Polymers

18 pages, 3795 KiB

Open AccessArticle

X-ray Photoelectron Spectroscopy Analysis of Chitosan–Graphene Oxide-Based Composite Thin Films for Potential Optical Sensing Applications

by Wan Mohd Ebtisyam Mustaqim Mohd Daniyal, Yap Wing Fen, Silvan Saleviter, Narong Chanlek, Hideki Nakajima, Jaafar Abdullah and Nor Azah Yusof

Polymers 2021, 13(3), 478; https://doi.org/10.3390/polym13030478 - 2 Feb 2021

Cited by 31 | Viewed by 4110

Abstract

In this study, X-ray photoelectron spectroscopy (XPS) was used to study chitosan–graphene oxide (chitosan–GO) incorporated with 4-(2-pyridylazo)resorcinol (PAR) and cadmium sulfide quantum dot (CdS QD) composite thin films for the potential optical sensing of cobalt ions (Co²⁺). From the XPS results, [...] Read more.

In this study, X-ray photoelectron spectroscopy (XPS) was used to study chitosan–graphene oxide (chitosan–GO) incorporated with 4-(2-pyridylazo)resorcinol (PAR) and cadmium sulfide quantum dot (CdS QD) composite thin films for the potential optical sensing of cobalt ions (Co²⁺). From the XPS results, it was confirmed that carbon, oxygen, and nitrogen elements existed on the PAR–chitosan–GO thin film, while for CdS QD–chitosan–GO, the existence of carbon, oxygen, cadmium, nitrogen, and sulfur were confirmed. Further deconvolution of each element using the Gaussian–Lorentzian curve fitting program revealed the sub-peak component of each element and hence the corresponding functional group was identified. Next, investigation using surface plasmon resonance (SPR) optical sensor proved that both chitosan–GO-based thin films were able to detect Co²⁺ as low as 0.01 ppm for both composite thin films, while the PAR had the higher binding affinity. The interaction of the Co²⁺ with the thin films was characterized again using XPS to confirm the functional group involved during the reaction. The XPS results proved that primary amino in the PAR–chitosan–GO thin film contributed more important role for the reaction with Co²⁺, as in agreement with the SPR results. Full article

(This article belongs to the Special Issue Functional Natural-Based Polymers)

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33 pages, 4836 KiB

Open AccessReview

Micellar Drug Delivery Systems Based on Natural Biopolymers

by Leonard Ionut Atanase

Polymers 2021, 13(3), 477; https://doi.org/10.3390/polym13030477 - 2 Feb 2021

Cited by 140 | Viewed by 9262

Abstract

The broad diversity of structures and the presence of numerous functional groups available for chemical modifications represent an enormous advantage for the development of safe, non-toxic, and cost-effective micellar drug delivery systems (DDS) based on natural biopolymers, such as polysaccharides, proteins, and peptides. [...] Read more.

The broad diversity of structures and the presence of numerous functional groups available for chemical modifications represent an enormous advantage for the development of safe, non-toxic, and cost-effective micellar drug delivery systems (DDS) based on natural biopolymers, such as polysaccharides, proteins, and peptides. Different drug-loading methods are used for the preparation of these micellar systems, but it appeared that dialysis is generally recommended, as it avoids the formation of large micellar aggregates. Moreover, the preparation method has an important influence on micellar size, morphology, and drug loading efficiency. The small size allows the passive accumulation of these micellar systems via the permeability and retention effect. Natural biopolymer-based micellar DDS are high-value biomaterials characterized by good compatibility, biodegradability, long blood circulation time, non-toxicity, non-immunogenicity, and high drug loading, and they are biodegraded to non-toxic products that are easily assimilated by the human body. Even if some recent studies reported better antitumoral effects for the micellar DDS based on polysaccharides than for commercial formulations, their clinical use is not yet generalized. This review is focused on the studies from the last decade concerning the preparation as well as the colloidal and biological characterization of micellar DDS based on natural biopolymers. Full article

(This article belongs to the Special Issue Polymer Micelles II)

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12 pages, 3948 KiB

Open AccessArticle

Numerical Simulation of a Core–Shell Polymer Strand in Material Extrusion Additive Manufacturing

by Hamid Narei, Maryam Fatehifar, Ashley Howard Malt, John Bissell, Mohammad Souri, Mohammad Nasr Esfahani and Masoud Jabbari

Polymers 2021, 13(3), 476; https://doi.org/10.3390/polym13030476 - 2 Feb 2021

Cited by 13 | Viewed by 3756

Abstract

Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Operating parameters play an important role in forming the overall quality of the [...] Read more.

Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Operating parameters play an important role in forming the overall quality of the 3D-printed manufactured products. Here we use numerical simulations within the framework of computation fluid dynamics (CFD) to identify the best combination of operating parameters for the 3D printing of a core–shell polymer strand. The objectives of these CFD simulations are to find strands with an ultimate volume fraction of core polymer. At the same time, complete encapsulations are obtained for the core polymer inside the shell one. In this model, the deposition flow is controlled by three dimensionless parameters: (i) the diameter ratio of core material to the nozzle,

d / D

; (ii) the normalised gap between the extruder and the build plate,

t / D

; (iii) the velocity ratio of the moving build plate to the average velocity inside the nozzle,

V / U

. Numerical results of the deposited strands’ cross-sections demonstrate the effects of controlling parameters on the encapsulation of the core material inside the shell and the shape and size of the strand. Overall we find that the best operating parameters are a diameter ratio of

d / D = 0.7

, a normalised gap of

t / D = 1

, and a velocity ratio of

V / U = 1

. Full article

(This article belongs to the Special Issue Modelling and Simulation of Polymers)

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13 pages, 6035 KiB

Open AccessArticle

Stability of Proton Exchange Membranes in Phosphate Buffer for Enzymatic Fuel Cell Application: Hydration, Conductivity and Mechanical Properties

by Luca Pasquini, Botagoz Zhakisheva, Emanuela Sgreccia, Riccardo Narducci, Maria Luisa Di Vona and Philippe Knauth

Polymers 2021, 13(3), 475; https://doi.org/10.3390/polym13030475 - 2 Feb 2021

Cited by 8 | Viewed by 3121

Abstract

Proton-conducting ionomers are widespread materials for application in electrochemical energy storage devices. However, their properties depend strongly on operating conditions. In bio-fuel cells with a separator membrane, the swelling behavior as well as the conductivity need to be optimized with regard to the [...] Read more.

