Polymers

18 pages, 6862 KiB

Open AccessArticle

Role of Maleic Anhydride-Grafted Poly(lactic acid) in Improving Shape Memory Properties of Thermoresponsive Poly(ethylene glycol) and Poly(lactic acid) Blends

by Wasana Nonkrathok, Tatiya Trongsatitkul and Nitinat Suppakarn

Polymers 2022, 14(18), 3923; https://doi.org/10.3390/polym14183923 - 19 Sep 2022

Cited by 13 | Viewed by 3491

Abstract

Generally, poly(ethylene glycol) (PEG) is added to poly(lactic acid) (PLA) to reduce brittleness and improve mechanical properties. However, shape memory properties of PEG/PLA blends suffered due to the blend’s incompatibility. To enhance shape memory abilities of the blends, 0.45% maleic anhydride-grafted poly(lactic acid) [...] Read more.

Generally, poly(ethylene glycol) (PEG) is added to poly(lactic acid) (PLA) to reduce brittleness and improve mechanical properties. However, shape memory properties of PEG/PLA blends suffered due to the blend’s incompatibility. To enhance shape memory abilities of the blends, 0.45% maleic anhydride-grafted poly(lactic acid) (PLA-g-MA) was used as a compatibilizer. Thermal and mechanical properties, morphologies, microstructures, and shape memory properties of the blends containing different PLA-g-MA contents were investigated. The compatibilized blend with 2 wt% PLA-g-MA exhibited enhanced tensile modulus, strength, and elongation at break, as well as a lower glass transition temperature and degree of crystallinity than the uncompatibilized blend. Results revealed that PLA-g-MA improved interfacial adhesion between phases and promoted chain entanglement. Shape fixity performance of the compatibilized blends were comparable to that of neat PLA. The compatibilized blend containing 2 wt% PLA-g-MA possessed the best shape fixity and recovery performance. Although a high recovery temperature was expected to enhance the recovery of the PEG/PLA blends, the compatibilized blends can be recovered to their original shape at a lower temperature than the PLA. This study illustrated the possibility of optimizing PLA properties to meet requirements necessary for biomedical applications. Full article

(This article belongs to the Special Issue Shape Memory and Functional Polymers)

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18 pages, 5087 KiB

Open AccessArticle

Polyaniline/Multi Walled Carbon Nanotubes—A Promising Photocatalyst Composite for Reactive Blue 4 Oxidation

by Ashraf H. Farha, Maha A. Tony, Shehab A. Mansour and Ahmed B. El Basaty

Polymers 2022, 14(18), 3922; https://doi.org/10.3390/polym14183922 - 19 Sep 2022

Cited by 4 | Viewed by 2037

Abstract

For the photocatalytic removal of the Reactive Blue 4 dye from an aqueous stream, new polyaniline/multi walled carbon nanotube nanocomposites (PANI-MWCNTs) were applied as a promising photocatalyst. The PANI-MWCNT nanocomposites were fabricated by aniline oxidation in the presence of MWCNTs using the typical [...] Read more.

For the photocatalytic removal of the Reactive Blue 4 dye from an aqueous stream, new polyaniline/multi walled carbon nanotube nanocomposites (PANI-MWCNTs) were applied as a promising photocatalyst. The PANI-MWCNT nanocomposites were fabricated by aniline oxidation in the presence of MWCNTs using the typical direct oxidation polymerization route. The morphology, the Fourier transform infrared (FTIR) spectra and the UV-Vis absorbance spectra of the fabricated nanocomposites were studied and the attained data confirmed the good interaction between the MWCNTs and PANI matrix. The PANI-MWCNTs nanocomposites were varied according to the wt%, the MWCNTs, which ranged from 0–10 wt% and the corresponding resultant samples are labeled as P-0, P-3, P-5, P-5, P-7 and P-10, respectively. Such composites showed the high potential for the removal of the Reactive Blue 4 dye containing pollutants from wastewater. The starting concentration of the dye pollutants was halved during the first 5 min of UV illumination. The oxidation technique of Reactive Blue 4 over the prepared nanocomposites were processed in a different way and the highest catalytic activity corresponded to P-7. The process reached the complete dye removal in low concentrations of contaminants. The kinetics of the removal followed the pseudo-second order regime which possesses high correlation coefficients with the k₂ in the range of 0.0036–0.1115 L.mg⁻¹.min⁻¹ for the Reactive Blue 4 oxidation. In this regard, the combination of the PANI and MWCNTs showed a superior novel photocatalytic activity in the oxidation of commercial textile dying wastewater, namely Reactive Blue 4. This study is the starting point for future applications on an industrial scale since the successful performances of the PANI-MWCNT on commercial dye oxidation. Full article

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

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18 pages, 7550 KiB

Open AccessArticle

Generation of One-Dimensional Fibrous Polyethylene Nanocrystals in Epoxy Thermosets

by Honggang Mei, Huaming Wang, Lei Li and Sixun Zheng

Polymers 2022, 14(18), 3921; https://doi.org/10.3390/polym14183921 - 19 Sep 2022

Cited by 3 | Viewed by 2190

Abstract

The one-dimensional (1D) polyethylene (PE) nanocrystals were generated in epoxy thermosets via crystallization-driven self-assembly. Toward this end, an ABA triblock copolymer composed of PE midblock and poly(ε-caprolactone) (PCL) endblocks was synthesized via the ring opening metathesis polymerization followed by hydrogenation approach. The nanostructured [...] Read more.

The one-dimensional (1D) polyethylene (PE) nanocrystals were generated in epoxy thermosets via crystallization-driven self-assembly. Toward this end, an ABA triblock copolymer composed of PE midblock and poly(ε-caprolactone) (PCL) endblocks was synthesized via the ring opening metathesis polymerization followed by hydrogenation approach. The nanostructured thermosets were obtained via a two-step curing approach, i.e., the samples were cured first at 80 °C and then at 150 °C. Under this condition, the one-dimensional (1D) fibrous PE microdomains with the lengths up to a couple of micrometers were created in epoxy thermosets. In contrast, only the spherical PE microdomains were generated while the thermosets were cured via a one-step curing at 150 °C. By the use of the triblock copolymer, the generation of 1D fibrous PE nanocrystals is attributable to crystallization-driven self-assembly mechanism whereas that of the spherical PE microdomains follows traditional self-assembly mechanism. Compared to the thermosets containing the spherical PE microdomains, the thermosets containing the 1D fibrous PE nanocrystals displayed quite different thermal and mechanical properties. More importantly, the nanostructured thermosets containing the 1D fibrous PE nanocrystals displayed the fracture toughness much higher than those only containing the spherical PE nanocrystals; the K_IC value was even three times as that of control epoxy. Full article

(This article belongs to the Section Smart and Functional Polymers)

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2 pages, 188 KiB

Open AccessEditorial

Advances and Challenges in Biopolymer-Based Films

by Swarup Roy and Jong-Whan Rhim

Polymers 2022, 14(18), 3920; https://doi.org/10.3390/polym14183920 - 19 Sep 2022

Cited by 9 | Viewed by 2504

Abstract

Today, biobased polymers derived from sustainable and renewable natural sources are of great interest as an alternative to control the severe damage already caused by petro-chemical-based polymers [...] Full article

(This article belongs to the Special Issue Bio-Based Polymeric Films)

28 pages, 11147 KiB

Open AccessArticle

Effects of Adding Methods of Fluorane Microcapsules and Shellac Resin Microcapsules on the Preparation and Properties of Bifunctional Waterborne Coatings for Basswood

by Lin Wang, Yan Han and Xiaoxing Yan

Polymers 2022, 14(18), 3919; https://doi.org/10.3390/polym14183919 - 19 Sep 2022

Cited by 15 | Viewed by 2002

Abstract

In this paper, urea-formaldehyde resin microcapsules with shellac resin as core material were prepared by in-situ polymerization. Morphologies of shellac resin microcapsules were characterized by optical microscope (OM) and scanning electron microscope (SEM). Both microcapsules were spherical in shape. The encapsulation property of [...] Read more.

