Polymers

14 pages, 3720 KiB

Open AccessArticle

Soft Wearable Piezoresistive Sensors Based on Natural Rubber Fabricated with a Customized Vat-Based Additive Manufacturing Process

by Antonia Georgopoulou, Sasitorn Srisawadi, Panithi Wiroonpochit and Frank Clemens

Polymers 2023, 15(10), 2410; https://doi.org/10.3390/polym15102410 - 22 May 2023

Cited by 5 | Viewed by 1527

Abstract

Piezoresistive sensors for monitoring human motions are essential for the prevention and treatment of injury. Natural rubber is a material of renewable origin that can be used for the development of soft wearable sensors. In this study, natural rubber was combined with acetylene [...] Read more.

Piezoresistive sensors for monitoring human motions are essential for the prevention and treatment of injury. Natural rubber is a material of renewable origin that can be used for the development of soft wearable sensors. In this study, natural rubber was combined with acetylene black to develop a soft piezoresistive sensing composite for monitoring the motion of human joints. An additive manufacturing technique based on stereolithography was used, and it was seen that the sensors produced with the method could detect even small strains (<10%) successfully. With the same sensor composite fabricated by mold casting, it was not possible to detect low strains reliably. TEM microscopy revealed that the distribution of the filler was not homogeneous for the cast samples, suggesting a directionality of the conductive filler network. For the sensors fabricated through the stereolithography-based method, a homogeneous distribution could be achieved. Based on mechano-electrical characterization, it was seen that the samples produced with AM combined the ability to endure large elongations with a monotonic sensor response. Under dynamic conditions, the sensor response of the samples produced by 3D printing showed lower drift and lower signal relaxation. The piezoresistive sensors were examined for monitoring the motion of the human finger joints. By increasing the bending angle of the sensor, it was possible to increase the sensitivity of the response. With the renewable origin of natural rubber and manufacturing method, the featured sensors can expand the applicability of soft flexible electronics in biomedical applications and devices. Full article

(This article belongs to the Special Issue Polymeric Nanocomposites for Wearable Applications)

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14 pages, 4634 KiB

Open AccessArticle

A Flexible Lithium-Ion-Conducting Membrane with Highly Loaded Titanium Oxide Nanoparticles to Promote Charge Transfer for Lithium–Air Battery

by Si-Han Peng, Yen-Hsiang Yu, Hsin-Chun Lu and Shingjiang Jessie Lue

Polymers 2023, 15(10), 2409; https://doi.org/10.3390/polym15102409 - 22 May 2023

Viewed by 1448

Abstract

In this research, we aim to investigate a flexible composite lithium-ion-conducting membrane (FC-LICM) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and titanium dioxide (TiO₂) nanoparticles with a TiO₂-rich configuration. PVDF-HFP was selected as the host polymer owing to its chemically compatible [...] Read more.

In this research, we aim to investigate a flexible composite lithium-ion-conducting membrane (FC-LICM) consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and titanium dioxide (TiO₂) nanoparticles with a TiO₂-rich configuration. PVDF-HFP was selected as the host polymer owing to its chemically compatible nature with lithium metal. TiO₂ (40–60 wt%) was incorporated into the polymer matrix, and the FC-LICM charge transfer resistance values (R_ct) were reduced by two-thirds (from 1609 Ω to 420 Ω) at the 50 wt% TiO₂ loading compared with the pristine PVDF-HFP. This improvement may be attributed to the electron transport properties enabled by the incorporation of semiconductive TiO₂. After being immersed in an electrolyte, the FC-LICM also exhibited a R_ct that was lower by 45% (from 141 to 76 Ω), suggesting enhanced ionic transfer upon the addition of TiO₂. The TiO₂ nanoparticles in the FC-LICM facilitated charge transfers for both electron transfer and ionic transport. The FC-LICM incorporated at an optimal load of 50 wt% TiO₂ was assembled into a hybrid electrolyte Li–air battery (HELAB). This battery was operated for 70 h with a cut-off capacity of 500 mAh g⁻¹ in a passive air-breathing mode under an atmosphere with high humidity. A 33% reduction in the overpotential of the HELAB was observed in comparison with using the bare polymer. The present work provides a simple FC-LICM approach for use in HELABs. Full article

(This article belongs to the Special Issue Functional and Conductive Polymer Thin Films III)

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15 pages, 1542 KiB

Open AccessArticle

Carboxymethyl Cellulose as a Food Emulsifier: Are Its Days Numbered?

by Eduardo M. Costa, Sara Silva, Carla F. Pereira, Alessandra B. Ribeiro, Francisca Casanova, Ricardo Freixo, Manuela Pintado and Óscar L. Ramos

Polymers 2023, 15(10), 2408; https://doi.org/10.3390/polym15102408 - 22 May 2023

Cited by 2 | Viewed by 2471

Abstract

Carboxymethyl cellulose use in industry is ubiquitous. Though it is recognized as safe by the EFSA and FDA, newer works have raised concerns related to its safety, as in vivo studies showed evidence of gut dysbiosis associated with CMC’s presence. Herein lies the [...] Read more.

Carboxymethyl cellulose use in industry is ubiquitous. Though it is recognized as safe by the EFSA and FDA, newer works have raised concerns related to its safety, as in vivo studies showed evidence of gut dysbiosis associated with CMC’s presence. Herein lies the question, is CMC a gut pro-inflammatory compound? As no work addressed this question, we sought to understand whether CMC was pro-inflammatory through the immunomodulation of GI tract epithelial cells. The results showed that while CMC was not cytotoxic up to 25 mg/mL towards Caco-2, HT29-MTX and Hep G2 cells, it had an overall pro-inflammatory behavior. In a Caco-2 monolayer, CMC by itself increased IL-6, IL-8 and TNF-α secretion, with the latter increasing by 1924%, and with these increases being 9.7 times superior to the one obtained for the IL-1β pro-inflammation control. In co-culture models, an increase in secretion in the apical side, particularly for IL-6 (692% increase), was observed, and when RAW 264.7 was added, data showed a more complex scenario as stimulation of pro-inflammatory (IL-6, MCP-1 and TNF-α) and anti-inflammatory (IL-10 and IFN-β) cytokines in the basal side was observed. Considering these results, CMC may exert a pro-inflammatory effect in the intestinal lumen, and despite more studies being required, the incorporation of CMC in foodstuffs must be carefully considered in the future to minimize potential GI tract dysbiosis. Full article

(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)

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28 pages, 13650 KiB

Open AccessEditor’s ChoiceArticle

Globular Proteins and Where to Find Them within a Polymer Brush—A Case Study

by Aikaterini A. Galata and Martin Kröger

Polymers 2023, 15(10), 2407; https://doi.org/10.3390/polym15102407 - 22 May 2023

Viewed by 1506

Abstract

Protein adsorption by polymerized surfaces is an interdisciplinary topic that has been approached in many ways, leading to a plethora of theoretical, numerical and experimental insight. There is a wide variety of models trying to accurately capture the essence of adsorption and its [...] Read more.

