Polymers

29 pages, 5194 KiB

Open AccessArticle

Development of Coarse-Grained Models for Poly(4-vinylphenol) and Poly(2-vinylpyridine): Polymer Chemistries with Hydrogen Bonding

by Utkarsh Kapoor, Arjita Kulshreshtha and Arthi Jayaraman

Polymers 2020, 12(11), 2764; https://doi.org/10.3390/polym12112764 - 23 Nov 2020

Cited by 5 | Viewed by 3956

Abstract

In this paper, we identify the modifications needed in a recently developed generic coarse-grained (CG) model that captured directional interactions in polymers to specifically represent two exemplary hydrogen bonding polymer chemistries—poly(4-vinylphenol) and poly(2-vinylpyridine). We use atomistically observed monomer-level structures (e.g., bond, angle and [...] Read more.

In this paper, we identify the modifications needed in a recently developed generic coarse-grained (CG) model that captured directional interactions in polymers to specifically represent two exemplary hydrogen bonding polymer chemistries—poly(4-vinylphenol) and poly(2-vinylpyridine). We use atomistically observed monomer-level structures (e.g., bond, angle and torsion distribution) and chain structures (e.g., end-to-end distance distribution and persistence length) of poly(4-vinylphenol) and poly(2-vinylpyridine) in an explicitly represented good solvent (tetrahydrofuran) to identify the appropriate modifications in the generic CG model in implicit solvent. For both chemistries, the modified CG model is developed based on atomistic simulations of a single 24-mer chain. This modified CG model is then used to simulate longer (36-mer) and shorter (18-mer and 12-mer) chain lengths and compared against the corresponding atomistic simulation results. We find that with one to two simple modifications (e.g., incorporating intra-chain attraction, torsional constraint) to the generic CG model, we are able to reproduce atomistically observed bond, angle and torsion distributions, persistence length, and end-to-end distance distribution for chain lengths ranging from 12 to 36 monomers. We also show that this modified CG model, meant to reproduce atomistic structure, does not reproduce atomistically observed chain relaxation and hydrogen bond dynamics, as expected. Simulations with the modified CG model have significantly faster chain relaxation than atomistic simulations and slower decorrelation of formed hydrogen bonds than in atomistic simulations, with no apparent dependence on chain length. Full article

(This article belongs to the Special Issue Semiflexible Polymers II)

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14 pages, 5699 KiB

Open AccessArticle

Rheological and Mechanical Properties of Silica/Nitrile Butadiene Rubber Vulcanizates with Eco-Friendly Ionic Liquid

by Munir Hussain, Sohail Yasin, Hafeezullah Memon, Zhiyun Li, Xinpeng Fan, Muhammad Adnan Akram, Wanjie Wang, Yihu Song and Qiang Zheng

Polymers 2020, 12(11), 2763; https://doi.org/10.3390/polym12112763 - 23 Nov 2020

Cited by 21 | Viewed by 3984

Abstract

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to [...] Read more.

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to formulate the nanocomposites. The impact of [EMIM]OAc on silica dispersion in a nitrile rubber (NBR) matrix was investigated by a transmission electron microscope and scanning electron microscopy. The combined use of the ionic liquid and silane in an NBR/silica system facilitates the homogeneous dispersion of the silica volume fraction (φ) from 0.041 to 0.177 and enhances crosslinking density of the matrix up to three-fold in comparison with neat NBR, and also it is beneficial for solving the risks of alcohol emission and ignition during the rubber manufacturing. The introduction of ionic liquid greatly improves the mechanical strength (9.7 MPa) with respect to neat NBR vulcanizate, especially at high temperatures e.g., 100 °C. Furthermore, it impacts on rheological behaviors of the nanocomposites and tends to reduce energy dissipation for the vulcanizates under large amplitude dynamic shear deformation. Full article

(This article belongs to the Collection Reinforced Polymer Composites)

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20 pages, 4746 KiB

Open AccessArticle

Effects of Post-Curing Time on the Mechanical and Color Properties of Three-Dimensional Printed Crown and Bridge Materials

by Dohyun Kim, Ji-Suk Shim, Dasun Lee, Seung-Ho Shin, Na-Eun Nam, Kyu-Hyung Park, June-Sung Shim and Jong-Eun Kim

Polymers 2020, 12(11), 2762; https://doi.org/10.3390/polym12112762 - 23 Nov 2020

Cited by 100 | Viewed by 6871

Abstract

Three-dimensional (3D) printing is increasingly being utilized in the dental field. After fabricating a prosthesis using a 3D printed resin, a post-curing process is required to improve its mechanical properties, but there has been insufficient research on the optimal post-curing conditions. We used [...] Read more.

Three-dimensional (3D) printing is increasingly being utilized in the dental field. After fabricating a prosthesis using a 3D printed resin, a post-curing process is required to improve its mechanical properties, but there has been insufficient research on the optimal post-curing conditions. We used various 3D printed crown and bridge materials in this study, and evaluated the changes in their properties according to post-curing time by evaluating the flexural strength, Weibull modulus, Vickers hardness, color change, degree of conversion, and biocompatibility. The obtained results confirmed that the strength of the 3D printed resin increased when it was post-cured for 60–90 min. The Vickers hardness, the degree of conversion, and biocompatibility of the 3D printed resins increased significantly around the beginning of the post-curing time, and then increased more gradually as the post-curing time increased further. It was observed that the color tone also changed as the post-curing time increased, with some groups showing a ΔE₀₀ value of ≥ 2.25, which can be recognized clinically. This study has confirmed that, after the printing process of a 3D printed resin was completed, a sufficient post-curing time of at least 60 min is required to improve the overall clinical performance of the produced material. Full article

(This article belongs to the Special Issue Polymers and Polymer-Based Composites for Additive Manufacturing)

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17 pages, 9253 KiB

Open AccessArticle

Cross-Linking Modification of Ammonium Polyphosphate via Ionic Exchange and Self-Assembly for Enhancing the Fire Safety Properties of Polypropylene

by Yingtong Pan, Zhonglin Luo and Biaobing Wang

Polymers 2020, 12(11), 2761; https://doi.org/10.3390/polym12112761 - 23 Nov 2020

Cited by 12 | Viewed by 2697

Abstract

Modified ammonium polyphosphate (MAPP) was prepared as a novel mono-component intumescent flame retardant (IFR) via the ionic exchange between ammonium polyphosphate (APP) and piperazine sulfonate, which is synthesized by self-assembly using 1-(2-aminoethyl) piperazine (AEP) and p-aminobenzene sulfonic acid (ASC) as raw materials. [...] Read more.

