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Polymers, Volume 15, Issue 9 (May-1 2023) – 257 articles

Cover Story (view full-size image): A new 3D-printed violoncello has been developed, motivated by the desire to create an affordable and durable instrument for beginners and professionals. The use of 3D printing technology allowed for greater precision and control in the instrument's design, resulting in a lightweight and easy-to-play cello. The project had a scientific approach, using acoustic analysis to ensure the instrument's sound quality and tuning. View this paper
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12 pages, 4714 KiB  
Article
Bio-Inspired Magnetically Controlled Reversibly Actuating Multimaterial Fibers
by Muhammad Farhan, Daniel S. Hartstein, Yvonne Pieper, Marc Behl, Andreas Lendlein and Axel T. Neffe
Polymers 2023, 15(9), 2233; https://doi.org/10.3390/polym15092233 - 08 May 2023
Viewed by 1276
Abstract
Movements in plants, such as the coiling of tendrils in climbing plants, have been studied as inspiration for coiling actuators in robotics. A promising approach to mimic this behavior is the use of multimaterial systems that show different elastic moduli. Here, we report [...] Read more.
Movements in plants, such as the coiling of tendrils in climbing plants, have been studied as inspiration for coiling actuators in robotics. A promising approach to mimic this behavior is the use of multimaterial systems that show different elastic moduli. Here, we report on the development of magnetically controllable/triggerable multimaterial fibers (MMFs) as artificial tendrils, which can reversibly coil and uncoil on stimulation from an alternating magnetic field. These MMFs are based on deformed shape-memory fibers with poly[ethylene-co-(vinyl acetate)] (PEVA) as their core and a silicone-based soft elastomeric magnetic nanocomposite shell. The core fiber provides a temperature-dependent expansion/contraction that propagates the coiling of the MMF, while the shell enables inductive heating to actuate the movements in these MMFs. Composites with mNP weight content ≥ 15 wt% were required to achieve heating suitable to initiate movement. The MMFs coil upon application of the magnetic field, in which a degree of coiling N = 0.8 ± 0.2 was achieved. Cooling upon switching OFF the magnetic field reversed some of the coiling, giving a reversible change in coiling ∆n = 2 ± 0.5. These MMFs allow magnetically controlled remote and reversible actuation in artificial (soft) plant-like tendrils, and are envisioned as fiber actuators in future robotics applications. Full article
(This article belongs to the Special Issue Frontier in Magneto-/ Electro-Active Elastomers)
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13 pages, 4690 KiB  
Article
Preparation and Optical Properties of PVDF-CaFe2O4 Polymer Nanocomposite Films
by Sultan Alhassan, Majed Alshammari, Khulaif Alshammari, Turki Alotaibi, Alhulw H. Alshammari, Yasir Fawaz, Taha Abdel Mohaymen Taha and Mohamed Henini
Polymers 2023, 15(9), 2232; https://doi.org/10.3390/polym15092232 - 08 May 2023
Cited by 13 | Viewed by 1605
Abstract
In this work, a synthesis technique for highly homogeneous PVDF-CaFe2O4 polymer films direct from solution was developed. The structural characterizations were conducted using XRD, FTIR, and ESEM experimental techniques. The XRD characteristic peaks of CaFe2O4 nanoparticles revealed [...] Read more.
In this work, a synthesis technique for highly homogeneous PVDF-CaFe2O4 polymer films direct from solution was developed. The structural characterizations were conducted using XRD, FTIR, and ESEM experimental techniques. The XRD characteristic peaks of CaFe2O4 nanoparticles revealed a polycrystalline structure. The average crystallite size for CaFe2O4 was calculated to be 17.0 nm. ESEM micrographs of PVDF nanocomposites containing 0.0, 0.25, 0.75, and 1.0 wt% of CaFe2O4 showed smooth surface topography. The direct Edir and indirect Eind band gap energies for the PVDF-CaFe2O4 nanocomposites were decreased with the additions of 0.0–1.0 wt% CaFe2O4. In addition, the refractive index (n0) increased from 3.38 to 10.36, and energy gaps (Eg) decreased from 5.50 to 4.95 eV. The nonlinear refractive index (n2) for the PVDF-CaFe2O4 nanocomposites was improved with the addition of CaFe2O4 nanoparticles, exceeding those reported in the literature for PVC, PVA, and PMMA nanocomposites. Therefore, the PVDF-CaFe2O4 nanocomposites are expected to take the lead in optoelectronic applications because of their unusual optical properties. Full article
(This article belongs to the Section Polymer Applications)
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14 pages, 3623 KiB  
Article
Improvement of Natural Polymeric Films Properties by Blend Formulation for Sustainable Active Food Packaging
by Emanuela Drago, Roberta Campardelli, Alberto Lagazzo, Giuseppe Firpo and Patrizia Perego
Polymers 2023, 15(9), 2231; https://doi.org/10.3390/polym15092231 - 08 May 2023
Cited by 4 | Viewed by 2383
Abstract
Active packaging manufactured with biopolymers extracted from agri-food waste is one of the most innovative and eco-sustainable strategies for maintaining food quality. However, biopolymers often present poor performances, which hinders their competitiveness compared with plastics. This work focused on developing and optimizing a [...] Read more.
Active packaging manufactured with biopolymers extracted from agri-food waste is one of the most innovative and eco-sustainable strategies for maintaining food quality. However, biopolymers often present poor performances, which hinders their competitiveness compared with plastics. This work focused on developing and optimizing a natural polymeric blend produced by solvent casting based on zein and chitosan to improve the pure biopolymers’ properties. The best results were obtained by blending zein and chitosan in a 1:2 weight ratio. The films were characterized in terms of morphology, mechanical and oxygen barrier properties, thermal stability, transparency and wettability. The blend production allowed us to obtain lower brittleness and lower stiffness materials compared with pure polymer films, with oxygen permeability values two orders of magnitude lower than pure zein, better optical properties with respect to pure chitosan and good thermal stability. The wettability properties of the blend did not result in being altered with respect to the single polymer, which was found to have hydrophilic behavior, highlighting the strong influence of glycerol used as a plasticizer. The results suggested that the polymer blending strategy is a viable and cost-effective method for producing packaging materials as alternatives to plastics. Full article
(This article belongs to the Special Issue Polymers in Food Technology and Food Packaging)
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16 pages, 5949 KiB  
Article
Investigation of the Effects of Chain Extender on Material Properties of PLA/PCL and PLA/PEG Blends: Comparative Study between Polycaprolactone and Polyethylene Glycol
by Karabo Innocent Matumba, Mpho Phillip Motloung, Vincent Ojijo, Suprakas Sinha Ray and Emmanuel Rotimi Sadiku
Polymers 2023, 15(9), 2230; https://doi.org/10.3390/polym15092230 - 08 May 2023
Cited by 8 | Viewed by 2011
Abstract
This study investigated the effect of the Joncryl concentration on the properties of polylactide/poly(ε-caprolactone) (PLA/PCL) and PLA/poly(ethylene glycol) (PEG) blends. The addition of Joncryl influenced the properties of both PLA-based blends. In the blend of PLA/PCL blends, the addition of Joncryl reduced the [...] Read more.