Protein adsorption by polymerized surfaces is an interdisciplinary topic that has been approached in many ways, leading to a plethora of theoretical, numerical and experimental insight. There is a wide variety of models trying to accurately capture the essence of adsorption and its effect on the conformations of proteins and polymers. However, atomistic simulations are case-specific and computationally demanding. Here, we explore universal aspects of the dynamics of protein adsorption through a coarse-grained (CG) model, that allows us to explore the effects of various design parameters. To this end, we adopt the hydrophobic-polar (HP) model for proteins, place them uniformly at the upper bound of a CG polymer brush whose multibead-spring chains are tethered to a solid implicit wall. We find that the most crucial factor affecting the adsorption efficiency appears to be the polymer grafting density, while the size of the protein and its hydrophobicity ratio come also into play. We discuss the roles of ligands and attractive tethering surfaces to the primary adsorption as well as secondary and ternary adsorption in the presence of attractive (towards the hydrophilic part of the protein) beads along varying spots of the backbone of the polymer chains. The percentage and rate of adsorption, density profiles and the shapes of the proteins, alongside with the respective potential of mean force are recorded to compare the various scenarios during protein adsorption. Full article

(This article belongs to the Collection Progress in Theory of Polymers at Interfaces)

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19 pages, 2150 KiB

Open AccessReview

Intrinsically Disordered Synthetic Polymers in Biomedical Applications

by Elif Yuce-Erarslan, Abraham (Avi) J. Domb, Haytam Kasem, Vladimir N. Uversky and Orkid Coskuner-Weber

Polymers 2023, 15(10), 2406; https://doi.org/10.3390/polym15102406 - 22 May 2023

Cited by 3 | Viewed by 1626

Abstract

In biology and medicine, intrinsically disordered synthetic polymers bio-mimicking intrinsically disordered proteins, which lack stable three-dimensional structures, possess high structural/conformational flexibility. They are prone to self-organization and can be extremely useful in various biomedical applications. Among such applications, intrinsically disordered synthetic polymers can [...] Read more.

In biology and medicine, intrinsically disordered synthetic polymers bio-mimicking intrinsically disordered proteins, which lack stable three-dimensional structures, possess high structural/conformational flexibility. They are prone to self-organization and can be extremely useful in various biomedical applications. Among such applications, intrinsically disordered synthetic polymers can have potential usage in drug delivery, organ transplantation, artificial organ design, and immune compatibility. The designing of new syntheses and characterization mechanisms is currently required to provide the lacking intrinsically disordered synthetic polymers for biomedical applications bio-mimicked using intrinsically disordered proteins. Here, we present our strategies for designing intrinsically disordered synthetic polymers for biomedical applications based on bio-mimicking intrinsically disordered proteins. Full article

(This article belongs to the Special Issue Bio-Mimicked and Bio-Inspired Synthetic Polymers)

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27 pages, 8055 KiB

Open AccessReview

Dental Materials Applied to 3D and 4D Printing Technologies: A Review

by HongXin Cai, Xiaotong Xu, Xinyue Lu, Menghua Zhao, Qi Jia, Heng-Bo Jiang and Jae-Sung Kwon

Polymers 2023, 15(10), 2405; https://doi.org/10.3390/polym15102405 - 22 May 2023

Cited by 4 | Viewed by 4465

Abstract

As computer-aided design and computer-aided manufacturing (CAD/CAM) technologies have matured, three-dimensional (3D) printing materials suitable for dentistry have attracted considerable research interest, owing to their high efficiency and low cost for clinical treatment. Three-dimensional printing technology, also known as additive manufacturing, has developed [...] Read more.

As computer-aided design and computer-aided manufacturing (CAD/CAM) technologies have matured, three-dimensional (3D) printing materials suitable for dentistry have attracted considerable research interest, owing to their high efficiency and low cost for clinical treatment. Three-dimensional printing technology, also known as additive manufacturing, has developed rapidly over the last forty years, with gradual application in various fields from industry to dental sciences. Four-dimensional (4D) printing, defined as the fabrication of complex spontaneous structures that change over time in response to external stimuli in expected ways, includes the increasingly popular bioprinting. Existing 3D printing materials have varied characteristics and scopes of application; therefore, categorization is required. This review aims to classify, summarize, and discuss dental materials for 3D printing and 4D printing from a clinical perspective. Based on these, this review describes four major materials, i.e., polymers, metals, ceramics, and biomaterials. The manufacturing process of 3D printing and 4D printing materials, their characteristics, applicable printing technologies, and clinical application scope are described in detail. Furthermore, the development of composite materials for 3D printing is the main focus of future research, as combining multiple materials can improve the materials’ properties. Updates in material sciences play important roles in dentistry; hence, the emergence of newer materials are expected to promote further innovations in dentistry. Full article

(This article belongs to the Special Issue Preparation and Applications of Biodegradable Polymer Materials)

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17 pages, 57138 KiB

Open AccessArticle

Poly(3-hydroxybutyrate) (PHB) and Polycaprolactone (PCL) Based Blends for Tissue Engineering and Bone Medical Applications Processed by FDM 3D Printing

by Štěpán Krobot, Veronika Melčová, Přemysl Menčík, Soňa Kontárová, Michala Rampichová, Věra Hedvičáková, Ema Mojžišová, Andrej Baco and Radek Přikryl

Polymers 2023, 15(10), 2404; https://doi.org/10.3390/polym15102404 - 22 May 2023

Cited by 6 | Viewed by 2095

Abstract

In the presented work, poly(3-hydroxybutyrate)–PHB-based composite blends for bone medical applications and tissue engineering are prepared and characterized. PHB used for the work was in two cases commercial and, in one case, was extracted by the chloroform-free route. PHB was then blended with [...] Read more.

In the presented work, poly(3-hydroxybutyrate)–PHB-based composite blends for bone medical applications and tissue engineering are prepared and characterized. PHB used for the work was in two cases commercial and, in one case, was extracted by the chloroform-free route. PHB was then blended with poly(lactic acid) (PLA) or polycaprolactone (PCL) and plasticized by oligomeric adipate ester (Syncroflex, SN). Tricalcium phosphate (TCP) particles were used as a bioactive filler. Prepared polymer blends were processed into the form of 3D printing filaments. The samples for all the tests performed were prepared by FDM 3D printing or compression molding. Differential scanning calorimetry was conducted to evaluate the thermal properties, followed by optimization of printing temperature by temperature tower test and determination of warping coefficient. Tensile test, three-point flexural test, and compression test were performed to study the mechanical properties of materials. Optical contact angle measurement was conducted to determine the surface properties of these blends and their influence on cell adhesion. Cytotoxicity measurement of prepared blends was conducted to find out whether the prepared materials were non-cytotoxic. The best temperatures for 3D printing were 195/190, 195/175, and 195/165 °C for PHB-soap/PLA-SN, PHB/PCL-SN, and PHB/PCL-SN-TCP, respectively. Their mechanical properties (strengths ~40 MPa, moduli ~2.5 GPa) were comparable with human trabecular bone. The calculated surface energies of all blends were ~40 mN/m. Unfortunately, only two out of three materials were proven to be non-cytotoxic (both PHB/PCL blends). Full article

(This article belongs to the Special Issue Processing and Applications of Biocompatible and Biodegradable Polymers and Their Composites)

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27 pages, 6021 KiB

Open AccessArticle

Numerical and Experimental Analysis of the Mode I Interlaminar Fracture Toughness in Multidirectional 3D-Printed Thermoplastic Composites Reinforced with Continuous Carbon Fiber

by Jonnathan D. Santos, José M. Guerrero, Norbert Blanco, Jorge I. Fajardo and César A. Paltán

Polymers 2023, 15(10), 2403; https://doi.org/10.3390/polym15102403 - 22 May 2023

Cited by 4 | Viewed by 1760

Abstract

It is well known that the use of continuous reinforcing fibers can largely improve the typical low in-plane mechanical properties of 3D-printed parts. However, there is very limited research on the characterization of the interlaminar fracture toughness of 3D-printed composites. In this study, [...] Read more.

