Polymers

18 pages, 1806 KiB

Open AccessReview

Toward Thermochromic VO₂ Nanoparticles Polymer Films Based Smart Windows Designed for Tropical Climates

by Natalia Murillo-Quirós, Victor Vega-Garita, Antony Carmona-Calvo, Edgar A. Rojas-González, Ricardo Starbird-Perez and Esteban Avendaño-Soto

Polymers 2022, 14(19), 4250; https://doi.org/10.3390/polym14194250 - 10 Oct 2022

Cited by 3 | Viewed by 2208

Abstract

Thermochromic smart windows have been extensively investigated due to two main benefits: first, the comfort for people in a room through avoiding high temperatures resulting from solar heating while taking advantage of the visible light, and second, the energy efficiency saving offered by [...] Read more.

Thermochromic smart windows have been extensively investigated due to two main benefits: first, the comfort for people in a room through avoiding high temperatures resulting from solar heating while taking advantage of the visible light, and second, the energy efficiency saving offered by using those systems. Vanadium dioxide (VO₂) is one of the most used materials in the development of thermochromic devices. The countries located in the tropics show little use of these technologies, although studies indicate that due to their characteristics of solar illumination and temperature, they could benefit greatly. To optimize and achieve maximum benefit, it is necessary to design a window that adjusts to tropical conditions and at the same time remains affordable for extensive implementation. VO₂ nanoparticles embedded in polymeric matrices are an option, but improvements are required by means of studying different particle sizes, dopants and polymeric matrices. The purpose of this review is to analyze what has been regarding toward the fabrication of smart windows based on VO₂ embedded in polymeric matrices for tropical areas and provide a proposal for what this device must comply with to contribute to these specific climatic needs. Full article

(This article belongs to the Special Issue Advanced Polymeric Materials for Flexible Electronics Energy Storage Devices and Biosensors)

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24 pages, 2875 KiB

Open AccessReview

Electro Fluid Dynamics: A Route to Design Polymers and Composites for Biomedical and Bio-Sustainable Applications

by Nergis Zeynep Renkler, Iriczalli Cruz-Maya, Irene Bonadies and Vincenzo Guarino

Polymers 2022, 14(19), 4249; https://doi.org/10.3390/polym14194249 - 10 Oct 2022

Cited by 10 | Viewed by 2113

Abstract

In the last two decades, several processes have been explored for the development of micro and/or nanostructured substrates by sagely physically and/or chemically manipulating polymer materials. These processes have to be designed to overcome some of the limitations of the traditional ones in [...] Read more.

In the last two decades, several processes have been explored for the development of micro and/or nanostructured substrates by sagely physically and/or chemically manipulating polymer materials. These processes have to be designed to overcome some of the limitations of the traditional ones in terms of feasibility, reproducibility, and sustainability. Herein, the primary aim of this work is to focus on the enormous potential of using a high voltage electric field to manipulate polymers from synthetic and/or natural sources for the fabrication of different devices based on elementary units, i.e., fibers or particles, with different characteristic sizes—from micro to nanoscale. Firstly, basic principles and working mechanisms will be introduced in order to correlate the effect of selected process parameters (i.e., an applied voltage) on the dimensional features of the structures. Secondly, a comprehensive overview of the recent trends and potential uses of these processes will be proposed for different biomedical and bio-sustainable application areas. Full article

(This article belongs to the Special Issue Fabrication and Application of Electrospun Nanofibers)

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17 pages, 3689 KiB

Open AccessArticle

Improving Deproteinization in Colombian Latex from Hevea brasiliensis: A Bibliometric Approximation

by Fabian Hernandez-Tenorio, Héctor Arroyave-Miranda, Alejandra M. Miranda, Sandra M. González, Carlos A. Rodríguez and Alex A. Sáez

Polymers 2022, 14(19), 4248; https://doi.org/10.3390/polym14194248 - 10 Oct 2022

Cited by 3 | Viewed by 1647

Abstract

Natural Rubber Field Latex (NRFL) allergens restrict its use in some markets due to health-threatening allergic reactions. These molecules are proteins that are related to asymptomatic sensitization and hypersensitivity mediated by immunoglobulin E (IgE). Although NRFL allergens have been investigated since the 1980s, [...] Read more.

Natural Rubber Field Latex (NRFL) allergens restrict its use in some markets due to health-threatening allergic reactions. These molecules are proteins that are related to asymptomatic sensitization and hypersensitivity mediated by immunoglobulin E (IgE). Although NRFL allergens have been investigated since the 1980s, there are still gaps in knowledge regarding the development of deproteinized natural rubber (DPNR). Therefore, in this study, the deproteinization of NRFL from the lower basin of the Cauca River, Antioquia-Colombia was evaluated using eight systems. The highest removal value was 84.4% and was obtained from the treatment containing SDS (Sodium dodecyl sulfate), Urea, and Ethanol. It was also possible to determine that at high concentrations of SDS, removal percentages higher than 70% are reached. On the other hand, all deproteinizing systems decreased NRFL Zeta potentials without self-coagulation, suggesting enhanced colloidal stability in DPNR latex. On the other hand, the bibliometric analysis presented technological advances in DPRN through different parameters and bibliometric networks. The analysis presented makes an important contribution from the bibliometric approach that could be positive for the development of research on DPNR. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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14 pages, 3320 KiB

Open AccessArticle

Durability against Wetting-Drying Cycles of Sustainable Biopolymer-Treated Soil

by Antonio Soldo and Marta Miletic

Polymers 2022, 14(19), 4247; https://doi.org/10.3390/polym14194247 - 10 Oct 2022

Cited by 10 | Viewed by 2093

Abstract

The world today is more oriented towards sustainable and environmental-friendly solutions in every field of science, technology, and engineering. Therefore, novel sustainable and eco-friendly approaches for soil improvement have also emerged. One of the effective, promising, and green solutions is the utilization of [...] Read more.

The world today is more oriented towards sustainable and environmental-friendly solutions in every field of science, technology, and engineering. Therefore, novel sustainable and eco-friendly approaches for soil improvement have also emerged. One of the effective, promising, and green solutions is the utilization of biopolymers. However, even though the biopolymers proved to be effective in enhancing the soil-mechanical properties, it is still unknown how they behave under real environmental conditions, such as fluctuating temperatures, moisture, plants, microorganisms, to name a few. The main research aim is to investigate the durability of biopolymer-improved soil on the cyclic processes of wetting and drying. Two types of biopolymers (Xanthan Gum and Guar Gum), and two types of soils (clean sand and silty sand) were investigated in this study. The results indicated that some biopolymer-amended specimens kept more than 70% of their original mass during wetting-drying cycles. During the compressive strength analysis, some biopolymer-treated specimens kept up to 45% of their initial strength during seven wetting-drying cycles. Furthermore, this study showed that certain damaged soil-biopolymer bonds could be restored with proper treatment. Repeating the process of wetting and drying can reactivate the bonding properties of biopolymers, which amends the broken bonds in soil. The regenerative property of biopolymers is an important feature that should not be neglected. It gives a clearer picture of the biopolymer utilization and makes it a good option for rapid temporary construction or long-standing construction in the areas with an arid climate. Full article

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

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21 pages, 26885 KiB

Open AccessReview

Graphene-Based Membranes for Water Desalination: A Literature Review and Content Analysis

by Yexin Dai, Miao Liu, Jingyu Li, Ning Kang, Afaque Ahmed, Yanping Zong, Jianbo Tu, Yanzhen Chen, Pingping Zhang and Xianhua Liu

Polymers 2022, 14(19), 4246; https://doi.org/10.3390/polym14194246 - 10 Oct 2022

Cited by 10 | Viewed by 3104

Abstract

Graphene-based membranes have unique nanochannels and can offer advantageous properties for the water desalination process. Although tremendous efforts have been devoted to heightening membrane performance and broadening their application, there is still lack of a systematic literature review on the development and future [...] Read more.

