittance of the coated glass substrate reaching 96.1% of that of the bare glass substrate. View this paper
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18 pages, 7051 KiB  
Article
Sound Absorption Performance of Ultralight Honeycomb Sandwich Panels Filled with “Network” Fibers—Juncus effusus
by Zhao Liu, Chenhao Dong, Lu Tong, Chris Rudd, Xiaosu Yi and Xiaoling Liu
Polymers 2024, 16(13), 1953; https://doi.org/10.3390/polym16131953 - 8 Jul 2024
Viewed by 545
Abstract
This study investigates lightweight and efficient candidates for sound absorption to address the growing demand for sustainable and eco-friendly materials in noise attenuation. Juncus effusus (JE) is a natural fiber known for its unique three-dimensional network, providing a viable and sustainable filler for [...] Read more.
This study investigates lightweight and efficient candidates for sound absorption to address the growing demand for sustainable and eco-friendly materials in noise attenuation. Juncus effusus (JE) is a natural fiber known for its unique three-dimensional network, providing a viable and sustainable filler for enhanced sound absorption in honeycomb panels. Microperforated-panel (MPP) honeycomb absorbers incorporating JE fillers were fabricated and designed, focusing on optimizing the absorber designs by varying JE filler densities, geometrical arrangements, and MPP parameters. At optimal filling densities, the MPP-type honeycomb structures filled with JE fibers achieved high noise reduction coefficients (NRC) of 0.5 and 0.7 at 20 mm and 50 mm thicknesses, respectively. Using an analytical model and an artificial neural network (ANN) model, the sound absorption characteristics of these absorbers were successfully predicted. This study demonstrates the potential of JE fibers in improving noise mitigation strategies across different industries, offering more sustainable and efficient solutions for construction and transportation. Full article
(This article belongs to the Section Circular and Green Polymer Science)
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21 pages, 10317 KiB  
Article
Preparation and Structure–Property Relationship Study of Piezoelectric–Conductive Composite Polymer Nanofiber Materials for Bone Tissue Engineering
by Zhengyang Jin, Suiyan Wei, Wenyang Jin, Bingheng Lu and Yan Xu
Polymers 2024, 16(13), 1952; https://doi.org/10.3390/polym16131952 - 8 Jul 2024
Viewed by 495
Abstract
This study aimed to develop Janus-, cross-network-, and coaxial-structured piezoelectric–conductive polymer nanofibers through electrospinning to mimic the piezoelectricity of bone and facilitate the conduction of electrical signals in bone tissue repair. These nanofibers were constructed using the piezoelectric polymer polyvinylidene fluoride, and the [...] Read more.
This study aimed to develop Janus-, cross-network-, and coaxial-structured piezoelectric–conductive polymer nanofibers through electrospinning to mimic the piezoelectricity of bone and facilitate the conduction of electrical signals in bone tissue repair. These nanofibers were constructed using the piezoelectric polymer polyvinylidene fluoride, and the conductive fillers reduced graphene oxide and polypyrrole. The influence of structural features on the electroactivity of the fibers was also explored. The morphology and components of the various structural samples were characterized using SEM, TEM, and FTIR. The electroactivity of the materials was assessed with a quasi-static d33 meter and the four-probe method. The results revealed that the piezoelectric–conductive phases were successfully integrated. The Janus-structured nanofibers demonstrated the best electroactivity, with a piezoelectric constant d33 of 24.5 pC/N and conductivity of 6.78 × 10−2 S/m. The tensile tests and MIP measurements showed that all samples had porosity levels exceeding 70%. The tensile strength of the Janus and cross-network structures exceeded that of the periosteum (3–4 MPa), with average pore sizes of 1194.36 and 2264.46 nm, respectively. These properties indicated good mechanical performance, allowing material support while preventing fibroblast invasion. The CCK-8 and ALP tests indicated that the Janus-structured samples were biocompatible and significantly promoted the proliferation of MC3T3-E1 cells. Full article
(This article belongs to the Special Issue 3D-Printed Polymers for Tissue Engineering or Bioelectronics)
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16 pages, 16484 KiB  
Article
Dual First and Second Surface Solar Mirrors of Polished WS2 and Silver by Dynamical Chemical Plating Technique on Polycarbonate
by Coraquetzali Magdaleno López, José de Jesús Pérez Bueno, Alejandra Xochitl Maldonado Pérez, Yunny Meas Vong, Jorge Morales Hernández, José Emanuel Ambrosio Juárez, Iván Toledo Manuel, José Antonio Cabello Mendez and David Meneses Rodríguez
Polymers 2024, 16(13), 1951; https://doi.org/10.3390/polym16131951 (registering DOI) - 8 Jul 2024
Viewed by 581
Abstract
This work proposes for the first time protecting–reflecting on both sides of plated mirrors and a solution to polycarbonate surface vulnerability to weathering and scratching using tungsten disulfide (WS2) by mechanical polishing. The ability of the dynamic chemical plating (DCP) technique [...] Read more.
This work proposes for the first time protecting–reflecting on both sides of plated mirrors and a solution to polycarbonate surface vulnerability to weathering and scratching using tungsten disulfide (WS2) by mechanical polishing. The ability of the dynamic chemical plating (DCP) technique to deposit Ag films at the nanometer scale on a polycarbonate (PC) substrate and its characteristics to be metallized is also shown. These deposits hold significant promise for concentrated solar power (CSP) applications. Complementarily, the application of WS2 as a reflective film for CSP by mechanical polishing on smooth polycarbonate surfaces is both novel and practical. This technique is innovative and scalable without needing reactants or electrical potential, making it highly applicable in real-world scenarios, including, potentially, on-site maintenance. The effects of surface morphology and adhesion, and the reflectivity parameters of the silver metallic surfaces were investigated. Wettability was investigated because it is important for polymeric surfaces in the activation and metal deposition immediately after redox reactions. The flame technique improved wettability by modifying the surface with carbonyl and carboxyl functional groups, with PC among the few industrial polymers that resisted such a part of the process. The change in the chemical composition, roughness, and wettability of the surfaces effectively improved the adhesion between the Ag film and the PC substrate. However, it did not significantly affect the adhesion between PC and WS2 and showed its possible implementation as a first surface mirror. Overall, this work provides a scalable, innovative method for improving the durability and reflectivity of polycarbonate-based mirrors, with significant implications for CSP applications. Full article
(This article belongs to the Special Issue Advances and Innovations in Recycled Polymer Composites)
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14 pages, 691 KiB  
Article
Analysis of Diffracted Mode Outcoupling in the Context of Amplified Spontaneous Emission of Organic Thin Films
by Thilo Pudleiner, Jan Hoinkis and Christian Karnutsch
Polymers 2024, 16(13), 1950; https://doi.org/10.3390/polym16131950 - 8 Jul 2024
Viewed by 425
Abstract
The existence of amplified spontaneous emission (ASE) is a fundamental principle of laser dyes. ASE indicates the spectral variation of the optical gain of a laser dye. Analyzing the spectral distribution of ASE is important for designing lasers. We demonstrate ASE investigations on [...] Read more.