In this paper, urea-formaldehyde resin microcapsules with shellac resin as core material were prepared by in-situ polymerization. Morphologies of shellac resin microcapsules were characterized by optical microscope (OM) and scanning electron microscope (SEM). Both microcapsules were spherical in shape. The encapsulation property of shellac resin was proved by Fourier transform infrared (FTIR). Shellac resin microcapsules and fluorane microcapsules were added to waterborne primer or topcoat at the same time to prepare waterborne coatings with thermochromic and self-healing dual functions. The effects of microcapsules on optical properties, mechanical properties, self-healing properties, anti-aging performance, and thermoreversible discolouration mechanism of coating films were studied. These results showed that the topcoat with 10.0% fluorane microcapsules and 5.0% shellac resin microcapsules had a better comprehensive performance. At this time, the colour of coating transformed yellow into colourless at 32 °C, and it had a good colour recovery. Shellac resin microcapsules endowed the coating with self-healing performance, and the self-healing rate was 35.9%. The research results provide a reference for the progression of multifunctional wood coatings. Full article

(This article belongs to the Collection Wood Composites)

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21 pages, 3022 KiB

Open AccessArticle

Potential Applications of an Exopolysaccharide Produced by Bacillus xiamenensis RT6 Isolated from an Acidic Environment

by Elisa Huang-Lin, Enrique Sánchez-León, Ricardo Amils and Concepcion Abrusci

Polymers 2022, 14(18), 3918; https://doi.org/10.3390/polym14183918 - 19 Sep 2022

Cited by 12 | Viewed by 2521

Abstract

The Bacillus xiamenensis RT6 strain was isolated and identified by morphological, biochemical and molecular tests from an extreme acidic environment, Rio Tinto (Huelva). Optimisation tests for exopolysaccharide (EPS) production in different culture media determined that the best medium was a minimal medium with [...] Read more.

The Bacillus xiamenensis RT6 strain was isolated and identified by morphological, biochemical and molecular tests from an extreme acidic environment, Rio Tinto (Huelva). Optimisation tests for exopolysaccharide (EPS) production in different culture media determined that the best medium was a minimal medium with glucose as the only carbon source. The exopolymer (EPS_t) produced by the strain was isolated and characterised using different techniques (GC-MS, HPLC/MSMS, ATR-FTIR, TGA, DSC). The molecular weight of EPS_t was estimated. The results showed that the average molecular weight of EPS_t was approximately 2.71 × 10⁴ Da and was made up of a heteropolysaccharide composed of glucose (60%), mannose (20%) and galactose (20%). The EPS_t showed antioxidant capabilities that significantly improved cell viability. Metal chelation determined that EPS_t could reduce the concentration of transition metals such as iron at the highest concentrations tested. Finally, the emulsification study showed that EPS_t was able to emulsify different natural polysaccharide oils, reaching up to an 80% efficiency (olive and sesame oil), and was a good candidate for the substitution of the most polluting emulsifiers. The EPS_t was found to be suitable for pharmaceutical and industrial applications. Full article

(This article belongs to the Special Issue Biobased and Natural Polymers)

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18 pages, 4733 KiB

Open AccessArticle

Carbon/Basalt Fibers Hybrid Composites: Hybrid Design and the Application in Automobile Engine Hood

by Yongfeng Pu, Baichuan Liu, Guilian Xue, Hongyu Liang, Fangwu Ma, Meng Yang and Guangdong Tian

Polymers 2022, 14(18), 3917; https://doi.org/10.3390/polym14183917 - 19 Sep 2022

Cited by 8 | Viewed by 2276

Abstract

The low-velocity impact properties and the optimal hybrid ratio range for improving the property of hybrid composites are studied, and the application of hybrid composites in automobile engine hoods is discussed in this paper. The low-velocity impact properties of the hybrid composite material [...] Read more.

The low-velocity impact properties and the optimal hybrid ratio range for improving the property of hybrid composites are studied, and the application of hybrid composites in automobile engine hoods is discussed in this paper. The low-velocity impact properties of the hybrid composite material are simulated under different stacking sequences and hybrid ratios by finite element simulation, and the accuracy of the finite element model (FEM) is verified through experiments. Increasing the proportion of carbon fiber (CF) in the hybrid layer and placing the basalt fiber (BF) on the compression side can improve the energy absorption capacity under low-velocity impact loads. CF/BF hybrid composite hoods are optimized based on the steel hood and the low-velocity impact performance of the hybrid composite. The BCCC layer absorbs the most energy under low-velocity impact loads. Compared with CFRP, the energy absorbed under 10 J and 20 J impact energy is increased by 26.1% and 14.2%, respectively. Through the low-velocity impact properties of hybrid composites, we found that placing BF on the side of the load and keep the ratio below 50%, while increasing the proportion of CF in the hybrid laminate can significantly improve the property of the hybrid laminate. The results show that the stiffness and modal properties of the hybrid composite can meet the design index requirements, and the pedestrian protection capability of the hood will also increase with the increase in the proportion of BF. Full article

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

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15 pages, 3627 KiB

Open AccessArticle

Alkaline Treatment Variables to Characterize Poly(Vinyl Alcohol)/Poly(Vinyl Butyral/Vinyl Alcohol) Blend Films

by Seong Baek Yang, Mohammad Rezaul Karim, Jungeon Lee, Jeong Hyun Yeum and Sabina Yeasmin

Polymers 2022, 14(18), 3916; https://doi.org/10.3390/polym14183916 - 19 Sep 2022

Cited by 9 | Viewed by 2491

Abstract

Novel poly(vinyl alcohol) (PVA)/poly(vinyl butyral–vinyl alcohol) (P(VB-VA)) films with improved hydrophobicity were prepared from poly(vinyl acetate) (PVAc)/poly(vinyl butyral) (PVB) blend films with various mass ratios by saponification in a heterogeneous medium. The successful conversion of PVAc to PVA and PVAc/PVB to PVA/P(VB-VA) films [...] Read more.

Novel poly(vinyl alcohol) (PVA)/poly(vinyl butyral–vinyl alcohol) (P(VB-VA)) films with improved hydrophobicity were prepared from poly(vinyl acetate) (PVAc)/poly(vinyl butyral) (PVB) blend films with various mass ratios by saponification in a heterogeneous medium. The successful conversion of PVAc to PVA and PVAc/PVB to PVA/P(VB-VA) films was confirmed by Fourier transform infrared spectrometry, X-ray diffraction, and proton nuclear magnetic resonance analysis. This study also shows that the degree of saponification (DS) depends on the saponification time. The maximum DS of 99.99% was obtained at 96 h of saponification for all films, and the presence of PVB did not affect the DS at saponification times of 48–96 h. The effects of the PVAc/PVB blend ratio before and after saponification were determined by contact angle measurement, and the hydrophobicity was found to increase in both cases with increasing PVB content. Additionally, all the films exhibited improved mechanical properties after saponification, and the treated films possessed an unusual porous and uneven surface, in contrast with the untreated films. The prepared films with improved hydrophobicity can be used for various applications, such as biomaterials, filters, and medical devices. Full article

(This article belongs to the Special Issue Surfaces and Interfaces of Polymer Composites)

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17 pages, 4012 KiB

Open AccessArticle

Composite Coatings of Chitosan and Silver Nanoparticles Obtained by Galvanic Deposition for Orthopedic Implants

by C. Zanca, S. Carbone, B. Patella, F. Lopresti, G. Aiello, V. Brucato, F. Carfì Pavia, V. La Carrubba and R. Inguanta

Polymers 2022, 14(18), 3915; https://doi.org/10.3390/polym14183915 - 19 Sep 2022

Cited by 8 | Viewed by 3057

Abstract

In this work, composite coatings of chitosan and silver nanoparticles were presented as an antibacterial coating for orthopedic implants. Coatings were deposited on AISI 304L using the galvanic deposition method. In galvanic deposition, the difference of the electrochemical redox potential between two metals [...] Read more.