Proton-conducting ionomers are widespread materials for application in electrochemical energy storage devices. However, their properties depend strongly on operating conditions. In bio-fuel cells with a separator membrane, the swelling behavior as well as the conductivity need to be optimized with regard to the use of buffer solutions for the stability of the enzyme catalyst. This work presents a study of the hydrolytic stability, conductivity and mechanical behavior of different proton exchange membranes based on sulfonated poly(ether ether ketone) (SPEEK) and sulfonated poly(phenyl sulfone) (SPPSU) ionomers in phosphate buffer solution. The results show that the membrane stability can be adapted by changing the casting solvent (DMSO, water or ethanol) and procedures, including a crosslinking heat treatment, or by blending the two ionomers. A comparison with Nafion^TM shows the different behavior of this ionomer versus SPEEK membranes. Full article

(This article belongs to the Special Issue Ionic Conductive Polymers for Electrochemical Devices)

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24 pages, 4369 KiB

Open AccessReview

3D Printable Electrically Conductive Hydrogel Scaffolds for Biomedical Applications: A Review

by Sandya Shiranthi Athukorala, Tuan Sang Tran, Rajkamal Balu, Vi Khanh Truong, James Chapman, Naba Kumar Dutta and Namita Roy Choudhury

Polymers 2021, 13(3), 474; https://doi.org/10.3390/polym13030474 - 2 Feb 2021

Cited by 83 | Viewed by 11641

Abstract

Electrically conductive hydrogels (ECHs), an emerging class of biomaterials, have garnered tremendous attention due to their potential for a wide variety of biomedical applications, from tissue-engineered scaffolds to smart bioelectronics. Along with the development of new hydrogel systems, 3D printing of such ECHs [...] Read more.

Electrically conductive hydrogels (ECHs), an emerging class of biomaterials, have garnered tremendous attention due to their potential for a wide variety of biomedical applications, from tissue-engineered scaffolds to smart bioelectronics. Along with the development of new hydrogel systems, 3D printing of such ECHs is one of the most advanced approaches towards rapid fabrication of future biomedical implants and devices with versatile designs and tuneable functionalities. In this review, an overview of the state-of-the-art 3D printed ECHs comprising conductive polymers (polythiophene, polyaniline and polypyrrole) and/or conductive fillers (graphene, MXenes and liquid metals) is provided, with an insight into mechanisms of electrical conductivity and design considerations for tuneable physiochemical properties and biocompatibility. Recent advances in the formulation of 3D printable bioinks and their practical applications are discussed; current challenges and limitations of 3D printing of ECHs are identified; new 3D printing-based hybrid methods for selective deposition and fabrication of controlled nanostructures are highlighted; and finally, future directions are proposed. Full article

(This article belongs to the Special Issue 3D/4D Printing with Polymers, Polymer Hydrogels and Adaptive Soft Materials)

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12 pages, 2279 KiB

Open AccessArticle

Fibre Alignment and Void Assessment in Thermoplastic Carbon Fibre Reinforced Polymers Manufactured by Automated Tape Placement

by Tamer A. Sebaey, Mohamed Bouhrara and Noel O’Dowd

Polymers 2021, 13(3), 473; https://doi.org/10.3390/polym13030473 - 2 Feb 2021

Cited by 13 | Viewed by 4987

Abstract

Automated Tape Placement (ATP) technology is one of the processes that is used for the production of the thermoplastic composite materials. The ATP process is complex, requiring multiple melting/crystallization cycles. In the current paper, laser-assisted ATP was used to manufacture two thermoplastic composites [...] Read more.

Automated Tape Placement (ATP) technology is one of the processes that is used for the production of the thermoplastic composite materials. The ATP process is complex, requiring multiple melting/crystallization cycles. In the current paper, laser-assisted ATP was used to manufacture two thermoplastic composites (IM7/PEEK and AS4/PA12). Those specimens were compared to specimens that were made of thermoset polymeric composites (IM7/8552) manufactured while using a standard autoclave cycle. In order assess the quality, void content, fibre distribution, and fibre misalignment were measured. After manufacturing, specimens from the three materials were assessed using optical microscopy and computed tomography (CT) scans. The results showed that, as compared to the thermoset composites, thermoplastics that are manufactured by the ATP have a higher amount of voids. On the other hand, manufacturing using the ATP showed an improvement in both the fibre distribution inside the matrix and the fibre misalignment. Full article

(This article belongs to the Special Issue Advanced Thermoplastic Polymers and Composites)

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25 pages, 792 KiB

Open AccessArticle

Constitutive Model of Isotropic Magneto-Sensitive Rubber with Amplitude, Frequency, Magnetic and Temperature Dependence under a Continuum Mechanics Basis

by Bochao Wang and Leif Kari

Polymers 2021, 13(3), 472; https://doi.org/10.3390/polym13030472 - 2 Feb 2021

Cited by 11 | Viewed by 2986

Abstract

A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temperature dependent mechanical property of isotropic magneto-sensitive (MS) rubber is developed. The main components of MS rubber are an elastomer matrix and magnetizable particles. When a magnetic field is applied, the modulus [...] Read more.

A three-dimensional nonlinear constitutive model of the amplitude, frequency, magnetic and temperature dependent mechanical property of isotropic magneto-sensitive (MS) rubber is developed. The main components of MS rubber are an elastomer matrix and magnetizable particles. When a magnetic field is applied, the modulus of MS rubber increases, which is known as the magnetic dependence of MS rubber. In addition to the magnetic dependence, there are frequency, amplitude and temperature dependencies of the dynamic modulus of MS rubber. A continuum mechanical framework-based constitutive model consisting of a fractional standard linear solid (SLS) element, an elastoplastic element and a magnetic stress term of MS rubber is developed to depict the mechanical behavior of MS rubber. The novelty is that the amplitude, frequency, magnetic and temperature dependent mechancial properties of MS rubber are integrated into a whole constitutive model under the continuum mechanics frame. Comparison between the simulation and measurement results shows that the fitting effect of the developed model is very good. Therefore, the constitutive model proposed enables the prediction of the mechanical properties of MS rubber under various operating conditions with a high accuracy, which will drive MS rubber’s application in engineering problems, especially in the area of MS rubber-based anti-vibration devices. Full article

(This article belongs to the Special Issue Magnetic Polymer Composites: Design and Application)

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45 pages, 6366 KiB

Open AccessReview

A Comprehensive Review on Advanced Sustainable Woven Natural Fibre Polymer Composites

by H. A. Aisyah, M. T. Paridah, S. M. Sapuan, R. A. Ilyas, A. Khalina, N. M. Nurazzi, S. H. Lee and C. H. Lee

Polymers 2021, 13(3), 471; https://doi.org/10.3390/polym13030471 - 2 Feb 2021

Cited by 166 | Viewed by 11676

Abstract

Over the last decade, the progressive application of natural fibres in polymer composites has had a major effect in alleviating environmental impacts. Recently, there is a growing interest in the development of green materials in a woven form by utilising natural fibres from [...] Read more.