It is well known that the use of continuous reinforcing fibers can largely improve the typical low in-plane mechanical properties of 3D-printed parts. However, there is very limited research on the characterization of the interlaminar fracture toughness of 3D-printed composites. In this study, we investigated the feasibility of determining the mode I interlaminar fracture toughness of 3D-printed cFRP composites with multidirectional interfaces. First, elastic calculations and different FE simulations of Double Cantilever Beam (DCB) specimens (using cohesive elements for the delamination, in addition to an intralaminar ply failure criterion) were carried out to choose the best interface orientations and laminate configurations. The objective was to ensure a smooth and stable propagation of the interlaminar crack, while preventing asymmetrical delamination growth and plane migration, also known as crack jumping. Then, the best three specimen configurations were manufactured and tested experimentally to validate the simulation methodology. The experimental results confirmed that, with the appropriate stacking sequence for the specimen arms, it is possible to characterize the interlaminar fracture toughness in multidirectional 3D-printed composites under mode I. The experimental results also show that both initiation and propagation values of the mode I fracture toughness depend on the interface angles, although a clear tendency could not be established. Full article

(This article belongs to the Special Issue Fibre-Reinforced Polymer Composite II)

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26 pages, 5602 KiB

Open AccessReview

Electrospinning and Electrospraying: Emerging Techniques for Probiotic Stabilization and Application

by Kun Feng, Lulu Huangfu, Chuanduo Liu, Laura Bonfili, Qisen Xiang, Hong Wu and Yanhong Bai

Polymers 2023, 15(10), 2402; https://doi.org/10.3390/polym15102402 - 22 May 2023

Cited by 6 | Viewed by 2551

Abstract

Probiotics are beneficial for human health. However, they are vulnerable to adverse effects during processing, storage, and passage through the gastrointestinal tract, thus reducing their viability. The exploration of strategies for probiotic stabilization is essential for application and function. Electrospinning and electrospraying, two [...] Read more.

Probiotics are beneficial for human health. However, they are vulnerable to adverse effects during processing, storage, and passage through the gastrointestinal tract, thus reducing their viability. The exploration of strategies for probiotic stabilization is essential for application and function. Electrospinning and electrospraying, two electrohydrodynamic techniques with simple, mild, and versatile characteristics, have recently attracted increased interest for encapsulating and immobilizing probiotics to improve their survivability under harsh conditions and promoting high-viability delivery in the gastrointestinal tract. This review begins with a more detailed classification of electrospinning and electrospraying, especially dry electrospraying and wet electrospraying. The feasibility of electrospinning and electrospraying in the construction of probiotic carriers, as well as the efficacy of various formulations on the stabilization and colonic delivery of probiotics, are then discussed. Meanwhile, the current application of electrospun and electrosprayed probiotic formulations is introduced. Finally, the existing limitations and future opportunities for electrohydrodynamic techniques in probiotic stabilization are proposed and analyzed. This work comprehensively explains how electrospinning and electrospraying are used to stabilize probiotics, which may aid in their development in probiotic therapy and nutrition. Full article

(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)

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17 pages, 3087 KiB

Open AccessReview

Recent Advances in Application of Polyoxometalates in Lignocellulose Pretreatment and Transformation

by Haoyu Deng, Wenbiao Xu, Dan Zhang, Xiangyu Li and Junyou Shi

Polymers 2023, 15(10), 2401; https://doi.org/10.3390/polym15102401 - 22 May 2023

Cited by 2 | Viewed by 1438

Abstract

Lignocellulose, composed of cellulose, hemicellulose, and lignin, holds immense promise as a renewable resource for the production of sustainable chemicals and fuels. Unlocking the full potential of lignocellulose requires efficient pretreatment strategies. In this comprehensive review, efforts were taken to survey the latest [...] Read more.

Lignocellulose, composed of cellulose, hemicellulose, and lignin, holds immense promise as a renewable resource for the production of sustainable chemicals and fuels. Unlocking the full potential of lignocellulose requires efficient pretreatment strategies. In this comprehensive review, efforts were taken to survey the latest developments in polyoxometalates (POMs)-assisted pretreatment and conversion of lignocellulosic biomass. An outstanding finding highlighted in this review is that the deformation of the cellulose structure from I to II accompanied by the removal of xylan/lignin through the synergistic effect of ionic liquids (ILs) and POMs resulted in a significant increase in glucose yield and improved cellulose digestibility. Furthermore, successful integration of POMs with deep eutectic solvents (DES) or γ-valerolactone/water (GVL/water) systems has demonstrated efficient lignin removal, opening avenues for advanced biomass utilization. This review not only presents the key findings and novel approaches in POMs-based pretreatment but also addresses the current challenges and prospects for large-scale industrial implementation. By offering a comprehensive assessment of the progress in this field, this review serves as a valuable resource for researchers and industry professionals aiming to harness the potential of lignocellulosic biomass for sustainable chemical and fuel production. Full article

(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)

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14 pages, 6679 KiB

Open AccessArticle

Robust, Flame-Retardant, and Anti-Corrosive Waterborne Polyurethane Enabled by a PN Synergistic Flame-Retardant Containing Benzimidazole and Phosphinate Groups

by Li-Ping Zhang, Zhen-Guo Zhao, Yuan-Yuan Huang, Chang-Jian Zhu, Xing Cao and Yan-Peng Ni

Polymers 2023, 15(10), 2400; https://doi.org/10.3390/polym15102400 - 22 May 2023

Cited by 1 | Viewed by 1594

Abstract

Waterborne polyurethanes (WPUs) have attracted great interest owing to their environmentally friendly properties, and are wildly applied in production and daily life. However, waterborne polyurethanes are flammable. Up to now, the challenge remains to prepare WPUs with excellent flame resistance, high emulsion stability, [...] Read more.

Waterborne polyurethanes (WPUs) have attracted great interest owing to their environmentally friendly properties, and are wildly applied in production and daily life. However, waterborne polyurethanes are flammable. Up to now, the challenge remains to prepare WPUs with excellent flame resistance, high emulsion stability, and outstanding mechanical properties. Herein, a novel flame-retardant additive, 2-hydroxyethan-1-aminium (2-(1H-benzo[d]imidazol-2-yl)ethyl)(phenyl)phosphinate (BIEP-ETA) has been synthesized and applied to improve the flame resistance of WPUs, which has both phosphorus nitrogen synergistic effect and the ability to form hydrogen bonds with WPUs. The WPU blends (WPU/FRs) exhibited a positive fire-retardant effect in both the vapor and condensed phases, with significantly improved self-extinguishing performance and reduced heat release value. Interestingly, thanks to the good compatibility between BIEP-ETA and WPUs, WPU/FRs not only have higher emulsion stability, but also have better mechanical properties with synchronously improved tensile strength and toughness. Moreover, WPU/FRs also exhibit excellent potential as a corrosion-resistant coating. Full article

(This article belongs to the Special Issue Developments in Multifunctional Flame-Retardant Polymer Composites)

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20 pages, 715 KiB

Open AccessReview

The Potential Applications of Reinforced Bioplastics in Various Industries: A Review

by Uwei Kong, Nurul Fazita Mohammad Rawi and Guan Seng Tay

Polymers 2023, 15(10), 2399; https://doi.org/10.3390/polym15102399 - 22 May 2023

Cited by 9 | Viewed by 7182

Abstract

The introduction of bioplastics has been an evolution for plastic industry since conventional plastics have been claimed to cause several environmental issues. Apart from its biodegradability, one of the advantages can be identified of using bioplastic is that they are produced by renewal [...] Read more.