In this work, composite coatings of chitosan and silver nanoparticles were presented as an antibacterial coating for orthopedic implants. Coatings were deposited on AISI 304L using the galvanic deposition method. In galvanic deposition, the difference of the electrochemical redox potential between two metals (the substrate and a sacrificial anode) has the pivotal role in the process. In the coupling of these two metals a spontaneous redox reaction occurs and thus no external power supply is necessary. Using this process, a uniform deposition on the exposed area and a good adherence of the composite coating on the metallic substrate were achieved. Physical-chemical characterizations were carried out to evaluate morphology, chemical composition, and the presence of silver nanoparticles. These characterizations have shown the deposition of coatings with homogenous and porous surface structures with silver nanoparticles incorporated and distributed into the polymeric matrix. Corrosion tests were also carried out in a simulated body fluid at 37 °C in order to simulate the same physiological conditions. Corrosion potential and corrosion current density were obtained from the polarization curves by Tafel extrapolation. The results show an improvement in protection against corrosion phenomena compared to bare AISI 304L. Furthermore, the ability of the coating to release the Ag⁺ was evaluated in the simulated body fluid at 37 °C and it was found that the release mechanism switches from anomalous to diffusion controlled after 3 h. Full article

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

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14 pages, 3862 KiB

Open AccessArticle

Compressive and Flexural Strengths of Mortars Containing ABS and WEEE Based Plastic Aggregates

by Youssef El Bitouri and Didier Perrin

Polymers 2022, 14(18), 3914; https://doi.org/10.3390/polym14183914 - 19 Sep 2022

Cited by 9 | Viewed by 2296

Abstract

The incorporation of plastic aggregates as a partial replacement of natural aggregates in cementitious materials is interesting in several ways. From a mechanical point of view, the partial substitution of sand with plastic aggregates could improve some properties (e.g., ductility, thermal insulation). This [...] Read more.

The incorporation of plastic aggregates as a partial replacement of natural aggregates in cementitious materials is interesting in several ways. From a mechanical point of view, the partial substitution of sand with plastic aggregates could improve some properties (e.g., ductility, thermal insulation). This paper deals with the mechanical strength of mortars containing plastic aggregates as a partial replacement of sand. Part of the volume of sand in cement mortars is substituted with plastic aggregates which originate from WEEE (Waste from Electrical and Electronic Equipment) and consist of a mix of ABS (acrylonitrile-butadiene styrene), HIPS (high impact polystyrene) and PP (Polypropylene), or of monomaterial ABS from WEEE sorting. Three rates of replacement (by volume of sand) were tested: 10%, 15% and 30%. Mechanical tests were performed according to European standard EN196-1. The results show that compressive and flexural strength decrease with rate of replacement, but remain satisfactory for structural purposes. In addition, the density of mortar is reduced with the incorporation of plastic aggregates. The decrease of mechanical strength is mainly due to the weak bond between cement paste and plastic aggregates leading to the increase of porosity. Furthermore, it appears that mortars containing plastic aggregates could present a ductile rupture. Full article

(This article belongs to the Special Issue Recycled Polymers: Eco-Design, Structure/Property Relationships and Compatibility)

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20 pages, 3764 KiB

Open AccessArticle

Biomimetic Synthesis of PANI/Graphitic Oxidized Carbon Nitride for Supercapacitor Applications

by Manuel Eduardo Martínez-Cartagena, Juan Bernal-Martínez, Arnulfo Banda-Villanueva, Javier Enríquez-Medrano, Víctor D. Lechuga-Islas, Ilse Magaña, Teresa Córdova, Diana Morales-Acosta, José Luis Olivares-Romero and Ramón Díaz-de-León

Polymers 2022, 14(18), 3913; https://doi.org/10.3390/polym14183913 - 19 Sep 2022

Cited by 9 | Viewed by 2173

Abstract

Polyaniline (PANI) composites have gained momentum as supercapacitive materials due to their high energy density and power density. However, some drawbacks in their performance remain, such as the low stability after hundreds of charge-discharge cycles and limitations in the synthesis scalability. Herein, we [...] Read more.

Polyaniline (PANI) composites have gained momentum as supercapacitive materials due to their high energy density and power density. However, some drawbacks in their performance remain, such as the low stability after hundreds of charge-discharge cycles and limitations in the synthesis scalability. Herein, we report for the first time PANI-Graphitic oxidized carbon nitride composites as potential supercapacitor material. The biomimetic polymerization of aniline assisted by hematin, supported by phosphorous and oxygen-modified carbon nitrides (g-POCN and g-OCN, respectively), achieved up to 89% yield. The obtained PAI/g-POCN and PANI/g-OCN show enhanced electrochemical properties, such as conductivity of up to 0.0375 S/cm, specific capacitances (C_s) of up to 294 F/g (at high current densities, 5 A/g) and a stable operation after 500 charge-discharge cycles (at 3 A/g). In contrast, the biomimetic synthesis of Free PANI, assisted by stabilized hematin in cosolvents, exhibited lower performance properties (65%). Due to their structural differences, the electrochemical properties of Free PANI (conductivity of 0.0045 S/cm and C_s of up to 82 F/g at 5 A/g) were lower than those of nanostructured PANI/g-POCN and g-OCN supports, which provide stability and improve the properties of biomimetically synthesized PANI. This work reveals the biomimetic synthesis of PANI, assisted by hematin supported by modified carbon nitrides, as a promising strategy to produce nanostructured supercapacitors with high performance. Full article

(This article belongs to the Special Issue Polymer Based Electronic Devices and Sensors)

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11 pages, 4276 KiB

Open AccessArticle

Corona−Poled Porous Electrospun Films of Gram−Scale Y−Doped ZnO and PVDF Composites for Piezoelectric Nanogenerators

by Juan Yi, Yiheng Song, Shixian Zhang, Zhilong Cao, Chenjian Li and Chuanxi Xiong

Polymers 2022, 14(18), 3912; https://doi.org/10.3390/polym14183912 - 19 Sep 2022

Cited by 11 | Viewed by 2597

Abstract

For digging out eco−friendly and well−performed energy harvesters, piezoelectric nanogenerators are preferred owing to their effortless assembly. Corona−poling promotes output performance of either aligned or porous PVDF electrospun films and higher piezoelectric output was achieved by corona−poled porous PVDF electrospun films due to [...] Read more.