This study investigated the effect of the Joncryl concentration on the properties of polylactide/poly(ε-caprolactone) (PLA/PCL) and PLA/poly(ethylene glycol) (PEG) blends. The addition of Joncryl influenced the properties of both PLA-based blends. In the blend of PLA/PCL blends, the addition of Joncryl reduced the size of PCL droplets, which implies the compatibility of the two phases, while PLA/PEG blends showed a co-continuous type of morphology at 0.1% and 0.3 wt.% of Joncryl loading. The crystallinity of PCL and PEG was studied on both PLA/PCL and PLA/PEG blend systems. In both scenarios, the crystallinity of the blends decreased upon the addition of Joncryl. Thermal stabilities were shown to depend on the addition of Joncryl. The toughness increased when 0.5 wt.% of Joncryl was added to both systems. However, the stiffness of PLA/PCL decreased, while the stiffness of PLA/PEG increased with the increasing concentration of Joncryl. This study provides new insight into the effect of chain extenders on the compatibility of PLA-based blends. Full article
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14 pages, 2933 KiB  
Article
Preparation of Polylactic Acid/Calcium Peroxide Composite Filaments for Fused Deposition Modelling
by Abdullah H. Mohammed, Nikolina Kovacev, Amr Elshaer, Ammar A. Melaibari, Javed Iqbal, Hany Hassanin, Khamis Essa and Adnan Memić
Polymers 2023, 15(9), 2229; https://doi.org/10.3390/polym15092229 - 08 May 2023
Cited by 4 | Viewed by 1888
Abstract
Fused Deposition Modelling (FDM) 3D printers have gained significant popularity in the pharmaceutical and biomedical industries. In this study, a new biomaterial filament was developed by preparing a polylactic acid (PLA)/calcium peroxide (CPO) composite using wet solution mixing and extrusion. The content of [...] Read more.
Fused Deposition Modelling (FDM) 3D printers have gained significant popularity in the pharmaceutical and biomedical industries. In this study, a new biomaterial filament was developed by preparing a polylactic acid (PLA)/calcium peroxide (CPO) composite using wet solution mixing and extrusion. The content of CPO varied from 3% to 24% wt., and hot-melt extruder parameters were optimised to fabricate 3D printable composite filaments. The filaments were characterised using an X-ray diffraction analysis, surface morphology assessment, evaluation of filament extrudability, microstructural analysis, and examination of their rheological and mechanical properties. Our findings indicate that increasing the CPO content resulted in increased viscosity at 200 °C, while the PLA/CPO samples showed microstructural changes from crystalline to amorphous. The mechanical strength and ductility of the composite filaments decreased except for in the 6% CPO filament. Due to its acceptable surface morphology and strength, the PLA/CPO filament with 6% CPO was selected for printability testing. The 3D-printed sample of a bone scaffold exhibited good printing quality, demonstrating the potential of the PLA/CPO filament as an improved biocompatible filament for FDM 3D printing. Full article
(This article belongs to the Special Issue Polylactic Acid (PLA)-Based Materials)
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16 pages, 3527 KiB  
Article
Effect of Alkaline Treatment on Mechanical and Thermal Properties of Miswak (Salvadora persica) Fiber-Reinforced Polylactic Acid
by S. Ayu Rafiqah, A. F. Nur Diyana, Khalina Abdan and S. M. Sapuan
Polymers 2023, 15(9), 2228; https://doi.org/10.3390/polym15092228 - 08 May 2023
Cited by 2 | Viewed by 1482
Abstract
This study examines the effects of alkaline treatment on the mechanical and thermal properties of miswak fiber-reinforced polylactic acid. The treatment was performed with three distinct concentrations of sodium hydroxide (NaOH): 1 wt %, 2 wt %, and 3 wt %. The difficulties [...] Read more.
This study examines the effects of alkaline treatment on the mechanical and thermal properties of miswak fiber-reinforced polylactic acid. The treatment was performed with three distinct concentrations of sodium hydroxide (NaOH): 1 wt %, 2 wt %, and 3 wt %. The difficulties of interaction between the surface of the fiber and the matrix, which led to this treatment, is caused by miswak fiber’s hydrophilic character, which impedes its ability to bind with hydrophobic polylactic acid. FTIR, tensile, TGA, and DMA measurements were used to characterize the composite samples. A scanning electron microscope (SEM) was used to examine the microstructures of many broken samples. The treatment is not yet especially effective in enhancing interfacial bonding, as seen by the uneven tensile strength data. The effect of the treated fiber surface significantly improves the tensile strength of miswak fiber-reinforced PLA composites. Tensile strength improves by 18.01%, 6.48%, and 14.50%, respectively, for 1 wt %, 2 wt %, and 3 wt %. Only 2 wt %-treated fiber exhibits an increase of 0.7% in tensile modulus. The modulus decreases by 4.15 % at 1 wt % and by 19.7% at 3 wt %, respectively. The TGA curve for alkali-treated fiber composites demonstrates a slight increase in thermal stability when compared to untreated fiber composites at high temperatures. For DMA, the composites with surface treatment have higher storage moduli than the composite with untreated miswak fiber, especially for the PLA reinforced with 2 wt % alkali miswak fiber, proving the effectiveness of the treatment. Full article
(This article belongs to the Special Issue Mechanical Properties of Polymer Composites II)
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19 pages, 7467 KiB  
Article
Comparative Studies on the Structure and Biological Activities of Two New Polysaccharides from Tricholoma sinoportentosum (TS-P) and Termitomyces albuminosus (TA-P)
by Xi Chen, Tong Yang, Qinghua Huang, Biao Li, Xiang Ding and Yiling Hou
Polymers 2023, 15(9), 2227; https://doi.org/10.3390/polym15092227 - 08 May 2023
Cited by 3 | Viewed by 1162
Abstract
Polysaccharides are important active ingredients of living organisms. In this study, two new polysaccharides, Tricholoma sinoportentosum polysaccharide (TS-P) and Termitomyces albuminosus (TA-P), were extracted and purified using anion exchange column chromatography. The structure of each polysaccharide was identified by HPGPC, FT-IR, HPLC, GC-MS [...] Read more.
Polysaccharides are important active ingredients of living organisms. In this study, two new polysaccharides, Tricholoma sinoportentosum polysaccharide (TS-P) and Termitomyces albuminosus (TA-P), were extracted and purified using anion exchange column chromatography. The structure of each polysaccharide was identified by HPGPC, FT-IR, HPLC, GC-MS and NMR, and the biological activities were also investigated. The results of the structure identification showed that TS-P was composed of arabinose, mannose, glucose and galactose at a ratio of 1:1:3:2 and its main chain was composed of (1→4)-Arap residues, (1→4,6)-D-Manp residues and two (1→6)-Galp residues. The TA-P was composed of arabinose, glucose and galactose at a ratio of 2:4:8. Its main chain was composed of two (1→4)-β-L-Arap residues, one (1→4)-Glcp residues, three (1→2,6)-Galp residues and five (1→6)-Galp residues. The immunoassay showed that TS-P and TA-P could significantly promote the proliferation of T cells, B cells and RAW264.7 cells. The cell cycle results showed that for B cells and macrophages, TS-P and TA-P mainly affected the G0/G1 phases of the cell cycle; for T cells, TS-P affected G2/M phase, while TA-P mainly affected the G0/G1 phases. TS-P could significantly promote B cells to secrete IgA, IgG and IgD (p < 0.01), while TA-P could significantly promote the secretion of IgA and IgG (p < 0.01). The chemical structure and biological activity of TS-P and TA-P were first studied and compared to lay a theoretical foundation for the application of fungal polysaccharide. Full article
(This article belongs to the Special Issue Natural Polysaccharides: Structure and Function)
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12 pages, 3894 KiB  
Article
Three-Dimensional-Bioprinted Bioactive Glass/Cellulose Composite Scaffolds with Porous Structure towards Bone Tissue Engineering
by Lei Li, Pengfei Lu, Yuting Liu, Junhe Yang and Shengjuan Li
Polymers 2023, 15(9), 2226; https://doi.org/10.3390/polym15092226 - 08 May 2023
Cited by 4 | Viewed by 1502
Abstract
In this study, three-dimensional (3D) bioactive glass/lignocellulose (BG/cellulose) composite scaffolds were successfully fabricated by the 3D-bioprinting technique with N-methylmorpholine-N-oxide (NMMO) as the ink solvent. The physical structure, morphology, mechanical properties, hydroxyapatite growth and cell response to the prepared BG/cellulose scaffolds [...] Read more.