The existence of amplified spontaneous emission (ASE) is a fundamental principle of laser dyes. ASE indicates the spectral variation of the optical gain of a laser dye. Analyzing the spectral distribution of ASE is important for designing lasers. We demonstrate ASE investigations on planar waveguides made of a (co-)polymer. Similar to organic DFB (distributed feedback) lasers, a line grating allows a partial decoupling of the guided radiation. This decoupled radiation is detected as an indicator of the guided radiation. The diffraction of the radiation is utilized to perform a spectrally selective investigation of the ASE by spatially splitting it. This analysis method reduces the influence of isotropic photoluminescence and allows ASE to be analyzed across its entire spectrum. We were able to observe ASE in F8BT over a range from λASE,min = 530 nm to λASE,max = 570 nm and determine ASE threshold power densities lower than EASE< 2.57 μJ/cm2. The study of the power density of the ASE threshold is performed spectrally selectively. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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13 pages, 3571 KiB  
Article
Fabrication of PVA–Silica Sol Wood Composites via Delignification and Freezing Pretreatment
by Rizheng Cong, Taoyang Cai, Shangjie Ge-Zhang, Hong Yang and Chang Zhang
Polymers 2024, 16(13), 1949; https://doi.org/10.3390/polym16131949 - 8 Jul 2024
Viewed by 431
Abstract
The efficient exploitation of planted fast-growing wood is crucial for enhancing wood resource utilization. In this study, the fast-growing poplar wood was modified by in situ impregnation through vacuum impregnation with polyvinyl alcohol and nano-silica sol as impregnation modifiers, combined with delignification–freezing pretreatment. [...] Read more.
The efficient exploitation of planted fast-growing wood is crucial for enhancing wood resource utilization. In this study, the fast-growing poplar wood was modified by in situ impregnation through vacuum impregnation with polyvinyl alcohol and nano-silica sol as impregnation modifiers, combined with delignification–freezing pretreatment. The samples were characterized by FTIR, XRD, SEM, and the universal mechanical testing machine. The results showed that the wrinkle deformation and cracking of the wood blocks were greatly alleviated after the delignification–freezing pretreatment and the polyvinyl alcohol and nano-silica sol were successfully integrated into the wood. The resulting polyvinyl alcohol–silica sol poplar composites exhibited about 216%, 80% and 43% higher compressive strength with respect to delignified wood, natural wood and impregnated natural wood, respectively, thereby demonstrating superior mechanical properties and potential opportunities for value-added and efficient utilization of low-quality wood. Full article
(This article belongs to the Special Issue Recent Developments in Wood Polymer Composites)
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13 pages, 5021 KiB  
Article
Towards Sustainable Temperature Sensor Production through CO2-Derived Polycarbonate-Based Composites
by Ane Martín-Ayerdi, Luis Rubio-Peña, Nikola Peřinka, Itziar Oyarzabal, José L. Vilas, Pedro Costa and Senentxu Lanceros-Méndez
Polymers 2024, 16(13), 1948; https://doi.org/10.3390/polym16131948 - 8 Jul 2024
Viewed by 413
Abstract
The steep increase in carbon dioxide (CO2) emissions has created great concern due to its role in the greenhouse effect and global warming. One approach to mitigate CO2 levels involves its application in specific technologies. In this context, CO2 [...] Read more.
The steep increase in carbon dioxide (CO2) emissions has created great concern due to its role in the greenhouse effect and global warming. One approach to mitigate CO2 levels involves its application in specific technologies. In this context, CO2 can be used for a more sustainable synthesis of polycarbonates (CO2-PCs). In this research, CO2-PC films and composites with multiwalled carbon nanotubes (MWCNTs, ranging from 0.2 to 7.0 wt.%) have been prepared to achieve more sustainable multifunctional sensing devices. The inclusion of the carbonaceous fillers allows for the electrical conductivity to be enhanced, reaching the percolation threshold (Pc) at 0.1 wt.% MWCNTs and a maximum electrical conductivity of 0.107 S·m−1 for the composite containing 1.5 wt.% MWCNTs. The composite containing 3.0 wt.% MWCNTs was also studied, showing a stable and linear response under temperature variations from 40 to 100 °C and from 30 to 45 °C, with a sensitivity of 1.3 × 10−4 °C−1. Thus, this investigation demonstrates the possibility of employing CO2-derived PC/MWCNT composites as thermoresistive sensing materials, allowing for the transition towards sustainable polymer-based electronics. Full article
(This article belongs to the Special Issue Conductive and Magnetic Properties of Polymer Nanocomposites)
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17 pages, 5347 KiB  
Article
Effect of Glycerol and Sisal Nanofiber Content on the Tensile Properties of Corn Starch/Sisal Nanofiber Films
by Mailson Batista de Vilhena, Marcos Vinícius da Silva Paula, Raul Costa de Oliveira, Diego Cardoso Estumano, Bruno Marques Viegas, Emerson Cardoso Rodrigues, Emanuel Negrão Macêdo, José Antônio da Silva Souza and Edinaldo José de Sousa Cunha
Polymers 2024, 16(13), 1947; https://doi.org/10.3390/polym16131947 - 8 Jul 2024
Viewed by 445
Abstract
Currently, petroleum-derived plastics are widely used despite the disadvantage of their long degradation time. Natural polymers, however, can be used as alternatives to overcome this obstacle, particularly cornstarch. The tensile properties of cornstarch films can be improved by adding plant-derived nanofibers. Sisal ( [...] Read more.
Currently, petroleum-derived plastics are widely used despite the disadvantage of their long degradation time. Natural polymers, however, can be used as alternatives to overcome this obstacle, particularly cornstarch. The tensile properties of cornstarch films can be improved by adding plant-derived nanofibers. Sisal (Agave sisalana), a very common low-cost species in Brazil, can be used to obtain plant nanofibers. The goal of this study was to obtain sisal nanofibers using low concentrations of sulfuric acid to produce thermoplastic starch nanocomposite films. The films were produced by a casting technique using commercial corn starch, glycerol, and sisal nanofibers, accomplished by acid hydrolysis. The effects of glycerol and sisal nanofiber content on the tensile mechanical properties of the nanocomposites were investigated. Transmission electron microscopy findings demonstrated that the lowest concentration of sulfuric acid produced fibers with nanometric dimensions related to the concentrations used. X-ray diffraction revealed that the untreated fibers and fibers subjected to acid hydrolysis exhibited a crystallinity index of 61.06 and 84.44%, respectively. When the glycerol and nanofiber contents were 28 and 1%, respectively, the tensile stress and elongation were 8.02 MPa and 3.4%. In general, nanocomposites reinforced with sisal nanofibers showed lower tensile stress and higher elongation than matrices without nanofibers did. These results were attributed to the inefficient dispersion of the nanofibers in the polymer matrix. Our findings demonstrate the potential of corn starch nanocomposite films in the packaging industry. Full article
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11 pages, 4107 KiB  
Article
Experimental Study on the Transport Properties of 12 Novel Deep Eutectic Solvents
by Jing Fan, Yuting Pan, Dazhi Gao and Hongwei Qu
Polymers 2024, 16(13), 1946; https://doi.org/10.3390/polym16131946 - 8 Jul 2024
Viewed by 404
Abstract
Deep eutectic solvents (DESs) are complex substances composed of two or three components, wherein hydrogen bond donors and acceptors engage in intricate interactions within a hydrogen bond network. They have attracted extensive attention from researchers due to their easy synthesis, cost-effectiveness, broad liquid [...] Read more.