For digging out eco−friendly and well−performed energy harvesters, piezoelectric nanogenerators are preferred owing to their effortless assembly. Corona−poling promotes output performance of either aligned or porous PVDF electrospun films and higher piezoelectric output was achieved by corona−poled porous PVDF electrospun films due to more poled electret dipoles in pores. Increasing the duration of electrospinning rendered more electret dipoles in PVDF porous electrospun films, resulting in higher piezoelectric output. Moreover, corona−poled PVDF/Y−ZnO porous electrospun films performed better than corona−poled PVDF/ZnO porous electrospun films because of the larger polar crystal face of Y−ZnO. Flexible piezoelectric polymer PVDF and high−piezoelectric Y−ZnO complement each other in electrospun films. With 15 wt% of Y−ZnO, corona−poled PVDF/Y−ZnO porous electrospun films generated maximum power density of 3.6 μW/cm², which is 18 times that of PVDF/BiCl₃ electrospun films. Full article

(This article belongs to the Special Issue Electrostatic Spinning Micro and Nano Fibers)

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11 pages, 3165 KiB

Open AccessArticle

Kinetics of Pectin Biopolymer Facial Erosion Characterized by Fluorescent Tracer Microfluidics

by Matthew W. Liao, Betty S. Liu, Joseph Sutlive, Willi L. Wagner, Hassan A. Khalil, Zi Chen, Maximilian Ackermann and Steven J. Mentzer

Polymers 2022, 14(18), 3911; https://doi.org/10.3390/polym14183911 - 19 Sep 2022

Cited by 2 | Viewed by 1668

Abstract

Pectin is a plant-derived heteropolysaccharide that has been implicated in drug development, tissue engineering, and visceral organ repair. Pectin demonstrates remarkable biostability in a variety of physiologic environments but is biodegradable in water. To understand the dynamics of pectin biodegradation in basic environments, [...] Read more.

Pectin is a plant-derived heteropolysaccharide that has been implicated in drug development, tissue engineering, and visceral organ repair. Pectin demonstrates remarkable biostability in a variety of physiologic environments but is biodegradable in water. To understand the dynamics of pectin biodegradation in basic environments, we developed a microfluidics system that facilitated the quantitative comparison of pectin films exposed to facial erosion. Pectin biodegradation was assessed using fluorescein tracer embedded in pectin, trypan blue quenching of released fluorescence, and highly sensitive microfluorimetry. The microfluidic perfusate, delivered through 6 um-pore synthetic membrane interface, demonstrated nonlinear erosion of the pectin film; 75% of tracer was released in 28 h. The microfluidics system was used to identify potential modifiers of pectin erosion. The polyphenolic compound tannic acid, loaded into citrus pectin films, demonstrated a dose-dependent decrease in pectin erosion. Tannic acid had no detectable impact on the physical properties of citrus pectin including adhesivity and cohesion. In contrast, tannic acid weakened the burst strength and cohesion of pectins derived from soy bean and potato sources. We conclude that facial erosion may explain the biostability of citrus pectin on visceral organ surfaces as well as provide a useful method for identifying modifiers of citrus pectin biodegradation. Full article

(This article belongs to the Special Issue Analysis and Characterization of Renewable Polymers)

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11 pages, 1161 KiB

Open AccessArticle

Impact of Traces of Hydrogen Sulfide on the Efficiency of Ziegler–Natta Catalyst on the Final Properties of Polypropylene

by Joaquín Hernández-Fernández, Heidi Cano and Miguel Aldas

Polymers 2022, 14(18), 3910; https://doi.org/10.3390/polym14183910 - 19 Sep 2022

Cited by 24 | Viewed by 3161

Abstract

Sulfur compounds are removed from propylene through purification processes. However, these processes are not 100% effective, so low concentrations of compounds such as H₂S may be present in polymer-grade propylene. This article studies the effects of H₂S content on [...] Read more.

Sulfur compounds are removed from propylene through purification processes. However, these processes are not 100% effective, so low concentrations of compounds such as H₂S may be present in polymer-grade propylene. This article studies the effects of H₂S content on polypropylene polymerization through the controlled dosage of this compound with concentrations between 0.07 and 5 ppm and its monitoring during the process to determine possible reaction mechanisms and evaluate variations in properties of the material by TGA, FTIR, MFI, and XDR analysis. It was found that the fluidity index increases directly proportional to the concentration of H₂S. In addition, the thermo-oxidative degradation is explained by means of the proposed reaction mechanisms of the active center of the Ziegler–Natta catalyst with the H₂S molecule and the formation of substances with functional groups such as alcohol, ketones, aldehydes, CO, and CO₂ by the oxidation of radical complexes. This study shows for the first time a reaction mechanism between the active center formed for polymerization and H₂S, in addition to showing how trace impurities in the raw materials can affect the process, highlighting the importance of optimizing the processes of removal and purification of polymer-grade materials. Full article

(This article belongs to the Special Issue Polymers and Nanotechnology for Industry 4.0)

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13 pages, 3059 KiB

Open AccessArticle

Bioabsorbable Carboxymethyl Starch–Calcium Ionic Assembly Powder as a Hemostatic Agent

by Young-Gwang Ko, Byeong Nam Kim, Eun Jin Kim, Ho Yun Chung, Seong Yong Park, Young-Jin Kim and Oh Hyeong Kwon

Polymers 2022, 14(18), 3909; https://doi.org/10.3390/polym14183909 - 19 Sep 2022

Cited by 12 | Viewed by 3800

Abstract

In contrast to hemostatic fabrics, foams, and gels, hemostatic spray powders may be conveniently applied on narrow and complex bleeding sites. However, powdered hemostatic agents are easily desorbed from the bleeding surface because of blood flow, which seriously decreases their hemostatic function. In [...] Read more.

In contrast to hemostatic fabrics, foams, and gels, hemostatic spray powders may be conveniently applied on narrow and complex bleeding sites. However, powdered hemostatic agents are easily desorbed from the bleeding surface because of blood flow, which seriously decreases their hemostatic function. In this study, the hemostatic performance of a bioabsorbable powder with decreased desorption was investigated. The proposed hemostatic powder (OOZFIX^TM) is an ionic assembly of carboxymethyl starch and calcium. The microstructure and chemical properties of the hemostatic powder were analyzed. The hemostatic performance (blood absorption, blood absorption rate, and coagulation time), thromboelastography (TEG), rheology, adhesion force, and C3a complement activation of the OOZFIX^TM were evaluated and compared with those of the carboxymethyl starch-based commercial hemostatic powder (Arista^TM AH). The in vivo rat hepatic hemorrhage model for hemostasis time and bioabsorption of the OOZFIX^TM showed quick biodegradation (<3 weeks) and a significantly improved hemostasis rate (78 ± 17 s) compared to that of Arista^TM AH (182 ± 11) because of the reduced desorption. The bioabsorbable hemostatic powder OOZFIX^TM is expected to be a promising hemostatic agent for precise medical surgical treatments. Full article

(This article belongs to the Special Issue Polymer Surface and Interfacial Control for Biomedical Applications)

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10 pages, 3558 KiB

Open AccessArticle

Electroactive Oxidized Alginate/Gelatin/MXene (Ti₃C₂T_x) Composite Hydrogel with Improved Biocompatibility and Self-Healing Property

by Hui Zhu, Weitao Dai, Liming Wang, Cong Yao, Chenxi Wang, Bingsong Gu, Dichen Li and Jiankang He

Polymers 2022, 14(18), 3908; https://doi.org/10.3390/polym14183908 - 19 Sep 2022

Cited by 24 | Viewed by 4012 | Correction

Abstract

Conductive hydrogels (CHs) have shown promising potential applied as wearable or epidermal sensors owing to their mechanical adaptability and similarity to natural tissues. However, it remains a great challenge to develop an integrated hydrogel combining outstanding conductive, self-healing and biocompatible performances with simple [...] Read more.