The introduction of bioplastics has been an evolution for plastic industry since conventional plastics have been claimed to cause several environmental issues. Apart from its biodegradability, one of the advantages can be identified of using bioplastic is that they are produced by renewal resources as the raw materials for synthesis. Nevertheless, bioplastics can be classified into two types, which are biodegradable and non-biodegradable, depending on the type of plastic that is produced. Although some of the bioplastics are non-biodegradable, the usage of biomass in synthesising the bioplastics helps in preserving non-renewable resources, which are petrochemical, in producing conventional plastics. However, the mechanical strength of bioplastic still has room for improvement as compared to conventional plastics, which is believed to limit its application. Ideally, bioplastics need to be reinforced for improving their performance and properties to serve their application. Before 21st century, synthetic reinforcement has been used to reinforce conventional plastic to achieve its desire properties to serve its application, such as glass fiber. Owing to several issues, the trend has been diversified to utilise natural resources as reinforcements. There are several industries that have started to use reinforced bioplastic, and this article focuses on the advantages of using reinforced bioplastic in various industries and its limitations. Therefore, this article aims to study the trend of reinforced bioplastic applications and the potential applications of reinforced bioplastics in various industries. Full article

(This article belongs to the Special Issue Advances in Bio-Based and Biodegradable Polymeric Composites II)

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22 pages, 6061 KiB

Open AccessArticle

Synthesis and Characterization of a New Molecularly Imprinted Polymer for Selective Extraction of Mandelic Acid Metabolite from Human Urine as a Biomarker of Environmental and Occupational Exposures to Styrene

by Murad. M. Qronfla, Bassem Jamoussi and Radhouane Chakroun

Polymers 2023, 15(10), 2398; https://doi.org/10.3390/polym15102398 - 21 May 2023

Cited by 3 | Viewed by 1513

Abstract

4-Vinylpyridine molecularly imprinted polymer (4-VPMIP) microparticles for mandelic acid (MA) metabolite as a major biomarker of exposure to styrene (S) were synthesized by bulk polymerization with a noncovalent approach. A common mole ratio of 1:4:20 (i.e., metabolite template: functional monomer: cross-linking agent, respectively) [...] Read more.

4-Vinylpyridine molecularly imprinted polymer (4-VPMIP) microparticles for mandelic acid (MA) metabolite as a major biomarker of exposure to styrene (S) were synthesized by bulk polymerization with a noncovalent approach. A common mole ratio of 1:4:20 (i.e., metabolite template: functional monomer: cross-linking agent, respectively) was applied to allow the selective solid-phase extraction of MA in a urine sample followed by high-performance liquid chromatography–diode array detection (HPLC-DAD). In this research, the 4-VPMIP components were carefully selected: MA was used as a template (T), 4-Vinylpyridine (4-VP) as a functional monomer (FM), ethylene glycol dimethacrylate (EGDMA) as a cross-linker (XL), and azobisisobutyronitrile (AIBN) as an initiator (I) and acetonitrile (ACN) as a porogenic solvent. Non-imprinted polymer (NIP) which serves as a “control” was also synthesized simultaneously under the same condition without the addition of MA molecules. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were used to characterize the imprinted and nonimprinted polymer to explain the structural and morphological characteristics of the 4-VPMIP and surface NIP. The results obtained from SEM depicted that the polymers were irregularly shaped microparticles. Moreover, MIPs surfaces had cavities and were rougher than NIP. In addition, all particle sizes were less than 40 µm in diameter. The IR spectra of 4-VPMIPs before washing MA were a little different from NIP, while 4-VPMIP after elution had a spectrum that was almost identical to the NIP spectrum. The adsorption kinetics, isotherms, competitive adsorption, and reusability of 4-VPMIP were investigated. 4-VPMIP showed good recognition selectivity as well as enrichment and separation abilities for MA in the extract of human urine with satisfactory recoveries. The results obtained in this research imply that 4-VPMIP might be used as a sorbent for MA solid-phase extraction (MISPE), for the exclusive extraction of MA in human urine. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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30 pages, 7242 KiB

Open AccessArticle

Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler—Part II: Mechanical, Thermal and Ageing (Chemical) Properties

by Jelena Lubura, Olga Kočková, Beata Strachota, Oskar Bera, Ewa Pavlova, Jelena Pavličević, Bojana Ikonić, Predrag Kojić and Adam Strachota

Polymers 2023, 15(10), 2397; https://doi.org/10.3390/polym15102397 - 21 May 2023

Cited by 1 | Viewed by 1394

Abstract

Natural rubber composites were reinforced by the co-fillers ‘hydrochar’ (HC), obtained by hydrothermal carbonization of hardwood sawdust and commercial carbon black (CB). The content of the combined fillers was kept constant while their ratio was varied. The aim was to test the suitability [...] Read more.

Natural rubber composites were reinforced by the co-fillers ‘hydrochar’ (HC), obtained by hydrothermal carbonization of hardwood sawdust and commercial carbon black (CB). The content of the combined fillers was kept constant while their ratio was varied. The aim was to test the suitability of HC as a partial filler in natural rubber. Due to its larger particle size and hence smaller specific surface area, large amounts of HC reduced the crosslinking density in the composites. On the other hand, due to its unsaturated organic character, HC was found to display interesting chemical effects: if it was used as the exclusive filler component, it displayed a very strong anti-oxidizing effect, which greatly stabilized the rubber composite against oxidative crosslinking (and hence embrittlement). HC also affected the vulcanization kinetics in different ways, depending on the HC/CB ratio. Composites with HC/CB ratios 20/30 and 10/40 displayed interesting chemical stabilization in combination with fairly good mechanical properties. The performed analyses included vulcanization kinetics, tensile properties, determination of density of permanent and reversible crosslinking in dry and swollen states, chemical stability tests including TGA, thermo-oxidative aging tests in air at 180 °C, simulated weathering in real use conditions (‘Florida test’), and thermo-mechanical analyses of degraded samples. Generally, the results indicate that HC could be a promising filler material due to its specific reactivity. Full article

(This article belongs to the Special Issue Application of Functional Polymer Materials for Advanced Technologies)

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12 pages, 5053 KiB

Open AccessArticle

Study on the Thermogravimetric Kinetics of Dehydrated Sewage Sludge Regulated by Cationic Polyacrylamide and Sawdust

by Kai Yang, Jianqi Sun, Hongning Liu, Weichao Yang and Lei Dong

Polymers 2023, 15(10), 2396; https://doi.org/10.3390/polym15102396 - 21 May 2023

Cited by 1 | Viewed by 1146

Abstract

With the continuous increase in sewage-sludge production worldwide, the pyrolytic disposal of sludge has received great attention. To build knowledge on the kinetics of pyrolysis, first, sludge was regulated using appropriate amounts of cationic polyacrylamide (CPAM) and sawdust to study their enhancing effect [...] Read more.