Graphene-based membranes have unique nanochannels and can offer advantageous properties for the water desalination process. Although tremendous efforts have been devoted to heightening membrane performance and broadening their application, there is still lack of a systematic literature review on the development and future directions of graphene-based membranes for desalination. In this mini-review, literature published between 2011 and 2022 were analyzed by using the bibliometric method. We found that the major contributors to these publications and the highest citations were from China and the USA. Nearly 80% of author keywords in this analysis were used less than twice, showing the broad interest and great dispersion in this field. The recent advances, remaining gaps, and strategies for future research, were discussed. The development of new multifunctional nanocomposite materials, heat-driven/solar-driven seawater desalination, and large-scale industrial applications, will be important research directions in the future. This literature analysis summarized the recent development of the graphene-based membranes for desalination application, and will be useful for researchers in gaining new insights into this field. Full article

(This article belongs to the Topic Novel Membranes for Energy Harvesting and Pollution Control)
(This article belongs to the Section Polymer Applications)

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33 pages, 5442 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Temperature-Responsive Polymer Brush Coatings for Advanced Biomedical Applications

by Svyatoslav Nastyshyn, Yuriy Stetsyshyn, Joanna Raczkowska, Yuriy Nastishin, Yuriy Melnyk, Yuriy Panchenko and Andrzej Budkowski

Polymers 2022, 14(19), 4245; https://doi.org/10.3390/polym14194245 - 10 Oct 2022

Cited by 34 | Viewed by 3542

Abstract

Modern biomedical technologies predict the application of materials and devices that not only can comply effectively with specific requirements, but also enable remote control of their functions. One of the most prospective materials for these advanced biomedical applications are materials based on temperature-responsive [...] Read more.

Modern biomedical technologies predict the application of materials and devices that not only can comply effectively with specific requirements, but also enable remote control of their functions. One of the most prospective materials for these advanced biomedical applications are materials based on temperature-responsive polymer brush coatings (TRPBCs). In this review, methods for the fabrication and characterization of TRPBCs are summarized, and possibilities for their application, as well as the advantages and disadvantages of the TRPBCs, are presented in detail. Special attention is paid to the mechanisms of thermo-responsibility of the TRPBCs. Applications of TRPBCs for temperature-switchable bacteria killing, temperature-controlled protein adsorption, cell culture, and temperature-controlled adhesion/detachment of cells and tissues are considered. The specific criteria required for the desired biomedical applications of TRPBCs are presented and discussed. Full article

(This article belongs to the Special Issue Polymer Brushes: Synthesis, Properties and Structure)

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11 pages, 3443 KiB

Open AccessArticle

The Aging Performance of PVDF in Acid Oil and Gas Medium

by Guoquan Qi, Hongxia Yan, Dongtao Qi, Houbu Li and Zhao Zhang

Polymers 2022, 14(19), 4244; https://doi.org/10.3390/polym14194244 - 10 Oct 2022

Cited by 3 | Viewed by 1414

Abstract

In the process of transporting oil and gas, the service performance of thermoplastic pipes will decline due to the multiple influences of medium, temperature, and pressure. In order to study the service performance changes of PVDF pipes under oil and gas transportation conditions, [...] Read more.

In the process of transporting oil and gas, the service performance of thermoplastic pipes will decline due to the multiple influences of medium, temperature, and pressure. In order to study the service performance changes of PVDF pipes under oil and gas transportation conditions, the high-temperature autoclave is used to simulate the service state of the pipe in the mediums. The PVDF samples are exposed to simulated oil and gas mediums for 1 week, 3 weeks, 5 weeks, and 7 weeks under 60 °C and 90 °C conditions. After the exposure test, the physical and chemical properties of the PVDF pipe are tested and compared with the initial samples. Compared with the initial sample, the sample quality after the exposure test has a slight increase, with growth rates of 2% and 3% at 60 °C and 90 °C, respectively. Meanwhile, the tensile strength of the samples is about 13% and 21% lower than that of the initial sample, respectively. According to the microscopic morphology analyses, there are some crack defects on the surface of the sample after the exposure test. Through infrared analysis, it is shown that no molecular chain breakage, crosslinking, or other reactions are found after the exposure test. The above analysis shows that the PVDF sample has slight penetration and swelling during the exposure test. However, due to the large force between the PVDF molecules, its mechanical properties have a small downward trend, showing excellent environmental stress crack resistance. Full article

(This article belongs to the Special Issue Development of Functional Polymer Composites)

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22 pages, 4746 KiB

Open AccessReview

Recent Advances in the Removal of Organic Dyes from Aqueous Media with Conducting Polymers, Polyaniline and Polypyrrole, and Their Composites

by Jaroslav Stejskal

Polymers 2022, 14(19), 4243; https://doi.org/10.3390/polym14194243 - 10 Oct 2022

Cited by 20 | Viewed by 2902

Abstract

Water pollution by organic dyes, and its remediation, is an important environmental issue associated with ever-increasing scientific interest. Conducting polymers have recently come to the forefront as advanced agents for removing dye. The present review reports on the progress represented by the literature [...] Read more.

Water pollution by organic dyes, and its remediation, is an important environmental issue associated with ever-increasing scientific interest. Conducting polymers have recently come to the forefront as advanced agents for removing dye. The present review reports on the progress represented by the literature published in 2020–2022 on the application of conducting polymers and their composites in the removal of dyes from aqueous media. Two composites, incorporating the most important polymers, polyaniline, and polypyrrole, have been used as efficient dye adsorbents or photocatalysts of dye decomposition. The recent application trends are outlined, and future uses also exploiting the electrical and electrochemical properties of conducting polymers are offered. Full article

(This article belongs to the Special Issue Conducting Polymer Composites for Water Purification)

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17 pages, 5225 KiB

Open AccessArticle

High-Transparency and Colorless Polyimide Film Prepared by Inhibiting the Formation of Chromophores

by Chuanxiang Su, Pengjia Liu, Jingyu Yue, Hengjian Huan, Zhenghui Yang, Kai Yang, Haiquan Guo and Jianying Zhao

Polymers 2022, 14(19), 4242; https://doi.org/10.3390/polym14194242 - 10 Oct 2022

Cited by 7 | Viewed by 2151

Abstract

Colorless polyimides (CPIs) with outstanding mechanical properties are essential materials in the production of flexible display panels, foldable windows, and even spacecraft cockpits. This paper specifically elaborates that the Morkit unit, and azo and nitro chromophores are important factors contributing to yellow PI, [...] Read more.