Conductive hydrogels (CHs) have shown promising potential applied as wearable or epidermal sensors owing to their mechanical adaptability and similarity to natural tissues. However, it remains a great challenge to develop an integrated hydrogel combining outstanding conductive, self-healing and biocompatible performances with simple approaches. In this work, we propose a “one-pot” strategy to synthesize multifunctional CHs by incorporating two-dimensional (2D) transition metal carbides/nitrides (MXenes) multi-layer nano-flakes as nanofillers into oxidized alginate and gelatin hydrogels to form the composite CHs with various MXene contents. The presence of MXene with abundant surface groups and outstanding conductivity could improve the mechanical property and electroactivity of the composite hydrogels compared to pure oxidized alginate dialdehyde-gelatin (ADA-GEL). MXene-ADA-GELs kept good self-healing properties due to the dynamic imine linkage of the ADA-GEL network and have a promoting effect on mouse fibroblast (NH3T3s) attachment and spreading, which could be a result of the integration of MXenes with stimulating conductivity and hydrophily surface. This study suggests that the electroactive MXene-ADA-GELs can serve as an appealing candidate for skin wound healing and flexible bio-electronics. Full article

(This article belongs to the Special Issue Current Trends in Polymeric Hydrogels for Tissue Engineering)

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15 pages, 4895 KiB

Open AccessArticle

Effect of Bacterial Cellulose Plasma Treatment on the Biological Activity of Ag Nanoparticles Deposited Using Magnetron Deposition

by Alexander Vasil’kov, Alexander Budnikov, Tatiana Gromovykh, Marina Pigaleva, Vera Sadykova, Natalia Arkharova and Alexander Naumkin

Polymers 2022, 14(18), 3907; https://doi.org/10.3390/polym14183907 - 19 Sep 2022

Cited by 7 | Viewed by 2669

Abstract

New functional medical materials with antibacterial activity based on biocompatible bacterial cellulose (BC) and Ag nanoparticles (Ag NPs) were obtained. Bacterial cellulose films were prepared by stationary liquid-phase cultivation of the Gluconacetobacter hansenii strain GH-1/2008 in Hestrin–Schramm medium with glucose as a carbon [...] Read more.

New functional medical materials with antibacterial activity based on biocompatible bacterial cellulose (BC) and Ag nanoparticles (Ag NPs) were obtained. Bacterial cellulose films were prepared by stationary liquid-phase cultivation of the Gluconacetobacter hansenii strain GH-1/2008 in Hestrin–Schramm medium with glucose as a carbon source. To functionalize the surface and immobilize Ag NPs deposited by magnetron sputtering, BC films were treated with low-pressure oxygen–nitrogen plasma. The composition and structure of the nanomaterials were studied using transmission (TEM) and scanning (SEM) electron microscopy and X-ray photoelectron spectroscopy (XPS). Using electron microscopy, it was shown that on the surface of the fibrils that make up the network of bacterial cellulose, Ag particles are stabilized in the form of aggregates 5–35 nm in size. The XPS C 1s spectra show that after the deposition of Ag NPs, the relative intensities of the C-OH and O-C-O bonds are significantly reduced. This may indicate the destruction of BC oxypyran rings and the oxidation of alcohol groups. In the Ag 3d_5/2 spectrum, two states at 368.4 and 369.7 eV with relative intensities of 0.86 and 0.14 are distinguished, which are assigned to Ag⁰ state and Ag acetate, respectively. Nanocomposites based on plasma-treated BC and Ag nanoparticles deposited by magnetron sputtering (BCP-Ag) exhibited antimicrobial activity against Aspergillus niger, S. aureus and Bacillus subtilis. Full article

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

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23 pages, 4923 KiB

Open AccessArticle

Application of Ensemble Machine Learning Methods to Estimate the Compressive Strength of Fiber-Reinforced Nano-Silica Modified Concrete

by Madiha Anjum, Kaffayatullah Khan, Waqas Ahmad, Ayaz Ahmad, Muhammad Nasir Amin and Afnan Nafees

Polymers 2022, 14(18), 3906; https://doi.org/10.3390/polym14183906 - 19 Sep 2022

Cited by 15 | Viewed by 2430

Abstract

In this study, compressive strength (CS) of fiber-reinforced nano-silica concrete (FRNSC) was anticipated using ensemble machine learning (ML) approaches. Four types of ensemble ML methods were employed, including gradient boosting, random forest, bagging regressor, and AdaBoost regressor, to achieve the study’s aims. The [...] Read more.

In this study, compressive strength (CS) of fiber-reinforced nano-silica concrete (FRNSC) was anticipated using ensemble machine learning (ML) approaches. Four types of ensemble ML methods were employed, including gradient boosting, random forest, bagging regressor, and AdaBoost regressor, to achieve the study’s aims. The validity of employed models was tested and compared using the statistical tests, coefficient of determination (R²), and k-fold method. Moreover, a Shapley Additive Explanations (SHAP) analysis was used to observe the interaction and effect of input parameters on the CS of FRNSC. Six input features, including fiber volume, coarse aggregate to fine aggregate ratio, water to binder ratio, nano-silica, superplasticizer to binder ratio, and specimen age, were used for modeling. In predicting the CS of FRNSC, it was observed that gradient boosting was the model of lower accuracy and the AdaBoost regressor had the highest precision in forecasting the CS of FRNSC. However, the performance of random forest and the bagging regressor was also comparable to that of the AdaBoost regressor model. The R² for the gradient boosting, random forest, bagging regressor, and AdaBoost regressor models were 0.82, 0.91, 0.91, and 0.92, respectively. Also, the error values of the models further validated the exactness of the ML methods. The average error values for the gradient boosting, random forest, bagging regressor, and AdaBoost regressor models were 5.92, 4.38, 4.24, and 3.73 MPa, respectively. SHAP study discovered that the coarse aggregate to fine aggregate ratio shows a greater negative correlation with FRNSC’s CS. However, specimen age affects FRNSC CS positively. Nano-silica, fiber volume, and the ratio of superplasticizer to binder have both positive and deleterious effects on the CS of FRNSC. Employing these methods will promote the building sector by presenting fast and economical methods for calculating material properties and the impact of raw ingredients. Full article

(This article belongs to the Special Issue Fiber-Reinforced Composite)

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11 pages, 3311 KiB

Open AccessArticle

Effect of Polycarboxylic Grinding Aid on Cement Chemistry and Properties

by Jianyu Yang, Guanglin Li, Weijun Yang and Junfeng Guan

Polymers 2022, 14(18), 3905; https://doi.org/10.3390/polym14183905 - 19 Sep 2022

Cited by 3 | Viewed by 2823

Abstract

In view of the disadvantages of polycarboxylic acid grinding aids, such as poor reinforcement effect and cumbersome synthesis process, a new type of polycarboxylic acid grinding aid was prepared to meet the requirements of multifunctional admixture for cement concrete. The polycarboxylate grinding aid [...] Read more.

In view of the disadvantages of polycarboxylic acid grinding aids, such as poor reinforcement effect and cumbersome synthesis process, a new type of polycarboxylic acid grinding aid was prepared to meet the requirements of multifunctional admixture for cement concrete. The polycarboxylate grinding aid (PC) was prepared using acrylic acid, sodium allyl sulfonate, and isoprenol polyoxyethylene ether (TPEG) as raw materials, and ammonium persulfate as initiator in the nitrogen atmosphere. The effect of PC and its compound with triethanolamine (TEA) and triisopropanolamine (TIPA) on cement particle size and strength, and hydration process and structures of hydrated products were investigated. Moreover, the grinding mechanism of grinding aids was also proposed. The results indicate that the PC has good performance in both grinding and high-efficiency water-reducing. The average particle diameter of cement was reduced by 3.65 μm when 0.03 wt% of PC was added as grinding aid. Moreover, a high initial fluidity of the cement paste, 290 mm, could be reached when 0.08 wt% of PC was added. The fluidity loss of cement paste after 30 min and 60 min was 265 mm and 260 mm, respectively. After PC compounding with TEA and TIPA, 4.07 μm and 4.7 μm of the average particle size of the cement can be reduced, respectively. Based on the investigations on the hydration rate of cement hydration, the phases, and the microstructures of the hardened slurry, it could be concluded that grinding aids can change the hydration process of cement and improve the morphologies and structures of hydration products without influence on the type of hydrated products. Note that the compounded grinding aids, such as PC with TEA or PC with TIPA, can more effectively enhance the early and late strength of cement. This shows excellent comprehensive performance. In this study, a new type of polycarboxylic acid grinding aid was prepared to meet the requirements of the versatility of cement concrete additives, and to simplify the synthesis process, reduce production costs, improve the grinding effect, and improve the performance of cement concrete. Full article