Modified ammonium polyphosphate (MAPP) was prepared as a novel mono-component intumescent flame retardant (IFR) via the ionic exchange between ammonium polyphosphate (APP) and piperazine sulfonate, which is synthesized by self-assembly using 1-(2-aminoethyl) piperazine (AEP) and p-aminobenzene sulfonic acid (ASC) as raw materials. This all-in-one IFR integrating three functional elements (carbon, acid, and gas source) showed more efficient flame retardancy and excellent smoke suppression as well as better mechanical properties than the conventional APP. The incorporation of 22.5 wt.% MAPP into polypropylene (PP) eliminated the melt dripping phenomenon and passed the UL-94 V-0 rating. The results of the cone calorimetry test (CCT) revealed that the release of heat, smoke, and CO is significantly decreased, demonstrating that this novel IFR endows PP with excellent fire safety more effectively. For PP/MAPP composites, a possible IFR mechanism was proposed based on the analysis of the pyrolysis gas and char residues. Full article

(This article belongs to the Section Polymer Chemistry)

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16 pages, 4633 KiB

Open AccessArticle

Influence of Oil–Pressboard Mass Ratio on the Equilibrium Characteristics of Furfural under Oil Replacement Conditions

by Jiefeng Liu, Zhanwei Cao, Xianhao Fan, Heng Zhang, Chuhan Geng and Yiyi Zhang

Polymers 2020, 12(11), 2760; https://doi.org/10.3390/polym12112760 - 23 Nov 2020

Cited by 8 | Viewed by 1965

Abstract

The distribution behavior of furfural in insulation systems is influenced by the oil–pressboard mass ratio. In addition, the equilibrium distribution of furfural between oil and pressboard will be disturbed after oil replacement. Therefore, it is of great significance to study the distribution ratio [...] Read more.

The distribution behavior of furfural in insulation systems is influenced by the oil–pressboard mass ratio. In addition, the equilibrium distribution of furfural between oil and pressboard will be disturbed after oil replacement. Therefore, it is of great significance to study the distribution ratio of furfural in oil with various oil–pressboard mass ratios after oil replacement. In this research, an accelerated thermal aging experiment and oil replacement experiment were conducted in the lab. Furthermore, the equilibrium characteristics of furfural dissolved in oil with various oil–pressboard mass ratios were studied. Multiple regression analysis was used to analyze the relationship between the oil–pressboard mass ratios and the distribution ratio of furfural in oil. The equilibrium distribution model of furfural was thus obtained. Afterwards, the modified furfural distribution model under oil replacement conditions was established. A novel scheme is provided for analyzing the equilibrium characteristics of furfural under various oil–pressboard mass ratios after oil replacement. The work of this paper is expected to improve the accuracy of furfural analysis. Full article

(This article belongs to the Special Issue Multi-Functional Smart Dielectric Materials for High Voltage Insulation)

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17 pages, 8665 KiB

Open AccessArticle

Polyurethane-Carbon Nanotubes Composite Dual Band Antenna for Wearable Applications

by Robert Olejník, Stanislav Goňa, Petr Slobodian, Jiří Matyáš, Robert Moučka and Romana Daňová

Polymers 2020, 12(11), 2759; https://doi.org/10.3390/polym12112759 - 23 Nov 2020

Cited by 3 | Viewed by 2258

Abstract

The design of a unipole and a dual band F-shaped antenna was conducted to find the best parameters of prepared antenna. Antenna radiator part is fully made of polymer and nonmetal base composite. Thermoplastic polyurethane (PU) was chosen as a matrix and multi-wall [...] Read more.

The design of a unipole and a dual band F-shaped antenna was conducted to find the best parameters of prepared antenna. Antenna radiator part is fully made of polymer and nonmetal base composite. Thermoplastic polyurethane (PU) was chosen as a matrix and multi-wall carbon nanotubes (MWCNT) as an electrical conductive filler, which creates conductive network. The use of the composite for the antenna has the advantage in simple preparation through dip coating technique. Minor disadvantage is the usage of solvent for composite preparation. Composite structure was used for radiator part of antenna. The antenna operates in 2.45 and 5.18 GHz frequency bands. DC conductivity of our PU/MWCNT composite is about 160 S/m. With this material, a unipole and a dual band F antenna were realized on 2 mm thick polypropylene substrate. Both antenna designs were also simulated using finite integration technique in the frequency domain (FI-FD). Measurements and full wave simulations of S₁₁ of the antenna showed good agreement between measurements and simulations. Except for S₁₁, the gain and radiation pattern of the antennas were measured and simulated. Maximum gain of the designed unipole antenna is around −10.0 and −5.5 dBi for 2.45 and 5.18 GHz frequency bands, respectively. The manufactured antennas are intended for application in wearable electronics, which can be used to monitor various activities such as walking, sleeping, heart rate or food consumption. Full article

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

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15 pages, 33139 KiB

Open AccessArticle

Crosslinked Pore-Filling Anion Exchange Membrane Using the Cylindrical Centrifugal Force for Anion Exchange Membrane Fuel Cell System

by Tae Yang Son, Tae-Hyun Kim and Sang Yong Nam

Polymers 2020, 12(11), 2758; https://doi.org/10.3390/polym12112758 - 23 Nov 2020

Cited by 15 | Viewed by 3960

Abstract

In this study, novel crosslinked pore-filling membranes were fabricated by using a centrifugal force from the cylindrical centrifugal machine. For preparing these crosslinked pore-filling membranes, the poly(phenylene oxide) containing long side chains to improve the water management (hydrophilic), porous polyethylene support (hydrophobic) and [...] Read more.

In this study, novel crosslinked pore-filling membranes were fabricated by using a centrifugal force from the cylindrical centrifugal machine. For preparing these crosslinked pore-filling membranes, the poly(phenylene oxide) containing long side chains to improve the water management (hydrophilic), porous polyethylene support (hydrophobic) and crosslinker based on the diamine were used. The resulting membranes showed a uniform thickness, flexible and transparent because it is well filled. Among them, PF-XAc-PPO70_25 showed good mechanical properties (56.1 MPa of tensile strength and 781.0 MPa of Young’s modulus) and dimensional stability due to the support. In addition, it has a high hydroxide conductivity (87.1 mS/cm at 80 °C) and low area specific resistance (0.040 Ω·cm²), at the same time showing stable alkaline stability. These data outperformed the commercial FAA-3-50 membrane sold by Fumatech in Germany. Based on the optimized properties, membrane electrode assembly using XAc-PPO70_25 revealed excellent cell performance (maximum power density: 239 mW/cm² at 0.49 V) than those of commercial FAA-3-50 Fumatech anion exchange membrane (maximum power density: 212 mW/cm² at 0.54 V) under the operating condition of 60 °C and 100% RH as well. It was expected that PF-XAc-PPO70_25 could be an excellent candidate based on the results superior to those of commercial membranes in these essential characteristics of fuel cells. Full article

(This article belongs to the Special Issue Advanced Polymers for Electrochemical Applications)