Over the last decade, the progressive application of natural fibres in polymer composites has had a major effect in alleviating environmental impacts. Recently, there is a growing interest in the development of green materials in a woven form by utilising natural fibres from lignocellulosic materials for many applications such as structural, non-structural composites, household utilities, automobile parts, aerospace components, flooring, and ballistic materials. Woven materials are one of the most promising materials for substituting or hybridising with synthetic polymeric materials in the production of natural fibre polymer composites (NFPCs). These woven materials are flexible, able to be tailored to the specific needs and have better mechanical properties due to their weaving structures. Seeing that the potential advantages of woven materials in the fabrication of NFPC, this paper presents a detailed review of studies related to woven materials. A variety of factors that influence the properties of the resultant woven NFRC such as yarn characteristics, fabric properties as well as manufacturing parameters were discussed. Past and current research efforts on the development of woven NFPCs from various polymer matrices including polypropylene, polylactic acid, epoxy and polyester and the properties of the resultant composites were also compiled. Last but not least, the applications, challenges, and prospects in the field also were highlighted. Full article

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

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17 pages, 2515 KiB

Open AccessReview

The Photoinitiators Used in Resin Based Dental Composite—A Review and Future Perspectives

by Andrea Kowalska, Jerzy Sokolowski and Kinga Bociong

Polymers 2021, 13(3), 470; https://doi.org/10.3390/polym13030470 - 2 Feb 2021

Cited by 116 | Viewed by 14124

Abstract

The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental [...] Read more.

The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental resins. PubMed, Academia.edu, Google Scholar, Elsevier, ResearchGate and Mendeley, analysis from 1985 to 2020 were searched electronically with appropriate keywords. Over 60 articles were chosen based on relevance to this review. Dental light-cured composites are the most common filling used in dentistry, but every photoinitiator system requires proper light-curing system with suitable spectrum of light. Alternation of photoinitiator might cause changing the values of biomechanical properties such as: degree of conversion, hardness, biocompatibility. This review contains comparison of biomechanical properties of dental composites including different photosensitizers among other: camphorquinone, phenanthrenequinone, benzophenone and 1-phenyl-1,2 propanedione, trimethylbenzoyl-diphenylphosphine oxide, benzoyl peroxide. The major aim of this article was to point out alternative photoinitiators which would compensate the disadvantages of camphorquinone such as: yellow staining or poor biocompatibility and also would have mechanical properties as satisfactory as camphorquinone. Research showed there is not an adequate photoinitiator which can be as sufficient as camphorquinone (CQ), but alternative photosensitizers like: benzoyl germanium or novel acylphosphine oxide photoinitiators used synergistically with CQ are able to improve aesthetic properties and degree of conversion of dental resin. Full article

(This article belongs to the Special Issue Polymers for Dental Restorative and Oral Tissue Engineering)

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15 pages, 3883 KiB

Open AccessArticle

Comparative Study of the Impact Wedge-Peel Performance of Epoxy Structural Adhesives Modified with Functionalized Silica Nanoparticles

by Gyeong-Seok Chae, Hee-Woong Park, Kiok Kwon and Seunghan Shin

Polymers 2021, 13(3), 469; https://doi.org/10.3390/polym13030469 - 2 Feb 2021

Cited by 7 | Viewed by 3167

Abstract

Epoxy structural adhesives have strong adhesion, minimal shrinkage and high thermal and chemical resistance. However, despite these excellent properties, their high-energy impact resistance should be improved to satisfy the increasing demands of the automotive industry. For this reason, we used four types of [...] Read more.

Epoxy structural adhesives have strong adhesion, minimal shrinkage and high thermal and chemical resistance. However, despite these excellent properties, their high-energy impact resistance should be improved to satisfy the increasing demands of the automotive industry. For this reason, we used four types of silica nanoparticles with different surface groups, such as polydimethylsiloxane (PDMS), hydroxyl, epoxy and amine groups, as toughening agents and examined their effect on the glass transition temperature (T_g), crosslinking density and phase separation of epoxy structural adhesives. High-energy impact resistance, mode I fracture toughness and lap shear strength were also measured to explain the effect of surface functional groups. Silica nanoparticles with reactive functional groups increased the mode I fracture toughness of epoxy structural adhesives without sacrificing the crosslinking density. Although the mode I fracture toughness of epoxy structural adhesives could not clearly show the effect of surface functional groups, the dynamic resistance to cleavage obtained by impact wedge-peel tests showed quite different values. At a 0.3 vol% content, epoxy-functionalized silica nanoparticles induced the highest value (40.2 N/mm) compared to PDMS (34.1 N/m), hydroxyl (34.9 N/mm), and amine (36.1 N/m). All of these values were significantly higher than those of pristine epoxy structural adhesive (27.7 N/mm). Full article

(This article belongs to the Section Polymer Chemistry)

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11 pages, 3540 KiB

Open AccessArticle

Alginate as Dispersing Agent for Compounding Natural Rubber with High Loading Microfibrillated Cellulose

by Goragot Supanakorn, Nanthaphak Varatkowpairote, Siriporn Taokaew and Muenduen Phisalaphong

Polymers 2021, 13(3), 468; https://doi.org/10.3390/polym13030468 - 1 Feb 2021

Cited by 20 | Viewed by 4534

Abstract

Natural rubber (NR) reinforced with high loading of microfibrillated cellulose (MFC) was fabricated in the presence of sodium alginate as a thickening and dispersing agent in NR latex. The tensile strength and Young’s moduli of the 50% wt. MFC loading-NR composites were 13.6 [...] Read more.

Natural rubber (NR) reinforced with high loading of microfibrillated cellulose (MFC) was fabricated in the presence of sodium alginate as a thickening and dispersing agent in NR latex. The tensile strength and Young’s moduli of the 50% wt. MFC loading-NR composites were 13.6 and 1085.7 MPa, which were about 11.3- and 329-times enhanced compared with those of the neat NR film. The maximum elongation at 313.3% was obtained from 30% MFC loading, which was a 3.3-fold increase of that of the NR film. The thermal stability of MFC–NR films was slightly reduced, while the glass transition temperature remained unchanged at −64 °C. The MFC–NR films exhibited high water adsorption ability, toluene resistance, and biodegradability. Full article

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

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13 pages, 4596 KiB

Open AccessArticle

High-Temperature Resistant Polyborosilazanes with Tailored Structures

by Bijie Wang, Ke Chen, Tianhao Li, Xun Sun, Ming Liu, Lingwei Yang, Xiao (Matthew) Hu, Jian Xu, Liu He, Qing Huang, Linbin Jiang and Yujie Song

Polymers 2021, 13(3), 467; https://doi.org/10.3390/polym13030467 - 1 Feb 2021

Cited by 5 | Viewed by 3419

Abstract

Boron-containing organosilicon polymers are widely used under harsh environments as preceramic polymers for advanced ceramics fabrication. However, harmful chemicals released during synthesis and the complex synthesis routes have limited their applications. To solve the problems, a two-component route was adopted to synthesize cross-linked [...] Read more.