(This article belongs to the Special Issue Fiber-Reinforced Composite)

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14 pages, 3036 KiB

Open AccessArticle

Synthesis and Characterization of a Self-Polycondensation Diazaphthalanone Monomer and Its Polymers from Polycondensation Reactions

by Xin Liu, Xiaozhou Zhang, Jiawei Jiang, Hongge Jia, Xigao Jian and Jinyan Wang

Polymers 2022, 14(18), 3904; https://doi.org/10.3390/polym14183904 - 19 Sep 2022

Cited by 2 | Viewed by 2405

Abstract

Polyether ketone (PEK) plastics are linear thermoplastic polymers connected by at least one ether bond and at least one ketone bond on the aryl group. The reason for their excellent heat resistance, rigidity, and mechanical strength is that their main molecular chain contains [...] Read more.

Polyether ketone (PEK) plastics are linear thermoplastic polymers connected by at least one ether bond and at least one ketone bond on the aryl group. The reason for their excellent heat resistance, rigidity, and mechanical strength is that their main molecular chain contains plenty of aromatic rings and polar carbonyl groups, and their molecular chain presents a large rigidity and strong intermolecular force. In addition, the main chain contains a considerable number of ether bonds, resulting in a certain toughness. However, polyether ketone materials have the disadvantage of poor solubility because of their excellent rigidity. To improve the solubility of polyether ketone, the preparation method of a novel nitrogenous heterocyclic polyaromatic ether monomer, 2-(4-chlorophenyl)-2,3-dihydrophthalazine-1,4-dione (CDD), was proposed, and its activity of polymerization was studied. The average molecular weight of the poly(aryl ether ketone) containing a nitrogenous heterocyclic polyaromatic ether group obtained by self-polycondensation of CDD was 4.181 × 10³ kg/mol, and the yield was 90.5%. In order to further explore the activity of monomers, novel copolymerized poly(aryl ether ketone) (PBCD) containing a nitrogenous heterocyclic polyaromatic ether structure was prepared by ternary copolymerization with 4,4-difluorobenzophenone (DFBP) and bisphenol fluorene (BHPF) with high activity. The average molecular weight of PBCD was 72.793 × 10³ kg/mol, the molecular weight distribution was 2.344, and the yield was 88.1%. Fourier transform infrared spectroscopy (FT-IR) and ¹H NMR were used to confirm the structure of the obtained polymer. Through thermogravimetric analysis (TGA), the determined weight loss temperature of 5% under nitrogen was higher than 500 °C, indicating excellent thermal stability. Compared with the solubility of the binary copolymer containing fluorenyl poly(aryl ether ketone) (PBD), the polymer showed reasonable solubility in selective solvents such as chloroform and N,N-dimethylacetamide. Full article

(This article belongs to the Special Issue Thermal Characterization and Applications of Polymer Composites)

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13 pages, 3226 KiB

Open AccessArticle

Insignificant Difference in Biocompatibility of Regenerated Silk Fibroin Prepared with Ternary Reagent Compared with Regenerated Silk Fibroin Prepared with Lithium Bromide

by Guotao Cheng, Xin Wang, Mengqiu Wu, Siyuan Wu, Lan Cheng, Xiaoning Zhang and Fangyin Dai

Polymers 2022, 14(18), 3903; https://doi.org/10.3390/polym14183903 - 18 Sep 2022

Cited by 6 | Viewed by 3694

Abstract

Bombyx mori silk fibroin (SF) is widely used in the field of biomaterials due to its excellent biocompatibility and mechanical properties. However, SF cannot be used directly in many applications and needs to be dissolved first. Lithium bromide (LiBr) is a traditional solvent [...] Read more.

Bombyx mori silk fibroin (SF) is widely used in the field of biomaterials due to its excellent biocompatibility and mechanical properties. However, SF cannot be used directly in many applications and needs to be dissolved first. Lithium bromide (LiBr) is a traditional solvent which is usually used to dissolve SF. However, LiBr has several limitations, e.g., it is expensive, it is toxic to organisms, and it is environmentally unfriendly. Herein, we investigate the possibility of developing a ternary reagent system that is inexpensive, non-toxic to organisms, and environmentally friendly as an alternative for silk fibroin solubilization. The results confirm that regenerated silk fibroin (RSF) prepared using a ternary reagent has the same morphology and amino acid composition as that prepared using LiBr, but the RSF prepared using a ternary reagent still had a small amount of calcium residue even after long-term dialysis. Further research found that the residual calcium does not cause significant differences in the structure and biological performance of the RSF, such as its cytotoxicity, blood compatibility, and antibacterial properties. Therefore, we believe that ternary reagents are an ideal alternative solvent for dissolving SF. Full article

(This article belongs to the Special Issue Advances in Fiber Materials and Manufacturing)

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15 pages, 2520 KiB

Open AccessArticle

New Self-Repairing System for Brittle Matrix Composites Using Corrosion-Induced Intelligent Fiber

by Yuyan Sun, Dongkai Wang, Zuquan Jin, Jianwei Sun and Ziguo Wang

Polymers 2022, 14(18), 3902; https://doi.org/10.3390/polym14183902 - 18 Sep 2022

Cited by 1 | Viewed by 1994

Abstract

Brittle matrix composites such as concrete are susceptible to damage in the form of cracks. Most of the current self-repair and self-healing techniques have repair limits on crack widths or high costs of an external stimulator, or have an unfavorable effect on the [...] Read more.

Brittle matrix composites such as concrete are susceptible to damage in the form of cracks. Most of the current self-repair and self-healing techniques have repair limits on crack widths or high costs of an external stimulator, or have an unfavorable effect on the composite’s strength. This paper proposes a new concept of corrosion-induced intelligent fiber (CIF) and a new self-repairing system that uses the CIFs to close cracks in brittle matrix composites within a corrosive environment without external help, and without compromising the strength. The CIF comprises an inner core fiber and an outer corrodible coating that are in equilibrium, with the core fiber in tension and the corrodible coating in compression. The preparation steps and shape recovery mechanism of the CIF and the self-repair mechanism of the CIF composites are explained. Based on these concepts, this paper also describes several mechanical models built to predict the magnitude of pre-stress stored in the core fiber, and the maximum pre-stress released to the matrix composites, and the minimum length of the reliable anchor ends of CIF. The sample calculation results show that the recovery strain was 0.5% for the CIF with the steel core fiber and 12.7% for the CIF with the nylon core fiber; the maximum crack closing force provided by the CIF to concrete can be increased by increasing the amount of the CIFs in concrete and the initial tensile stress of the core fiber. This paper provides some suggestions for enhancing the self-repair capability of brittle composites in complex working environments. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites for Building and Bridge Applications)

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15 pages, 3249 KiB

Open AccessArticle

Two-Stage Evolution of Gamma-Phase Spherulites of Poly (Vinylidene Fluoride) Induced by Alkylammonium Salt

by Tatsuaki Miyashita and Hiromu Saito

Polymers 2022, 14(18), 3901; https://doi.org/10.3390/polym14183901 - 18 Sep 2022

Cited by 2 | Viewed by 1952

Abstract

We investigated the evolution of the γ-phase spherulites of poly(vinylidene fluoride) (PVDF) added to 1 wt% of tetrabutylammonium hydrogen sulfate during the isothermal crystallization at 165 °C through polarized optical microscopy and light scattering measurements. Optically isotropic domains grew, and then optical anisotropy [...] Read more.