Deep eutectic solvents (DESs) are complex substances composed of two or three components, wherein hydrogen bond donors and acceptors engage in intricate interactions within a hydrogen bond network. They have attracted extensive attention from researchers due to their easy synthesis, cost-effectiveness, broad liquid range, good stability, and for being green and non-toxic. However, studies on the physical properties of DESs are still scarce and many theories are not perfect enough, which limits the application of DESs in engineering practice. In this study, twelve DESs were synthesized by using choline chloride and betaine as HBAs, and ethylene glycol, polyethylene glycol 600, o-cresol, glycerol, and lactic acid as HBDs. The variation rules of their thermal conductivity and viscosity with temperature at atmospheric pressure were systematically investigated. The experimental results showed that the thermal conductivity of the 1:4 choline chloride/glycerol solvent was the largest at 294 K, reaching 0.2456 W·m−1·K−1, which could satisfy the demand for high efficiency heat transfer by heat-transferring workpieces. The temperature–viscosity relationship of the DESs was fitted using the Arrhenius model, and the maximum average absolute deviation was 6.77%. Full article
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13 pages, 5394 KiB  
Article
Natural Rubber/Styrene–Butadiene Rubber Blend Composites Potentially Applied in Damping Bearings
by Saifeng Tang, Zhanxu Li, Weichong Sun, Yangling Liu, Jian Wang, Xiong Wang and Jun Lin
Polymers 2024, 16(13), 1945; https://doi.org/10.3390/polym16131945 - 8 Jul 2024
Viewed by 436
Abstract
Natural rubber (NR) composites have been widely applied in damping products to reduce harmful vibrations, while rubber with only a single composition barely meets performance requirements. In this study, rubber blend composites including various ratios of NR and styrene butadiene rubber (SBR) were [...] Read more.
Natural rubber (NR) composites have been widely applied in damping products to reduce harmful vibrations, while rubber with only a single composition barely meets performance requirements. In this study, rubber blend composites including various ratios of NR and styrene butadiene rubber (SBR) were prepared via the conventional mechanical blending method. The effects of the rubber components on the compression set, compression fatigue temperature rising and the thermal oxidative aging properties of the NR/SBR blend composites were investigated. Meanwhile, the dynamic mechanical thermal analyzer and rubber processing analyzer were used to characterize the dynamic viscoelasticity of the NR/SBR blend composites. It was shown that, with the increase in the SBR ratio, the vulcanization rate of the composites increased significantly, while the compression fatigue temperature rising of the composites decreased gradually from 47 °C (0% SBR ratio) to 31 °C (50% SBR ratio). The compression set of the composites remained at ~33% when the SBR ratio was no more than 20%, and increased gradually when the SBR ratio was more than 20%. Full article
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14 pages, 2002 KiB  
Article
Study on the Aging Characteristics of a ±500 kV Composite Dead-End Insulator in Longtime Service
by Zhijin Zhang, Bingbing Wang, Xuze Li, Shude Jing, Yuan Gao, Dong Zeng and Xingliang Jiang
Polymers 2024, 16(13), 1944; https://doi.org/10.3390/polym16131944 - 8 Jul 2024
Viewed by 392
Abstract
Composite insulators have been widely used in power grids due to their excellent electrical-external-insulation performance. Long-term operation at high voltage levels accelerates the aging of composite insulators; however, there is a scarcity of research on aged composite insulators operating at 500 kV for [...] Read more.
Composite insulators have been widely used in power grids due to their excellent electrical-external-insulation performance. Long-term operation at high voltage levels accelerates the aging of composite insulators; however, there is a scarcity of research on aged composite insulators operating at 500 kV for over ten years. In this paper, the mechanical, electrical, and microscopic properties were tested on different sheds along a 500 kV composite insulator that had been running for 18 years. Additionally, the results were compared with a new insulator and the standards for live insulator operation. The results showed that the aging of the high-voltage end of composite insulators was the most serious. The results of the physical properties test indicated that the insulator’s hardness was compliant but its tensile strength and break elongation did not meet standards. Under wet conditions, the pollution flashover voltage decreases by about 50% compared to the new insulator. Combined with the microscopic test results, the shed skeleton structure could be damaged and the filler might be lost during the aging process of polydimethylsiloxane (PDMS). The hardness of the insulator would increase by the precipitation of inorganic silicon; however, inorganic silicon might destroy the hydrophobicity and other properties of insulator sheds. These results can provide theoretical references for insulator life prediction and operation protection. Full article
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15 pages, 5829 KiB  
Article
Disclosing Topographical and Chemical Patterns in Confined Films of High-Molecular-Weight Block Copolymers under Controlled Solvothermal Annealing
by Xiao Cheng, Jenny Tempeler, Serhiy Danylyuk, Alexander Böker and Larisa Tsarkova
Polymers 2024, 16(13), 1943; https://doi.org/10.3390/polym16131943 - 8 Jul 2024
Viewed by 485
Abstract
The microphase separation of high-molecular-weight block copolymers into nanostructured films is strongly dependent on the surface fields. Both, the chain mobility and the effective interaction parameters can lead to deviations from the bulk morphologies in the structures adjacent to the substrate. Resolving frustrated [...] Read more.
The microphase separation of high-molecular-weight block copolymers into nanostructured films is strongly dependent on the surface fields. Both, the chain mobility and the effective interaction parameters can lead to deviations from the bulk morphologies in the structures adjacent to the substrate. Resolving frustrated morphologies with domain period L0 above 100 nm is an experimental challenge. Here, solvothermal annealing was used to assess the contribution of elevated temperatures of the vapor Tv and of the substrate Ts on the evolution of the microphase-separated structures in thin films symmetric of polystyrene-b-poly(2vinylpyridine) block copolymer (PS-PVP) with L0 about 120 nm. Pronounced topographic mesh-like and stripe patterns develop on a time scale of min and are attributed to the perforated lamella (PL) and up-standing lamella phases. By setting Tv/Ts combinations it is possible to tune the sizes of the resulting PL patterns by almost 10%. Resolving chemical periodicity using selective metallization of the structures revealed multiplication of the topographic stripes, i.e., complex segregation of the component within the topographic pattern, presumably as a result of morphological phase transition from initial non-equilibrium spherical morphology. Reported results reveal approaches to tune the topographical and chemical periodicity of microphase separation of high-molecular-weight block copolymers under strong confinement, which is essential for exploiting these structures as functional templates. Full article
(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly and Application)
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16 pages, 16472 KiB  
Article
Dispersion and Lubrication of Zinc Stearate in Polypropylene/Sodium 4-[(4-chlorobenzoyl) amino] Benzoate Nucleating Agent Composite
by Yapeng Dong, Fuhua Lin, Tianjiao Zhao, Meizhen Wang, Dingyi Ning, Xinyu Hao, Yanli Zhang, Dan Zhou, Yuying Zhao, Xinde Chen and Bo Wang
Polymers 2024, 16(13), 1942; https://doi.org/10.3390/polym16131942 - 7 Jul 2024
Viewed by 514
Abstract
Zinc stearate (Znst) was physically blended with the sodium 4-[(4 chlorobenzoyl) amino] benzoate (SCAB) to obtain the SCAB-Znst composite nucleating agent. Znst was used to improve the dispersion property of SCAB and exert a lubricating effect on the PP matrix. The scanning electron [...] Read more.