Colorless polyimides (CPIs) with outstanding mechanical properties are essential materials in the production of flexible display panels, foldable windows, and even spacecraft cockpits. This paper specifically elaborates that the Morkit unit, and azo and nitro chromophores are important factors contributing to yellow PI, together with the well-known charge transfer complex (CTC) theory. Three diamine monomers, two anhydrides monomers, and three blockers were used to inhibit chromophores formation and, thus, obtain CPI films. The cut-off wavelength was blue-shifts to 334 nm and the transmittance is improved to 98.9% in the UV–vis range. Mechanical and thermal properties of the CPI films are not reduced through coupling effects of the blockers. Therefore, the inhibition method of the Morkit units and chromophore groups is a promising process for preparing CPIs to be used as flexible display materials. Full article

(This article belongs to the Special Issue High Performance Functional Polyimide)

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19 pages, 1319 KiB

Open AccessArticle

Recursive Settling of Particles in Shear Thinning Polymer Solutions: Two Velocity Mathematical Model

by Vladimir Neverov and Vladimir Shelukhin

Polymers 2022, 14(19), 4241; https://doi.org/10.3390/polym14194241 - 10 Oct 2022

Viewed by 1121

Abstract

Processing of the available experimental data on particles settling in shear-thinning polymer solutions is performed. Conclusions imply that sedimentation should be recursive, since settling also occurs within the sediment. To capture such an effect, a mathematical model of two continua has been developed, [...] Read more.

Processing of the available experimental data on particles settling in shear-thinning polymer solutions is performed. Conclusions imply that sedimentation should be recursive, since settling also occurs within the sediment. To capture such an effect, a mathematical model of two continua has been developed, which corresponds to experimental data. The model is consistent with basic thermodynamics laws. The rheological component of this model is a correlation formula for gravitational mobility. This closure is justified by comparison with known experimental data available for particles settling in vertical vessels. In addition, the closure is validated by comparison with analytical solutions to the Kynch one-dimensional equation, which governs dynamics of particle concentration. An explanation is given for the Boycott effect and it is proven that sedimentation is enhanced in a 2D inclined vessel. In tilted vessels, the flow is essentially two-dimensional and the one-dimensional Kynch theory is not applicable; vortices play an important role in sedimentation. Full article

(This article belongs to the Special Issue Polymer Theory and Simulation)

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20 pages, 4051 KiB

Open AccessArticle

Preparation and Laboratory Testing of Polymeric Scale Inhibitor Colloidal Materials for Oilfield Mineral Scale Control

by Hanji Wang, Huaxia Dong, Xianbin Liu and Ping Zhang

Polymers 2022, 14(19), 4240; https://doi.org/10.3390/polym14194240 - 10 Oct 2022

Cited by 1 | Viewed by 1503

Abstract

Mineral scale refers to the hard crystalline inorganic solid deposit from the water phase. Although scale formation is very common in the natural environment, deposited scale particles can seriously threaten the integrity and safety of various industries, particularly oilfield productions. Scale deposition is [...] Read more.

Mineral scale refers to the hard crystalline inorganic solid deposit from the water phase. Although scale formation is very common in the natural environment, deposited scale particles can seriously threaten the integrity and safety of various industries, particularly oilfield productions. Scale deposition is one of the three most serious water-related production chemistry threats in the petroleum industry. The most commonly adopted engineering approach to control the scale threat is chemical inhibition by applying scale inhibitor chemicals. Aminophosphonates and polymeric inhibitors are the two major groups of scale inhibitors. To address the drawbacks of conventional inhibitors, scale inhibitor colloidal materials have been prepared as an alternative delivery vehicle of inhibitors for scale control. Quite a few studies have reported on the laboratory synthesis and testing of scale inhibitor colloidal materials composed mainly of pre-precipitated metal-aminophosphonate solids. However, limited research has been conducted on the preparation of polymeric inhibitor-based colloidal materials. This study reports the synthesis approach and laboratory testing of novel polystyrene sulfonate (PSS) based inhibitor colloidal material. PSS was selected in this study due to its high thermal stability and calcium tolerance with no phosphorus in its molecule. Both precipitation and surfactant surface modification methods were employed to prepare a barium-PSS colloidal inhibitor (BaPCI) material with an average diameter of several hundred nanometers. Experimental results indicate that the prepared BaPCI material has a decent migration capacity in the formation medium, and this material is superior to the conventional PSS inhibitor in terms of inhibitor return performance. The prepared novel BaPCI material has a great potential to be adopted for field scale control where environmentally friendly, thermal stable, and/or calcium tolerating requirements should be satisfied. This study further expands and promotes our capacity to fabricate and utilize functional colloidal materials for mineral scale control. Full article

(This article belongs to the Special Issue Polymers for Oilfield Production Chemistry)

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18 pages, 5665 KiB

Open AccessArticle

Fabrication of Polysaccharide-Based Halochromic Nanofibers via Needle-Less Electrospinning and Their Characterization: A Study of the Leaching Effect

by Beste Elveren, Silvo Hribernik and Manja Kurečič

Polymers 2022, 14(19), 4239; https://doi.org/10.3390/polym14194239 - 10 Oct 2022

Cited by 5 | Viewed by 1769

Abstract

Responsive materials, i.e., smart materials, have the ability to change their physical or chemical properties upon certain external signals. The development of nanofibrous halochromic materials, specifically combining the pH-sensitive functionality and unique nanofiber properties, could yield interesting new applications, especially when the common [...] Read more.

Responsive materials, i.e., smart materials, have the ability to change their physical or chemical properties upon certain external signals. The development of nanofibrous halochromic materials, specifically combining the pH-sensitive functionality and unique nanofiber properties, could yield interesting new applications, especially when the common problem of dye leaching is successfully tackled. Therefore, in this article, we studied the fabrication process of polysaccharide-based halochromic nanofibrous materials by using a combination of various halochromic dyes (bromothymol blue, bromocresol green, and thymol blue) and cellulose acetate in a spinning solution using a one-pot strategy. The inhibition of leaching was addressed by using a complexing agent: poly-diallyl-dimethylammonium chloride (PDADMAC). The preparation of hybrid spinning solutions, their characterization, and ability to form continuous nanofibers were studied using a high production needle-less electrospinning system. The produced hybrid solutions and nanofibers were characterized, in terms of their rheological properties, chemical structure, morphology, and functionality. Fabricated nanofibrous halochromic structures show a clear color change upon exposure to different pH values, as well as the reduced leaching of dyes, upon the addition of a complexing agent. The leaching decreased by 61% in the case of bromocresol green, while, in the case of bromothymol blue and thymol blue, the leaching was reduced by 95 and 99%, respectively. Full article

(This article belongs to the Special Issue Biopolymer-Based Micro/Nanoparticles: Fabrication, Characterization and Applications)

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19 pages, 5416 KiB

Open AccessArticle

Controlled and Accelerated Hydrolysis of Polylactide (PLA) through Pentaerythritol Phosphites with Acid Scavengers

by Matthias Polidar, Elke Metzsch-Zilligen and Rudolf Pfaendner

Polymers 2022, 14(19), 4237; https://doi.org/10.3390/polym14194237 - 10 Oct 2022

Cited by 9 | Viewed by 3209

Abstract

This study provides insight into the accelerated hydrolysis of polyester PLA through the addition of phosphites based on pentaerythritol. To control hydrolysis and ensure processing stability, different types of phosphites and combinations of phosphites with acid scavengers were studied. Therefore, commercially available PLA [...] Read more.