In this study, three-dimensional (3D) bioactive glass/lignocellulose (BG/cellulose) composite scaffolds were successfully fabricated by the 3D-bioprinting technique with N-methylmorpholine-N-oxide (NMMO) as the ink solvent. The physical structure, morphology, mechanical properties, hydroxyapatite growth and cell response to the prepared BG/cellulose scaffolds were investigated. Scanning electron microscopy (SEM) images showed that the BG/cellulose scaffolds had uniform macropores of less than 400 μm with very rough surfaces. Such BG/cellulose scaffolds have excellent mechanical performance to resist compressive force in comparison with pure cellulose scaffolds and satisfy the strength requirement of human trabecular bone (2–12 MPa). Furthermore, BG significantly increased the excellent hydroxyapatite-forming capability of the cellulose scaffolds as indicated by the mineralization of the scaffolds in simulated body fluid (SBF). The BG/cellulose scaffolds showed low cytotoxicity to human bone marrow mesenchymal stem cells (hBMSCs) in the CCK8 assay. The cell viability reached maximum (percent of the control group) when the weight ratio of cellulose to BG was 2 in the scaffold. Therefore, the 3D-printed BG/cellulose scaffolds show a potential application in the field of bone tissue engineering. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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22 pages, 3023 KiB  
Article
Synthesis and Micellization Behavior of Amphiphilic Block Copolymers of Poly(N-vinyl Pyrrolidone) and Poly(Benzyl Methacrylate): Block versus Statistical Copolymers
by Nikoletta Roka and Marinos Pitsikalis
Polymers 2023, 15(9), 2225; https://doi.org/10.3390/polym15092225 - 08 May 2023
Cited by 1 | Viewed by 1728
Abstract
Block copolymers of N-vinyl pyrrolidone (NVP) and benzyl methacrylate (BzMA), PNVP-b-PBzMA, were prepared by RAFT polymerization techniques and sequential addition of monomers. The copolymers were characterized by Size Exclusion Chromatography (SEC) and NMR spectroscopy. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) [...] Read more.
Block copolymers of N-vinyl pyrrolidone (NVP) and benzyl methacrylate (BzMA), PNVP-b-PBzMA, were prepared by RAFT polymerization techniques and sequential addition of monomers. The copolymers were characterized by Size Exclusion Chromatography (SEC) and NMR spectroscopy. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG) were employed to study the thermal properties of these copolymers. The micellization behavior in THF, which is a selective solvent for the PBzMA blocks, was examined. For comparison the self-assembly properties of the corresponding statistical copolymers, PNVP-stat-PBzMA, were studied. In addition, the association behavior in aqueous solutions was analyzed for the block copolymers, PNVP-b-PBzMA. In this case, the solvent is selective for the PNVP blocks. Dilute solution viscometry, static (SLS) and dynamic light scattering (DLS) were employed as the tools to investigate the micellar assemblies. The efficient encapsulation of the hydrophobic curcumin within the micellar core of the supramolecular structures in aqueous solutions was demonstrated by UV-Vis spectroscopy and DLS measurements. Full article
(This article belongs to the Special Issue Block Copolymers: Self-Assembly and Applications)
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13 pages, 4374 KiB  
Article
Harnessing Data Augmentation and Normalization Preprocessing to Improve the Performance of Chemical Reaction Predictions of Data-Driven Model
by Boyu Zhang, Jiaping Lin, Lei Du and Liangshun Zhang
Polymers 2023, 15(9), 2224; https://doi.org/10.3390/polym15092224 - 08 May 2023
Cited by 1 | Viewed by 1275
Abstract
As a template-free, data-driven methodology, the molecular transformer model provides an alternative by which to predict the outcome of chemical reactions and design the route of the retrosynthetic plane in the field of organic synthesis and polymer chemistry. However, in consideration of the [...] Read more.
As a template-free, data-driven methodology, the molecular transformer model provides an alternative by which to predict the outcome of chemical reactions and design the route of the retrosynthetic plane in the field of organic synthesis and polymer chemistry. However, in consideration of the small datasets of chemical reactions, the data-driven model suffers from the difficulty of low accuracy in the prediction tasks of chemical reactions. In this contribution, we integrate the molecular transformer model with the strategies of data augmentation and normalization preprocessing to accomplish the three tasks of chemical reactions, including the forward predictions of chemical reactions, and single-step retrosynthetic predictions with and without the reaction classes. It is clearly demonstrated that the prediction accuracy of the molecular transformer model can be significantly raised by the use of proposed strategies for the three tasks of chemical reactions. Notably, after the introduction of the 40-level data augmentation and normalization preprocessing, the top-1 accuracy of the forward prediction increases markedly from 71.6% to 84.2% and the top-1 accuracy of the single-step retrosynthetic prediction with additional reaction class increases from 53.2% to 63.4%. Furthermore, it is found that the superior performance of the data-driven model originates from the correction of the grammatical errors of the SMILES strings, especially for the case of the reaction classes with small datasets. Full article
(This article belongs to the Special Issue Machine Learning and Simulation of Polymers)
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14 pages, 2072 KiB  
Article
Modification of Macromolecules of Polyimide Films by Electron Irradiation
by Roza Abdulkarimova, Abyl Muradov, Kanat Mukashev, Gulmira Yar-Mukhamedova and Nursultan Japashov
Polymers 2023, 15(9), 2223; https://doi.org/10.3390/polym15092223 - 08 May 2023
Viewed by 1086
Abstract
New polymeric materials formation by controlling their properties is the primary and most challenging problem in developing a methodology for synthesizing a chosen technology and its use. The combined effect of high-energy electron radiation and tensile stress will cause a decrease in crystallinity [...] Read more.