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4 pages, 167 KiB

Open AccessEditorial

Surface Chemistry of Polymers

by Alenka Vesel

Polymers 2020, 12(11), 2757; https://doi.org/10.3390/polym12112757 - 23 Nov 2020

Cited by 1 | Viewed by 1847

Abstract

Surface chemistry plays a key role in modern applications of polymer materials [...] Full article

(This article belongs to the Special Issue Surface Chemistry of Polymers)

12 pages, 2115 KiB

Open AccessArticle

Development of Energy-Efficient Superhydrophobic Polypropylene Fabric by Oxygen Plasma Etching and Thermal Aging

by Shinyoung Kim, Ji-Hyun Oh and Chung Hee Park

Polymers 2020, 12(11), 2756; https://doi.org/10.3390/polym12112756 - 23 Nov 2020

Cited by 16 | Viewed by 3497

Abstract

This study developed a human-friendly energy-efficient superhydrophobic polypropylene (PP) fabric by oxygen plasma etching and short-term thermal aging without additional chemicals. The effect of the microroughness on the superhydrophobicity was examined by adjusting the weave density. After the PP fabric was treated with [...] Read more.

This study developed a human-friendly energy-efficient superhydrophobic polypropylene (PP) fabric by oxygen plasma etching and short-term thermal aging without additional chemicals. The effect of the microroughness on the superhydrophobicity was examined by adjusting the weave density. After the PP fabric was treated with oxygen plasma etching for 15 min and thermal aging at 120 °C for 1 h (E15H120 1 h), the static contact and shedding angles were 162.7° ± 2.4° and 5.2° ± 0.7° and the energy consumption was 136.4 ± 7.0 Wh. Oxygen plasma etching for 15 min and thermal aging at 120 °C for 24 h (E15H120 24 h) resulted in a static contact and shedding angle of 180.0° ± 0.0° and 1.8° ± 0.2° and energy consumption of 3628.5 ± 82.6 Wh. E15H120 1 h showed a lower shedding angle but had a higher sliding angle of 90°. E15H120 24 h exhibited shedding and sliding angles of less than 10°. Regardless of the thermal aging time, superhydrophobicity was higher in high-density fabrics than in low-density fabrics. The superhydrophobic PP fabric had a similar water vapor transmission rate and air permeability with the untreated PP fabric, and it showed a self-heading property after washing followed by tumble drying and hot pressing. Full article

(This article belongs to the Special Issue Advanced Textiles for Health and Safety, Environmental Protection Applications)

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12 pages, 1419 KiB

Open AccessArticle

Enhancing Biosludge Dewaterability with Hemoglobin from Waste Blood as a Bioflocculant

by Hamed Ghazisaidi, Rafael A. Garcia, Honghi Tran, Runlin Yuan and D. Grant Allen

Polymers 2020, 12(11), 2755; https://doi.org/10.3390/polym12112755 - 22 Nov 2020

Cited by 4 | Viewed by 2136

Abstract

Synthetic polymers are widely used in the treatment of biosludge (waste activated sludge) to enhance its dewaterability. This paper discusses the results of a systematic study using hemoglobin (Hb) from animal blood and methylated hemoglobin (MeHb), a derivative in which a methyl group [...] Read more.

Synthetic polymers are widely used in the treatment of biosludge (waste activated sludge) to enhance its dewaterability. This paper discusses the results of a systematic study using hemoglobin (Hb) from animal blood and methylated hemoglobin (MeHb), a derivative in which a methyl group replaces the hydrogen carboxyl groups, to replace synthetic polymers to improve the dewatering efficiency of biosludge. With regular hemoglobin, no improvement in biosludge dewatering was found. With 10% of methylated hemoglobin per total solids content, however, the dry solids content of biosludge increased from 10.2 (±0.3) wt% to 15.0 (±1.0) wt%. Zeta potential measurements showed a decrease in the negative surface charge of the particles in biosludge from −34.3 (±3.2) mV to −19.0 (±2.1) mV after the treatment with methylated hemoglobin. This, along with an unchanged particle size distribution after conditioning, suggests that charge neutralization is likely the main cause of particle flocculation. With charges neutralized, the extracellular polymeric substances (EPS) around the biosludge flocs become loose, releasing the trapped water, thus increasing dewaterability. Full article

(This article belongs to the Special Issue Application and Performance of Biopolymers)

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19 pages, 2292 KiB

Open AccessReview

Progress in the Applications of Smart Piezoelectric Materials for Medical Devices

by Angelika Zaszczyńska, Arkadiusz Gradys and Paweł Sajkiewicz

Polymers 2020, 12(11), 2754; https://doi.org/10.3390/polym12112754 - 22 Nov 2020

Cited by 83 | Viewed by 9019

Abstract

Smart piezoelectric materials are of great interest due to their unique properties. Piezoelectric materials can transform mechanical energy into electricity and vice versa. There are mono and polycrystals (piezoceramics), polymers, and composites in the group of piezoelectric materials. Recent years show progress in [...] Read more.

Smart piezoelectric materials are of great interest due to their unique properties. Piezoelectric materials can transform mechanical energy into electricity and vice versa. There are mono and polycrystals (piezoceramics), polymers, and composites in the group of piezoelectric materials. Recent years show progress in the applications of piezoelectric materials in biomedical devices due to their biocompatibility and biodegradability. Medical devices such as actuators and sensors, energy harvesting devices, and active scaffolds for neural tissue engineering are continually explored. Sensors and actuators from piezoelectric materials can convert flow rate, pressure, etc., to generate energy or consume it. This paper consists of using smart materials to design medical devices and provide a greater understanding of the piezoelectric effect in the medical industry presently. A greater understanding of piezoelectricity is necessary regarding the future development and industry challenges. Full article

(This article belongs to the Special Issue Bioactive Polymer Scaffolds and Thin Films for Biomedical Applications: State-of-the-Art and Challenges)

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16 pages, 9992 KiB

Open AccessEditor’s ChoiceArticle

Reliability of Free Inflation and Dynamic Mechanics Tests on the Prediction of the Behavior of the Polymethylsilsesquioxane–High-Density Polyethylene Nanocomposite for Thermoforming Applications

by Fouad Erchiqui, Khaled Zaafrane, Abdessamad Baatti, Hamid Kaddami and Abdellatif Imad

Polymers 2020, 12(11), 2753; https://doi.org/10.3390/polym12112753 - 21 Nov 2020

Cited by 2 | Viewed by 1868

Abstract

Numerical modeling of the thermoforming process of polymeric sheets requires precise knowledge of the viscoelastic behavior under conjugate effect pressure and temperature. Using two different experiments, bubble inflation and dynamic mechanical testing on a high-density polyethylene (HDPE) nanocomposite reinforced with polymethylsilsesquioxane HDPE (PMSQ–HDPE) [...] Read more.