Zinc stearate (Znst) was physically blended with the sodium 4-[(4 chlorobenzoyl) amino] benzoate (SCAB) to obtain the SCAB-Znst composite nucleating agent. Znst was used to improve the dispersion property of SCAB and exert a lubricating effect on the PP matrix. The scanning electron microscopy and the fracture surface morphology of the PP/SCAB composite illustrated that the addition of Znst greatly reduced the aggregation phenomenon of SCAB in the PP matrix. The result of the rotary rheometer indicated that Znst exhibits internal lubrication in PP. The DSC result illustrated that the crystallization properties of PP were improved. Compared with pure PP, the Tc of the PP/SCAB composite increased by 1.44 °C (PP/Znst), 13.48 °C (PP/SCAB), and 14.96 °C (PP/SCAB-Znst), respectively. The flexural strength of pure PP, PP/SCAB, and PP/SCAB-Znst were 35.8 MPa, 38.8 MPa, and 40.6 MPa, respectively. The tensile strength of the PP/SCAB and PP/SCAB-Znst reached the values of 39.8 MPa and 42.9 MPa, respectively, compared with pure PP (34.1 MPa). The results demonstrated that Znst can promote the dispersion of SCAB in the PP matrix while exerting a lubricating effect, which enabled the enhancement of the crystalline and mechanical properties of PP. Full article
(This article belongs to the Special Issue Additive Agents for Polymer Functionalization Modification)
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17 pages, 3358 KiB  
Article
Enhancing Tensile Modulus of Polyurethane-Based Shape Memory Polymers for Wound Closure Applications through the Addition of Palm Oil
by Sirasit Kampangsat, Todsapol Kajornprai, Warakarn Tangjatuporn, Nitinat Suppakarn and Tatiya Trongsatitkul
Polymers 2024, 16(13), 1941; https://doi.org/10.3390/polym16131941 - 7 Jul 2024
Viewed by 805
Abstract
Thermo-responsive, biocompatible polyurethane (PU) with shape memory properties is highly desirable for biomedical applications. An innovative approach to producing wound closure strips using shape memory polymers (SMPs) is of significant interest. In this work, PU composed of polycaprolactone (PCL) and 1,4-butanediol (BDO) was [...] Read more.
Thermo-responsive, biocompatible polyurethane (PU) with shape memory properties is highly desirable for biomedical applications. An innovative approach to producing wound closure strips using shape memory polymers (SMPs) is of significant interest. In this work, PU composed of polycaprolactone (PCL) and 1,4-butanediol (BDO) was synthesized using two-step polymerization. Palm oil (PO) was added to PU for enhancing the Young’s modulus of the PU beyond the set criterion of 130 MPa. It was found that PU had the ability to crystallize at room temperature and the segments of individual PCL and BDO polyurethanes crystallized separately. The crystalline domains and hard segment of PU greatly affected the tensile properties. The reduction of crystalline domains by the addition of PO and deformation at the higher melting temperature of the crystalline PCL polyurethane phase improved the shape fixity and shape recovery ratios. The new irreversible phase, raised from the permanent deformation upon stretching at the between melting temperature of the crystalline PCL and BDO polyurethanes of 70 °C, resulted in a decrease in shape fixity ratio after the first thermomechanical stretching–recovering cycles. The demonstration of PU as a wound closure strip showed its efficiency and potential until the surgical wound healed. Full article
(This article belongs to the Special Issue Smart and Bio-Medical Polymers)
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13 pages, 5276 KiB  
Article
Flexible Resistive Gas Sensor Based on Molybdenum Disulfide-Modified Polypyrrole for Trace NO2 Detection
by Kuo Zhao, Yunbo Shi, Mingrui Cui, Bolun Tang, Canda Zheng, Qinglong Chen and Yuhan Hu
Polymers 2024, 16(13), 1940; https://doi.org/10.3390/polym16131940 - 7 Jul 2024
Viewed by 500
Abstract
High sensitivity and selectivity and short response and recovery times are important for practical conductive polymer gas sensors. However, poor stability, poor selectivity, and long response times significantly limit the applicability of single-phase conducting polymers, such as polypyrrole (PPy). In this study, PPy/MoS [...] Read more.
High sensitivity and selectivity and short response and recovery times are important for practical conductive polymer gas sensors. However, poor stability, poor selectivity, and long response times significantly limit the applicability of single-phase conducting polymers, such as polypyrrole (PPy). In this study, PPy/MoS2 composite films were prepared via chemical polymerization and mechanical blending, and flexible thin-film resistive NO2 sensors consisting of copper heating, fluorene polyester insulating, and PPy/MoS2 sensing layers with a silver fork finger electrode were fabricated on a flexible polyimide substrate using a flexible electronic printer. The PPy/MoS2 composite films were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and field-emission scanning electron microscopy. A home-built gas sensing test platform was built to determine the resistance changes in the composite thin-film sensor with temperature and gas concentration. The PPy/MoS2 sensor exhibited better sensitivity, selectivity, and stability than a pure PPy sensor. Its response to 50 ppm NO2 was 38% at 150 °C, i.e., 26% higher than that of the pure PPy sensor, and its selectivity and stability were also higher. The greater sensitivity was attributed to p–n heterojunction formation after MoS2 doping and more gas adsorption sites. Thus, PPy/MoS2 composite film sensors have good application prospects. Full article
(This article belongs to the Special Issue Polymers for Biosensors and Detection)
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16 pages, 7646 KiB  
Article
Impact of Composition and Autoclave Sterilization on the Mechanical and Biological Properties of ECM-Mimicking Cryogels
by Laura Di Muzio, Susi Zara, Amelia Cataldi, Claudia Sergi, Vito Cosimo Carriero, Barbara Bigi, Simone Carradori, Jacopo Tirillò, Stefania Petralito, Maria Antonietta Casadei and Patrizia Paolicelli
Polymers 2024, 16(13), 1939; https://doi.org/10.3390/polym16131939 - 7 Jul 2024
Viewed by 509
Abstract
Cryogels represent a valid strategy as scaffolds for tissue engineering. In order to adequately support adhesion and proliferation of anchorage-dependent cells, different polymers need to be combined within the same scaffold trying to mimic the complex features of a natural extracellular matrix (ECM). [...] Read more.
Cryogels represent a valid strategy as scaffolds for tissue engineering. In order to adequately support adhesion and proliferation of anchorage-dependent cells, different polymers need to be combined within the same scaffold trying to mimic the complex features of a natural extracellular matrix (ECM). For this reason, in this work, gelatin (Gel) and chondroitin sulfate (CS), both functionalized with methacrylic groups to produce CSMA and GelMA derivatives, were selected to prepare cryogel networks. Both homopolymer and heteropolymer cryogels were produced, via radical crosslinking reactions carried out at −12 °C for 2 h. All the scaffolds were characterized for their mechanical, swelling and morphological properties, before and after autoclave sterilization. Moreover, they were evaluated for their biocompatibility and ability to support the adhesion of human gingival fibroblasts and tenocytes. GelMA-based homopolymer networks better withstood the autoclave sterilization process, compared to CSMA cryogels. Indeed, GelMA cryogels showed a decrease in stiffness of approximately 30%, whereas CSMA cryogels of approximately 80%. When GelMA and CSMA were blended in the same network, an intermediate outcome was observed. However, the hybrid scaffolds showed a general worsening of the biological performance. Indeed, despite their ability to withstand autoclave sterilization with limited modification of the mechanical and morphological properties, the hybrid cryogels exhibited poor cell adhesion and high LDH leakage. Therefore, not only do network components need to be properly selected, but also their combination and ability to withstand effective sterilization process should be carefully evaluated for the development of efficient scaffolds designed for tissue engineering purposes. Full article
(This article belongs to the Special Issue Biopolymer-Based Biomimetic Scaffolds II)
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16 pages, 3386 KiB  
Article
Chemosensitive Properties of Electrochemically Synthesized Poly-3-Thienylboronic Acid: Conductometric Detection of Glucose and Other Diol-Containing Compounds under Electrical Affinity Control
by Yulia Efremenko and Vladimir M. Mirsky
Polymers 2024, 16(13), 1938; https://doi.org/10.3390/polym16131938 - 7 Jul 2024
Viewed by 414
Abstract
Due to the presence of the boronic acid moieties, poly-3-thienylboronic acid has an affinity for saccharides and other diol-containing compounds. Thin films of this novel chemosensitive polymer were synthesized electrochemically on the gold surface. The adhesion of the polymer was enhanced by the [...] Read more.