New polymeric materials formation by controlling their properties is the primary and most challenging problem in developing a methodology for synthesizing a chosen technology and its use. The combined effect of high-energy electron radiation and tensile stress will cause a decrease in crystallinity and the breakage of chemical bonds in polyimide film macromolecules and is a new approach in their production technology. The effect of uniaxial tension and electron irradiation on the modification of polyimide film at room temperature was studied. Irradiation of the films caused an increase in the intensity of the IR spectrum by ~2–6 times and an increase in the width of the bands. The intensity in the range of 1700–3500 cm−1 increased, indicating an increase in the content of radicals as a result of irradiation. The amplitudes of the electron paramagnetic resonance signal from non-irradiated films increased from 3 × 103 to 5 × 103 as a result of uniaxial tension to fracture, indicating an increase in radicals in the material. The lines of the electron paramagnetic resonance spectrum shifted from 3475.0 cm−1 to 3512.5 cm−1, with a simultaneous decrease in the signal’s amplitude from 6 ×103 to 4 × 103, as a result of the electron irradiation of the films, followed by their subjection to tension. This was due to a decrease in the concentration of the radicals of the =N-H and –N-H2 groups until their disappearance and the formation of new ones. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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13 pages, 9888 KiB  
Article
Preparation of Bio-Foam Material from Steam-Exploded Corn Straw by In Situ Esterification Modification
by Yu Pan, Yufan Zhou, Xiaoqing Du, Wangjie Xu, Yuan Lu, Feng Wang and Man Jiang
Polymers 2023, 15(9), 2222; https://doi.org/10.3390/polym15092222 - 08 May 2023
Cited by 2 | Viewed by 1656
Abstract
In this work, we engineered a corn-straw-based bio-foam material under the inspiration of the intrinsic morphology of the corn stem. The explosion pretreatment was applied to obtain a fibrillated cellulose starting material rich in lignin. The in situ esterification of cellulose was adopted [...] Read more.
In this work, we engineered a corn-straw-based bio-foam material under the inspiration of the intrinsic morphology of the corn stem. The explosion pretreatment was applied to obtain a fibrillated cellulose starting material rich in lignin. The in situ esterification of cellulose was adopted to improve the cross-linking network of the as-developed foam bio-material. The esterification of lignin was observed in the same procedure, which provides a better cross-linking interaction. The esterified corn-straw-derived bio-foam material showed excellent elastic resilience performance with an elastic recovery ratio of 83% and an elastic modulus of 20 kPa. Meanwhile, with surface modification by hexachlorocyclotriphosphazene-functionalized lignin as the flame retardant (Lig-HCCP), the as-obtained bio-foam material demonstrated quite a good flame retardancy (with 27.3% of the LOI), as well as a heat insulation property. The corn-straw-derived bio-foam material is prospected to be a potential substitution packaging material for widely used petroleum-derived products. This work provides a new value-added application of the abundant agricultural straw biomass resources. Full article
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12 pages, 8616 KiB  
Article
In-Process Orbiting Laser-Assisted Technique for the Surface Finish in Material Extrusion-Based 3D Printing
by Pu Han, Sihan Zhang, Zhong Yang, M. Faisal Riyad, Dan O. Popa and Keng Hsu
Polymers 2023, 15(9), 2221; https://doi.org/10.3390/polym15092221 - 08 May 2023
Cited by 1 | Viewed by 1330
Abstract
Material extrusion-based polymer 3D printing, one of the most commonly used additive manufacturing processes for thermoplastics and composites, has drawn extensive attention due to its capability and cost effectiveness. However, the low surface finish quality of the printed parts remains a drawback due [...] Read more.
Material extrusion-based polymer 3D printing, one of the most commonly used additive manufacturing processes for thermoplastics and composites, has drawn extensive attention due to its capability and cost effectiveness. However, the low surface finish quality of the printed parts remains a drawback due to the nature of stacking successive layers along one direction and the nature of rastering of the extruded tracks of material. In this work, an in-process thermal radiation-assisted, surface reflow method is demonstrated that significantly improves the surface finish of the sidewalls of printed parts. It is observed that the surface finish of the printed part is drastically improved for both flat and curved surfaces. The effect of surface reflow on roughness reduction was characterized using optical profilometry and scanning electron microscopy (SEM), while the local heated spot temperature was quantified using a thermal camera. Full article
(This article belongs to the Special Issue Progress in 3D Printing)
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25 pages, 4905 KiB  
Article
Screening the Impact of Surfactants and Reaction Conditions on the De-Inkability of Different Printing Ink Systems for Plastic Packaging
by Jinyang Guo, Cong Luo, Christian Wittkowski, Ingo Fehr, Zhikai Chong, Magdalena Kitzberger, Ayah Alassali, Xuezhi Zhao, Ralf Leineweber, Yujun Feng and Kerstin Kuchta
Polymers 2023, 15(9), 2220; https://doi.org/10.3390/polym15092220 - 08 May 2023
Cited by 1 | Viewed by 3222
Abstract
One of the major applications (40% in Europe) of plastic is packaging, which is often printed to display required information and to deliver an attractive aesthetic for marketing purposes. However, printing ink can cause contamination in the mechanical recycling process. To mitigate this [...] Read more.
One of the major applications (40% in Europe) of plastic is packaging, which is often printed to display required information and to deliver an attractive aesthetic for marketing purposes. However, printing ink can cause contamination in the mechanical recycling process. To mitigate this issue, the use of surfactants in an alkaline washing process, known as de-inking, has been employed to remove printing ink and improve the quality of recyclates. Despite the existence of this technology, there are currently no data linking the de-inking efficiency with typical printing ink compositions. Additionally, it is necessary to investigate the de-inking process under the process parameters of existing recycling plants, including temperature, NaOH concentration, and retention time. This study aims to evaluate the performance of commonly used printing inks with different compositions under various washing scenarios for plastic recycling in conjunction with different de-inking detergents containing surfactants or mixtures of surfactants. The results indicate that the pigments applied to the ink have no significant effect on the de-inking process, except for carbon black (PBk 7). Nitrocellulose (NC) binder systems exhibit high de-inkability (over 95%) under the condition of 55 °C and 1 wt.% NaOH. However, crosslinked binder systems can impede the de-inking effect, whether used as a binder system or as an overprint varnish (OPV). The de-inking process requires heating to 55 °C with 1 wt.% NaOH to achieve a substantial effect. Based on the findings in this work, breaking the Van der Waals forces, hydrogen bonds, and covalent bonds between the printing ink and plastic film is an essential step to achieve the de-inking effect. Further research is needed to understand the interaction between surfactants and printing inks, enabling the development of de-inkable printing inks and high-performance surfactants that allow for de-inking with less energy consumption. The surfactant and NaOH have a synergistic effect in cleaning the printing ink. NaOH provides a negative surface charge for the adsorption of the cationic head of the surfactant and can hydrolyze the covalent bonds at higher concentrations (>2 wt.%). Full article
(This article belongs to the Special Issue Advances in Recycling of Polymers)
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27 pages, 5672 KiB  
Review
Design and Application of Hybrid Polymer-Protein Systems in Cancer Therapy
by Qi Sun, Zhenzhen Yang and Xianrong Qi
Polymers 2023, 15(9), 2219; https://doi.org/10.3390/polym15092219 - 08 May 2023
Viewed by 2728
Abstract
Polymer-protein systems have excellent characteristics, such as non-toxic, non-irritating, good water solubility and biocompatibility, which makes them very appealing as cancer therapeutics agents. Inspiringly, they can achieve sustained release and targeted delivery of drugs, greatly improving the effect of cancer therapy and reducing [...] Read more.