Numerical modeling of the thermoforming process of polymeric sheets requires precise knowledge of the viscoelastic behavior under conjugate effect pressure and temperature. Using two different experiments, bubble inflation and dynamic mechanical testing on a high-density polyethylene (HDPE) nanocomposite reinforced with polymethylsilsesquioxane HDPE (PMSQ–HDPE) nanoparticles, material constants for Christensen’s model were determined by the least squares optimization. The viscoelastic identification relative to the inflation test seemed to be the most appropriate for the numerical study of thermoforming of a thin PMSQ–HDPE part. For this purpose, the finite element method was considered. Full article

(This article belongs to the Special Issue Rheology and Processing of Polymers)

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20 pages, 5107 KiB

Open AccessArticle

Investigation of the Evaporation Rate of Water from Colloidal Unimolecular Polymer (CUP) Systems by Isothermal TGA

by Peng Geng, Ashish Zore and Michael R. Van De Mark

Polymers 2020, 12(11), 2752; https://doi.org/10.3390/polym12112752 - 21 Nov 2020

Cited by 7 | Viewed by 3160

Abstract

Studies of the evaporation of aqueous nanoparticle solutions have been limited due to lack of homogeneity of the solution, difficulties in obtaining reproducible samples and stability of substrates, as well as the effect of other volatile components or contaminants such as surfactants. Colloidal [...] Read more.

Studies of the evaporation of aqueous nanoparticle solutions have been limited due to lack of homogeneity of the solution, difficulties in obtaining reproducible samples and stability of substrates, as well as the effect of other volatile components or contaminants such as surfactants. Colloidal unimolecular polymer (CUP) is a spheroidal nanoparticle with charged hydrophilic groups on the surface, and the particle size ranges from 3 to 9 nm. The large amount of surface water on the CUP surface provides the opportunity to evaluate the evaporation of surface water, which may contribute to the investigation the factors that affect the evaporation rate in solutions of ultra-small particles, like protein, micelle, colloidal, etc. Six CUP systems were evaluated by thermogravimetric analysis (TGA) with respect to time and solids content. The evaporation rate of water was initially enhanced due to the deformation of the air-water interface at low to moderate concentration due to particle charge repulsive forces. At higher concentrations, above 20%, surface charge condensation and increasing viscosity began to dominate. At higher concentration where the CUP reached the gel point the rate of diffusion controlled the evaporation. The final drying point was the loss of three waters of hydration for each carboxylate on the CUP surface. Full article

(This article belongs to the Special Issue Single-Chain Polymer Nanotechnology)

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16 pages, 3544 KiB

Open AccessArticle

Optimized Encapsulation of the FLAP/PGES-1 Inhibitor BRP-187 in PVA-Stabilized PLGA Nanoparticles Using Microfluidics

by Mira Behnke, Antje Vollrath, Lea Klepsch, Baerbel Beringer-Siemers, Steffi Stumpf, Justyna A. Czaplewska, Stephanie Hoeppener, Oliver Werz and Ulrich S. Schubert

Polymers 2020, 12(11), 2751; https://doi.org/10.3390/polym12112751 - 20 Nov 2020

Cited by 8 | Viewed by 3013

Abstract

The dual inhibitor of the 5-lipoxygenase-activating protein (FLAP) and the microsomal prostaglandin E₂ synthase-1 (mPGES-1), named BRP-187, represents a promising drug candidate due to its improved anti-inflammatory efficacy along with potentially reduced side effects in comparison to non-steroidal anti-inflammatory drugs (NSAIDs). However, [...] Read more.

The dual inhibitor of the 5-lipoxygenase-activating protein (FLAP) and the microsomal prostaglandin E₂ synthase-1 (mPGES-1), named BRP-187, represents a promising drug candidate due to its improved anti-inflammatory efficacy along with potentially reduced side effects in comparison to non-steroidal anti-inflammatory drugs (NSAIDs). However, BRP-187 is an acidic lipophilic drug and reveals only poor water solubility along with a strong tendency for plasma protein binding. Therefore, encapsulation in polymeric nanoparticles is a promising approach to enable its therapeutic use. With the aim to optimize the encapsulation of BRP-187 into poly(lactic-co-glycolic acid) (PLGA) nanoparticles, a single-phase herringbone microfluidic mixer was used for the particle preparation. Various formulation parameters, such as total flow rates, flow rate ratio, the concentration of the poly(vinyl alcohol) (PVA) as a surfactant, initial polymer concentration, as well as presence of a co-solvent on the final particle size distribution and drug loading, were screened for best particle characteristics and highest drug loading capacities. While the size of the particles remained in the targeted region between 121 and 259 nm with low polydispersities (0.05 to 0.2), large differences were found in the BRP-187 loading capacities (LC = 0.5 to 7.29%) and drug crystal formation during the various formulations. Full article

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

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15 pages, 1813 KiB

Open AccessArticle

Investigation of Acetone Vapour Sensing Properties of a Ternary Composite of Doped Polyaniline, Reduced Graphene Oxide and Chitosan Using Surface Plasmon Resonance Biosensor

by Fahad Usman, John Ojur Dennis, E M Mkawi, Yas Al-Hadeethi, Fabrice Meriaudeau, Thomas L. Ferrell, Osamah Aldaghri and Abdelmoneim Sulieman

Polymers 2020, 12(11), 2750; https://doi.org/10.3390/polym12112750 - 20 Nov 2020

Cited by 8 | Viewed by 2703

Abstract

This work reports the use of a ternary composite that integrates p-Toluene sulfonic acid doped polyaniline (PANI), chitosan, and reduced graphene oxide (RGO) as the active sensing layer of a surface plasmon resonance (SPR) sensor. The SPR sensor is intended for application in [...] Read more.

This work reports the use of a ternary composite that integrates p-Toluene sulfonic acid doped polyaniline (PANI), chitosan, and reduced graphene oxide (RGO) as the active sensing layer of a surface plasmon resonance (SPR) sensor. The SPR sensor is intended for application in the non-invasive monitoring and screening of diabetes through the detection of low concentrations of acetone vapour of less than or equal to 5 ppm, which falls within the range of breath acetone concentration in diabetic patients. The ternary composite film was spin-coated on a 50-nm-thick gold layer at 6000 rpm for 30 s. The structure, morphology and chemical composition of the ternary composite samples were characterized by FTIR, UV-VIS, FESEM, EDX, AFM, XPS, and TGA and the response to acetone vapour at different concentrations in the range of 0.5 ppm to 5 ppm was measured at room temperature using SPR technique. The ternary composite-based SPR sensor showed good sensitivity and linearity towards acetone vapour in the range considered. It was determined that the sensor could detect acetone vapour down to 0.88 ppb with a sensitivity of 0.69 degree/ppm with a linearity correlation coefficient of 0.997 in the average SPR angular shift as a function of the acetone vapour concentration in air. The selectivity, repeatability, reversibility, and stability of the sensor were also studied. The acetone response was 87%, 94%, and 99% higher compared to common interfering volatile organic compounds such as propanol, methanol, and ethanol, respectively. The attained lowest detection limit (LOD) of 0.88 ppb confirms the potential for the utilisation of the sensor in the non-invasive monitoring and screening of diabetes. Full article