Boron-containing organosilicon polymers are widely used under harsh environments as preceramic polymers for advanced ceramics fabrication. However, harmful chemicals released during synthesis and the complex synthesis routes have limited their applications. To solve the problems, a two-component route was adopted to synthesize cross-linked boron-containing silicone polymer (CPBCS) via a solventless process. The boron content and CPBCSs’ polymeric structures could be readily tuned through controlling the ratio of multifunctional boron hybrid silazane monomers (BSZ12) and poly[imino(methylsilylene)]. The CPBCSs showed high thermal stability and good mechanical properties. The CPBCS with Si-H/C=C ratio of 10:1 showed 75 wt% char yields at 1000 °C in argon, and the heat release capacity (HRC) and total heat release (THR) are determined to be 37.9 J/g K and 6.2 KJ/g, demonstrating high thermal stability and flame retardancy. The reduced modulus and hardness of CPBCS are 0.30 GPa and 2.32 GPa, respectively. The novel polysilazanes can be potentially used under harsh environments, such as high temperatures or fire hazards. Full article

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

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15 pages, 11380 KiB

Open AccessArticle

Bioactivity of a Novel Polycaprolactone-Hydroxyapatite Scaffold Used as a Carrier of Low Dose BMP-2: An In Vitro Study

by Pawornwan Rittipakorn, Nuttawut Thuaksuban, Katanchalee Mai-ngam, Satrawut Charoenla and Warobon Noppakunmongkolchai

Polymers 2021, 13(3), 466; https://doi.org/10.3390/polym13030466 - 1 Feb 2021

Cited by 10 | Viewed by 2681

Abstract

Scaffolds of polycaprolactone-30% hydroxyapatite (PCL-30% HA) were fabricated using melt stretching and multilayer deposition (MSMD), and the in vitro response of osteoblasts to the scaffolds was assessed. In group A, the scaffolds were immersed in 10 µg/mL bone morphogenetic protein-2 (BMP-2) solution prior [...] Read more.

Scaffolds of polycaprolactone-30% hydroxyapatite (PCL-30% HA) were fabricated using melt stretching and multilayer deposition (MSMD), and the in vitro response of osteoblasts to the scaffolds was assessed. In group A, the scaffolds were immersed in 10 µg/mL bone morphogenetic protein-2 (BMP-2) solution prior to being seeded with osteoblasts, and they were cultured in the medium without BMP-2. In group B, the cell-scaffold constructs without BMP-2 were cultured in medium containing 10 µg/mL BMP-2. The results showed greater cell proliferation in group A. The upregulation of runt-related transcription factor 2 and osteocalcin genes correlated with the release of BMP-2 from the scaffolds. The PCL-30% HA MSMD scaffolds appear to be suitable for use as osteoconductive frameworks and BMP-2 carriers. Full article

(This article belongs to the Special Issue Applications of Biopolymer Scaffolds)

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15 pages, 5626 KiB

Open AccessArticle

Morphology, Structural, Thermal, and Tensile Properties of Bamboo Microcrystalline Cellulose/Poly(Lactic Acid)/Poly(Butylene Succinate) Composites

by Masrat Rasheed, Mohammad Jawaid, Bisma Parveez, Aamir Hussain Bhat and Salman Alamery

Polymers 2021, 13(3), 465; https://doi.org/10.3390/polym13030465 - 1 Feb 2021

Cited by 32 | Viewed by 4585

Abstract

The present study aims to develop a biodegradable polymer blend that is environmentally friendly and has comparable tensile and thermal properties with synthetic plastics. In this work, microcrystalline cellulose (MCC) extracted from bamboo-chips-reinforced poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blend [...] Read more.

The present study aims to develop a biodegradable polymer blend that is environmentally friendly and has comparable tensile and thermal properties with synthetic plastics. In this work, microcrystalline cellulose (MCC) extracted from bamboo-chips-reinforced poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blend composites were fabricated by melt-mixing at 180 °C and then hot pressing at 180 °C. PBS and MCC (0.5, 1, 1.5 wt%) were added to improve the brittle nature of PLA. Field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), thermogravimetric analysis (TGA), differential thermogravimetry (DTG), differential scanning calorimetry (DSC)), and universal testing machine were used to analyze morphology, crystallinity, physiochemical, thermal, and tensile properties, respectively. The thermal stability of the PLA-PBS blends enhanced on addition of MCC up to 1wt % due to their uniform dispersion in the polymer matrix. Tensile properties declined on addition of PBS and increased with MCC above (0.5 wt%) however except elongation at break increased on addition of PBS then decreased insignificantly on addition of MCC. Thus, PBS and MCC addition in PLA matrix decreases the brittleness, making it a potential contender that could be considered to replace plastics that are used for food packaging. Full article

(This article belongs to the Special Issue Bio-Based Materials: Contribution to Advancing Circular Economy)

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17 pages, 5024 KiB

Open AccessArticle

The Role of the Fiber/Bead Hierarchical Microstructure on the Properties of PVDF Coatings Deposited by Electrospinning

by Adrián Vicente, Pedro J. Rivero, José F. Palacio and Rafael Rodríguez

Polymers 2021, 13(3), 464; https://doi.org/10.3390/polym13030464 - 1 Feb 2021

Cited by 13 | Viewed by 3045

Abstract

Among the various polymeric options employed for the deposition of electrospun coatings, poly(vinylidene fluoride) (PVDF) has been widely investigated thanks to its excellent mechanical properties, high chemical resistance, and good thermal stability. In this work, the electrospinning technique is used for the fabrication [...] Read more.