Due to the presence of the boronic acid moieties, poly-3-thienylboronic acid has an affinity for saccharides and other diol-containing compounds. Thin films of this novel chemosensitive polymer were synthesized electrochemically on the gold surface. The adhesion of the polymer was enhanced by the deposition of a monomolecular layer of thiophenol. The technology was used to fabricate conductometric sensors for glucose and other diol-containing compounds. Simultaneous two- and four-electrode conductivity measurements were performed. The chemical sensitivity to sorbitol, fructose, glucose, and ethylene glycol was studied at different pH and electrode potentials, and the corresponding binding constants were obtained. Depending on the electrode potential, the reciprocal values of the binding constants of glucose to poly-3-thienylboronic acid at neutral pH are in the range of 0.2 mM–1.0 mM. The affinity for glucose has been studied in buffer solutions and in solutions containing the major components of human blood. It was shown that the presence of human serum albumin increases the affinity of poly-3-thienylboronic acid for diol-containing compounds. Full article
(This article belongs to the Special Issue Design and Characterization of Polymer-Based Electrode Materials)
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30 pages, 15394 KiB  
Review
Principles and Design of Bionic Hydrogel Adhesives for Skin Wound Treatment
by Chunxiao Wang, Xinyu Zhang, Yinuo Fan, Shuhan Yu, Man Liu, Linhan Feng, Qisen Sun and Panpan Pan
Polymers 2024, 16(13), 1937; https://doi.org/10.3390/polym16131937 - 6 Jul 2024
Viewed by 935
Abstract
Over millions of years of evolution, nature has developed a myriad of unique features that have inspired the design of adhesives for wound healing. Bionic hydrogel adhesives, capable of adapting to the dynamic movements of tissues, possess superior biocompatibility and effectively promote the [...] Read more.
Over millions of years of evolution, nature has developed a myriad of unique features that have inspired the design of adhesives for wound healing. Bionic hydrogel adhesives, capable of adapting to the dynamic movements of tissues, possess superior biocompatibility and effectively promote the healing of both external and internal wounds. This paper provides a systematic review of the design and principles of these adhesives, focusing on the treatment of skin wounds, and explores the feasibility of incorporating nature-inspired properties into their design. The adhesion mechanisms of bionic adhesives are analyzed from both chemical and physical perspectives. Materials from natural and synthetic polymers commonly used as adhesives are detailed regarding their biocompatibility and degradability. The multifunctional design elements of hydrogel adhesives for skin trauma treatment, such as self-healing, drug release, responsive design, and optimization of mechanical and physical properties, are further explored. The aim is to overcome the limitations of conventional treatments and offer a safer, more effective solution for the application of bionic wound dressings. Full article
(This article belongs to the Special Issue Biomedical Polymer Materials for Wound Healing)
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23 pages, 6509 KiB  
Article
Chemical Modification of Nanocrystalline Cellulose for Manufacturing of Osteoconductive Composite Materials
by Olga Solomakha, Mariia Stepanova, Anatoliy Dobrodumov, Iosif Gofman, Yulia Nashchekina, Alexey Nashchekin and Evgenia Korzhikova-Vlakh
Polymers 2024, 16(13), 1936; https://doi.org/10.3390/polym16131936 - 6 Jul 2024
Viewed by 515
Abstract
Cellulose is one of the main renewable polymers whose properties are very attractive in many fields, including biomedical applications. The modification of nanocrystalline cellulose (NCC) opens up the possibility of creating nanomaterials with properties of interest as well as combining them with other [...] Read more.
Cellulose is one of the main renewable polymers whose properties are very attractive in many fields, including biomedical applications. The modification of nanocrystalline cellulose (NCC) opens up the possibility of creating nanomaterials with properties of interest as well as combining them with other biomedical polymers. In this work, we proposed the covalent modification of NCC with amphiphilic polyanions such as modified heparin (Hep) and poly(αL-glutamic acid) (PGlu). The modification of NCC should overcome two drawbacks in the production of composite materials based on poly(ε-caprolactone) (PCL), namely, (1) to improve the distribution of modified NCC in the PCL matrix, and (2) to provide the composite material with osteoconductive properties. The obtained specimens of modified NCC were characterized by Fourier-transform infrared spectroscopy and solid-state 13C nuclear magnetic resonance spectroscopy, dynamic and electrophoretic light scattering, as well as thermogravimetric analysis. The morphology of PCL-based composites containing neat or modified NCC as filler was studied by optical and scanning electron microscopy. The mechanical properties of the obtained composites were examined in tensile tests. The homogeneity of filler distribution as well as the mechanical properties of the composites depended on the method of NCC modification and the amount of attached polyanion. In vitro biological evaluation showed improved adhesion of human fetal mesenchymal stem cells (FetMSCs) and human osteoblast-like cells (MG-63 osteosarcoma cell line) to PCL-based composites filled with NCC bearing Hep or PGlu derivatives compared to pure PCL. Furthermore, these composites demonstrated the osteoconductive properties in the experiment on the osteogenic differentiation of FetMSCs. Full article
(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)
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16 pages, 5462 KiB  
Article
Various Morphologies of Graphitic Carbon Nitride (g-C3N4) and Their Effect on the Thermomechanical Properties of Thermoset Epoxy Resin Composites
by Dina Al Mais, Samir Mustapha, Yasmine N. Baghdadi, Kamal Bouhadir and Ali R. Tehrani-Bagha
Polymers 2024, 16(13), 1935; https://doi.org/10.3390/polym16131935 - 6 Jul 2024
Viewed by 660
Abstract
This research aims to highlight the importance of diverse forms of graphitic carbon nitride (g-C3N4) as strengthening elements in epoxy composites. It explores the influence of three different forms of g-C3N4 and their concentrations on the [...] Read more.