With the continuous increase in sewage-sludge production worldwide, the pyrolytic disposal of sludge has received great attention. To build knowledge on the kinetics of pyrolysis, first, sludge was regulated using appropriate amounts of cationic polyacrylamide (CPAM) and sawdust to study their enhancing effect on dehydration. Due to the effects of the charge neutralization and skeleton hydrophobicity, a certain dose of CPAM and sawdust reduced the sludge’s moisture content from 80.3% to 65.7%. Next, the pyrolysis characteristics of the dehydrated sludge regulated by CPAM and sawdust were investigated at a heating rate of 10~40 °C/min by using TGA method. The addition of sawdust enhanced the release of volatile substances and reduced the apparent activation energy of the sample. The maximum weight-loss rate decreased with the heating rate, and the DTG curves moved in the direction of high temperature. A model-free method, namely the Starink method, was adopted to calculate the apparent activation energies, which ranged from 135.3 kJ/mol to 174.8 kJ/mol. Combined with the master-plots method, the most appropriate mechanism function ultimately obtained was the nucleation-and-growth model. Full article

(This article belongs to the Special Issue Functional Polymer Composites for Emerging Contaminants Control)

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18 pages, 4545 KiB

Open AccessArticle

Thermal and Oxidative Aging Effects of Polyamide-11 Powder Used in Multi-Jet Fusion

by Chrysoula Pandelidi, Ryan Blakis, Kok Peng Marcian Lee, Stuart Bateman, Milan Brandt and Mladenko Kajtaz

Polymers 2023, 15(10), 2395; https://doi.org/10.3390/polym15102395 - 21 May 2023

Viewed by 1271

Abstract

The transition of additive manufacturing (AM) from a technique for rapid prototyping to one for manufacturing of near net or net components has been led by the development of methods that can repeatedly fabricate quality parts. High-speed laser sintering and the recently developed [...] Read more.

The transition of additive manufacturing (AM) from a technique for rapid prototyping to one for manufacturing of near net or net components has been led by the development of methods that can repeatedly fabricate quality parts. High-speed laser sintering and the recently developed multi-jet fusion (MJF) processes have seen quick adoption from industry due to their ability to produce high-quality components relatively quickly. However, the recommended refresh ratios of new powder led to notable amounts of used powder being discarded. In this research, polyamide-11 powder, typically used in AM, was thermally aged to investigate its properties at extreme levels of reuse. The powder was exposed to 180 °C in air for up to 168 h and its chemical, morphological, thermal, rheological, and mechanical properties were examined. To decouple the thermo-oxidative aging phenomena from AM process related effects, such as porosity, rheological and mechanical properties characterisation was performed on compression-moulded specimens. It was found that exposure notably affected the properties of both the powder and the derived compression-moulded specimens within the first 24 h of exposure; however, consecutive exposure did not have a significant effect. Full article

(This article belongs to the Special Issue Polymer Materials and Design Processes for Additively Manufactured Products)

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12 pages, 4405 KiB

Open AccessArticle

The Tailored Material Removal Distribution on Polyimide Membrane Can Be Obtained by Introducing Additional Electrodes

by Xiang Wu, Bin Fan, Qiang Xin, Guohan Gao, Peiqi Jiao, Junming Shao, Qian Luo and Zhaoyu Liang

Polymers 2023, 15(10), 2394; https://doi.org/10.3390/polym15102394 - 21 May 2023

Cited by 2 | Viewed by 991

Abstract

Reactive ion etching (RIE) is a promising material removal method for processing membrane diffractive optical elements and fabrication of meter-scale aperture optical substrates because of its high-efficiency parallel processing and low surface damage. However, the non-uniformity of the etching rate in the existing [...] Read more.

Reactive ion etching (RIE) is a promising material removal method for processing membrane diffractive optical elements and fabrication of meter-scale aperture optical substrates because of its high-efficiency parallel processing and low surface damage. However, the non-uniformity of the etching rate in the existing RIE technology will obviously reduce the machining accuracy of diffractive elements, deteriorate the diffraction efficiency and weaken the surface convergence rate of optical substrates. In the etching process of the polyimide (PI) membrane, additional electrodes were introduced for the first time to achieve the modulation of the plasma sheath properties on the same spatial surface, thus changing the etch rate distribution. Using the additional electrode, a periodic profile structure similar to the additional electrode was successfully processed on the surface of a 200-mm diameter PI membrane substrate by a single etching iteration. By combining etching experiments with plasma discharge simulations, it is demonstrated that additional electrodes can affect the material removal distribution, and the reasons for this are analyzed and discussed. This work demonstrates the feasibility of etching rate distribution modulation based on additional electrodes, and lays a foundation for realizing tailored material removal distribution and improving etching uniformity in the future. Full article

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

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20 pages, 10549 KiB

Open AccessArticle

Copolymer-Green-Synthesized Copper Oxide Nanoparticles Enhance Folate-Targeting in Cervical Cancer Cells In Vitro

by Keelan Jagaran and Moganavelli Singh

Polymers 2023, 15(10), 2393; https://doi.org/10.3390/polym15102393 - 20 May 2023

Cited by 6 | Viewed by 1869

Abstract

Cervical cancer is fast becoming a global health crisis, accounting for most female deaths in low- and middle-income countries. It is the fourth most frequent cancer affecting women, and due to its complexity, conventional treatment options are limited. Nanomedicine has found a niche [...] Read more.

Cervical cancer is fast becoming a global health crisis, accounting for most female deaths in low- and middle-income countries. It is the fourth most frequent cancer affecting women, and due to its complexity, conventional treatment options are limited. Nanomedicine has found a niche in gene therapy, with inorganic nanoparticles becoming attractive tools for gene delivery strategies. Of the many metallic nanoparticles (NPs) available, copper oxide NPs (CuONPs) have been the least investigated in gene delivery. In this study, CuONPs were biologically synthesized using Melia azedarach leaf extract, functionalized with chitosan and polyethylene glycol (PEG), and conjugated to the targeting ligand folate. A peak at 568 nm from UV-visible spectroscopy and the characteristic bands for the functional groups using Fourier-transform infrared (FTIR) spectroscopy confirmed the successful synthesis and modification of the CuONPs. Spherical NPs within the nanometer range were evident from transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). The NPs portrayed exceptional binding and protection of the reporter gene, pCMV-Luc-DNA. In vitro cytotoxicity studies revealed cell viability >70% in human embryonic kidney (HEK293), breast adenocarcinoma (MCF-7), and cervical cancer (HeLa) cells, with significant transgene expression, obtained using the luciferase reporter gene assay. Overall, these NPs showed favorable properties and efficient gene delivery, suggesting their potential role in gene therapy. Full article

(This article belongs to the Special Issue Polymeric Nanoparticles for Biomedical Applications)

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17 pages, 4887 KiB

Open AccessArticle

Enhancing the Performance of Triboelectric Generator: A Novel Approach Using Solid–Liquid Interface-Treated Foam and Metal Contacts

by Quang Tan Nguyen, Duy Linh Vu, Chau Duy Le and Kyoung Kwan Ahn

Polymers 2023, 15(10), 2392; https://doi.org/10.3390/polym15102392 - 20 May 2023

Cited by 4 | Viewed by 1595

Abstract

This work introduces a novel approach for enhancing the performance of a triboelectric generator (TEG) by using a solid–liquid interface-treated foam (SLITF) as its active layer, combined with two metal contacts of different work functions. SLITF is made by absorbing water into a [...] Read more.

This work introduces a novel approach for enhancing the performance of a triboelectric generator (TEG) by using a solid–liquid interface-treated foam (SLITF) as its active layer, combined with two metal contacts of different work functions. SLITF is made by absorbing water into a cellulose foam, which enables charges generated by friction energy during the sliding motion to be separated and transferred through the conductive path formed by the hydrogen-bonded network of water molecules. Unlike traditional TEGs, the SLITF-TEG demonstrates an impressive current density of 3.57 A/m² and can harvest electric power up to 0.174 W/m² with an induced voltage of approximately 0.55 V. The device generates a direct current in the external circuit, eliminating the limitations of low current density and alternating current found in traditional TEGs. By connecting six-unit cells of SLITF-TEG in series and parallel, the peak voltage and current can be increased up to 3.2 V and 12.5 mA, respectively. Furthermore, the SLITF-TEG has the potential to serve as a self-powered vibration sensor with high accuracy (R² = 0.99). The findings demonstrate the significant potential of the SLITF-TEG approach for efficiently harvesting low-frequency mechanical energy from the natural environment, with broad implications for a range of applications. Full article

(This article belongs to the Section Polymer Applications)

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20 pages, 7074 KiB

Open AccessArticle

Modification of the Structure and Linear/Nonlinear Optical Characteristics of PVA/Chitosan Blend through CuO Doping for Eco-Friendly Applications

by Sami S. Alharthi and Ali Badawi

Polymers 2023, 15(10), 2391; https://doi.org/10.3390/polym15102391 - 20 May 2023

Cited by 16 | Viewed by 1385

Abstract

The solution casting technique is utilized to fabricate blank and CuO-doped polyvinyl alcohol/chitosan (PVA/CS) blends for eco-friendly applications. The structure and surface morphologies of prepared samples were explored by Fourier transform infrared (FT-IR) spectrophotometry and scanning electron microscopy (SEM), respectively. FT-IR analysis reveals [...] Read more.