Among the various polymeric options employed for the deposition of electrospun coatings, poly(vinylidene fluoride) (PVDF) has been widely investigated thanks to its excellent mechanical properties, high chemical resistance, and good thermal stability. In this work, the electrospinning technique is used for the fabrication of functional PVDF fibers in order to identify and evaluate the influence of the experimental conditions on the nanofiber properties in terms of optical transmittance, wettability, corrosion resistance, and surface morphology. Some of these properties can play a relevant role in the prevention of ice formation in aircrafts. According to this, a matrix of 4 × 4 samples of aluminum alloy AA 6061T6 was successfully coated by controlling two operational input parameters such as the resultant applied voltage (from 10 up to 17.5 KV) and the flow rate (from 800 up to 1400 µL/h) for a fixed polymeric precursor concentration (15 wt.%). The experimental results have shown a multilevel fiber-bead structure where the formation of a fiber mesh directly depends on the selected operational parameters. Several microscopy and surface analysis techniques such as confocal microscopy (CM), field emission scanning electron microscopy (FE-SEM), UV/vis spectroscopy, and water contact angle (WCA) were carried out in order to corroborate the morphology, transmittance, and hydrophobicity of the electrospun fiber composite. Finally, the corrosion behavior was also evaluated by electrochemical tests (Tafel curves measurement), showing that the presence of electrospun PVDF fibers produces a relevant improvement in the resultant corrosion resistance of the coated aluminum alloys. Full article

(This article belongs to the Section Polymer Applications)

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12 pages, 4243 KiB

Open AccessArticle

Fabrication of Core-Shell Chopped C_f-Phenolic Resin Composite Powder for Laser Additive Manufacturing of C_f/SiC Composites

by Xiao Chen, Jie Yin, Xuejian Liu, Aidong Xia and Zhengren Huang

Polymers 2021, 13(3), 463; https://doi.org/10.3390/polym13030463 - 1 Feb 2021

Cited by 6 | Viewed by 2830

Abstract

Laser additive manufacturing is a promising technique for the preparation of complex-shaped SiC composites. High-quality powders are critical for high-precision laser printing. In this work, core-shell C_f @phenolic resin (PR) composites for selective laser sintering of carbon fiber reinforced silicon carbide (C [...] Read more.

Laser additive manufacturing is a promising technique for the preparation of complex-shaped SiC composites. High-quality powders are critical for high-precision laser printing. In this work, core-shell C_f @phenolic resin (PR) composites for selective laser sintering of carbon fiber reinforced silicon carbide (C_f/SiC) composites were fabricated by surface modification using 3-aminopropyltriethoxy silane coupling agent (KH550) in combination with planetary ball milling. PR coated uniformly on the fiber surface to form a core-shell structure. The effects of PR on the morphology, elemental composition, interfacial interactions, and laser absorption of the core-shell composite powder were investigated in detail. Results indicated that the composite powder exhibited good laser absorption within the infrared band. Full article

(This article belongs to the Special Issue Polymer/Ceramics Composites)

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13 pages, 3010 KiB

Open AccessArticle

Morphology-Mechanical Performance Relationship at the Micrometrical Level within Molded Polypropylene Obtained with Non-Symmetric Mold Temperature Conditioning

by Sara Liparoti, Andrea Sorrentino and Vito Speranza

Polymers 2021, 13(3), 462; https://doi.org/10.3390/polym13030462 - 31 Jan 2021

Cited by 5 | Viewed by 2403

Abstract

The control of the structural properties of a polymeric material at the micro and nano-metrical scale is strategic to obtaining parts with high performance, durability and free from sudden failures. The characteristic skin-core morphology of injection molded samples is intimately linked to the [...] Read more.

The control of the structural properties of a polymeric material at the micro and nano-metrical scale is strategic to obtaining parts with high performance, durability and free from sudden failures. The characteristic skin-core morphology of injection molded samples is intimately linked to the complex shear flow, pressure and temperature evolutions experienced by the polymer chains during processing. An accurate analysis of this morphology can allow for the assessment of the quality and confidence of the process. Non-symmetric mold temperature conditions are imposed to produce complex morphologies in polypropylene parts. Morphological and micromechanical characterizations of the samples are used to quantify the effects of the processing conditions on the part performance. Asymmetric distribution of temperatures determines asymmetric distribution of both morphology and mechanical properties. The inhomogeneity degree depends on the time that one side of the cavity experiences high temperatures. The spherulites, which cover the thickest of the parts obtained with high temperatures at one cavity side, show smaller values of elastic modulus than the fibrils. When the polymer molecules experience high temperatures for long periods, the solid-diffusion and the partial melting and recrystallization phenomena determine a better structuring of the molecules with a parallel increase of the elastic modulus. Full article

(This article belongs to the Special Issue Materials and Methods for New Technologies in Polymer Processing II)

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10 pages, 4058 KiB

Open AccessArticle

Impact of Water and UV Irradiation on Nonwoven Polylactide/Natural Rubber Fiber

by Yulia Tertyshnaya, Maria Podzorova and Maksim Moskovskiy

Polymers 2021, 13(3), 461; https://doi.org/10.3390/polym13030461 - 31 Jan 2021

Cited by 26 | Viewed by 2649

Abstract

A nonwoven fiber made of polylactide/natural rubber with a rubber content from 0 to 15 wt.% was obtained by electrospinning from a solution. The water sorption test showed that the addition of natural rubber into the polylactide matrix did not significantly affect the [...] Read more.

A nonwoven fiber made of polylactide/natural rubber with a rubber content from 0 to 15 wt.% was obtained by electrospinning from a solution. The water sorption test showed that the addition of natural rubber into the polylactide matrix did not significantly affect the degree of water absorption of the fibers, which was in the range of 48.9–50.6%. The melt flow rate only increased by 0.5 g/10 min at a content of 15 wt.% natural rubber. The thermal characteristics after 120 days of degradation in distilled water and UV irradiation (50 h) at a wavelength of 365 nm were determined using differential scanning calorimetry. Changes in the values of the phase transition temperatures and the degree of crystallinity were determined. It was determined that the fiber samples from all compositions retained the propensity for photo- and hydrolytic degradation. Full article

(This article belongs to the Special Issue Natural and Synthetic Polymers-Hopes and Fears in an Era of Ecological Modernization)

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12 pages, 3554 KiB

Open AccessArticle

Effect of Molecular Architecture on Associating Behavior of Star-Like Amphiphilic Polymers Consisting of Plural Poly(ethylene oxide) and One Alkyl Chain

by Daisuke Kugimoto, Aoi Taniguchi, Masaki Kinoshita and Isamu Akiba

Polymers 2021, 13(3), 460; https://doi.org/10.3390/polym13030460 - 31 Jan 2021

Viewed by 2584

Abstract

Associating behavior of star-like amphiphilic polymers consisting of two or three poly(ethylene oxide) (PEO) chains and one stearyl chain (C18) was investigated. Although the aggregation number (N_agg) of linear analogue of amphiphilic polymers monotonically decreased with increasing number-average molecular weight [...] Read more.