(This article belongs to the Special Issue Graphene-Based Polymer Nanocomposites: Recent Advances)

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15 pages, 2819 KiB

Open AccessArticle

Glucosamine Modified the Surface of pH-Responsive Poly(2-(diethylamino)ethyl Methacrylate) Brushes Grafted on Hollow Mesoporous Silica Nanoparticles as Smart Nanocarrier

by Abeer Beagan, Shatha Lahmadi, Ahlam Alghamdi, Majed Halwani, Mohammed Almeataq, Abdulaziz Alhazaa, Khalid Alotaibi and Abdullah Alswieleh

Polymers 2020, 12(11), 2749; https://doi.org/10.3390/polym12112749 - 20 Nov 2020

Cited by 12 | Viewed by 2835

Abstract

This work presents the synthesis of pH-responsive poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA) brushes anchored on hollow mesoporous silica nanoparticles (HMSN-PDEAEMA) via a surface-initiated ARGET ATRP technique. The average size of HMSNs was ca. 340 nm, with a 90 nm mesoporous silica shell. The dry [...] Read more.

This work presents the synthesis of pH-responsive poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA) brushes anchored on hollow mesoporous silica nanoparticles (HMSN-PDEAEMA) via a surface-initiated ARGET ATRP technique. The average size of HMSNs was ca. 340 nm, with a 90 nm mesoporous silica shell. The dry thickness of grafted PDEAEMA brushes was estimated to be ca 30 nm, as estimated by SEM and TEM. The halogen group on the surface of PDEAMA brushes was successfully derivatized with glucosamine, as confirmed by XPS. The effect of pH on the size of the hybrid nanoparticles was investigated by DLS. The size of fabricated nanoparticle decreased from ca. 950 nm in acidic media to ca. 500 nm in basic media due to the deprotonation of tertiary amine in the PDEAEMA. The PDEAEMA modified HMSNs nanocarrier was efficiently loaded with doxorubicin (DOX) with a loading capacity of ca. 64%. DOX was released in a relatively controlled pH-triggered manner from hybrid nanoparticles. The cytotoxicity studies demonstrated that DOX@HMSN-PDEAEMA-Glucosamine showed a strong ability to kill breast cancer cells (MCF-7 and MCF-7/ADR) at low drug concentrations, in comparison to free DOX. Full article

(This article belongs to the Section Polymer Applications)

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3 pages, 153 KiB

Open AccessEditorial

“Polymer Analysis” Section, in Journal Polymers

by Giulio Malucelli

Polymers 2020, 12(11), 2748; https://doi.org/10.3390/polym12112748 - 20 Nov 2020

Viewed by 1411

Abstract

Dear colleagues and friends, [...] Full article

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

12 pages, 1636 KiB

Open AccessArticle

Facile Synthesis of Ultrahigh Molecular Weight Poly(Methyl Methacrylate) by Organic Halides in the Presence of Palladium Nanoparticles

by Ming Yuan, Lili Xu, Xuetao Cui, Jiaxing Lv, Panpan Zhang and Huadong Tang

Polymers 2020, 12(11), 2747; https://doi.org/10.3390/polym12112747 - 20 Nov 2020

Cited by 8 | Viewed by 2516

Abstract

A facile and versatile approach for the synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) at mild conditions was developed. Certain organic halides combined with a catalytical amount of palladium nanoparticles (Pd NPs) were found to be very effective in initiating polymerizations of [...] Read more.

A facile and versatile approach for the synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) at mild conditions was developed. Certain organic halides combined with a catalytical amount of palladium nanoparticles (Pd NPs) were found to be very effective in initiating polymerizations of methyl methacrylate (MMA), methyl acrylate, vinyl acetate and other vinyl monomers. An ultrahigh molecular weight PMMA with a number-average molecular weight of 4.65 × 10⁶ Da and a weight-average molecular weight of 8.08 × 10⁶ Da was synthesized at 70 °C using 2-bromoisobutyric acid ethyl ester (EBiB) as an initiator in the presence of catalytical amount (10.1 ppm) of Pd NPs. A kinetic investigation found that the orders of polymerization with respect to EBiB, Pd NP and MMA were 0.23, 0.50, and 0.58, respectively. Proton nuclear magnetic resonance (¹H NMR) combined with matrix-assisted laser desorption ionization time of flight mass spectroscopy (MALDI-TOF) and gel permeation chromatography (GPC) were used to prove that the macromolecular chain had an end-group of EBiB residue. The electron spin resonance (ESR), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) results reveal that the reaction of EBiB with Pd NPs caused a bromo atom (Br) transfer from EBiB to Pd NPs and resulted in the generation of EBiB residue radical to initiate the polymerization of MMA and the formation of Pd^IIBr₂ on the surface of Pd nanoparticles. Full article

(This article belongs to the Section Polymer Chemistry)

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12 pages, 4138 KiB

Open AccessArticle

Unique Slow Crack Growth Behavior of Isotactic Polypropylene: The Role of Shear Layer-Spherulites Layer Alternated Structure

by Mingjin Liu, Jiaxu Luo, Jin Chen, Xueqin Gao, Qiang Fu and Jie Zhang

Polymers 2020, 12(11), 2746; https://doi.org/10.3390/polym12112746 - 20 Nov 2020

Cited by 2 | Viewed by 1738

Abstract

With the development of polymer science, more attention is being paid to the longevity of polymer products. Slow crack growth (SCG), one of the most important factors that reveal the service life of the products, has been investigated widely in the past decades. [...] Read more.

With the development of polymer science, more attention is being paid to the longevity of polymer products. Slow crack growth (SCG), one of the most important factors that reveal the service life of the products, has been investigated widely in the past decades. Here, we manufactured an isotactic polypropylene (iPP) sample with a novel shear layer–spherulites layer alternated structure using multiflow vibration injection molding (MFVIM). However, the effect of the alternated structure on the SCG behavior has never been reported before. Surprisingly, the results showed that the resistivity of polymer to SCG can be enhanced remarkably due to the special alternated structure. Moreover, this sample shows unique slow crack propagation behavior in contrast to the sample with the same thickness of shear layer, presenting multiple microcracks in the spherulites layer, which can explain the reason of the resistivity improvement of polymer to SCG. Full article

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

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17 pages, 6765 KiB

Open AccessArticle

Effect of Fillers on the Recovery of Rubber Foam: From Theory to Applications

by Thridsawan Prasopdee and Wirasak Smitthipong

Polymers 2020, 12(11), 2745; https://doi.org/10.3390/polym12112745 - 19 Nov 2020

Cited by 24 | Viewed by 3725

Abstract

Natural rubber foam (NRF) can be prepared from concentrated natural latex, providing specific characteristics such as density, compression strength, compression set, and so on, suitable for making shape-memory products. However, many customers require NRF products with a low compression set. This study aims [...] Read more.