This study provides insight into the accelerated hydrolysis of polyester PLA through the addition of phosphites based on pentaerythritol. To control hydrolysis and ensure processing stability, different types of phosphites and combinations of phosphites with acid scavengers were studied. Therefore, commercially available PLA was compounded with selected additives on a twin-screw extruder, and hydrolysis experiments were performed at 23 °C, 35 °C and 58 °C in deionized water. Hydrolysis of PLA was evaluated by the melt volume rate (MVR) and size-exclusion chromatography (SEC). For example, after 4 days of water storage at 58 °C, the number average molecular weight of the PLA comparison sample was reduced by 31.3%, whereas PLA compounded with 0.8% phosphite P1 had a 57.7% lower molecular weight. The results are in good agreement with the expected and tested stability against hydrolysis of the investigated phosphite structures. ³¹P-NMR spectroscopy was utilized to elucidate the hydrolysis of phosphites in the presence of lactic acid. With the addition of phosphites based on pentaerythritol, the hydrolysis rate can be enhanced, and faster biodegradation behavior of biodegradable polyesters is expected. Accelerated biodegradation is beneficial for reducing the residence time of polymers in composting facilities or during home composting and as litter or microplastic residues. Full article

(This article belongs to the Special Issue Polyester-Based Materials)

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10 pages, 2744 KiB

Open AccessArticle

Preparation of Thermosensitive Fluorescent Polyacrylamide Nanofiber Membrane and Visual Temperature Sensing

by Xuejiao Tao, Zhao Dai, Yue Ma and Nan Li

Polymers 2022, 14(19), 4238; https://doi.org/10.3390/polym14194238 - 09 Oct 2022

Cited by 1 | Viewed by 1269

Abstract

Fluorescent fibers are capable of discoloration behavior under special light sources, showing great potential for applications in biomedicine, environmental monitoring, heavy-metal-ion detaction, and anti-counterfeiting. In the current paper, temperature-sensitive fluorescent poly-acrylamide (PAM) nanofiber (AuNCs@PAM NF) membranes are prepared by mixing red fluorescent gold [...] Read more.

Fluorescent fibers are capable of discoloration behavior under special light sources, showing great potential for applications in biomedicine, environmental monitoring, heavy-metal-ion detaction, and anti-counterfeiting. In the current paper, temperature-sensitive fluorescent poly-acrylamide (PAM) nanofiber (AuNCs@PAM NF) membranes are prepared by mixing red fluorescent gold nanoclusters (AuNCs) synthesized in-house with PAM using the electrospinning technique. The AuNCs@PAM nanofibers obtained using this method present excellent morphology, and the AuNCs are uniformly dispersed in the fibers. The average diameter of the AuNCs@PAM NFs is 298 nm, and the diameter of AuNCs doped in the fibers is approximately 2.1 nm. Furthermore, the AuNCs@PAM NF films present excellent fluorescence and temperature-sensitive performance between 15 and 65 degrees. While under the 365 nm UV light source, the fiber film changes from white to red; this discoloration behavior weakens with the increase in temperature, and changes from deep to light red. Therefore, the approximate temperature can be identified using the color change, and a visual temperature-sensing effect can be achieved. The dual functions of temperature-sensitivity and fluorescent properties improve the scientificity and safety of nanofibers in the use of anti-counterfeiting technology. Full article

(This article belongs to the Special Issue New Polymeric Materials for Extreme Environments)

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15 pages, 2734 KiB

Open AccessArticle

Chitosan-Functionalized-Graphene Oxide (GO@CS) Beads as an Effective Adsorbent to Remove Cationic Dye from Wastewater

by AbdElAziz A. Nayl, Ahmed I. Abd-Elhamid, Wael A. A. Arafa, Ismail M. Ahmed, Ahmed A. El-Shanshory, Mohamed A. Abu-Saied, Hesham M. A. Soliman, Mohamed A. Abdelgawad, Hazim M. Ali and Stefan Bräse

Polymers 2022, 14(19), 4236; https://doi.org/10.3390/polym14194236 - 09 Oct 2022

Cited by 14 | Viewed by 1695

Abstract

In this study, the preparation of graphene oxide@chitosan (GO@CS) composite beads was investigated via continuous dropping techniques to remove methylene blue (MB)-dye from an aqueous media. The prepared beads were characterized using various techniques before and after the adsorption of MB. The experimental [...] Read more.

In this study, the preparation of graphene oxide@chitosan (GO@CS) composite beads was investigated via continuous dropping techniques to remove methylene blue (MB)-dye from an aqueous media. The prepared beads were characterized using various techniques before and after the adsorption of MB. The experimental results showed that the adsorption processes fit the kinetic pseudo-second-order and Langmuir isotherm models. Moreover, the GO@CS beads achieve maximum adsorption capacities of 23.26 mg g⁻¹, which was comparable with other adsorbents in the literature. An important advantage of our adsorbent is that the GO@CS can remove 82.1% of the real sample color within 135 min. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Saudi Arabia (2021,2022))

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21 pages, 2724 KiB

Open AccessReview

4D Multiscale Origami Soft Robots: A Review

by Hyegyo Son, Yunha Park, Youngjin Na and ChangKyu Yoon

Polymers 2022, 14(19), 4235; https://doi.org/10.3390/polym14194235 - 09 Oct 2022

Cited by 11 | Viewed by 5684

Abstract

Time-dependent shape-transferable soft robots are important for various intelligent applications in flexible electronics and bionics. Four-dimensional (4D) shape changes can offer versatile functional advantages during operations to soft robots that respond to external environmental stimuli, including heat, pH, light, electric, or pneumatic triggers. [...] Read more.