We investigated the evolution of the γ-phase spherulites of poly(vinylidene fluoride) (PVDF) added to 1 wt% of tetrabutylammonium hydrogen sulfate during the isothermal crystallization at 165 °C through polarized optical microscopy and light scattering measurements. Optically isotropic domains grew, and then optical anisotropy started to increase in the domain to yield spherulite. Double peaks were seen in the time variation of the Vv light scattering intensity caused by the density fluctuation and optical anisotropy, and the Hv light scattering intensity caused by the optical anisotropy started to increase during the second increase in the Vv light scattering intensity. These results suggest the two-stage evolution of the γ-phase spherulites, i.e., the disordered domain grows in the first stage and ordering in the spherulite increases due to the increase in the fraction of the lamellar stacks in the spherulite without a change in the spherulite size in the second stage. Owing to the characteristic crystallization behavior, the birefringence in the γ-phase spherulites of the PVDF/TBAHS was much smaller than that in the α-phase spherulites of the neat PVDF. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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12 pages, 2829 KiB

Open AccessArticle

Design and Performance Evaluation of Polymer Matrix Composite Helical Springs

by Ling Chen, Liwei Wu, Hongjun Fu and Youhong Tang

Polymers 2022, 14(18), 3900; https://doi.org/10.3390/polym14183900 - 18 Sep 2022

Cited by 4 | Viewed by 1986

Abstract

Helical springs are indispensable mechanical parts widely used in industry. Lightweight is one of the development trends of helical springs. In this study, three kinds of lightweight polymer matrix composite helical springs (PMCHSs) with unidirectional, multistrand, and wrapped textile structural reinforcement (PMCHS-U, PMCHS-M, [...] Read more.

Helical springs are indispensable mechanical parts widely used in industry. Lightweight is one of the development trends of helical springs. In this study, three kinds of lightweight polymer matrix composite helical springs (PMCHSs) with unidirectional, multistrand, and wrapped textile structural reinforcement (PMCHS-U, PMCHS-M, and PMCHS-W) were designed, manufactured, and evaluated. The performance of these PMCHSs and the relationship between their performance and their corresponding polymer matrix composite spring wire rods (PMCRs) were studied through the torsion test of the PMCRs and the compression and resilience tests of the PMCHSs. The results showed that the performance of the PMCHSs could be effectively improved by using the wrapped structure as the reinforcement. The compression capacity of PMCHS-W was 72.6% and 137.5% higher than that of PMCHS-M and PMCHS-U, respectively. The resilience performance of the PMCHSs decreased with the increase in the spring constant. The performances of the PMCHSs and a steel spring were compared. The results showed that the spring constant of the steel spring could be achieved when the masses of PMCHS-U, PMCHS-M, and PMCHS-W were only 75%, 63%, and 49% of the mass of the steel spring, respectively. This research is of great significance to the improvement in lightweight spring performance. Full article

(This article belongs to the Special Issue Advances in Polymer Matrix Composites: Synthesis, Characterization and Simulation)

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15 pages, 1929 KiB

Open AccessArticle

Properties and Hydrolysis Behavior of Celluloses of Different Origin

by Ekaterina I. Kashcheyeva, Yulia A. Gismatulina, Galina F. Mironova, Evgenia K. Gladysheva, Vera V. Budaeva, Ekaterina A. Skiba, Vladimir N. Zolotuhin, Nadezhda A. Shavyrkina, Aleksey N. Kortusov and Anna A. Korchagina

Polymers 2022, 14(18), 3899; https://doi.org/10.3390/polym14183899 - 18 Sep 2022

Cited by 9 | Viewed by 2185

Abstract

The present paper is a fundamental study on the physicochemical properties and hydrolysis behavior of cellulose samples differing in origin: bacterial, synthetic, and vegetal. Bacterial cellulose was produced by Medusomyces gisevii Sa-12 in an enzymatic hydrolyzate derived from oat-hull pulp. Synthetic cellulose was [...] Read more.

The present paper is a fundamental study on the physicochemical properties and hydrolysis behavior of cellulose samples differing in origin: bacterial, synthetic, and vegetal. Bacterial cellulose was produced by Medusomyces gisevii Sa-12 in an enzymatic hydrolyzate derived from oat-hull pulp. Synthetic cellulose was obtained from an aqueous glucose solution by electropolymerization. Plant-based cellulose was isolated by treatment of Miscanthus sacchariflorus with dilute NaOH and HNO₃ solutions. We explored different properties of cellulose samples, such as chemical composition, degree of polymerization (DP), degree of crystallinity (DC), porosity, and reported infrared spectroscopy and scanning electron microscopy results. The hydrolysis behavior was most notable dependent on the origin of cellulose. For the bacterial cellulose sample (2010 DP, 90% DC, 89.4% RS yield), the major property affecting the hydrolysis behavior was its unique nanoscale reticulate structure promoting fast penetration of cellulases into the substrate structure. The study on enzymatic hydrolysis showed that the hydrolysis behavior of synthetic and Miscanthus celluloses was most influenced by the substrate properties such as DP, DC and morphological structure. The yield of reducing sugars (RS) by hydrolysis of synthetic cellulose exhibiting a 3140 DP, 80% DC, and highly depolymerization-resistant fibers was 27%. In contrast, the hydrolysis of Miscanthus-derived cellulose with a 1030 DP, 68% DC, and enzyme-accessible fibers provided the highest RS yield of 90%. The other properties examined herein (absence/presence of non-cellulosic impurities, specific surface, pore volume) had no considerable effect on the bioconversion of the cellulosic substrates. Full article

(This article belongs to the Special Issue Biopolymers from Agricultural Waste)

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15 pages, 5908 KiB

Open AccessArticle

Bone Healing in Rat Segmental Femur Defects with Graphene-PCL-Coated Borate-Based Bioactive Glass Scaffolds

by Ozgur Basal, Ozlem Ozmen and Aylin M. Deliormanlı

Polymers 2022, 14(18), 3898; https://doi.org/10.3390/polym14183898 - 18 Sep 2022

Cited by 5 | Viewed by 2208

Abstract

Bone is a continually regenerating tissue with the ability to heal after fractures, though healing significant damage requires intensive surgical treatment. In this study, borate-based 13-93B3 bioactive glass scaffolds were prepared though polymer foam replication and coated with a graphene-containing poly (ε-caprolactone) (PCL) [...] Read more.

Bone is a continually regenerating tissue with the ability to heal after fractures, though healing significant damage requires intensive surgical treatment. In this study, borate-based 13-93B3 bioactive glass scaffolds were prepared though polymer foam replication and coated with a graphene-containing poly (ε-caprolactone) (PCL) layer to support bone repair and regeneration. The effects of graphene concentration (1, 3, 5, 10 wt%) on the healing of rat segmental femur defects were investigated in vivo using male Sprague–Dawley rats. Radiographic imaging, histopathological and immuno-histochemical (bone morphogenetic protein (BMP-2), smooth muscle actin (SMA), and alkaline phosphatase (ALP) examinations were performed 4 and 8 weeks after implantation. Results showed that after 8 weeks, both cartilage and bone formation were observed in all animal groups. Bone growth was significant starting from the 1 wt% graphene-coated bioactive glass-implanted group, and the highest amount of bone formation was seen in the group containing 10 wt% graphene (p < 0.001). Additionally, the presence of graphene nanoplatelets enhanced BMP-2, SMA and ALP levels compared to bare bioactive glass scaffolds. It was concluded that pristine graphene-coated bioactive glass scaffolds improve bone formation in rat femur defects. Full article

(This article belongs to the Special Issue Biomaterials for Tissue Engineering and Regeneration)

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9 pages, 1671 KiB

Open AccessArticle

The Effects of Carbon–Silica Dual-Phase Filler on the Crosslink Structure of Natural Rubber

by Jingyi Wang and Hongbing Jia

Polymers 2022, 14(18), 3897; https://doi.org/10.3390/polym14183897 - 18 Sep 2022

Cited by 9 | Viewed by 2186

Abstract

Carbon–silica dual-phase filler (CSDPF)/natural rubber (NR) vulcanizate was prepared by mechanical blending, followed by a hot-press vulcanization. The dispersion of CSDPF in the NR matrix and the effects of CSDPF on the filler–rubber interaction and structure of the rubber network were studied. Scanning [...] Read more.