Polymer-protein systems have excellent characteristics, such as non-toxic, non-irritating, good water solubility and biocompatibility, which makes them very appealing as cancer therapeutics agents. Inspiringly, they can achieve sustained release and targeted delivery of drugs, greatly improving the effect of cancer therapy and reducing side effects. However, many challenges, such as reducing the toxicity of materials, protecting the activities of proteins and controlling the release of proteins, still need to be overcome. In this review, the design of hybrid polymer–protein systems, including the selection of polymers and the bonding forms of polymer–protein systems, is presented. Meanwhile, vital considerations, including reaction conditions and the release of proteins in the design process, are addressed. Then, hybrid polymer–protein systems developed in the past decades for cancer therapy, including targeted therapy, gene therapy, phototherapy, immunotherapy and vaccine therapy, are summarized. Furthermore, challenges for the hybrid polymer–protein systems in cancer therapy are exemplified, and the perspectives of the field are covered. Full article
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13 pages, 3227 KiB  
Article
Cellulose Nanocrystals Induced Loose and Porous Graphite Phase Carbon Nitride/Porous Carbon Composites for Capturing and Determining of Organochlorine Pesticides from Water and Fruit Juice by Solid-Phase Microextraction
by Huimin Li, Panlong Dong, Anying Long, Suling Feng, Jing Fan and Shengrui Xu
Polymers 2023, 15(9), 2218; https://doi.org/10.3390/polym15092218 - 08 May 2023
Cited by 3 | Viewed by 1379
Abstract
Herein, novel, loose, and porous graphite phase carbon nitride/porous carbon (g-C3N4@PC) composites were prepared by decorating cellulose nanocrystals (CNCs). The characterization results demonstrate that the as-prepared composites presented high specific surface areas, porous structures, and abundant chemical groups, with [...] Read more.
Herein, novel, loose, and porous graphite phase carbon nitride/porous carbon (g-C3N4@PC) composites were prepared by decorating cellulose nanocrystals (CNCs). The characterization results demonstrate that the as-prepared composites presented high specific surface areas, porous structures, and abundant chemical groups, with the modification of CNCs. In view of the unique advantages, g-C3N4@PC was used as the coating material for the solid-phase microextraction (SPME) of organochlorine pesticides (OCPs) in water and juice samples. The g-C3N4@PC-coated fibers showed better extraction efficiencies than commercial fibers (100/7 μm PDMS and PA) toward the OCPs, with the enrichment factors of the g-C3N4@PC-coated fibers 5–30 times higher than the latter. Using a gas chromatography–mass spectrometry (GC-MS) instrument, the g-C3N4@PC-coated fibers exhibited a gratifying analytical performance for determining low concentrations of OCPs, with a wide linear range (0.1–1600 ng L−1 for water; 0.1–1000 ng L−1 for juice), low limits of detection (0.0141–0.0942 ng L−1 for water; 0.0245–0.0777 ng L−1 for juice), and good reproducibility and repeatability in optimal conditions. The established method showed good sensitivity and recovery in the determination of OCPs in the water and fruit juice samples, which displayed broad prospects for analyzing organic pollutants from environmental samples. Full article
(This article belongs to the Special Issue Nanoporous Polymer Composites)
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14 pages, 2860 KiB  
Article
TCAD Device Simulation of All-Polymer Solar Cells for Indoor Applications: Potential for Tandem vs. Single Junction Cells
by Tarek I. Alanazi
Polymers 2023, 15(9), 2217; https://doi.org/10.3390/polym15092217 - 08 May 2023
Cited by 1 | Viewed by 1561
Abstract
The utilization of indoor photovoltaics makes it feasible to harvest energy from artificial light sources. Although single-junction indoor photovoltaics have demonstrated exceptional efficacy when using LED lighting, there is still a need for more comprehensive testing of tandem structures. Herein, the first systematic [...] Read more.
The utilization of indoor photovoltaics makes it feasible to harvest energy from artificial light sources. Although single-junction indoor photovoltaics have demonstrated exceptional efficacy when using LED lighting, there is still a need for more comprehensive testing of tandem structures. Herein, the first systematic TCAD simulation study on the potential for tandem all-polymer solar cells (all-PSCs) for indoor applications is provided. The presented all-PSCs are based on experimental work in which the top wide bandgap subcell comprises a polymer blend PM7:PIDT, while the bottom narrow bandgap subcell has a polymer blend PM6:PY-IT. Standalone and tandem cells are simulated under AM1.5G solar radiation, and the simulation results are compared with measurements to calibrate the physical models and material parameters revealing PCE values of 10.11%, 16.50%, and 17.58% for the front, rear, and tandem cells, respectively. Next, we assessed the performance characteristics of the three cells under a white LED environment for different color temperatures and light intensities. The results showed a superior performance of the front cell, while a deterioration in the performance was observed for the tandem cell, reflecting in a lower PCE of 16.22% at a color temperature of 2900 K. Thus, an optimized tandem for outdoor applications was not suitable for indoor conditions. In order to alleviate this issue, we propose designing the tandem for indoor lightening by an appropriate choice of thicknesses of the top and bottom absorber layers in order to achieve the current matching point. Reducing the top absorber thickness while slightly increasing the bottom thickness resulted in a higher PCE of 27.80% at 2900 K. Full article
(This article belongs to the Special Issue Advanced Polymers for Solar Cells Applications)
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19 pages, 41061 KiB  
Article
Experimental Study on Shear-Peeling Debonding Behavior of BFRP Sheet-to-Steel Interfaces
by Hanyang Xue, Dafu Cao, Zhanzhan Tang, Qing Liu, Siji Zhu, Jiaqi Liu and Chuanzhi Sun
Polymers 2023, 15(9), 2216; https://doi.org/10.3390/polym15092216 - 08 May 2023
Viewed by 1175
Abstract
In order to study the failure mode and debonding behavior of the interface between BFRP (basalt fiber reinforced polymer) sheet and structural steel under mixed-mode loading conditions, eighteen specimens with different initial angles were tested in this study. The specimens were designed with [...] Read more.
In order to study the failure mode and debonding behavior of the interface between BFRP (basalt fiber reinforced polymer) sheet and structural steel under mixed-mode loading conditions, eighteen specimens with different initial angles were tested in this study. The specimens were designed with different initial angles to ensure that the interface performed under mixed-mode loading conditions. The relations between the bond strengths, failure modes, and initial angles were investigated. A new evaluation method to predict the interfacial bond strength under shear-peeling loading mode was proposed. The test results show that specimens with a smaller initial angle are more likely to exhibit a shear debonding failure at the interface between the steel plate and adhesive. In contrast, specimens with a larger initial angle are more likely to exhibit peeling of the interface. The ultimate tensile strength of the specimen is higher with a smaller initial angle. The results predicted by the proposed method are in good agreement with the experimental results. Full article
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14 pages, 4008 KiB  
Article
3D ZnO/Activated Carbon Alginate Beads for the Removal of Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes
by Zhe Liu, Xi Yu, Zhenchao Zhou, Jinyu Zhou, Xinyi Shuai, Zejun Lin and Hong Chen
Polymers 2023, 15(9), 2215; https://doi.org/10.3390/polym15092215 - 07 May 2023
Viewed by 1651
Abstract
The worldwide prevalence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have become one of the most urgent issues for public health. Thus, it is critical to explore more sustainable methods with less toxicity for the long-term removal of both ARB and [...] Read more.