The solution casting technique is utilized to fabricate blank and CuO-doped polyvinyl alcohol/chitosan (PVA/CS) blends for eco-friendly applications. The structure and surface morphologies of prepared samples were explored by Fourier transform infrared (FT-IR) spectrophotometry and scanning electron microscopy (SEM), respectively. FT-IR analysis reveals the incorporation of CuO particles within the PVA/CS structure. SEM analysis exposes the well-dispersion of CuO particles in the host medium. The linear/nonlinear optical characteristics were found on the basis of UV-visible-NIR measurements. The transmittance of the PVA/CS decreases upon CuO increasing to 20.0 wt%. The optical bandgap (E_{g dir.}/E_{g ind.}) decreases from 5.38/4.67 eV (blank PVA/CS) to 3.72/3.12 eV (20.0 wt% CuO-PVA/CS). An obvious improvement in the optical constants of the PVA/CS blend is achieved by CuO doping. The Wemple-DiDomenico (WDD) and Sellmeier oscillator models were utilized to examine the CuO role dispersion behavior of the PVA/CS blend. The optical analysis shows clear enrichment of the optical parameters of the PVA/CS host. The novel findings in the current study nominate CuO-doped PVA/CS films for applications in linear/nonlinear optical devices. Full article

(This article belongs to the Special Issue Polymer Blends and Composites)

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13 pages, 5906 KiB

Open AccessArticle

Effect of Scarf Repair Geometry on the Impact Performance of Aerospace Composites

by Sridharan Vijay Shankar and Sridhar Idapalapati

Polymers 2023, 15(10), 2390; https://doi.org/10.3390/polym15102390 - 20 May 2023

Viewed by 1339

Abstract

This experimental study investigates the effect of scarf geometry in restoring the impact response of scarf-patched 3 mm thick glass-fiber reinforced polymer (GFRP) matrix composite laminates. Traditional circular along with rounded rectangular scarf patch configurations are considered repair patches. Experimental measurements revealed that [...] Read more.

This experimental study investigates the effect of scarf geometry in restoring the impact response of scarf-patched 3 mm thick glass-fiber reinforced polymer (GFRP) matrix composite laminates. Traditional circular along with rounded rectangular scarf patch configurations are considered repair patches. Experimental measurements revealed that the temporal variations of force and energy response of the pristine specimen are close to that of circular repaired specimens. The predominant failure modes were witnessed only in the repair patch which includes matrix cracking, fiber fracture, and delamination, and no discontinuity in the adhesive interface was witnessed. When compared with the pristine samples, the top ply damage size of the circular repaired specimens are larger by 9.91%, while that of the rounded rectangular repaired specimens is larger by 434.23%. The results show that circular scarf repair is a more suitable choice of repair approach under the condition of a 37 J low-velocity impact event even though the global force-time response is similar. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer-Based Composites: Processing, Characterization and Performance II)

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10 pages, 827 KiB

Open AccessArticle

Effects of Alkyl Ester Chain Length on the Toughness of PolyAcrylate-Based Network Materials

by Yutaro Kawano, Hiroshi Masai, Shintaro Nakagawa, Naoko Yoshie and Jun Terao

Polymers 2023, 15(10), 2389; https://doi.org/10.3390/polym15102389 - 20 May 2023

Cited by 1 | Viewed by 1477

Abstract

Polyacrylate-based network materials are widely used in various products owing to their facile synthesis via radical polymerization reactions. In this study, the effects of alkyl ester chains on the toughness of polyacrylate-based network materials were investigated. Polymer networks were fabricated via the radical [...] Read more.

Polyacrylate-based network materials are widely used in various products owing to their facile synthesis via radical polymerization reactions. In this study, the effects of alkyl ester chains on the toughness of polyacrylate-based network materials were investigated. Polymer networks were fabricated via the radical polymerization of methyl acrylate (MA), ethyl acrylate (EA), and butyl acrylate (BA) in the presence of 1,4-butanediol diacrylate as a crosslinker. Differential scanning calorimetry and rheological measurements revealed that the toughness of MA-based networks drastically increased compared with that of EA- and BA-based networks; the fracture energy of the MA-based network was approximately 10 and 100 times greater than that of EA and BA, respectively. The high fracture energy was attributed to the glass transition temperature of the MA-based network (close to room temperature), resulting in large energy dissipation via viscosity. Our results set a new basis for expanding the applications of polyacrylate-based networks as functional materials. Full article

(This article belongs to the Section Polymer Physics and Theory)

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17 pages, 6475 KiB

Open AccessArticle

Toward a Circular Bioeconomy: Development of Pineapple Stem Starch Composite as a Plastic-Sheet Substitute for Single-Use Applications

by Chanaporn Thongphang, Atitiya Namphonsane, Sombat Thanawan, Chin Hua Chia, Rungtiwa Wongsagonsup, Siwaporn Meejoo Smith and Taweechai Amornsakchai

Polymers 2023, 15(10), 2388; https://doi.org/10.3390/polym15102388 - 19 May 2023

Cited by 3 | Viewed by 3232

Abstract

Plastic waste poses a significant challenge for the environment, particularly smaller plastic products that are often difficult to recycle or collect. In this study, we developed a fully biodegradable composite material from pineapple field waste that is suitable for small-sized plastic products that [...] Read more.

Plastic waste poses a significant challenge for the environment, particularly smaller plastic products that are often difficult to recycle or collect. In this study, we developed a fully biodegradable composite material from pineapple field waste that is suitable for small-sized plastic products that are difficult to recycle, such as bread clips. We utilized starch from waste pineapple stems, which is high in amylose content, as the matrix, and added glycerol and calcium carbonate as the plasticizer and filler, respectively, to improve the material’s moldability and hardness. We varied the amounts of glycerol (20–50% by weight) and calcium carbonate (0–30 wt.%) to produce composite samples with a wide range of mechanical properties. The tensile moduli were in the range of 45–1100 MPa, with tensile strengths of 2–17 MPa and an elongation at break of 10–50%. The resulting materials exhibited good water resistance and had lower water absorption (~30–60%) than other types of starch-based materials. Soil burial tests showed that the material completely disintegrated into particles smaller than 1 mm within 14 days. We also created a bread clip prototype to test the material’s ability to hold a filled bag tightly. The obtained results demonstrate the potential of using pineapple stem starch as a sustainable alternative to petroleum-based and biobased synthetic materials in small-sized plastic products while promoting a circular bioeconomy. Full article

(This article belongs to the Special Issue Sustainable Biopolymer-Based Composites: Processing, Characterization, and Application)

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15 pages, 2257 KiB

Open AccessArticle

The Effects of Cross-Linking Agents on the Mechanical Properties of Poly (Methyl Methacrylate) Resin

by Gulsum Ceylan, Serkan Emik, Tuncer Yalcinyuva, Emin Sunbuloğlu, Ergun Bozdag and Fatma Unalan

Polymers 2023, 15(10), 2387; https://doi.org/10.3390/polym15102387 - 19 May 2023

Cited by 1 | Viewed by 2864

Abstract

Cross-linking agents are incorporated into denture base materials to improve their mechanical properties. This study investigated the effects of various cross-linking agents, with different cross-linking chain lengths and flexibilities, on the flexural strength, impact strength, and surface hardness of polymethyl methacrylate (PMMA). The [...] Read more.