Time-dependent shape-transferable soft robots are important for various intelligent applications in flexible electronics and bionics. Four-dimensional (4D) shape changes can offer versatile functional advantages during operations to soft robots that respond to external environmental stimuli, including heat, pH, light, electric, or pneumatic triggers. This review investigates the current advances in multiscale soft robots that can display 4D shape transformations. This review first focuses on material selection to demonstrate 4D origami-driven shape transformations. Second, this review investigates versatile fabrication strategies to form the 4D mechanical structures of soft robots. Third, this review surveys the folding, rolling, bending, and wrinkling mechanisms of soft robots during operation. Fourth, this review highlights the diverse applications of 4D origami-driven soft robots in actuators, sensors, and bionics. Finally, perspectives on future directions and challenges in the development of intelligent soft robots in real operational environments are discussed. Full article

(This article belongs to the Special Issue Advanced Additive Processes and 3D Printing for Polymer Composites)

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12 pages, 2914 KiB

Open AccessArticle

Synthesis of a Novel Hyperbranched Polyimide for Reinforcing Toughness and Insulating Properties of Bismaleimide Resin

by Lida Yu, Yang Yu, Jiahao Shi, Xiaorui Zhang, Feng Gao, Chenhao Li, Zhou Yang and Jingui Zhao

Polymers 2022, 14(19), 4234; https://doi.org/10.3390/polym14194234 - 09 Oct 2022

Cited by 5 | Viewed by 1968

Abstract

Bismaleimide (BMI) resin has great potential in aerospace, electronic, and machinery fields due to its extraordinary thermal stability. Owing to BMI’s lower impact strength, various modified BMI resins have been prepared using CTBN, PEEK, fillers, and hyperbranched polymer to achieve higher impact strength. [...] Read more.

Bismaleimide (BMI) resin has great potential in aerospace, electronic, and machinery fields due to its extraordinary thermal stability. Owing to BMI’s lower impact strength, various modified BMI resins have been prepared using CTBN, PEEK, fillers, and hyperbranched polymer to achieve higher impact strength. However, enhancement of toughness causes deterioration of other performance, such as Tg, thermal stability, and brittleness. In this work, BMI resin modified by hyperbranched polyimide (HBPI) was obtained. HBPI designed with flexible segments, unsaturated bonds, and a low degree of branching was synthesized. FT-IR and ¹³C-NMR were applied to confirm the successful fabrication of HBPI. The mechanical strength and dielectric properties of cured BMI resin containing various levels of HBPI were analyzed systematically. The impact and bending strength were improved significantly with increased HBPI content. When the content of HBPI is 40 wt.%, the impact strength and bending strength reach the maximum value of 32 kJ/mm and 88 MPa. In addition, the BMI cured with HBPI exhibits enhanced bending modulus to the value of 5.9 GPa. Furthermore, the dielectric strength of cured resin was improved to 28.3 kV/mm. The improved mechanical strength and enhanced dielectric properties are attributed to the increasing free volume induced by HBPI. These results indicate the promise of BMI resin modified by HBPI applied in insulating coatings and low dielectric laminates used in high frequency. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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12 pages, 4021 KiB

Open AccessArticle

Preparation and Properties of Partial-Degradable ZrO₂–Chitosan Particles–GelMA Composite Scaffolds

by Yang Ji, Mengdie Hou, Jin Zhang, Meiqi Jin, Tianlin Wang, Huazhe Yang and Xiaodong Zhang

Polymers 2022, 14(19), 4233; https://doi.org/10.3390/polym14194233 - 09 Oct 2022

Cited by 1 | Viewed by 1431

Abstract

In the field of bone repair, the inorganic–organic composite scaffold is a promising strategy for mimicking the compositions of the natural bone. In addition, as implants for repairing load-bearing sites, an inert permanent bone substitute composites with bioactive degradable ingredients may make full [...] Read more.

In the field of bone repair, the inorganic–organic composite scaffold is a promising strategy for mimicking the compositions of the natural bone. In addition, as implants for repairing load-bearing sites, an inert permanent bone substitute composites with bioactive degradable ingredients may make full use of the composite scaffold. Herein, the porous zirconia (ZrO₂) matrix was prepared via the template replication method, and the partial degradable ZrO₂–chitosan particles–GelMA composite scaffolds with different chitosan/GelMA volume ratios were prepared through the vacuum infiltration method. Dynamic light scattering (DLS) and the scanning electron microscope (SEM) were adopted to observe the size of the chitosan particles and the morphologies of the composites scaffold. The mechanical properties, swelling properties, and degradation properties of the composite scaffolds were also characterized by the mechanical properties testing machine and immersion tests. The CCK-8 assay was adopted to test the biocompatibility of the composite scaffold preliminarily. The results show that chitosan particles as small as 60 nm were obtained. In addition, the ratio of chitosan/GelMA can influence the mechanical properties and the swelling and degradation behaviors of the composites scaffold. Furthermore, improved cell proliferation performance was obtained for the composite scaffolds. Full article

(This article belongs to the Special Issue Biomedical Applications of Intelligent Hydrogel)

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11 pages, 977 KiB

Open AccessArticle

Surface Modification on Polyimide Yarn by Plasma Treatment to Enhance Adhesion with Polypropylene Resin

by Hong Cui and Xiuli Gao

Polymers 2022, 14(19), 4232; https://doi.org/10.3390/polym14194232 - 09 Oct 2022

Cited by 1 | Viewed by 1246

Abstract

Polyimide yarn as a kind of high performance fiber material has to improve the adhesion between the material surface and the resin in order to get a deeper application. The surface of polyimide yarn is modified by low temperature plasma treatment, and the [...] Read more.

Polyimide yarn as a kind of high performance fiber material has to improve the adhesion between the material surface and the resin in order to get a deeper application. The surface of polyimide yarn is modified by low temperature plasma treatment, and the effect of plasma treatment parameters on the adhesion between polyimide yarn and polypropylene resin is studied. By comparing the extraction force on the surface of polyimide yarn before and after treatment, the effect of plasma treatment parameters such as treatment time, processing gas and treating power on yarn adhesion is investigated. Furthermore, the adhesive force between polyimide yarn and polypropylene resin is analyzed by a single factor to optimize the process parameters to obtain higher adhesive force. Additionally, the Box–Behnken design is utilized to optimize the plasma treatment parameters, and the significance of the influence of the plasma treatment parameters on the adhesion between the polyimide fiber and the resin is discussed. The optimal process parameters are obtained through analysis: the treatment time 90 s, the processing gas oxygen, and the treating power 150 W. Full article

(This article belongs to the Special Issue Textile Materials and Textile Design)

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19 pages, 6558 KiB

Open AccessArticle

In-Situ Oxidative Polymerization of Pyrrole Composited with Cellulose Nanocrystal by Reactive Ink-Jet Printing on Fiber Substrates

by Xu Li, Meijuan Cao, Shasha Li, Luhai Li, Yintang Yang, Ruping Liu, Zhicheng Sun, Lixin Mo, Zhiqing Xin, Yinjie Chen, Yaling Li, Yi Fang and Yuansheng Qi

Polymers 2022, 14(19), 4231; https://doi.org/10.3390/polym14194231 - 09 Oct 2022

Cited by 3 | Viewed by 1848

Abstract

A simple and novel method for the deposition of polypyrrole (PPy) and cellulose nanocrystal (CNC) composites on different fiber substrates by reactive ink-jet printing was proposed. PPy/CNCs composites were successfully prepared, and the surface resistance of conductive layer deposited on different fiber substrates [...] Read more.