Natural rubber foam (NRF) can be prepared from concentrated natural latex, providing specific characteristics such as density, compression strength, compression set, and so on, suitable for making shape-memory products. However, many customers require NRF products with a low compression set. This study aims to develop and prepare NRF to investigate its recoverability and other related characteristics by the addition of charcoal and silica fillers. The results showed that increasing filler loading increases physical and mechanical properties. The recoverability of NRF improves as silica increases, contrary to charcoal loading, due to the higher specific surface area of silica. Thermodynamic aspects showed that increasing filler loading increases the compression force (F) as well as the proportion of internal energy to the compression force (F_u/F). The entropy (S) also increases with increasing filler loading, which is favorable for thermodynamic systems. The activation enthalpy (∆H_a) of the NRF with silica is higher than the control NRF, which is due to rubber–filler interactions created within the NRF. A thermodynamic concept of crosslinked rubber foam with filler is proposed. From theory to application, in this study, the NRF has better recoverability with silica loading. Full article

(This article belongs to the Special Issue Elastomers: From Theory to Applications)

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17 pages, 5606 KiB

Open AccessArticle

Numerical Technique for Study of Noise Grating Dynamics in Holographic Photopolymers

by Robert R. McLeod

Polymers 2020, 12(11), 2744; https://doi.org/10.3390/polym12112744 - 19 Nov 2020

Cited by 3 | Viewed by 1720

Abstract

Although the angular distribution of noise gratings in holographic photopolymer is understood to arise from Bragg matching, the details of scatter strength and dynamics are not fully understood. This confounds development of materials and recording techniques that minimize haze. Here, the kinetics are [...] Read more.

Although the angular distribution of noise gratings in holographic photopolymer is understood to arise from Bragg matching, the details of scatter strength and dynamics are not fully understood. This confounds development of materials and recording techniques that minimize haze. Here, the kinetics are studied using a multi-physics numerical approach coupling diffraction of light from the dynamic material including scatter centers, reactions of chemical species initiated by this light, diffusion and swelling of these constituents, and the formation of the refractive index from the resulting composition. The approach is validated in the case of two-beam transmission holography by comparison to traditional harmonic series and rigorous coupled-mode approaches. Two beam holography in the presence of scatter is then used to study haze development. This reveals that haze due to weak noise gratings grows significantly above initial scatter only in reaction-limited materials, consistent with proposed Bragg-matched amplification mechanisms. Amplified haze is found to be proportional to initial scatter, quantifying the impact of clean sample fabrication. Conversely, haze is found to grow super-linearly with sample thickness, illustrating the significant challenge for applications requiring low haze in large thickness. Full article

(This article belongs to the Special Issue Polymeric and Polymer Nanocomposite Materials for Photonic Applications)

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22 pages, 7012 KiB

Open AccessEditor’s ChoiceArticle

Composites Based on Poly(Lactic Acid) (PLA) and SBA-15: Effect of Mesoporous Silica on Thermal Stability and on Isothermal Crystallization from Either Glass or Molten State

by Tamara M. Díez-Rodríguez, Enrique Blázquez-Blázquez, Ernesto Pérez and María L. Cerrada

Polymers 2020, 12(11), 2743; https://doi.org/10.3390/polym12112743 - 19 Nov 2020

Cited by 15 | Viewed by 2619

Abstract

Several composites based on an L-rich poly(lactic acid) (PLA) with different contents of mesoporous Santa Barbara Amorphous (SBA-15) silica were prepared in order to evaluate the effect of the mesoporous silica on the resultant PLA materials by examining morphological aspects, changes in [...] Read more.

Several composites based on an L-rich poly(lactic acid) (PLA) with different contents of mesoporous Santa Barbara Amorphous (SBA-15) silica were prepared in order to evaluate the effect of the mesoporous silica on the resultant PLA materials by examining morphological aspects, changes in PLA phases and their transitions, and, primarily, the influence on some final properties. Melt extrusion was chosen for the obtainment of the composites, followed by quenching from the melt to prepare films. Completely amorphous samples were then attained, as deduced from X-ray diffraction and differential scanning calorimetry (DSC) analyses. Thermogravimetric analysis (TGA) results demonstrated that the presence of SBA-15 particles in the PLA matrix did not exert any significant influence on the thermal decomposition of these composites. An important nucleation effect of the silica was found in PLA, especially under isothermal crystallization either from the melt or from its glassy state. As expected, isothermal crystallization from the glass was considerably faster than from the molten state, and these high differences were also responsible for a more considerable nucleating role of SBA-15 when crystallizing from the melt. It is remarkable that the PLA under analysis showed very close temperatures for cold crystallization and its subsequent melting. Moreover, the type of developed polymorphs did not accomplish the common rules previously described in the literature. Thus, all the isothermal experiments led to exclusive formation of the α modification, and the observation of the α’ crystals required the annealing for long times at temperatures below 80 °C, as ascertained by both DSC and X-ray diffraction experiments. Finally, microhardness (MH) measurements indicated a competition between the PLA physical aging and the silica reinforcement effect in the as-processed amorphous films. Physical aging in the neat PLA was much more important than in the PLA matrix that constituted the composites. Accordingly, the MH trend with SBA-15 content was strongly dependent on aging times. Full article

(This article belongs to the Special Issue Biodegradable Polymer Nanocomposites)

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13 pages, 1793 KiB

Open AccessEditor’s ChoiceArticle

Kinetic Study of the Thermal and Thermo-Oxidative Degradations of Polystyrene Reinforced with Multiple-Cages POSS

by Ignazio Blanco, Gianluca Cicala, Claudio Tosto and Francesco Agatino Bottino

Polymers 2020, 12(11), 2742; https://doi.org/10.3390/polym12112742 - 19 Nov 2020

Cited by 6 | Viewed by 1933

Abstract

A comprehensive kinetics degradation study is carried out on novel multiple cages polyhedral oligomeric silsesquioxane (POSS)/polystyrene (PS) composites at 5% (w/w) of POSS to assess their thermal behavior with respect to the control PS and other similar POSS/PS systems [...] Read more.