Cross-linking agents are incorporated into denture base materials to improve their mechanical properties. This study investigated the effects of various cross-linking agents, with different cross-linking chain lengths and flexibilities, on the flexural strength, impact strength, and surface hardness of polymethyl methacrylate (PMMA). The cross-linking agents used were ethylene glycol dimethacrylate (EGDMA), tetraethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TEGDA), and polyethylene glycol dimethacrylate (PEGDMA). These agents were added to the methyl methacrylate (MMA) monomer component in concentrations of 5%, 10%, 15%, and 20% by volume and 10% by molecular weight. A total of 630 specimens, comprising 21 groups, were fabricated. Flexural strength and elastic modulus were assessed using a 3-point bending test, impact strength was measured via the Charpy type test, and surface Vickers hardness was determined. Statistical analyses were performed using the Kolmogorov–Smirnov Test, Kruskal–Wallis Test, Mann–Whitney U Test, and ANOVA with post hoc Tamhane test (p ≤ 0.05). No significant increase in flexural strength, elastic modulus, or impact strength was observed in the cross-linking groups compared to conventional PMMA. However, surface hardness values notably decreased with the addition of 5% to 20% PEGDMA. The incorporation of cross-linking agents in concentrations ranging from 5% to 15% led to an improvement in the mechanical properties of PMMA. Full article

(This article belongs to the Special Issue Advanced Polymeric Materials for Dental Applications II)

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17 pages, 2961 KiB

Open AccessArticle

Poly(Lactic Acid) Composites with Lignin and Nanolignin Synthesized by In Situ Reactive Processing

by Sofia P. Makri, Eleftheria Xanthopoulou, Miguel Angel Valera, Ana Mangas, Giacomo Marra, Víctor Ruiz, Savvas Koltsakidis, Dimitrios Tzetzis, Alexandros Zoikis Karathanasis, Ioanna Deligkiozi, Nikolaos Nikolaidis, Dimitrios Bikiaris and Zoi Terzopoulou

Polymers 2023, 15(10), 2386; https://doi.org/10.3390/polym15102386 - 19 May 2023

Cited by 5 | Viewed by 2634

Abstract

Poly(lactic acid) (PLA) composites with 0.5 wt% lignin or nanolignin were prepared with two different techniques: (a) conventional melt-mixing and (b) in situ Ring Opening Polymerization (ROP) by reactive processing. The ROP process was monitored by measuring the torque. The composites were synthesized [...] Read more.

Poly(lactic acid) (PLA) composites with 0.5 wt% lignin or nanolignin were prepared with two different techniques: (a) conventional melt-mixing and (b) in situ Ring Opening Polymerization (ROP) by reactive processing. The ROP process was monitored by measuring the torque. The composites were synthesized rapidly using reactive processing that took under 20 min. When the catalyst amount was doubled, the reaction time was reduced to under 15 min. The dispersion, thermal transitions, mechanical properties, antioxidant activity, and optical properties of the resulting PLA-based composites were evaluated with SEM, DSC, nanoindentation, DPPH assay, and DRS spectroscopy. All reactive processing-prepared composites were characterized by means of SEM, GPC, and NMR to assess their morphology, molecular weight, and free lactide content. The benefits of the size reduction of lignin and the use of in situ ROP by reactive processing were demonstrated, as the reactive processing-produced nanolignin-containing composites had superior crystallization, mechanical, and antioxidant properties. These improvements were attributed to the participation of nanolignin in the ROP of lactide as a macroinitiator, resulting in PLA-grafted nanolignin particles that improved its dispersion. Full article

(This article belongs to the Special Issue From Biomass Fractionation to Final Biobased Polymer Nanocomposites in European Sustainable Biobased Nanomaterials Community (BIOMAC))

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16 pages, 4921 KiB

Open AccessArticle

High Wear Resistance of POSS Grafted-Polyimide/Silica Composites under Atomic Oxygen Conditions

by Huimin Qi, Yang Lei, Xuemei Lei, Ding Zhang, Yafeng Zhang, Jiaxin Yu and Baogang Guo

Polymers 2023, 15(10), 2385; https://doi.org/10.3390/polym15102385 - 19 May 2023

Viewed by 1129

Abstract

Polyimide-bearing retainer has been successfully used in space environment. However, the structural damage of polyimide induced by space irradiation limits its wide use. In order to further improve the atomic oxygen resistance of polyimide and comprehensively investigate the tribological mechanism of polyimide composites [...] Read more.

Polyimide-bearing retainer has been successfully used in space environment. However, the structural damage of polyimide induced by space irradiation limits its wide use. In order to further improve the atomic oxygen resistance of polyimide and comprehensively investigate the tribological mechanism of polyimide composites exposed in simulate space environment, 3-amino-polyhedral oligomeric silsesquioxane (NH₂-POSS) was incorporated into a polyimide molecular chain and silica (SiO₂) nanoparticles were in situ added into polyimide matrix and the combined effect of vacuum environment, and atomic oxygen (AO) on the tribological performance of polyimide was studied using bearing steel as the counterpart by a ball on disk tribometer. XPS analysis demonstrated the formation of protective layer induced by AO. The wear resistance of polyimide after modification was enhanced under AO attack. FIB-TEM confirmed that the inert protective layer of Si was formed on the counterpart during the sliding process. Mechanisms behind this are discussed based on the systematic characterization of worn surfaces of the samples and the tribofilms formed on the counterbody. Full article

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

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19 pages, 5850 KiB

Open AccessArticle

A Novel P/N/Si-Containing Vanillin-Based Compound for a Flame-Retardant, Tough Yet Strong Epoxy Thermoset

by Siyuan He, Cheng Chi, Chaohua Peng, Birong Zeng, Yongming Chen, Zhongxi Miao, Hui Xu, Weiang Luo, Guorong Chen, Zhenping Fu and Lizong Dai

Polymers 2023, 15(10), 2384; https://doi.org/10.3390/polym15102384 - 19 May 2023

Viewed by 1505

Abstract

It is still extremely challenging to endow epoxy resins (EPs) with excellent flame retardancy and high toughness. In this work, we propose a facile strategy of combining rigid–flexible groups, promoting groups and polar phosphorus groups with the vanillin compound, which implements a dual [...] Read more.