Associating behavior of star-like amphiphilic polymers consisting of two or three poly(ethylene oxide) (PEO) chains and one stearyl chain (C18) was investigated. Although the aggregation number (N_agg) of linear analogue of amphiphilic polymers monotonically decreased with increasing number-average molecular weight of PEO (M_n_,PEO), the N_agg of micelles of star-like amphiphilic polymers with M_n_,PEO = 550 g/mol was smaller than that with M_n_,PEO = 750 g/mol, whereas that with M_n_,PEO ≥ 750 g/mol showed general M_n_,PEO dependence. Small-angle X-ray scattering analyses revealed that the occupied area of one PEO chain on the interface between hydrophobic core and corona layer in the micelles of star-like polymers was much narrower than that in the linear amphiphilic polymers. This result indica ted the PEO chains of star-like polymers partially took unfavorable conformation near the core–corona interface in polymer micelles. The effect of local conformation of PEO chains near the interface on the associating behavior became significant as M_n_,PEO decreased. Therefore, in polymer micelles of star-like amphiphilic polymers containing PEO with M_n_,PEO = 550 g/mol, the enlargement of occupied area of PEO on the core–corona interface should be caused to avoid the formation of unfavorable conformations of partial PEO chains, resulting in a decrease in N_aggs. Full article

(This article belongs to the Special Issue Polymer Micelles II)

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17 pages, 4621 KiB

Open AccessArticle

Hypergravity-Induced Accumulation: A New, Efficient, and Simple Strategy to Improve the Thermal Conductivity of Boron Nitride Filled Polymer Composites

by Kangkang Yu, Tao Yuan, Songdi Zhang and Chenlu Bao

Polymers 2021, 13(3), 459; https://doi.org/10.3390/polym13030459 - 31 Jan 2021

Cited by 9 | Viewed by 3936

Abstract

Thermal conductive polymer composites (filled type) consisting of thermal conductive fillers and a polymer matrix have been widely used in a range of areas. More than 10 strategies have been developed to improve the thermal conductivity of polymer composites. Here we report a [...] Read more.

Thermal conductive polymer composites (filled type) consisting of thermal conductive fillers and a polymer matrix have been widely used in a range of areas. More than 10 strategies have been developed to improve the thermal conductivity of polymer composites. Here we report a new “hypergravity accumulation” strategy. Raw material mixtures of boron nitride/silicone rubber composites were treated in hypergravity fields (800–20,000 g, relative gravity acceleration) before heat-curing. A series of comparison studies were made. It was found that hypergravity treatments could efficiently improve the microstructures and thermal conductivity of the composites. When the hypergravity was about 20,000 g (relative gravity acceleration), the obtained spherical boron nitride/silicone rubber composites had highly compacted microstructures and high and isotropic thermal conductivity. The highest thermal conductivity reached 4.0 W/mK. Thermal interface application study showed that the composites could help to decrease the temperature on a light-emitting diode (LED) chip by 5 °C. The mechanism of the improved microstructure increased thermal conductivity, and the high viscosity problem in the preparation of boron nitride/silicone rubber composites, and the advantages and disadvantages of the hypergravity accumulation strategy, were discussed. Overall, this work has provided a new, efficient, and simple strategy to improve the thermal conductivity of boron nitride/silicone rubber and other polymer composites (filled type). Full article

(This article belongs to the Special Issue Reinforced Polymer Composites III)

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15 pages, 698 KiB

Open AccessArticle

Formation and Evaluation of a Two-Phase Polymer System in Human Plasma as a Method for Extracellular Nanovesicle Isolation

by Maria Slyusarenko, Nadezhda Nikiforova, Elena Sidina, Inga Nazarova, Vladimir Egorov, Yuri Garmay, Anastasiia Merdalimova, Natalia Yevlampieva, Dmitry Gorin and Anastasia Malek

Polymers 2021, 13(3), 458; https://doi.org/10.3390/polym13030458 - 31 Jan 2021

Cited by 18 | Viewed by 4743

Abstract

The aim of the study was to explore the polyethylene glycol–dextran two-phase polymer system formed in human plasma to isolate the exosome-enriched fraction of plasma extracellular nanovesicles (ENVs). Systematic analysis was performed to determine the optimal combination of the polymer mixture parameters (molecular [...] Read more.

The aim of the study was to explore the polyethylene glycol–dextran two-phase polymer system formed in human plasma to isolate the exosome-enriched fraction of plasma extracellular nanovesicles (ENVs). Systematic analysis was performed to determine the optimal combination of the polymer mixture parameters (molecular mass and concentration) that resulted in phase separation. The separated phases were analyzed by nanoparticle tracking analysis and Raman spectroscopy. The isolated vesicles were characterized by atomic force microscopy and dot blotting. In conclusion, the protein and microRNA contents of the isolated ENVs were assayed by flow cytometry and by reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR), respectively. The presented results revealed the applicability of a new method for plasma ENV isolation and further analysis with a diagnostic purpose. Full article

(This article belongs to the Special Issue The Diagnostics Based on Polymers)

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49 pages, 17600 KiB

Open AccessArticle

Processability of Different Polymer Fractions Recovered from Mixed Wastes and Determination of Material Properties for Recycling

by Selina Möllnitz, Michael Feuchter, Ivica Duretek, Gerald Schmidt, Roland Pomberger and Renato Sarc

Polymers 2021, 13(3), 457; https://doi.org/10.3390/polym13030457 - 31 Jan 2021

Cited by 22 | Viewed by 3973

Abstract

To achieve future recycling targets and CO₂ and waste reduction, the transfer of plastic contained in mixed waste from thermal recovery to mechanical recycling is a promising option. This requires extensive knowledge of the necessary processing depth of mixed wastes to enrich [...] Read more.

To achieve future recycling targets and CO₂ and waste reduction, the transfer of plastic contained in mixed waste from thermal recovery to mechanical recycling is a promising option. This requires extensive knowledge of the necessary processing depth of mixed wastes to enrich plastics and their processability in polymer processing machines. Also, the selection of a suitable processing method and product application area requires appropriate material behaviour. This paper investigates these aspects for a commercial processed, mixed waste, and two different mixed polyolefin fractions. The wastes are processed at different depths (e.g., washed/not washed, sorted into polyethylene, polypropylene, polyethylene terephthalate, polystyrene/unsorted) and then either homogenised in the extruder in advance or processed heterogeneously in the compression moulding process into plates. The produced recyclates in plate form are then subjected to mechanical, thermal, and rheological characterisation. Most investigated materials could be processed with simple compression moulding. The results show that an upstream washing process improves the achievable material properties, but homogenisation does not necessarily lead to an improvement. It was also found that a higher treatment depth (recovery of plastic types) is not necessary. The investigations show that plastic waste recovery with simple treatment from mixed, contaminated wastes into at least downcycling products is possible. Full article

(This article belongs to the Special Issue Polymer Waste Recycling and Management)

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10 pages, 2942 KiB

Open AccessArticle

Thermal Properties of Surface-Modified and Cross-Linked Boron Nitride/Polyethylene Glycol Composite as Phase Change Material

by Jaehyun Wie and Jooheon Kim

Polymers 2021, 13(3), 456; https://doi.org/10.3390/polym13030456 - 31 Jan 2021

Cited by 35 | Viewed by 4053

Abstract

A thermally conductive phase change material (PCM) was fabricated using polyethylene glycol (PEG) and boron nitride (BN). However, the interfacial adhesion between the BN and the PEG was poor, hindering efficient heat conduction. Grafting polyvinyl alcohol (PVA) onto the surface of BN and [...] Read more.