The worldwide prevalence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have become one of the most urgent issues for public health. Thus, it is critical to explore more sustainable methods with less toxicity for the long-term removal of both ARB and ARGs. In this study, we fabricated a novel material by encapsulating zinc oxide (ZnO) nanoflowers and activated carbon (AC) in an alginate biopolymer. When the dosage of ZnO was 1.0 g (≈2 g/L), the composite beads exhibited higher removal efficiency and a slight release of Zn2+ in water treatment. Fixed bed column experiments demonstrated that ZnO/AC alginate beads had excellent removal capacities. When the flow rate was 1 mL/min, and the initial concentration was 107 CFU/mL, the removal efficiency of ARB was 5.69-log, and the absolute abundance of ARGs was decreased by 2.44–2.74-log. Moreover, the mechanism demonstrated that ZnO significantly caused cell lysis, cytoplasmic leakage, and the increase of reactive oxygen species induced subsequent oxidative stress state. These findings suggested that ZnO/AC alginate beads can be a promising material for removing ARB and ARGs from wastewater with eco-friendly and sustainable properties. Full article
(This article belongs to the Special Issue Functional Polymer Composites for Emerging Contaminants Control)
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37 pages, 21436 KiB  
Review
Nafion: New and Old Insights into Structure and Function
by Barry W. Ninham, Matthew J. Battye, Polina N. Bolotskova, Rostislav Yu. Gerasimov, Valery A. Kozlov and Nikolai F. Bunkin
Polymers 2023, 15(9), 2214; https://doi.org/10.3390/polym15092214 - 07 May 2023
Cited by 4 | Viewed by 2636
Abstract
The work reports a number of results on the dynamics of swelling and inferred nanostructure of the ion-exchange polymer membrane Nafion in different aqueous solutions. The techniques used were photoluminescent and Fourier transform IR (FTIR) spectroscopy. The centers of photoluminescence were identified as [...] Read more.
The work reports a number of results on the dynamics of swelling and inferred nanostructure of the ion-exchange polymer membrane Nafion in different aqueous solutions. The techniques used were photoluminescent and Fourier transform IR (FTIR) spectroscopy. The centers of photoluminescence were identified as the sulfonic groups localized at the ends of the perfluorovinyl ether (Teflon) groups that form the backbone of Nafion. Changes in deuterium content of water induced unexpected results revealed in the process of polymer swelling. In these experiments, deionized (DI) water (deuterium content 157 ppm) and deuterium depleted water (DDW) with deuterium content 3 PPM, were investigated. The strong hydration of sulfonic groups involves a competition between ortho- and para-magnetic forms of a water molecule. Deuterium, as it seems, adsorbs competitively on the sulfonic groups and thus can change the geometry of the sulfate bonds. With photoluminescent spectroscopy experiments, this is reflected in the unwinding of the polymer fibers into the bulk of the adjoining water on swelling. The unwound fibers do not tear off from the polymer substrate. They form a vastly extended “brush” type structure normal to the membrane surface. This may have implications for specificity of ion transport in biology, where the ubiquitous glycocalyx of cells and tissues invariably involves highly sulfated polymers such asheparan and chondroitin sulfate. Full article
(This article belongs to the Special Issue Advance in Functional Biological Polymer Membranes)
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12 pages, 2072 KiB  
Article
Promising Energetic Polymers from Nanostructured Bacterial Cellulose
by Yulia A. Gismatulina
Polymers 2023, 15(9), 2213; https://doi.org/10.3390/polym15092213 - 07 May 2023
Cited by 4 | Viewed by 1913
Abstract
This study investigated the nitration of nanostructured bacterial cellulose (NBC). The NBC, obtained using symbiotic Medusomyces gisevii Sa-12 as the microbial producer and then freeze-dried, was nitrated herein by two methods, the first using mixed sulphuric–nitric acids (MA) and the second using concentrated [...] Read more.
This study investigated the nitration of nanostructured bacterial cellulose (NBC). The NBC, obtained using symbiotic Medusomyces gisevii Sa-12 as the microbial producer and then freeze-dried, was nitrated herein by two methods, the first using mixed sulphuric–nitric acids (MA) and the second using concentrated nitric acid in the presence of methylene chloride (NA+MC). The synthesized samples of NBC nitrates (NBCNs) exhibited 11.77–12.27% nitrogen content, a viscosity of 1086 mPa·s or higher, 0.7–14.5% solubility in an alcohol–ester mixture, and 0.002% ash. Scanning electron microscopy showed that the nitration compacted the NBC structure, with the original reticulate pattern of the structure being preserved in full. Infrared spectroscopy for the presence of functional nitro groups at 1658–1659, 1280, 838–840, 749–751 and 693–694 cm−1 confirmed the synthesis of cellulose nitrates in particular. Thermogravimetric and differential thermal analyses showed the resultant NBCNs to have a high purity and high specific heats of decomposition of 6.94–7.08 kJ/g. The NBCN samples differ conceptually from plant-based cellulose nitrates by having a viscosity above 1086 mPa·s and a unique 3D reticulate structure that is retained during the nitration. The findings suggest that the NBCNs can be considered for use in novel high-tech materials and science-driven fields distinct from the application fields of plant-based cellulose nitrates. The NBCN sample obtained with NA+MC has the ability to generate an organogel when it is dissolved in acetone. Because of the said property, this NBCN sample can find use as a classical adhesive scaffold and an energetic gel matrix for creating promising energetic polymers. Full article
(This article belongs to the Special Issue Cellulose Based Composites)
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23 pages, 5244 KiB  
Article
Evolutionary Multi-Objective Optimization of Extrusion Barrier Screws: Data Mining and Decision Making
by António Gaspar-Cunha, Paulo Costa, Alexandre Delbem, Francisco Monaco, Maria José Ferreira and José Covas
Polymers 2023, 15(9), 2212; https://doi.org/10.3390/polym15092212 - 07 May 2023
Cited by 1 | Viewed by 1632
Abstract
Polymer single-screw extrusion is a major industrial processing technique used to obtain plastic products. To assure high outputs, tight dimensional tolerances, and excellent product performance, extruder screws may show different design characteristics. Barrier screws, which contain a second flight in the compression zone, [...] Read more.
Polymer single-screw extrusion is a major industrial processing technique used to obtain plastic products. To assure high outputs, tight dimensional tolerances, and excellent product performance, extruder screws may show different design characteristics. Barrier screws, which contain a second flight in the compression zone, have become quite popular as they promote and stabilize polymer melting. Therefore, it is important to design efficient extruder screws and decide whether a conventional screw will perform the job efficiently, or a barrier screw should be considered instead. This work uses multi-objective evolutionary algorithms to design conventional and barrier screws (Maillefer screws will be studied) with optimized geometry. The processing of two polymers, low-density polyethylene and polypropylene, is analyzed. A methodology based on the use of artificial intelligence (AI) techniques, namely, data mining, decision making, and evolutionary algorithms, is presented and utilized to obtain results with practical significance, based on relevant performance measures (objectives) used in the optimization. For the various case studies selected, Maillefer screws were generally advantageous for processing LDPE, while for PP, the use of both types of screws would be feasible. Full article
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12 pages, 5706 KiB  
Article
Preventing the Distortion of CoO6 Octahedra of LiCoO2 at High-Voltage Operation of Lithium-Ion Battery: An Organic Surface Reinforcement
by Fu-Ming Wang
Polymers 2023, 15(9), 2211; https://doi.org/10.3390/polym15092211 - 06 May 2023
Cited by 1 | Viewed by 1556
Abstract
Lithium cobalt oxide (LiCoO2, LCO) has been widely used in electronic markets due to its high energy density and wide voltage range applications. Recently, high-voltage (HV, >4.5 V) operation has been required to obey the requirements of high energy density and [...] Read more.