It is still extremely challenging to endow epoxy resins (EPs) with excellent flame retardancy and high toughness. In this work, we propose a facile strategy of combining rigid–flexible groups, promoting groups and polar phosphorus groups with the vanillin compound, which implements a dual functional modification for EPs. With only 0.22% phosphorus loading, the modified EPs obtain a limiting oxygen index (LOI) value of 31.5% and reach V-0 grade in UL-94 vertical burning tests. Particularly, the introduction of P/N/Si-containing vanillin-based flame retardant (DPBSi) improves the mechanical properties of EPs, including toughness and strength. Compared with EPs, the storage modulus and impact strength of EP composites can increase by 61.1% and 240%, respectively. Therefore, this work introduces a novel molecular design strategy for constructing an epoxy system with high-efficiency fire safety and excellent mechanical properties, giving it immense potential for broadening the application fields of EPs. Full article

(This article belongs to the Special Issue Mechanical and Structure–Property Relationships of Polymer Composites)

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17 pages, 6028 KiB

Open AccessArticle

Urushiol-Based Benzoxazine Containing Sulfobetaine Groups for Sustainable Marine Antifouling Applications

by Jing Zhao, Jipeng Chen, Xiaoxiao Zheng, Qi Lin, Guocai Zheng, Yanlian Xu and Fengcai Lin

Polymers 2023, 15(10), 2383; https://doi.org/10.3390/polym15102383 - 19 May 2023

Cited by 2 | Viewed by 1523

Abstract

Benzoxazine resins are new thermosetting resins with excellent thermal stability, mechanical properties, and a flexible molecular design, demonstrating promise for applications in marine antifouling coatings. However, designing a multifunctional green benzoxazine resin-derived antifouling coating that combines resistance to biological protein adhesion, a high [...] Read more.

Benzoxazine resins are new thermosetting resins with excellent thermal stability, mechanical properties, and a flexible molecular design, demonstrating promise for applications in marine antifouling coatings. However, designing a multifunctional green benzoxazine resin-derived antifouling coating that combines resistance to biological protein adhesion, a high antibacterial rate, and low algal adhesion is still challenging. In this study, a high-performance coating with a low environmental impact was synthesized using urushiol-based benzoxazine containing tertiary amines as the precursor, and a sulfobetaine moiety into the benzoxazine group was introduced. This sulfobetaine-functionalized urushiol-based polybenzoxazine coating (poly(U−ea/sb)) was capable of clearly killing marine biofouling bacteria adhered to the coating surface and significantly resisting protein attachment. poly(U−ea/sb) exhibited an antibacterial rate of 99.99% against common Gram negative bacteria (e.g., Escherichia coli and Vibrio alginolyticus) and Gram positive bacteria (e.g., Staphylococcus aureus and Bacillus sp.), with >99% its algal inhibition activity, and it effectively prevented microbial adherence. Here, a dual-function crosslinkable zwitterionic polymer, which used an “offensive-defensive” tactic to improve the antifouling characteristics of the coating was presented. This simple, economic, and feasible strategy provides new ideas for the development of green marine antifouling coating materials with excellent performance. Full article

(This article belongs to the Special Issue Biomass-Based Polymer Membranes and Films: Synthesis, Characterization, and Applications)

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16 pages, 3323 KiB

Open AccessArticle

FDM 3D Printing and Soil-Burial-Degradation Behaviors of Residue of Astragalus Particles/Thermoplastic Starch/Poly(lactic acid) Biocomposites

by Zhibing Ni, Jianan Shi, Mengya Li, Wen Lei and Wangwang Yu

Polymers 2023, 15(10), 2382; https://doi.org/10.3390/polym15102382 - 19 May 2023

Cited by 4 | Viewed by 1303

Abstract

Astragalus residue powder (ARP)/thermoplastic starch (TPS)/poly(lactic acid) (PLA) biocomposites were prepared by fused-deposition modeling (FDM) 3D-printing technology for the first time in this paper, and certain physico-mechanical properties and soil-burial-biodegradation behaviors of the biocomposites were investigated. The results showed that after raising the [...] Read more.

Astragalus residue powder (ARP)/thermoplastic starch (TPS)/poly(lactic acid) (PLA) biocomposites were prepared by fused-deposition modeling (FDM) 3D-printing technology for the first time in this paper, and certain physico-mechanical properties and soil-burial-biodegradation behaviors of the biocomposites were investigated. The results showed that after raising the dosage of ARP, the tensile and flexural strengths, the elongation at break and the thermal stability of the sample decreased, while the tensile and flexural moduli increased; after raising the dosage of TPS, the tensile and flexural strengths, the elongation at break and the thermal stability all decreased. Among all of the samples, sample C—which was composed of 11 wt.% ARP, 10 wt.% TPS and 79 wt.% PLA—was the cheapest and also the most easily degraded in water. The soil-degradation-behavior analysis of sample C showed that, after being buried in soil, the surfaces of the samples became grey at first, then darkened, after which the smooth surfaces became rough and certain components were found to detach from the samples. After soil burial for 180 days, there was weight loss of 21.40%, and the flexural strength and modulus, as well as the storage modulus, reduced from 82.1 MPa, 11,922.16 MPa and 2395.3 MPa to 47.6 MPa, 6653.92 MPa and 1476.5 MPa, respectively. Soil burial had little effect on the glass transition, cold crystallization or melting temperatures, while it reduced the crystallinity of the samples. It is concluded that the FDM 3D-printed ARP/TPS/PLA biocomposites are easy to degrade in soil conditions. This study developed a new kind of thoroughly degradable biocomposite for FDM 3D printing. Full article

(This article belongs to the Special Issue Advances in Sustainable Polymeric Materials II)

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19 pages, 3651 KiB

Open AccessArticle

Melanin Nanoparticles Obtained from Preformed Recombinant Melanin by Bottom-Up and Top-Down Approaches

by Sergio Alcalá-Alcalá, José Eduardo Casarrubias-Anacleto, Maximiliano Mondragón-Guillén, Carlos Alberto Tavira-Montalvan, Marcos Bonilla-Hernández, Diana Lizbeth Gómez-Galicia, Guillermo Gosset and Angélica Meneses-Acosta

Polymers 2023, 15(10), 2381; https://doi.org/10.3390/polym15102381 - 19 May 2023

Cited by 1 | Viewed by 1779

Abstract

Melanin is an insoluble, amorphous polymer that forms planar sheets that aggregate naturally to create colloidal particles with several biological functions. Based on this, here, a preformed recombinant melanin (PRM) was utilized as the polymeric raw material to generate recombinant melanin nanoparticles (RMNPs). [...] Read more.

Melanin is an insoluble, amorphous polymer that forms planar sheets that aggregate naturally to create colloidal particles with several biological functions. Based on this, here, a preformed recombinant melanin (PRM) was utilized as the polymeric raw material to generate recombinant melanin nanoparticles (RMNPs). These nanoparticles were prepared using bottom-up (nanocrystallization—NC, and double emulsion–solvent evaporation—DE) and top-down (high-pressure homogenization—HP) manufacturing approaches. The particle size, Z-potential, identity, stability, morphology, and solid-state properties were evaluated. RMNP biocompatibility was determined in human embryogenic kidney (HEK293) and human epidermal keratinocyte (HEKn) cell lines. RMNPs prepared by NC reached a particle size of 245.9 ± 31.5 nm and a Z-potential of −20.2 ± 1.56 mV; 253.1 ± 30.6 nm and −39.2 ± 0.56 mV compared to that obtained by DE, as well as RMNPs of 302.2 ± 69.9 nm and −38.6 ± 2.25 mV using HP. Spherical and solid nanostructures in the bottom-up approaches were observed; however, they were an irregular shape with a wide size distribution when the HP method was applied. Infrared (IR) spectra showed no changes in the chemical structure of the melanin after the manufacturing process but did exhibit an amorphous crystal rearrangement according to calorimetric and PXRD analysis. All RMNPs presented long stability in an aqueous suspension and resistance to being sterilized by wet steam and ultraviolet (UV) radiation. Finally, cytotoxicity assays showed that RMNPs are safe up to 100 μg/mL. These findings open new possibilities for obtaining melanin nanoparticles with potential applications in drug delivery, tissue engineering, diagnosis, and sun protection, among others. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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