A thermally conductive phase change material (PCM) was fabricated using polyethylene glycol (PEG) and boron nitride (BN). However, the interfacial adhesion between the BN and the PEG was poor, hindering efficient heat conduction. Grafting polyvinyl alcohol (PVA) onto the surface of BN and cross-linking due to hydrogen bonding between the hydroxyl groups in PVA and oxygen atoms in PEG improved the wettability of fillers. By employing this strategy, we achieved a thermal conductivity value of 0.89 W/mK, a 286% improvement compared to the thermal conductivity of the pristine PEG (0.23 W/mK). Although the latent heat of composites decreased due to the mobility of the polymer chain, the value was still reasonable for PCM applications. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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24 pages, 94239 KiB

Open AccessArticle

The Effect of Stacking Sequence and Ply Orientation on the Mechanical Properties of Pineapple Leaf Fibre (PALF)/Carbon Hybrid Laminate Composites

by Mohd Khairul Rabani Hashim, Mohd Shukry Abdul Majid, Mohd Ridzuan Mohd Jamir, Farizul Hafiz Kasim and Mohamed Thariq Hameed Sultan

Polymers 2021, 13(3), 455; https://doi.org/10.3390/polym13030455 - 31 Jan 2021

Cited by 33 | Viewed by 4536

Abstract

In this paper, the effects of stacking sequence and ply orientation on the mechanical properties of pineapple leaf fibre (PALF)/carbon hybrid laminate composites were investigated. The hybrid laminates were fabricated using a vacuum infusion technique in which the stacking sequences and ply orientations [...] Read more.

In this paper, the effects of stacking sequence and ply orientation on the mechanical properties of pineapple leaf fibre (PALF)/carbon hybrid laminate composites were investigated. The hybrid laminates were fabricated using a vacuum infusion technique in which the stacking sequences and ply orientations were varied, which were divided into the categories of cross-ply symmetric, angle-ply symmetric, and symmetric quasi-isotropic. The results of tensile and flexural tests showed that the laminate with interior carbon plies and ply orientation [0°, 90°] exhibited the highest tensile strength (187.67 MPa) and modulus (5.23 GPa). However, the highest flexural strength (289.46 MPa) and modulus (4.82 GPa) were recorded for the laminate with exterior carbon plies and the same ply orientation. The fracture behaviour of the laminates was determined by using scanning electron microscopy, and the results showed that failure usually initiated at the weakest PALF layer. The failure modes included fibre pull-out, fibre breaking, matrix crack, debonding, and delamination. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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9 pages, 1759 KiB

Open AccessEditor’s ChoiceCommunication

Viscosity-Regulated Control of RNA Microstructure Fabrication

by Sunghyun Moon, Hyejin Kim, Dajeong Kim and Jong Bum Lee

Polymers 2021, 13(3), 454; https://doi.org/10.3390/polym13030454 - 31 Jan 2021

Cited by 3 | Viewed by 3052

Abstract

The development of RNA self-assemblies offers a powerful platform for a wide range of biomedical applications. The fabrication process has become more elaborate in order to achieve functional structures with maximized potential. As a facile means to control the structure, here, we report [...] Read more.

The development of RNA self-assemblies offers a powerful platform for a wide range of biomedical applications. The fabrication process has become more elaborate in order to achieve functional structures with maximized potential. As a facile means to control the structure, here, we report a new approach to manipulate the polymerization rate and subsequent self-assembly process through regulation of the reaction viscosity. As the RNA polymerization rate has a dependence on solution viscosity, the resulting assembly, crystallization, and overall sizes of the product could be manipulated. The simple and precise control of RNA polymerization and self-assembly by reaction viscosity will provide a way to widen the utility of RNA-based materials. Full article

(This article belongs to the Special Issue Polymeric Materials in Biomedical Applications)

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3 pages, 173 KiB

Open AccessEditorial

Biomacromolecules, Biobased and Biodegradable Polymers: 2018–2019

by Seunho Jung

Polymers 2021, 13(3), 453; https://doi.org/10.3390/polym13030453 - 31 Jan 2021

Cited by 1 | Viewed by 2100

Abstract

This editorial introduces the most cited papers published in the years 2018–2019 in the section “Biomacromolecules, Biobased and Biodegradable Polymers” of the journal Polymers [...] Full article

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

20 pages, 7378 KiB

Open AccessArticle

Preparation and Properties of Poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)/Polyglycolic Acid (PETG/PGA) Blends

by Kai Wang, Jianing Shen, Zhao Ma, Yipeng Zhang, Nai Xu and Sujuan Pang

Polymers 2021, 13(3), 452; https://doi.org/10.3390/polym13030452 - 31 Jan 2021

Cited by 15 | Viewed by 5119

Abstract

Polyglycolic acid (PGA) is used as a reinforcing component to enhance the mechanical properties of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG). The tensile performance, micromorphology, crystallinity, heat resistance, and melt mass flow rates (MFRs) of PETG/PGA blends with varying PGA contents were studied. Both the [...] Read more.