This research aims to highlight the importance of diverse forms of graphitic carbon nitride (g-C3N4) as strengthening elements in epoxy composites. It explores the influence of three different forms of g-C3N4 and their concentrations on the mechanical properties of the epoxy composites. Various characterization techniques, such as scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR), were utilized to comprehend the effects of g-C3N4 morphology and particle size on the physical and chemical characteristics of epoxy resin. Mechanical properties, such as tensile strength, strain, modulus, and fracture toughness, were determined for the composite samples. SEM analysis was performed to examine crack morphology in samples with different reinforcements. Findings indicate that optimal mechanical properties were achieved with a 0.5 wt% bulk g-C3N4 filler, enhancing tensile strength by 14%. SEM micrographs of fracture surfaces revealed a transition from brittle to rough morphology, suggesting increased toughness in the composites. While the TGA results showed no significant impact on degradation temperature, dynamic mechanical analysis demonstrated a 17% increase in glass transition temperature. Furthermore, the improvement in thermal breakdown up to 600 °C was attributed to reinforced covalent bonds between carbon and nitrogen, supported by FTIR results. Full article
(This article belongs to the Topic Advanced Composites Manufacturing and Plastics Processing)
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17 pages, 3725 KiB  
Article
Electrospun Ibuprofen-Loaded Blend PCL/PEO Fibers for Topical Drug Delivery Applications
by Diala Bani Mustafa, Tsuyoshi Sakai, Osamu Sato, Mitsuo Ikebe and Shih-Feng Chou
Polymers 2024, 16(13), 1934; https://doi.org/10.3390/polym16131934 - 6 Jul 2024
Viewed by 551
Abstract
Electrospun drug-eluting fibers have demonstrated potentials in topical drug delivery applications, where drug releases can be modulated by polymer fiber compositions. In this study, blend fibers of polycaprolactone (PCL) and polyethylene oxide (PEO) at various compositions were electrospun from 10 wt% of polymer [...] Read more.
Electrospun drug-eluting fibers have demonstrated potentials in topical drug delivery applications, where drug releases can be modulated by polymer fiber compositions. In this study, blend fibers of polycaprolactone (PCL) and polyethylene oxide (PEO) at various compositions were electrospun from 10 wt% of polymer solutions to encapsulate a model drug of ibuprofen (IBP). The results showed that the average polymer solution viscosities determined the electrospinning parameters and the resulting average fiber diameters. Increasing PEO contents in the blend PCL/PEO fibers decreased the average elastic moduli, the average tensile strength, and the average fracture strains, where IBP exhibited a plasticizing effect in the blend PCL/PEO fibers. Increasing PEO contents in the blend PCL/PEO fibers promoted the surface wettability of the fibers. The in vitro release of IBP suggested a transition from a gradual release to a fast release when increasing PEO contents in the blend PCL/PEO fibers up to 120 min. The in vitro viability of blend PCL/PEO fibers using MTT assays showed that the fibers were compatible with MEF-3T3 fibroblasts. In conclusion, our results explained the scientific correlations between the solution properties and the physicomechanical properties of electrospun fibers. These blend PCL/PEO fibers, having the ability to modulate IBP release, are suitable for topical drug delivery applications. Full article
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15 pages, 3111 KiB  
Article
Novel Optical Methodology Unveils the Impact of a Polymeric Pour-Point Depressant on the Phase Morphology of Waxy Crude Oils
by Irene Perna, Rosalia Ferraro, Consiglia Carillo, Salvatore Coppola and Sergio Caserta
Polymers 2024, 16(13), 1933; https://doi.org/10.3390/polym16131933 - 6 Jul 2024
Viewed by 440
Abstract
Crude oil, also known as petroleum, plays a crucial role in global economies, politics, and technological advancements due to its widespread applications in industrial organic chemistry. Despite environmental concerns, the dwindling supply of easily accessible oil reservoirs necessitates the exploration of unconventional resources, [...] Read more.
Crude oil, also known as petroleum, plays a crucial role in global economies, politics, and technological advancements due to its widespread applications in industrial organic chemistry. Despite environmental concerns, the dwindling supply of easily accessible oil reservoirs necessitates the exploration of unconventional resources, such as heavy and extra-heavy oils. These oils, characterized by high viscosity and complex composition, pose challenges in extraction, transportation, and refinement. With decreasing temperatures, heavy oils undergo phase changes, with transitions from Newtonian to non-Newtonian fluid behavior, leading to difficulties in transportation. Alternative methods, such as the use of polymeric pour-point depressants, help mitigate flowability issues by preventing wax precipitation. Understanding the properties of waxy crude oil, such as the wax appearance temperature (WAT), is crucial for effective mitigation strategies. The objective of this research is to determine the WATs of different types of waxy crude oils through a comparative analysis using advanced techniques such as cross-polar microscopy (CPM), standard rheology, and differential scanning calorimetry (DSC). Disparities in WAT identified through different analytical methods highlight the potential of microscopy to enhance our understanding of complex fluid dynamics in real time in order to proactively identify and address crystallization issues in oilfields. Full article
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16 pages, 16327 KiB  
Article
3D-Bioprinted Gelatin Methacryloyl-Strontium-Doped Hydroxyapatite Composite Hydrogels Scaffolds for Bone Tissue Regeneration
by Cosmin Iulian Codrea, Dilruba Baykara, Raul-Augustin Mitran, Ayşe Ceren Çalıkoğlu Koyuncu, Oguzhan Gunduz and Anton Ficai
Polymers 2024, 16(13), 1932; https://doi.org/10.3390/polym16131932 - 6 Jul 2024
Viewed by 710
Abstract
New gelatin methacryloyl (GelMA)—strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, [...] Read more.
New gelatin methacryloyl (GelMA)—strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair. Full article
(This article belongs to the Special Issue Polymeric Materials and Their Application in 3D Printing, 2nd Edition)
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19 pages, 3657 KiB  
Article
Shaping in the Third Direction: Colloidal Photonic Crystals with Quadratic Surfaces Self-Assembled by Hanging-Drop Method
by Ion Sandu, Iulia Antohe, Claudiu Teodor Fleaca, Florian Dumitrache, Iuliana Urzica and Marius Dumitru
Polymers 2024, 16(13), 1931; https://doi.org/10.3390/polym16131931 - 6 Jul 2024
Viewed by 550
Abstract
High-quality, 3D-shaped, SiO2 colloidal photonic crystals (ellipsoids, hyperboloids, and others) were fabricated by self-assembly. They possess a quadratic surface and are wide-angle-independent, direction-dependent, diffractive reflection crystals. Their size varies between 1 and 5 mm and can be achieved as mechanical-resistant, free-standing, thick [...] Read more.
High-quality, 3D-shaped, SiO2 colloidal photonic crystals (ellipsoids, hyperboloids, and others) were fabricated by self-assembly. They possess a quadratic surface and are wide-angle-independent, direction-dependent, diffractive reflection crystals. Their size varies between 1 and 5 mm and can be achieved as mechanical-resistant, free-standing, thick (hundreds of ordered layers) objects. High-quality, 3D-shaped, polystyrene inverse-opal photonic superstructures (highly similar to diatom frustules) were synthesized by using an inside infiltration method as wide-angle-independent, reflective diffraction objects. They possess multiple reflection bands given by their special architecture (a torus on the top of an ellipsoid) and by their different sized holes (384 nm and 264 nm). Our hanging-drop self-assembly approach uses setups which deform the shape of an ordinary spherical drop; thus, the colloidal self-assembly takes place on a non-axisymmetric liquid/air interface. The deformed drop surface is a kind of topological interface which changes its shape in time, remaining as a quality template for the self-assembly process. Three-dimensional-shaped colloidal photonic crystals might be used as devices for future spectrophotometers, aspheric or freeform diffracting mirrors, or metasurfaces for experiments regarding space-time curvature analogy. Full article
(This article belongs to the Special Issue Smart Polymers and Composites: Multifunctionality and Recyclability)
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21 pages, 9201 KiB  
Article
Nucleation, Development and Healing of Micro-Cracks in Shape Memory Polyurethane Subjected to Subsequent Tension Cycles
by Maria Staszczak, Leszek Urbański, Arkadiusz Gradys, Mariana Cristea and Elżbieta Alicja Pieczyska
Polymers 2024, 16(13), 1930; https://doi.org/10.3390/polym16131930 - 6 Jul 2024
Viewed by 414
Abstract
Thermoresponsive shape memory polymers (SMPs) have garnered increasing interest for their exceptional ability to retain a temporary shape and recover the original configuration through temperature changes, making them promising in various applications. The SMP shape change and recovery that happen due to a [...] Read more.