A comprehensive kinetics degradation study is carried out on novel multiple cages polyhedral oligomeric silsesquioxane (POSS)/polystyrene (PS) composites at 5% (w/w) of POSS to assess their thermal behavior with respect to the control PS and other similar POSS/PS systems studied in the past. The composites are synthesized by in situ polymerization of styrene in the presence of POSSs and characterized by ¹H-NMR. The characteristics of thermal parameters are determined using kinetics literature methods, such as those developed by Kissinger and Flynn, Wall, and Ozawa (FWO), and discussed and compared with each other and with those obtained in the past for similar POSS/PS composites. A good improvement in the thermal stability with respect to neat polymer is found, but not with respect to those obtained in the past for polystyrene reinforced with single- or double-POSS cages. This behavior is attributed to the greater steric hindrance of the three-cages POSS compared with those of single- or double-cage POSS molecules. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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22 pages, 6936 KiB

Open AccessArticle

Thermal Mechanical Properties of Graphene Nano-Composites with Kevlar-Nomex Copolymer: A Comparison of the Physical and Chemical Interactions

by Jessy Shiju, Fakhreia Al-Sagheer and Zahoor Ahmad

Polymers 2020, 12(11), 2740; https://doi.org/10.3390/polym12112740 - 19 Nov 2020

Cited by 16 | Viewed by 2776

Abstract

This paper reports the preparation of Kevlar-Nomex copolymer nano-composites with exfoliated pristine and functionalized graphene sheets (Grs). The graphene oxide (GrO) platelets were amidized by the reaction of amine-terminated aramid (Ar) with the functional groups present on the GrO surface to prepare the [...] Read more.

This paper reports the preparation of Kevlar-Nomex copolymer nano-composites with exfoliated pristine and functionalized graphene sheets (Grs). The graphene oxide (GrO) platelets were amidized by the reaction of amine-terminated aramid (Ar) with the functional groups present on the GrO surface to prepare the nano-composites films with different loadings of GrO. Chemical changes involved during the oxidation and subsequent amidation were monitored by Raman, FTIR and XP spectroscopic analyses. Morphology of the composite films was studied by atomic force and scanning electron microscopies. Viscoelastic properties of the hybrid films were studied for their glass transition temperature (Tg) and storage modulus by dynamical mechanical thermal analysis (DMTA). A higher shift in glass transition temperature was obtained by chemically binding the aramid copolymer chains on the functionalized Gr sheets. The increase in tensile strength and modulus at various loadings of GrO are compared with the composites using pristine Gr. The effect of interfacial interactions between the matrix chains and the reinforcement on the properties of these hybrids have been explained. Full article

(This article belongs to the Special Issue Carbon-Based Polymer Nanocomposites for High-Performance Applications II)

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17 pages, 2226 KiB

Open AccessArticle

Ca-Zn-Ag Alginate Aerogels for Wound Healing Applications: Swelling Behavior in Simulated Human Body Fluids and Effect on Macrophages

by Claudia Keil, Christopher Hübner, Constanze Richter, Sandy Lier, Lars Barthel, Vera Meyer, Raman Subrahmanyam, Pavel Gurikov, Irina Smirnova and Hajo Haase

Polymers 2020, 12(11), 2741; https://doi.org/10.3390/polym12112741 - 18 Nov 2020

Cited by 19 | Viewed by 3008

Abstract

Chronic non-healing wounds represent a substantial economic burden to healthcare systems and cause a considerable reduction in quality of life for those affected. Approximately 0.5–2% of the population in developed countries are projected to experience a chronic wound in their lifetime, necessitating further [...] Read more.

Chronic non-healing wounds represent a substantial economic burden to healthcare systems and cause a considerable reduction in quality of life for those affected. Approximately 0.5–2% of the population in developed countries are projected to experience a chronic wound in their lifetime, necessitating further developments in the area of wound care materials. The use of aerogels for wound healing applications has increased due to their high exudate absorbency and ability to incorporate therapeutic substances, amongst them trace metals, to promote wound-healing. This study evaluates the swelling behavior of Ca-Zn-Ag-loaded alginate aerogels and their metal release upon incubation in human sweat or wound fluid substitutes. All aerogels show excellent liquid uptake from any of the formulas and high liquid holding capacities. Calcium is only marginally released into the swelling solvents, thus remaining as alginate bridging component aiding the absorption and fast transfer of liquids into the aerogel network. The zinc transfer quota is similar to those observed for common wound dressings in human and animal injury models. With respect to the immune regulatory function of zinc, cell culture studies show a high availability and anti-inflammatory activity of aerogel released Zn-species in RAW 264.7 macrophages. For silver, the balance between antibacterial effectiveness versus cytotoxicity remains a significant challenge for which the alginate aerogels need to be improved in the future. An increased knowledge of the transformations that alginate aerogels undergo in the course of the fabrication as well as during wound fluid exposure is necessary when aiming to create advanced, tissue-compatible aerogel products. Full article

(This article belongs to the Special Issue Processing, Characterization and Uses of Aerogels for Biomedical and Environmental Applications)

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17 pages, 4579 KiB

Open AccessArticle

Pyrolysis Kinetic Study and Reaction Mechanism of Epoxy Glass Fiber Reinforced Plastic by Thermogravimetric Analyzer (TG) and TG–FTIR (Fourier-Transform Infrared) Techniques

by Yuanhua Qiao, Oisik Das, Shu-Na Zhao, Tong-Sheng Sun, Qiang Xu and Lin Jiang

Polymers 2020, 12(11), 2739; https://doi.org/10.3390/polym12112739 - 18 Nov 2020

Cited by 27 | Viewed by 2733

Abstract

TG–FTIR combined technology was used to study the degradation process and gas phase products of epoxy glass fiber reinforced plastic (glass fiber reinforced plastic) under the atmospheres of high purity nitrogen. The pyrolysis characteristics of epoxy glass fiber reinforced plastic were measured under [...] Read more.

TG–FTIR combined technology was used to study the degradation process and gas phase products of epoxy glass fiber reinforced plastic (glass fiber reinforced plastic) under the atmospheres of high purity nitrogen. The pyrolysis characteristics of epoxy glass fiber reinforced plastic were measured under different heating rates (5, 10, 15, 20 °C min⁻¹) from 25 to 1000 °C. The thermogravimetric analyzer (TG) and differential thermogravimetric analyzer (DTG) curves show that the initial temperature, terminal temperature, and temperature of maximum weight loss rate in the pyrolysis reaction phase all move towards high temperature, as the heating rate increases. Epoxy glass fiber reinforced plastic has two stages of thermal weightlessness. The temperature range of the first stage of weight loss is 290–460 °C. The second stage is 460–1000 °C. The above two weight loss stages are caused by pyrolysis of the epoxy resin matrix, and the glass fiber will not decompose. The dynamic parameters of glass fiber reinforced plastic were obtained through the Kissinger-Akahira-Sunose (KAS), Flynn–Wall-Ozawa (FWO) and advanced Vyazovkin methods in model-free and the Coats–Redfern (CR) method in model fitting. FTIR spectrum result shows that the main components of the product gas are CO₂, H₂O, carbonyl components, and aromatic components during its pyrolysis. Full article