Polyglycolic acid (PGA) is used as a reinforcing component to enhance the mechanical properties of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG). The tensile performance, micromorphology, crystallinity, heat resistance, and melt mass flow rates (MFRs) of PETG/PGA blends with varying PGA contents were studied. Both the tensile yield strength and tensile modulus of the PETG/PGA blends increased gradually with an increase in the PGA content from 0 to 35 wt%. The tensile yield strength of the PETG/PGA (65/35) blend increased by 8.7% (44.38 to 48.24 MPa), and the tensile modulus increased by 40.2% (1076 to 1509 MPa). However, its tensile ductility decreased drastically, owing to the poor interfacial compatibility of PETG/PGA and the oversized PGA domains. A multiple epoxy chain extender (ADR) was introduced into the PETG/PGA (65/35) blend to improve its interfacial compatibility and rheological properties. The tensile performance, micromorphology, rheological properties, crystallinity, and heat resistance of PETG/PGA (65/35) blends with varying ADR contents were studied. The strong chain extension effect of ADR along with its reactive compatibilization improved the rheological properties and tensile ductility. By carefully controlling the ADR concentration, the performance of PETG/PGA blends can be regulated for different applications. Full article

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

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14 pages, 2574 KiB

Open AccessArticle

Synthesis of Multi-Functional Nano-Vectors for Target-Specific Drug Delivery

by Tzu-Chien Wu, Pei-Yuan Lee, Chiao-Ling Lai and Chian-Hui Lai

Polymers 2021, 13(3), 451; https://doi.org/10.3390/polym13030451 - 30 Jan 2021

Cited by 9 | Viewed by 3178

Abstract

Magnetic nanoparticles have gained attention in cancer therapy due to their non-toxic properties and high bio-compatibility. In this report, we synthesize a dual-responsive magnetic nanoparticle (MNP) that is sensitive to subtle pH and temperature change as in the tumor microenvironment. Thus, the functional [...] Read more.

Magnetic nanoparticles have gained attention in cancer therapy due to their non-toxic properties and high bio-compatibility. In this report, we synthesize a dual-responsive magnetic nanoparticle (MNP) that is sensitive to subtle pH and temperature change as in the tumor microenvironment. Thus, the functional doxorubicin (DOX)-loaded MNP (DOX-PNIPAM-PMAA@Fe₃O₄) can perform specific DOX releases in the cancer cell. The particle was characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta-potential, Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The microscopy data revealed the particle as having a spherical shape. The zeta-potential and size distribution analysis data demonstrated the difference for the stepwise modified MNPs. The FTIR spectrum showed characteristic absorption bands of NH₂-SiO₂@Fe₃O₄, CPDB@Fe₃O₄, PMAA@Fe₃O₄, and PNIPAM-PMAA@Fe₃O₄. Drug-loading capacity and releasing efficiency were evaluated under different conditions. Through an in vitro analysis, we confirmed that PNIPAM-PMAA@Fe₃O₄ has enhanced drug releasing efficiency under acidic and warmer conditions. Finally, cellular uptake and cell viability were estimated via different treatments in an MDA-MB-231 cell line. Through the above analysis, we concluded that the DOX-loaded particles can be internalized by cancer cells, and such a result is positive and prospective. Full article

(This article belongs to the Special Issue Bio-Based Polymers for Industrial Applications)

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17 pages, 3212 KiB

Open AccessArticle

Novel, Environment-Friendly Cellulose-Based Derivatives for Tetraconazole Removal from Aqueous Solution

by Bayan Khalaf, Othman Hamed, Shehdeh Jodeh, Ghadir Hanbali, Roland Bol, Omar Dagdag and Subhi Samhan

Polymers 2021, 13(3), 450; https://doi.org/10.3390/polym13030450 - 30 Jan 2021

Cited by 10 | Viewed by 2906

Abstract

In this study, cellulose-based derivatives with heterocyclic moieties were synthesized by reacting cellulose with furan-2-carbonyl chloride (Cell-F) and pyridine-2,6-dicarbonyl dichloride (Cell-P). The derivatives were evaluated as adsorbents for the pesticide tetraconazole from aqueous solution. The prepared adsorbents were characterized by SEM, TGA, IR, [...] Read more.

In this study, cellulose-based derivatives with heterocyclic moieties were synthesized by reacting cellulose with furan-2-carbonyl chloride (Cell-F) and pyridine-2,6-dicarbonyl dichloride (Cell-P). The derivatives were evaluated as adsorbents for the pesticide tetraconazole from aqueous solution. The prepared adsorbents were characterized by SEM, TGA, IR, and H¹ NMR instruments. To maximize the adsorption efficiency of tetraconazole, the optimum conditions of contact time, pH, temperature, adsorbent dose, and initial concentration of adsorbate were determined. The highest removal percentage of tetraconazole from water was 98.51% and 95% using Cell-F and Cell-P, respectively. Underivatized nanocellulose was also evaluated as an adsorbent for tetraconazole for comparison purpose, and it showed a removal efficiency of about 91.73%. The best equilibrium adsorption isotherm model of each process was investigated based on the experimental and calculated R² values of Freundlich and Langmuir models. The adsorption kinetics were also investigated using pseudo-first-order, pseudo-second-order, and intra-particle-diffusion adsorption kinetic models. The Van’t Hoff plot was also studied for each adsorption to determine the changes in adsorption enthalpy (∆H), Gibbs free energy (∆G), and entropy (∆S). The obtained results showed that adsorption by Cell-F and Cell-P follow the Langmuir adsorption isotherm and the mechanism follows the pseudo-second-order kinetic adsorption model. The obtained negative values of the thermodynamic parameter ∆G (−4.693, −4.792, −5.549 kJ) for nanocellulose, Cell-F, and Cell-P, respectively, indicate a spontaneous adsorption process. Cell-F and Cell-P could be promising absorbents on a commercial scale for tetraconazole and other pesticides. Full article

(This article belongs to the Special Issue Polymer Nanocomposite Membranes for Environmental Applications)

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17 pages, 4471 KiB

Open AccessReview

Current Technologies in Depolymerization Process and the Road Ahead

by Yu Miao, Annette von Jouanne and Alexandre Yokochi

Polymers 2021, 13(3), 449; https://doi.org/10.3390/polym13030449 - 30 Jan 2021

Cited by 81 | Viewed by 14885

Abstract

Although plastic is considered an indispensable commodity, plastic pollution is a major concern around the world due to its rapid accumulation rate, complexity, and lack of management. Some political policies, such as the Chinese import ban on plastic waste, force us to think [...] Read more.

Although plastic is considered an indispensable commodity, plastic pollution is a major concern around the world due to its rapid accumulation rate, complexity, and lack of management. Some political policies, such as the Chinese import ban on plastic waste, force us to think about a long-term solution to eliminate plastic wastes. Converting waste plastics into liquid and gaseous fuels is considered a promising technique to eliminate the harm to the environment and decrease the dependence on fossil fuels, and recycling waste plastic by converting it into monomers is another effective solution to the plastic pollution problem. This paper presents the critical situation of plastic pollution, various methods of plastic depolymerization based on different kinds of polymers defined in the Society of the Plastics Industry (SPI) Resin Identification Coding System, and the opportunities and challenges in the future. Full article

(This article belongs to the Section Circular and Green Polymer Science)

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Polymers, Volume 13, Issue 3 (February-1 2021) – 165 articles

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