Lithium cobalt oxide (LiCoO2, LCO) has been widely used in electronic markets due to its high energy density and wide voltage range applications. Recently, high-voltage (HV, >4.5 V) operation has been required to obey the requirements of high energy density and cycle life in several applications such as electric vehicles and energy storage. However, the HV operation causes structure instability due to the over de-lithiation of LCO, as well as decomposing common carbonate solvents, thereby incurring the decay of battery performance. Moreover, a distortion of the CoO6 octahedra of LCO during de-lithiation induces a rehybridization of the Co 3d and O 2p orbitals. According to above reasons, decreasing the Co-O covalent bond promptly triggers high risks that significantly limit further use of LCO. In this research, an organic surface reinforcement by using bismaleimide–uracil (BU) that electrochemically forms a cathode electrolyte interphase (CEI) on LCO was explored. The results of electrochemical impedance spectroscopy and battery performance, such as the c-rate and cyclability tests, demonstrated that the modified CEI formed from BU significantly prevents the distortion of CoO6 octahedra. X-ray photoelectronic spectroscopy and in situ XAS indicated less LiF formation and higher bond energy of Co-O improved. Finally, the differential scanning calorimetry showed the onset temperature of decomposition of LCO was extended from 245 to 270 °C at 100% state of charge, which is about a 25 °C extension. The exothermic heat of LCO decreased by approximately 30% for high-safety use. This research confirms that the BU is eligible for high voltage (>4.5 V) LCO and presents outstanding electrochemical properties and safety performances. Full article
(This article belongs to the Special Issue Polymer Composite Materials for Energy Storage)
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12 pages, 2667 KiB  
Article
Enzymatic Crosslinking of Amino Acids Improves the Repair Effect of Keratin on Hair Fibre
by Yang Liu, Jingjing Liu and Jing Xiao
Polymers 2023, 15(9), 2210; https://doi.org/10.3390/polym15092210 - 06 May 2023
Cited by 1 | Viewed by 1820
Abstract
Although keratin can effectively repair hair fibres and enhance their moisture content and flexibility, it has a relatively low affinity for hair. In this study, the effects of transglutaminase (TGase)—commonly used to catalyse crosslinking of proteins or amino acids—in crosslinking serine and hydrolysed [...] Read more.
Although keratin can effectively repair hair fibres and enhance their moisture content and flexibility, it has a relatively low affinity for hair. In this study, the effects of transglutaminase (TGase)—commonly used to catalyse crosslinking of proteins or amino acids—in crosslinking serine and hydrolysed wool keratin to repair damaged hair and protect healthy hair were studied. Treatment with a repair solution containing hydrolysed wool keratin, serine, and TGase improved the physical and chemical properties of damaged hair samples. The alkali solubility of damaged hair samples decreased by 50.53%, fracture stress increased from 1.031 to 1.806 N, and fracture strain increased from 9.51 to 19.88 mm. Fourier transform infrared spectroscopy and X-ray analysis showed that amide bonds increased in damaged hair samples treated with the repair solution and hair crystallinity increased. Differential scanning calorimetry showed that the repair solution improved the thermal stability of damaged hair. After five cycles of washing, the effects of the repair solution were still apparent in damaged hair samples. The enzymatic solution had stronger repair effects than general hair care products and reduced water loss rates in damaged hair samples; repaired hair samples were also softer and brighter. The repair solution was effective in protecting healthy hair samples against chemical damage. The materials used to prepare the repair solution are all bio-based, and treatment with this product is safer and longer lasting. Full article
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17 pages, 9834 KiB  
Article
Effect of 3D Printing Process Parameters and Heat Treatment Conditions on the Mechanical Properties and Microstructure of PEEK Parts
by Honglei Zhen, Bin Zhao, Long Quan and Junyu Fu
Polymers 2023, 15(9), 2209; https://doi.org/10.3390/polym15092209 - 06 May 2023
Cited by 5 | Viewed by 2333
Abstract
Fused deposition modeling (FDM) processed Poly-ether-ether-ketone (PEEK) materials are widely used in aerospace, automobile, biomedical, and electronics industries and other industries due to their excellent mechanical properties, thermal properties, chemical resistance, wear resistance, and biocompatibility, etc. However, the manufacture of PEEK materials and [...] Read more.
Fused deposition modeling (FDM) processed Poly-ether-ether-ketone (PEEK) materials are widely used in aerospace, automobile, biomedical, and electronics industries and other industries due to their excellent mechanical properties, thermal properties, chemical resistance, wear resistance, and biocompatibility, etc. However, the manufacture of PEEK materials and parts utilizing the FDM process faces the challenge of fine-tuning a list of process parameters and heat treatment conditions to reach the best-suiting mechanical properties and microstructures. It is non-trivial to make the selection only according to theoretical analysis while counting on a vast number of experiments is the general situation. Therefore, in this paper, the extrusion rate, filling angle, and printing orientation are investigated to adjust the mechanical properties of 3D-printed PEEK parts; then, a variety of heat treatment conditions were applied to tune the crystallinity and strength. The results show that the best mechanical performance is achieved at 1.0 times the extrusion rate, varied angle cross-fillings with ±10° intervals, and vertical printing. Horizontal printing performs better with reduced warpage. Additionally, both crystallinity and mechanical properties are significantly improved after heat treatment, and the best state is achieved after holding at 300 °C for 2 h. The resulting tensile strength is close to 80% of the strength of injection-molded PEEK parts. Full article
(This article belongs to the Special Issue Mechanical and Physical Properties of 3D Printed Polymer Materials)
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15 pages, 2159 KiB  
Article
Formulation and Performance of NBR/CR-Based High-Damping Rubber Composites for Soundproof Using Orthogonal Test
by Xiankui Zeng, Jinmei Zhu, Gaowei Li, Qing Miao, Mohini Sain and Ranran Jian
Polymers 2023, 15(9), 2208; https://doi.org/10.3390/polym15092208 - 06 May 2023
Viewed by 1684
Abstract
Multiple functional-material-filled nitrile butadiene rubber/chloroprene rubber (NBR/CR) acoustic composites were extensively studied and prepared. According to the orthogonal test table L25 (56), 25 groups of samples were prepared by using a low-temperature one-time rubber mixing process. With tensile strength, average transmission [...] Read more.
Multiple functional-material-filled nitrile butadiene rubber/chloroprene rubber (NBR/CR) acoustic composites were extensively studied and prepared. According to the orthogonal test table L25 (56), 25 groups of samples were prepared by using a low-temperature one-time rubber mixing process. With tensile strength, average transmission loss, and damping peak as indexes, the influence degree of different factors and levels on the properties of acoustic composites was quantitatively discussed and analyzed. The matrix weight analysis was employed to optimize the material formula of rubber composites, and the corresponding influence weight was given. Results showed that the acoustic composite with blending ratio of 70/30 for NBR/CR matrix had preferable mechanical and acoustic properties; adding mica powder (MP) and montmorillonite (MMT) in matrix contributed to improve all above three indexes owing to their specific lamellar structures; hollow glass beads (HGB) had a positive influence on improving acoustic property due to its hollow microcavities, however, it had a negative impact on damping property because of the smooth spherical surfaces. Accordingly, the optimal formulation was found to be NBR/CR blending ratio of 70/30, MP of 10 phr (per hundred rubber), HGB of 4 phr, and MMT of 10 phr. Full article
(This article belongs to the Special Issue Innovative Injection Molding and Polymer Processing Technology)
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39 pages, 30650 KiB  
Article
Identification of Cement Pavement with Temperature Effect and Evaluation of Polymer Grouting Effect
by Xifeng Du, Haoyuan Cheng, Shengjie Xu and Wenjun Pei
Polymers 2023, 15(9), 2207; https://doi.org/10.3390/polym15092207 - 06 May 2023
Viewed by 932
Abstract
The falling weight deflectometer (FWD) detection system benefits from its outstanding characteristics of no damage, fast speed, and high precision. The warping deformation of cement concrete pavement occurs due to the temperature difference along the depth of the slab, which makes FWD detect [...] Read more.