Thermoresponsive shape memory polymers (SMPs) have garnered increasing interest for their exceptional ability to retain a temporary shape and recover the original configuration through temperature changes, making them promising in various applications. The SMP shape change and recovery that happen due to a combination of mechanical loading and appropriate temperatures are related to its particular microstructure. The deformation process leads to the formation and growth of micro-cracks in the SMP structure, whereas the subsequent heating over its glass transition temperature Tg leads to the recovery of its original shape and properties. These processes also affect the SMP microstructure. In addition to the observed macroscopic shape recovery, the healing of micro-crazes and micro-cracks that have nucleated and developed during the loading occurs. Therefore, our study delves into the microscopic aspect, specifically addressing the healing of micro-cracks in the cyclic loading process. The proposed research concerns a thermoplastic polyurethane shape memory polymer (PU-SMP) MM4520 with a Tg of 45 °C. The objective of the study is to investigate the effect of the number of tensile loading-unloading cycles and thermal shape recovery on the evolution of the PU-SMP microstructure. To this end, comprehensive research starting from structural characterization of the initial state and at various stages of the PU-SMP mechanical loading was conducted. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM) were used. Moreover, the shape memory behavior in the thermomechanical loading program was investigated. The obtained average shape fixity value was 99%, while the shape recovery was 92%, which confirmed good shape memory properties of the PU-SMP. Our findings reveal that even during a single loading-unloading tension cycle, crazes and cracks nucleate on the surface of the PU-SMP specimen, whereas the subsequent temperature-induced shape recovery process carried out at the temperature above Tg enables the healing of micro-cracks. Interestingly, the surface of the specimen after three and five loading-unloading cycles did not exhibit crazes and cracks, although some traces of cracks were visible. The traces disappeared after exposing the material to heating at Tg + 20 °C (65 °C) for 30 min. The crack closure phenomenon during deformation, even without heating over Tg, occurred within three and five subsequent cycles of loading-unloading. Notably, in the case of eight loading-unloading cycles, cracks appeared on the surface of the PU-SMP and were healed only after thermal recovery at the particular temperature over Tg. Upon reaching a critical number of cycles, the proper amount of energy required for crack propagation was attained, resulting in wide-open cracks on the material’s surface. It is worth noting that WAXS analysis did not indicate strong signs of typical highly ordered structures in the PU-SMP specimens in their initial state and after the loading history; however, some orientation after the cyclic deformation was observed. Full article
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21 pages, 3932 KiB  
Article
Study on the Performance of Asphalt Modified with Bio-Oil, SBS and the Crumb Rubber Particle Size Ratio
by Fengqi Guo, Zhaolong Shen, Liqiang Jiang, Qiuliang Long and Yujie Yu
Polymers 2024, 16(13), 1929; https://doi.org/10.3390/polym16131929 - 6 Jul 2024
Viewed by 523
Abstract
To enhance the properties of SBS and crumb rubber-modified asphalts, four different amounts (5%, 10%, 15%, and 20%) of castor oil were added to crumb rubber-modified asphalts to mitigate the adverse effects of high levels of fine crumb rubber particles on the aging [...] Read more.
To enhance the properties of SBS and crumb rubber-modified asphalts, four different amounts (5%, 10%, 15%, and 20%) of castor oil were added to crumb rubber-modified asphalts to mitigate the adverse effects of high levels of fine crumb rubber particles on the aging resistance of SBS and crumb rubber-modified asphalt. Initially, a conventional test was conducted to assess the preliminary effects of bio-oil on the high-temperature and anti-aging properties of SBS and crumb rubber-modified asphalt. Subsequently, dynamic shear rheometer and bending beam rheometer tests were employed to evaluate the impact of bio-oil on the high- and low-temperature and anti-fatigue properties of SBS and crumb rubber-modified asphalt. Finally, fluorescence microscopy and Fourier transform infrared spectroscopy were used to examine the micro-dispersion state of the modifier and functional groups in bio-oil, SBS and crumb rubber composite-modified asphalts. The experimental results indicated that bio-oil increased the penetration of SBS and crumb rubber-modified asphalt, decreased the softening point and viscosity, and significantly improved its aging resistance. The addition of bio-oil enhanced the anti-fatigue properties of SBS and crumb rubber-modified asphalt. The optimal amount of added bio-oil was identified. Bio-oil also positively influenced the low-temperature properties of SBS and crumb rubber-modified asphalt. Although the addition of bio-oil had some adverse effects on the asphalt’s high-temperature properties, the asphalt mixture modified with bio-oil, SBS, and crumb rubber still exhibited superior high-temperature properties compared to unmodified asphalt. Furthermore, fluorescence microscopy and Fourier transform infrared spectroscopy results demonstrated that bio-oil can be uniformly dispersed in asphalt, forming a more uniform cross-linked structure and thereby enhancing the aging resistance of SBS and crumb rubber-modified asphalt. The modification process involved the physical blending of bio-oil, SBS, and crumb rubber within the asphalt. Comprehensive research confirmed that the addition of bio-oil has a significant and positive role in enhancing the properties of SBS and crumb rubber-modified asphalt with different composite crumb rubber particle size ratios. Full article
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15 pages, 5668 KiB  
Article
Development and Application of a Lignin-Based Polyol for Sustainable Reactive Polyurethane Adhesives Synthesis
by Víctor M. Serrano-Martínez, Carlota Hernández-Fernández, Henoc Pérez-Aguilar, María Pilar Carbonell-Blasco, Avelina García-García and Elena Orgilés-Calpena
Polymers 2024, 16(13), 1928; https://doi.org/10.3390/polym16131928 - 6 Jul 2024
Viewed by 515
Abstract
In response to the environmental impacts of conventional polyurethane adhesives derived from fossil fuels, this study introduces a sustainable alternative utilizing lignin-based polyols extracted from rice straw through a process developed at INESCOP. This research explores the partial substitution of traditional polyols with [...] Read more.