A simple and novel method for the deposition of polypyrrole (PPy) and cellulose nanocrystal (CNC) composites on different fiber substrates by reactive ink-jet printing was proposed. PPy/CNCs composites were successfully prepared, and the surface resistance of conductive layer deposited on different fiber substrates is the least when the monomer concentration is 0.6 M. PPy/CNCs were deposited on polyethylene terephthalate (PET) to form a conductive layer by adding polyvinyl alcohol (PVA), and the optimum sintering temperature is 100 °C (monomer/PVA ratio 4.0, conductivity 0.769 S cm⁻¹). The PPy/CNCs conductive layer deposited on the paper has the lowest surface resistance and the best adhesion, and the surface resistance of PPy/CNCs conductive layer decreases first and then increases with the increase of sulfonate concentration. Moreover, the volume of anion in sulfonate will affect the arrangement and aggregation of PPy molecular chain in composite materials. Appropriate sulfonate doping can improve the conductivity and stability of conductive paper, and the maximum conductivity is 0.813 S cm⁻¹. Three devices based on PPy/CNCs conductive paper were proposed and fabricated. Therefore, this ink-jet printing provides a new method for the preparation of conductive materials, sensors, energy storage and electromagnetic shielding, etc. Full article

(This article belongs to the Section Polymer Fibers)

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16 pages, 14590 KiB

Open AccessArticle

The Preparation and Wear Behaviors of Phenol–Formaldehyde Resin/BN Composite Coatings

by Chao Zang, Yaping Xing, Tingting Yang, Qi Teng, Jinming Zhen, Ran Zhang, Zhengfeng Jia and Weifang Han

Polymers 2022, 14(19), 4230; https://doi.org/10.3390/polym14194230 - 09 Oct 2022

Cited by 5 | Viewed by 1547

Abstract

Phenolic-matrix composites possess excellent synergistic effects on mechanical and tribological properties and can be used in the aerospace, medical, and automobile industries. In this work, a series of phenol–formaldehyde resin/hexagonal boron nitride nanocomposites (PF/BNs) were in situ synthesized using an easy method. PF/BN [...] Read more.

Phenolic-matrix composites possess excellent synergistic effects on mechanical and tribological properties and can be used in the aerospace, medical, and automobile industries. In this work, a series of phenol–formaldehyde resin/hexagonal boron nitride nanocomposites (PF/BNs) were in situ synthesized using an easy method. PF/BN coatings (PF/BNCs) on 316L steels were prepared through a spin-casting method. The wear behaviors of these PF/BNCs were investigated by dry sliding with steel balls. The percentage of BN, the thickness of the coating, and the heat treatment temperature affected the coefficients of friction (COFs) and wear rates of these coatings. After heat treatment at 100 °C, the tribological properties of the PF/BNCs were remarkably improved, which might be attributed to both the transformation of carbon on the worn surfaces from C-O/C=O into C=N, carbide, and other chemical bonds and the cross-linking of the prepolymers. Full article

(This article belongs to the Special Issue Polymer-Based Lubricating Materials)

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12 pages, 3394 KiB

Open AccessArticle

Water−Processed Organic Solar Cell with Efficiency Exceeding 11%

by Chen Xie, Songqiang Liang, Guangye Zhang and Shunpu Li

Polymers 2022, 14(19), 4229; https://doi.org/10.3390/polym14194229 - 09 Oct 2022

Cited by 8 | Viewed by 2268

Abstract

Water processing is an ideal strategy for the ecofriendly fabrication of organic photovoltaics (OPVs) and exhibits a strong market−driven demand. Here, we report a state−of−the−art active material, namely PM6:BTP−eC9, for the synthesis of water−borne nanoparticle (NP) dispersion towards ecofriendly OPV fabrication. The surfactant−stripping [...] Read more.

Water processing is an ideal strategy for the ecofriendly fabrication of organic photovoltaics (OPVs) and exhibits a strong market−driven demand. Here, we report a state−of−the−art active material, namely PM6:BTP−eC9, for the synthesis of water−borne nanoparticle (NP) dispersion towards ecofriendly OPV fabrication. The surfactant−stripping technique, combined with a poloxamer, facilitates purification and eliminates excess surfactant in water−dispersed organic semiconducting NPs. The introduction of 1,8−diiodooctane (DIO) for the synthesis of surfactant−stripped NP (ssNP) further promotes a percolated microstructure of the polymer and NFA in each ssNP, yielding water−processed OPVs with a record efficiency of over 11%. The use of an additive during water−borne ssNP synthesis is a promising strategy for morphology optimization in NP OPVs. It is believed that the findings in this work will engender more research interest and effort relating to water−processing in preparation of the industrial production of OPVs. Full article

(This article belongs to the Special Issue Eco-Friendly Polymers: Synthesis, Characterization and Applications)

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18 pages, 13001 KiB

Open AccessArticle

Facile Fabrication of Flexible Polymeric Membranes with Micro and Nano Apertures over Large Areas

by Kebin Li, Javier Alejandro Hernández-Castro, Keith Morton and Teodor Veres

Polymers 2022, 14(19), 4228; https://doi.org/10.3390/polym14194228 - 09 Oct 2022

Cited by 2 | Viewed by 2019

Abstract

Freestanding, flexible and open through-hole polymeric micro- and nanostructured membranes were successfully fabricated over large areas (>16 cm²) via solvent removal of sacrificial scaffolds filled with polymer resin by spontaneous capillary flow. Most of the polymeric membranes were obtained through a [...] Read more.

Freestanding, flexible and open through-hole polymeric micro- and nanostructured membranes were successfully fabricated over large areas (>16 cm²) via solvent removal of sacrificial scaffolds filled with polymer resin by spontaneous capillary flow. Most of the polymeric membranes were obtained through a rapid UV curing processes via cationic or free radical UV polymerisation. Free standing microstructured membranes were fabricated across a range of curable polymer materials, including: EBECRYL3708 (radical UV polymerisation), CUVR1534 (cationic UV polymerisation) UV lacquer, fluorinated perfluoropolyether urethane methacrylate UV resin (MD700), optical adhesive UV resin with high refractive index (NOA84) and medical adhesive UV resin (1161-M). The present method was also extended to make a thermal set polydimethylsiloxane (PDMS) membranes. The pore sizes for the as-fabricated membranes ranged from 100 µm down to 200 nm and membrane thickness could be varied from 100 µm down to 10 µm. Aspect ratios as high as 16.7 were achieved for the 100 µm thick membranes for pore diameters of approximately 6 µm. Wide-area and uniform, open through-hole 30 µm thick membranes with 15 µm pore size were fabricated over 44 × 44 mm² areas. As an application example, arrays of Au nanodots and Pd nanodots, as small as 130 nm, were deposited on Si substrates using a nanoaperture polymer through-hole membrane as a stencil. Full article

(This article belongs to the Special Issue High Performance Polymer Membranes)

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16 pages, 964 KiB

Open AccessReview

Application Prospect and Preliminary Exploration of GelMA in Corneal Stroma Regeneration

by Guanyu Su, Guigang Li, Wei Wang and Lingjuan Xu

Polymers 2022, 14(19), 4227; https://doi.org/10.3390/polym14194227 - 09 Oct 2022

Cited by 4 | Viewed by 1749

Abstract

Corneal regeneration has become a prominent study area in recent decades. Because the corneal stroma contributes about 90% of the corneal thickness in the corneal structure, corneal stromal regeneration is critical for the treatment of cornea disease. Numerous materials, including deacetylated chitosan, hydrophilic [...] Read more.