The falling weight deflectometer (FWD) detection system benefits from its outstanding characteristics of no damage, fast speed, and high precision. The warping deformation of cement concrete pavement occurs due to the temperature difference along the depth of the slab, which makes FWD detect different results under different temperature fields. In this study, we systematically carried out the cement pavement’s temperature field and deflection test. The experimental data were analyzed to obtain the temperature variation law of the top and bottom of the pavement slab every day. By establishing a three-dimensional finite element model of cement pavement with a multi-layer elastic foundation type, the influence of the temperature difference at the bottom of the slab on the deflection of the center point of the slab corner load under different working conditions, different seasons, different loads and whether there is polymer filling in the void area was studied. We summarize the correlation between the temperature difference and the influence coefficient and propose the cement pavement void identification and polymer grouting effect evaluation method considering the temperature effect. Full article
(This article belongs to the Section Polymer Applications)
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17 pages, 6519 KiB  
Article
Super-Resolution Processing of Synchrotron CT Images for Automated Fibre Break Analysis of Unidirectional Composites
by Radmir Karamov, Christian Breite, Stepan V. Lomov, Ivan Sergeichev and Yentl Swolfs
Polymers 2023, 15(9), 2206; https://doi.org/10.3390/polym15092206 - 06 May 2023
Cited by 1 | Viewed by 1739
Abstract
Fibre breaks govern the strength of unidirectional composite materials under tension. The progressive development of fibre breaks is studied using in situ X-ray computed tomography, especially with synchrotron radiation. However, even with synchrotron radiation, the resolution of the time-resolved in situ images is [...] Read more.
Fibre breaks govern the strength of unidirectional composite materials under tension. The progressive development of fibre breaks is studied using in situ X-ray computed tomography, especially with synchrotron radiation. However, even with synchrotron radiation, the resolution of the time-resolved in situ images is not sufficient for a fully automated analysis of continuous mechanical deformations. We therefore investigate the possibility of increasing the quality of low-resolution in situ scans by means of super-resolution (SR) using 3D deep learning techniques, thus facilitating the subsequent fibre break identification. We trained generative neural networks (GAN) on datasets of high—(0.3 μm) and low-resolution (1.6 μm) statically acquired images. These networks were then applied to a low-resolution (1.1 μm) noisy image of a continuously loaded specimen. The statistical parameters of the fibre breaks used for the comparison are the number of individual breaks and the number of 2-plets and 3-plets per specimen volume. The fully automated process achieves an average accuracy of 82% of manually identified fibre breaks, while the semi-automated one reaches 92%. The developed approach allows the use of faster, low-resolution in situ tomography without losing the quality of the identified physical parameters. Full article
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14 pages, 2993 KiB  
Article
On Structural and Molecular Order in Cellulose Acetate Butyrate Films
by Malin Nejström, Bo Andreasson, Johanna Sjölund, Alireza Eivazi, Ida Svanedal, Håkan Edlund and Magnus Norgren
Polymers 2023, 15(9), 2205; https://doi.org/10.3390/polym15092205 - 06 May 2023
Cited by 1 | Viewed by 1749
Abstract
Cellulose acetate butyrate (CAB) is a possible candidate, being a raw material derived from renewable resources, to replace fossil-based materials. This is due to its thermoplastic properties and the relative ease with which it could be implemented within the existing industry. With a [...] Read more.
Cellulose acetate butyrate (CAB) is a possible candidate, being a raw material derived from renewable resources, to replace fossil-based materials. This is due to its thermoplastic properties and the relative ease with which it could be implemented within the existing industry. With a significant amount of variation in CAB on the market today, a knowledge gap has been identified regarding the understanding of the polymer structural arrangement in films. This relates to the underlying mechanisms that regulate CAB film material properties, insights that are important in product development. In this study, commercially available CAB was investigated with XRD, SEM, AFM, and TOPEM DSC in order to obtain physicochemical information related to its micro-structural features in solvent-cast films. The film-forming ability relates mostly to the number of hydroxyl groups, and the semi-crystallinity of the films depends on the type and position of the side groups along the cellulose backbone. The appearance of signs of possible cholesteric ordering in the films could be connected to higher amounts of hydroxyl groups along the backbone that disturb the helix arrangement, while the overall order was primarily related to the butyrate substitution and secondarily related to the molecular weight of the particular CAB studied. Cold crystallization was also observed in one CAB sample. Full article
(This article belongs to the Topic Cellulose and Cellulose Derivatives)
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18 pages, 4891 KiB  
Article
A Comparison of Interpolyelectrolyte Complexes (IPECs) Made from Anionic Block Copolymer Micelles and PDADMAC or q-Chitosan as Polycation
by Özge Azeri, Dennis Schönfeld, Bin Dai, Uwe Keiderling, Laurence Noirez and Michael Gradzielski
Polymers 2023, 15(9), 2204; https://doi.org/10.3390/polym15092204 - 06 May 2023
Viewed by 1278
Abstract
Block copolymers synthesized via Atom Transfer Radical Polymerization from alkyl acrylate and t-butyl acrylate and the subsequent hydrolysis of the t-butyl acrylate to acrylic acid were systematically varied with respect to their hydrophobic part by the variation in the alkyl chain length and [...] Read more.
Block copolymers synthesized via Atom Transfer Radical Polymerization from alkyl acrylate and t-butyl acrylate and the subsequent hydrolysis of the t-butyl acrylate to acrylic acid were systematically varied with respect to their hydrophobic part by the variation in the alkyl chain length and the degree of polymerisation in this block. Depending on the architecture of the hydrophobic part, they had a more or less pronounced tendency to form copolymer micelles in an aqueous solution. They were employed for the preparation of IPECs by mixing the copolymer aggregates with the polycations polydiallyldimethylammonium chloride (PDADMAC) or q-chit. The IPEC structure as a function of the composition was investigated by Static Light and Small Angle Neutron Scattering. For weakly-associated block copolymers (short alkyl chain), complexation with polycation led to the formation of globular complexes, while already existing micelles (long alkyl chain) grew further in mass. In general, aggregates became larger upon the addition of further polycation, but this growth was much more pronounced for PDADMAC compared to q-chit, thereby leading to the formation of clusters of aggregates. Accordingly, the structure of such IPECs with a hydrophobic block depended largely on the type of complexing polyelectrolyte, which allowed for controlling the structural organisation via the molecular architecture of the two oppositely charged polyelectrolytes. Full article
(This article belongs to the Special Issue Polyelectrolytes and Interpolyelectrolyte Complexes)
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