Carbon–silica dual-phase filler (CSDPF)/natural rubber (NR) vulcanizate was prepared by mechanical blending, followed by a hot-press vulcanization. The dispersion of CSDPF in the NR matrix and the effects of CSDPF on the filler–rubber interaction and structure of the rubber network were studied. Scanning electron microscope results showed that CSDPF dispersed uniformly; however, there were some aggregates of CSDPF when loading too many fillers. With an increase in CSDPF, the interaction between CSDPF and NR chains increases, which was detected by bound rubber in the CSDPF/NR compound. The spectra of solid-state nuclear magnetic resonance revealed that CSDPF could promote the formation of poly-sulfidic crosslink in the rubber vulcanization network. Further, the molecular chain movement ability of vulcanizates decreases according to the spin–spin relaxation of ¹H nuclei in CSDPF/NR compounds. The crosslink density of vulcanizate increases, while the chemical crosslink and physical crosslink in the vulcanization network also increase according to the tube model. Full article

(This article belongs to the Special Issue Carbonaceous Fillers-Reinforced Polymer Matrix Composite for Multi-Functional Applications II)

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23 pages, 7383 KiB

Open AccessArticle

Effect of Fuel Preheating on Engine Characteristics of Waste Animal Fat-Oil Biodiesel in Compression Ignition Engine

by Gokul Raghavendra Srinivasan, Ranjitha Jambulingam, Amel Gacem, Akil Ahmad, Javed Khan Bhutto, Krishna Kumar Yadav, Amine Mezni, Omar Khulaif R. Alharbi, Saiful Islam, Yongtae Ahn and Byong-Hun Jeon

Polymers 2022, 14(18), 3896; https://doi.org/10.3390/polym14183896 - 18 Sep 2022

Cited by 6 | Viewed by 2409

Abstract

The present study aims at understanding the effects of fuel preheating on engine characteristics of waste animal fat-oil (WAF-O) biodiesel in a single-cylinder CI engine, with the preheating technique proposed as an effective means for enhancing the fuel properties. To understand the effects [...] Read more.

The present study aims at understanding the effects of fuel preheating on engine characteristics of waste animal fat-oil (WAF-O) biodiesel in a single-cylinder CI engine, with the preheating technique proposed as an effective means for enhancing the fuel properties. To understand the effects of the preheated fuel, the WAF-O biodiesel was preheated at 60, 80, 100 and 120 °C and tested along with neat diesel and unheated WAF-O biodiesel. For this purpose, biodiesel was produced from different animal wastes by means of KOH-assisted ethanol-based transesterification, reporting its maximum yield as 96.37 ± 1.8%, with significant distribution of unsaturated oleic acid, saturated palmitic acid and stearic acid. Upon evaluating its fuel characteristics as per ASTM D6751 standards, a rise in preheating temperature by 1 °C reduced the density and kinematic viscosity of WAF-O biodiesel by 0.383 kg/m³ and 0.025 mm²/s, respectively, and was explained by the weakening of intermolecular forces between its fatty acid ester molecules. Preheated samples reported superior combustion characteristics by exhibiting increased in-cylinder pressure (2.24%, on average) and heat release rates in addition to their shortened ignition delay (1–4 °CA). Furthermore, preheating of WAF-O biodiesel reduced its specific fuel consumption and increased its brake thermal efficiency by 7.86% (on average) and 9.23% (on average), respectively. However, higher preheating temperatures (>120 °C) resulted in increased fuel consumption owing to its varied flow characteristics. In addition to the changes in combustion characteristics, preheating WAF-O bio-diesel also resulted in reduced carbon monoxide, nitrous oxide and hydrocarbon emission by 13.88%, 7.21% and 26.94%, respectively, and increased carbon dioxide emission by 7.58%. Summing up, the enhancements in overall engine characteristics of preheated samples were accounted for by their improvised fuel injection characteristics due to their reduced density and viscosity, which ensured for their effective combustion. Full article

(This article belongs to the Special Issue Advanced Polymers for Energy and Environment Science)

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19 pages, 4774 KiB

Open AccessReview

Magnetic 3D-Printed Composites—Production and Applications

by Guido Ehrmann, Tomasz Blachowicz and Andrea Ehrmann

Polymers 2022, 14(18), 3895; https://doi.org/10.3390/polym14183895 - 17 Sep 2022

Cited by 17 | Viewed by 4995

Abstract

Three-dimensional printing enables building objects shaped with a large degree of freedom. Additional functionalities can be included by modifying the printing material, e.g., by embedding nanoparticles in the molten polymer feedstock, the resin, or the solution used for printing, respectively. Such composite materials [...] Read more.

Three-dimensional printing enables building objects shaped with a large degree of freedom. Additional functionalities can be included by modifying the printing material, e.g., by embedding nanoparticles in the molten polymer feedstock, the resin, or the solution used for printing, respectively. Such composite materials may be stronger or more flexible, conductive, magnetic, etc. Here, we give an overview of magnetic composites, 3D-printed by different techniques, and their potential applications. The production of the feedstock is described as well as the influence of printing parameters on the magnetic and mechanical properties of such polymer/magnetic composites. Full article

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

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13 pages, 3444 KiB

Open AccessArticle

Synthesis and Performance Evaluation of a Novel Heat and Salt-Resistant Gel Plugging Agent

by Xuejiao Li, Meilong Fu, Jie Liu, Qi Xiao, Wenhao Tang and Guike Yang

Polymers 2022, 14(18), 3894; https://doi.org/10.3390/polym14183894 - 17 Sep 2022

Cited by 4 | Viewed by 1900

Abstract

Tahe oil field is a typical fissure cave carbonate reservoir with a temperature of up to 120~140 °C and a total salinity of formation water of (20~25) × 10⁴ mg/L. In this paper, AM/AMPS was selected as the polymer, 1, 5-dihydroxy naphthol [...] Read more.

Tahe oil field is a typical fissure cave carbonate reservoir with a temperature of up to 120~140 °C and a total salinity of formation water of (20~25) × 10⁴ mg/L. In this paper, AM/AMPS was selected as the polymer, 1, 5-dihydroxy naphthol as the cross-linking agent, and polypropylene fiber as the system stabilizer to synthesize a novel gel plugging agent independently; the gel has good thermal stability at a high temperature of 130 °C and increased salinity of 20 × 10⁴ mg/L, and has a dense and relatively stable three-dimensional network structure under a scanning electron microscope. The performance evaluation of the gel plugging agent indicated that: the gel dehydration rate increased gradually with the increase in temperature and salinity, making it suitable for reservoirs with temperatures below 140 °C and formation water salinity below 250,000 mg/L; the viscosity of the gel bulk was 125.3 mPa∙s, the post-gelatinizing viscosity was 42,800 mPa∙s, and the gelatinizing time at 120 °C, 130 °C and 140 °C was 10–20 h, 8–18 h, and 7–16 h, respectively. Full article

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

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