Corneal regeneration has become a prominent study area in recent decades. Because the corneal stroma contributes about 90% of the corneal thickness in the corneal structure, corneal stromal regeneration is critical for the treatment of cornea disease. Numerous materials, including deacetylated chitosan, hydrophilic gel, collagen, gelatin methacrylate (GelMA), serine protein, glycerol sebacate, and decellularized extracellular matrix, have been explored for keratocytes regeneration. GelMA is one of the most prominent materials, which is becoming more and more popular because of its outstanding three-dimensional scaffold structure, strong mechanics, good optical transmittance, and biocompatibility. This review discussed recent research on corneal stroma regeneration materials and related GelMA. Full article

(This article belongs to the Special Issue Polymers Composed of Natural Molecules in Drug Delivery Systems)

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25 pages, 3381 KiB

Open AccessArticle

Biosynthesis and Properties of a P(3HB-co-3HV-co-4HV) Produced by Cupriavidus necator B-10646

by Natalia O. Zhila, Kristina Yu. Sapozhnikova, Evgeniy G. Kiselev, Ivan V. Nemtsev, Anna V. Lukyanenko, Ekaterina I. Shishatskaya and Tatiana G. Volova

Polymers 2022, 14(19), 4226; https://doi.org/10.3390/polym14194226 - 09 Oct 2022

Cited by 3 | Viewed by 1437

Abstract

Synthesis of P(3HB-co-3HV-co-4HV) copolymers by the wild-type strain Cupriavidus necator B-10646 on fructose or sodium butyrate as the main C-substrate with the addition of γ-valerolactone as a precursor of 3HV and 4HV monomers was studied. Bacterial cells were cultivated [...] Read more.

Synthesis of P(3HB-co-3HV-co-4HV) copolymers by the wild-type strain Cupriavidus necator B-10646 on fructose or sodium butyrate as the main C-substrate with the addition of γ-valerolactone as a precursor of 3HV and 4HV monomers was studied. Bacterial cells were cultivated in the modes that enabled production of a series of copolymers with molar fractions of 3HV (from 7.3 to 23.4 mol.%) and 4HV (from 1.9 to 4.7 mol.%) with bacterial biomass concentration (8.2 ± 0.2 g/L) and PHA content (80 ± 2%). Using HPLC, DTA, DSC, X-Ray, SEM, and AFM, the physicochemical properties of copolymers and films prepared from them have been investigated as dependent on proportions of monomers. Copolymers are characterized by a reduced degree of crystallinity (C_x 38–49%) molecular weight characteristics M_n (45–87 kDa), and M_w (201–248 kDa) compared with P(3HB). The properties of the films surface of various composition including the porosity and surface roughness were studied. Most of the samples showed a decrease in the average pore area and an increase in their number with a total increase in 3HV and 4HV monomers. The results allow scaling up the productive synthesis of P(3HB-co-3HV-co-4HV) copolymers using Cupriavidus necator B-10646. Full article

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

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14 pages, 1167 KiB

Open AccessReview

Film-Forming Polymers for Tooth Erosion Prevention

by Marina Gullo Augusto, Tais Scaramucci, Tiago Moreira Bastos Campos, Idalina Vieira Aoki, Nadine Schlueter and Alessandra Bühler Borges

Polymers 2022, 14(19), 4225; https://doi.org/10.3390/polym14194225 - 09 Oct 2022

Cited by 3 | Viewed by 1665

Abstract

Different agents have been proposed to prevent the progression of acid induced dental substance losses, which are called erosive tooth wear (ETW), such as fluorides, calcium, and phosphate-based products; however, there is a need for a further increase in efficacy. Recently, the ability [...] Read more.

Different agents have been proposed to prevent the progression of acid induced dental substance losses, which are called erosive tooth wear (ETW), such as fluorides, calcium, and phosphate-based products; however, there is a need for a further increase in efficacy. Recently, the ability of polymers to interact with the tooth surface, forming acid resistant films, has come into the focus of research; nevertheless, there is still the need for a better understanding of their mode of action. Thus, this article provides an overview of the chemical structure of polymers, their mode of action, as well as the effect of their incorporation into oral care products, acid beverages, and antacid formulations, targeting the prevention of ETW. Recent evidence indicates that this may be a promising approach, however, additional studies are needed to confirm their efficacy under more relevant clinical conditions that consider salivary parameters such as flow rate, composition, and clearance. The standardization of methodological procedures such as acid challenge, treatment duration, and combination with fluorides is necessary to allow further comparisons between studies. In conclusion, film-forming polymers may be a promising cost-effective approach to prevent and control erosive demineralization of the dental hard tissue. Full article

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

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19 pages, 4810 KiB

Open AccessArticle

Thermal, Mechanical, and Morphological Characterisations of Graphene Nanoplatelet/Graphene Oxide/High-Hard-Segment Polyurethane Nanocomposite: A Comparative Study

by Muayad Albozahid, Haneen Zuhair Naji, Zoalfokkar Kareem Alobad, Jacek K. Wychowaniec and Alberto Saiani

Polymers 2022, 14(19), 4224; https://doi.org/10.3390/polym14194224 - 09 Oct 2022

Cited by 10 | Viewed by 2344

Abstract

The current work investigates the effect of the addition of graphene nanoplatelets (GNPs) and graphene oxide (GO) to high hard-segment polyurethane (75% HS) on its thermal, morphological, and mechanical properties. Polyurethane (PU) and its nanocomposites were prepared with different ratios of GNP and [...] Read more.