In response to the environmental impacts of conventional polyurethane adhesives derived from fossil fuels, this study introduces a sustainable alternative utilizing lignin-based polyols extracted from rice straw through a process developed at INESCOP. This research explores the partial substitution of traditional polyols with lignin-based equivalents in the synthesis of reactive hot melt polyurethane adhesives (HMPUR) for the footwear industry. The performance of these eco-friendly adhesives was rigorously assessed through Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), rheological analysis, and T-peel tests to ensure their compliance with relevant industry standards. Preliminary results demonstrate that lignin-based polyols can effectively replace a significant portion of fossil-derived polyols, maintaining essential adhesive properties and marking a significant step towards more sustainable adhesive solutions. This study not only highlights the potential of lignin in the realm of sustainable adhesive production but also emphasises the valorisation of agricultural by-products, thus aligning with the principles of green chemistry and sustainability objectives in the polymer industry. Full article
(This article belongs to the Special Issue Progress in Polyurethane and Composites)
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14 pages, 2486 KiB  
Article
Comparing End-of-Life Vehicle (ELV) and Packaging-Based Recyclates as Components in Polypropylene-Based Compounds for Automotive Applications
by Markus Gall, Daniela Mileva, Wolfgang Stockreiter, Christophe Salles and Markus Gahleitner
Polymers 2024, 16(13), 1927; https://doi.org/10.3390/polym16131927 - 6 Jul 2024
Viewed by 1032
Abstract
Increasing recycled plastic content in cars to 25% by 2030 is one of the key measures for decarbonizing the automotive industry defined by the European Commission. This should include the recovery of plastics from end-of-life vehicles (ELVs), but such materials are hardly used [...] Read more.
Increasing recycled plastic content in cars to 25% by 2030 is one of the key measures for decarbonizing the automotive industry defined by the European Commission. This should include the recovery of plastics from end-of-life vehicles (ELVs), but such materials are hardly used in compounds today. To close the knowledge gap, two ELV recyclate grades largely based on bumper recycling were analyzed in comparison to a packaging-based post-consumer recyclate (PCR). The composition data were used to design polypropylene (PP) compounds for automotive applications with virgin base material and mineral reinforcement, which were characterized in relation to a commercial virgin-based compound. A compound with a 40 wt.-% ELV-based bumper recyclate can exceed one with just a 25 wt.-% packaging-based recyclate in terms of stiffness/impact balance. While the virgin reference can nearly be matched regarding mechanics, the flowability is not reached by any of the PCR compounds, making further development work necessary. Full article
(This article belongs to the Topic Advanced Composites Manufacturing and Plastics Processing)
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15 pages, 3535 KiB  
Article
Toughness Evolution of Flax-Fiber-Reinforced Composites under Repeated Salt Fog–Dry Aging Cycles
by Luigi Calabrese, Carmelo Sanfilippo, Antonino Valenza, Edoardo Proverbio and Vincenzo Fiore
Polymers 2024, 16(13), 1926; https://doi.org/10.3390/polym16131926 - 6 Jul 2024
Viewed by 426
Abstract
This research examined the response of flax-fiber-reinforced composites (FFRCs) to simulated outdoor conditions involving repeated exposure to salt fog and drying. The study investigated the effect of cycles on the toughness of the FFRCs. To achieve this, the composites were exposed to humidity [...] Read more.
This research examined the response of flax-fiber-reinforced composites (FFRCs) to simulated outdoor conditions involving repeated exposure to salt fog and drying. The study investigated the effect of cycles on the toughness of the FFRCs. To achieve this, the composites were exposed to humidity (salt fog) for 10 days, followed by 18 days of drying in cycles. A total of up to 3 cycles, each lasting 4 weeks, were conducted over a 12-week period. Throughout this process, changes in the material’s weight, water absorption, and mechanical properties were monitored by water uptake and three-point bending tests. The findings revealed the significant impact of these humid–dry cycles on the mechanical response of the FFRCs. When exposed to humid environments without drying, the composite’s toughness increased significantly, due to a weakening effect more pronounced for stiffness, with strength reductions of about 20%. However, subsequent drying partially restored the material’s performance. After 18 days of drying, the composite regained most of its initial performance. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymers: Manufacture, Properties and Applications)
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22 pages, 18271 KiB  
Article
Behavior of Composites Made of Quadriaxial Glass Fiber Fabrics and Epoxy Resin under Three-Point Bending
by Ioana Gabriela Chiracu, George Ghiocel Ojoc, George Cătălin Cristea, Mihail Boțan, Alina Cantaragiu Ceoromila, Cătălin Pîrvu, Alexandru Viorel Vasiliu and Lorena Deleanu
Polymers 2024, 16(13), 1925; https://doi.org/10.3390/polym16131925 - 5 Jul 2024
Viewed by 422
Abstract
This paper presents experimental results from three-point bending tests for a composite made of quadriaxial glass fiber fabrics and an epoxy resin. Two composites were tested, one with 8 layers and the other with 16 layers; both had the same matrix (the epoxy [...] Read more.
This paper presents experimental results from three-point bending tests for a composite made of quadriaxial glass fiber fabrics and an epoxy resin. Two composites were tested, one with 8 layers and the other with 16 layers; both had the same matrix (the epoxy resin). Tests were carried out, using five different test rates from 10 mm/min to 1000 mm/min. The following parameters were recorded and calculated: Young’s modulus, flexural stress, flexural strain, energy, force, and all four for the first peak. The experimental data reveal no sensitivity for these materials based on the test rates, at least for the analyzed range; but, the characteristics for the thicker composite, with 16 layers of fabric, are slightly lower than those for the thinner composite, with 8 layers. The results pointed out that, for the same thickness of composite, certain characteristics, such as stress at the first peak, the flexural modulus, strain at the first peak, and energy at the first peak, are not sensitive to the test rate in the range 10–1000 mm/min. The energy at the first peak is double for the 16-layer composite compared to the 8-layer composite, but the specific energy (as energy on cross-sectional area) has close values: 103.47 kJ/m2 for the 8-layer composite and 106.51 kJ/m2 for the 16-layer composite. The results recommend this composite for applications in components with resistance to bending or for low-velocity impact protection. Full article
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14 pages, 6543 KiB  
Article
Metal–Organic Framework-Derived Co9S8 Nanowall Array Embellished Polypropylene Separator for Dendrite-Free Lithium Metal Anodes
by Deshi Feng, Ruiling Zheng, Li Qiao, Shiteng Li, Fengzhao Xu, Chuangen Ye, Jing Zhang and Yong Li
Polymers 2024, 16(13), 1924; https://doi.org/10.3390/polym16131924 - 5 Jul 2024
Viewed by 512
Abstract
Developing a reasonable design of a lithiophilic artificial solid electrolyte interphase (SEI) to induce the uniform deposition of Li+ ions and improve the Coulombic efficiency and energy density of batteries is a key task for the development of high-performance lithium metal anodes. [...] Read more.
Developing a reasonable design of a lithiophilic artificial solid electrolyte interphase (SEI) to induce the uniform deposition of Li+ ions and improve the Coulombic efficiency and energy density of batteries is a key task for the development of high-performance lithium metal anodes. Herein, a high-performance separator for lithium metal anodes was designed by the in situ growth of a metal–organic framework (MOF)-derived transition metal sulfide array as an artificial SEI on polypropylene separators (denoted as Co9S8-PP). The high ionic conductivity and excellent morphology provided a convenient transport path and fast charge transfer kinetics for lithium ions. The experimental data illustrate that, compared with commercial polypropylene separators, the Li//Cu half-cell with a Co9S8-PP separator can be cycled stably for 2000 h at 1 mA cm−2 and 1 mAh cm−2. Meanwhile, a Li//LiFePO4 full cell with a Co9S8-PP separator exhibits ultra-long cycle stability at 0.2 C with an initial capacity of 148 mAh g−1 and maintains 74% capacity after 1000 cycles. This work provides some new strategies for using transition metal sulfides to induce the uniform deposition of lithium ions to create high-performance lithium metal batteries. Full article
(This article belongs to the Special Issue Polymer Composites: Design, Manufacture and Characterization)
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