The current work investigates the effect of the addition of graphene nanoplatelets (GNPs) and graphene oxide (GO) to high hard-segment polyurethane (75% HS) on its thermal, morphological, and mechanical properties. Polyurethane (PU) and its nanocomposites were prepared with different ratios of GNP and GO (0.25, 0.5, and 0.75 wt.%). A thermal stability analysis demonstrated an enhancement in the thermal stability of PU with GNP and GO incorporated compared to pure PU. Differential Scanning Calorimetry (DSC) showed that both GNP and GO act as heterogeneous nucleation agents within a PU matrix, leading to an increase in the crystallinity of PU. The uniform dispersion and distribution of GNP and GO flakes in the PU matrix were confirmed by SEM and TEM. In terms of the mechanical properties of the PU nanocomposites, it was found that the interaction between PU and GO was better than that of GNP due to the functional groups on the GO’s surface. This leads to a significant increase in tensile strength for 0.5 wt.% GNP and GO compared with pure PU. This can be attributed to interfacial interaction between the GO and PU chains, resulting in an improvement in stress transferring from the matrix to the filler and vice versa. This work sheds light on the understanding of the interactions between graphene-based fillers and their influence on the mechanical properties of PU nanocomposites. Full article

(This article belongs to the Special Issue Development in Fiber-Reinforced Polymer Composites)

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16 pages, 6418 KiB

Open AccessArticle

Effect of Fiber Type and Content on Surface Quality and Removal Mechanism of Fiber-Reinforced Polyetheretherketone in Ultra-Precision Grinding

by Shang Gao, Xinyu Zhou, Jiani Guo and Renke Kang

Polymers 2022, 14(19), 4223; https://doi.org/10.3390/polym14194223 - 08 Oct 2022

Viewed by 1615

Abstract

Polyetheretherketone (PEEK) is a promising thermo-plastic polymer material due to its excellent mechanical properties. To further improve the mechanical properties of PEEK, different kinds of short fibers are added into the PEEK matrix. The grinding machinability of short-fiber-reinforced PEEK varies with the effect [...] Read more.

Polyetheretherketone (PEEK) is a promising thermo-plastic polymer material due to its excellent mechanical properties. To further improve the mechanical properties of PEEK, different kinds of short fibers are added into the PEEK matrix. The grinding machinability of short-fiber-reinforced PEEK varies with the effect of fiber type and content. Therefore, it is crucial to investigate the surface quality and removal mechanism of fiber-reinforced PEEK in ultra-precision grinding. In this paper, different fiber types and mass fractions of short-fiber-reinforced PEEK, including carbon-fiber-reinforced PEEK (CF/PEEK) and glass-fiber-reinforced PEEK (GF/PEEK), are employed. The grinding machinability of short-fiber-reinforced PEEK was investigated using grinding experiments with grinding wheels of different grit sizes. The effects of the fiber type and mass fraction on the surface quality and removal mechanism during grinding were discussed. The results showed that the brittle–ductile transition depth of carbon fiber was much larger than that of glass fiber, so it was easier to achieve ductile removal in grinding with the carbon fiber. Therefore, the ground surface roughness of CF/PEEK was smaller than that of GF/PEEK under the same grinding conditions. With the increase in carbon fiber mass fraction, the ground surface roughness of CF/PEEK decreased due to the higher hardness. The brittle–ductile transition depth of glass fiber was small, and it was easy to achieve brittle removal when grinding. When the glass fiber removal mode was brittle removal, the GF/PEEK surface roughness increased with the increase in glass fiber content. Full article

(This article belongs to the Special Issue Sustainable Polymeric Composites: Fabrication and Application)

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19 pages, 11762 KiB

Open AccessArticle

Experimental, Analytical, and Numerical Assessments for the Controversial Elastic Stiffness Enhancement of CFRP-Strengthened Timber Beams

by Khaled Saad and András Lengyel

Polymers 2022, 14(19), 4222; https://doi.org/10.3390/polym14194222 - 08 Oct 2022

Cited by 3 | Viewed by 1617

Abstract

The strengthening of timber beams with carbon-fibre-reinforced polymers (CFRP) has been widely used in the last decades to enhance the behaviour of historical or new timber structures, usually for bending. While considerable improvement in capacity and ductility is typically achieved, the increase in [...] Read more.

The strengthening of timber beams with carbon-fibre-reinforced polymers (CFRP) has been widely used in the last decades to enhance the behaviour of historical or new timber structures, usually for bending. While considerable improvement in capacity and ductility is typically achieved, the increase in stiffness was, in many cases, well short of analytical expectations, which tend to overestimate stiffness. This study addresses the problem by investigating the underlying mechanical behaviour using experimental, analytical, and numerical tools on a sample of Norway spruce (Picea abies) beams reinforced with carbon-fibre fabric. In the experimental program, each beam is tested for bending with and without CFRP reinforcement in order to determine specimen-specific stiffness increase on an individual basis. The reinforcement yielded an increase of

27 %

in capacity,

53 %

in ultimate displacement, and

133 %

in compliance, verifying its efficiency. Axial compression tests on an independent sample are also performed to verify modulus of elasticity in compression. Numerical computations based on a beam model and a three-dimensional finite element model are performed with the introduction of separate moduli of elasticity for tension and compression in timber. Inverse computation using the experimental load–deflection curves yielded the moduli and the compression yield stress of timber to provide the best match between tests and simulations. The mean difference of only

6 %

in stiffness between FEM and the tests is obtained. The dominance of normal stresses in the longitudinal direction is found, in correspondence with the experimentally observed tensile failure of timber (apart from a few defected specimens). Compression yield stresses are within

7 %

(beam model) and

2 %

(FEM) error compared with the control axial tests. The differences between FE simulations and tests in ultimate load and compliance are within

1 %

. This study concludes that the application of CFRP in the composite beams enables the determination of timber material properties opposed to pure timber beams without reinforcement, and the adoption of separate moduli of elasticity for tension and compression leads to adequate modelling of reinforced timber beams. Full article

(This article belongs to the Special Issue Development in Fiber-Reinforced Polymer Composites)

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15 pages, 8366 KiB

Open AccessArticle

Infill Strategy in 3D Printed PLA Carbon Composites: Effect on Tensile Performance

by Sofiane Guessasma and Sofiane Belhabib

Polymers 2022, 14(19), 4221; https://doi.org/10.3390/polym14194221 - 08 Oct 2022

Cited by 5 | Viewed by 1465

Abstract

Tuning the infill pattern is one of the key features in additive manufacturing to optimise part weight. In this work, the effect of the infill strategy, including rate and pattern type, is studied on the mechanical performance of polylactic acid (PLA)-carbon composite. In [...] Read more.

Tuning the infill pattern is one of the key features in additive manufacturing to optimise part weight. In this work, the effect of the infill strategy, including rate and pattern type, is studied on the mechanical performance of polylactic acid (PLA)-carbon composite. In particular, three types of patterns and four filling levels are combined. These combinations are evaluated by tensile loading applied on dogbone specimens. In addition, the underlined deformation mechanisms are further explored using filament-based finite element model. The numerical simulation is built from sliced models and converted into 3D meshes to predict tensile performance. The results show that the infill rate has a nonlinear effect on the density of PLA–carbon composites, and its magnitude depends on the complexity of the generated pattern. In addition, tensile loading is found to activate varied modes of shearing and uniaxial deformations depending on the pattern type. This leads to different profiles and rankings of the tensile performance and allows the infill strategy to significantly affect the part performance, along with its density. Full article

(This article belongs to the Special Issue Mechanical and Dynamic Characterization of Polymeric Composites)

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