(This article belongs to the Special Issue Performance and Application of Novel Biocomposites II)

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20 pages, 64450 KiB

Open AccessArticle

Chitosan Modified Cationic Polyacrylamide Initiated by UV-H₂O₂ for Sludge Flocculation and New Insight on the Floc Characteristics Study

by Jie Chen, Xiaojun Xu, Rui Nie, Li Feng, Xuhao Li and Bingzhi Liu

Polymers 2020, 12(11), 2738; https://doi.org/10.3390/polym12112738 - 18 Nov 2020

Cited by 6 | Viewed by 2307

Abstract

In the present study, a novel graft modified flocculant CTS-g-PAMD was synthesized and applied to conduct sludge conditioning and dewatering. CTS-g-PAMD was copolymerized with AM, DMC and chitosan (CTS) under UV-H₂O₂ initiation. In addition, the effects of single factor experiments [...] Read more.

In the present study, a novel graft modified flocculant CTS-g-PAMD was synthesized and applied to conduct sludge conditioning and dewatering. CTS-g-PAMD was copolymerized with AM, DMC and chitosan (CTS) under UV-H₂O₂ initiation. In addition, the effects of single factor experiments on the molecular weight (MW) CTS grafting efficiency (GE) of CTS-g-PAMD were determined and the optimal copolymerization conditions were achieved. The GE of CTS-g-PAMD reached 91.1% and the MW was 4.82 × 10⁶ Da. As revealed from the characterized results of Fourier-transform infrared spectra (FT-IR), ¹H/ NMR, X-ray diffraction (XRD), scanning electron microscopic (SEM) and X-ray photoelectron spectroscopy (XPS), the successful synthesis of CTS-g-PAMD was confirmed, which is considered to be conducive to explaining sludge dewatering performance. Under the optimal conditions (pH = 7.0, flocculant dosage = 35 mg/L), the best flocculating performance (FCMC: 73.7%; SRF: 4.7 × 10¹² m·kg⁻¹, turbidity: 9.4 NTU) and large and dense sludge flocs (floc size d₅₀ = 379.142 µm, floc fractal dimension D_f = 1.58) were formed. The DMC and CTS chain segments exhibiting cationic properties significantly improved the positive charge density and enhanced the electrical patching effect of CTS-g-PAMD. The long molecular chain of CTS-g-PAMD exhibited superior extensibility, which enhanced bridging effect on adsorption. Moreover, the sludge floc after undergoing CTS-g-PAMD conditioning exhibited robust shear resistance and regeneration ability. After the sludge floc was crushed and broken, a large and dense sludge floc was formed, helping significantly reduce the sludge specific resistance (SRF), turbidity and cake moisture content (FCMC) and enhance the sludge dewatering effect. The novel CTS-g-PAMD flocculant shows promising practical applications and high market value. Full article

(This article belongs to the Section Polymer Applications)

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9 pages, 691 KiB

Open AccessArticle

A Novel Lightweight Polyurethane Composite for Application on Ultra-High-Voltage Insulator Core Filler

by Sizhu Yu, Xiaodong Li, Yage Zhao and Meishuai Zou

Polymers 2020, 12(11), 2737; https://doi.org/10.3390/polym12112737 - 18 Nov 2020

Cited by 10 | Viewed by 1893

Abstract

This study aimed to prepare a new lightweight ultra-high-voltage insulator core filler composite, which can solve the problem of bulkiness. In this study, rigid polyurethane foam pellets with different densities are used as lightweight fillers and polyurethane resins to compound lightweight composite materials. [...] Read more.

This study aimed to prepare a new lightweight ultra-high-voltage insulator core filler composite, which can solve the problem of bulkiness. In this study, rigid polyurethane foam pellets with different densities are used as lightweight fillers and polyurethane resins to compound lightweight composite materials. On accounting for working conditions, the density, insulation, heat resistance, water absorption and mechanical properties are tested. The compressive properties of composites are determined by a foam skeleton and a process. Among three kinds of composites, in which the composites with the best comprehensive performance are materials filled with pellets to a density of 0.15g·cm⁻³. The density, surface resistance, volume resistance, leakage current, initial decomposition temperature, water absorption, force, rupture displacement and limiting oxygen index (LOI) of composites are 0.665 g·cm⁻³, 1.17 × 10¹⁴ Ω, 9.68 × 10¹⁴ Ω·cm, 0.079 mA, 208 °C, 0.047%, 2262 N, 2.54 mm, and 23.3%, respectively. The ultra-high-voltage insulator core filler in this study can reduce the weight of the solid core insulator crossarm for Ultra-High Voltage (UHV) by 50–75%. Full article

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

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12 pages, 4348 KiB

Open AccessArticle

Enhancement of the Surface Properties on Polypropylene Film Using Side-Chain Crystalline Block Copolymers

by Sho Hirai, Patchiya Phanthong, Hikaru Okubo and Shigeru Yao

Polymers 2020, 12(11), 2736; https://doi.org/10.3390/polym12112736 - 18 Nov 2020

Cited by 2 | Viewed by 2809

Abstract

The consumption of polypropylene (PP) has significantly increased over that of other materials because of its light weight, easy molding, and high mechanical strength. However, the applications of PP are limited, owing to the lack of surface properties, especially with respect to adhesive [...] Read more.

The consumption of polypropylene (PP) has significantly increased over that of other materials because of its light weight, easy molding, and high mechanical strength. However, the applications of PP are limited, owing to the lack of surface properties, especially with respect to adhesive properties and hydrophilicity. In this study, we developed a surface modification method for enhancing the adhesive properties and hydrophilicity on the PP surface using a side-chain crystalline block copolymer (SCCBC). This method was simple and involved the dipping of a PP film in a diluted SCCBC solution. The optimized modification conditions for enhancing the adhesive properties of PP were investigated. The results revealed that the adhesion strength of PP modified with the SCCBC of behenyl acrylate and 2-(tert-butylamino)ethyl methacrylate was enhanced to 2.00 N/mm (T-peel test) and 1.05 N/mm² (tensile shear test). In addition, the hydrophilicity of PP modified with the SCCBC of behenyl acrylate and di(ethylene glycol)ethyl ether acrylate was enhanced to a water contact angle of 69 ± 4°. Surface analysis was also performed to elucidate a plausible mechanism for PP modification by the SCCBCs. This surface modification method is facile and enhances desirable properties for the wide application of PP. Full article

(This article belongs to the Special Issue Enhanced Polymer Composite Thin Films)

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12 pages, 5428 KiB

Open AccessArticle

Mechanistic Study of Synergistic Antimicrobial Effects between Poly (3-hydroxybutyrate) Oligomer and Polyethylene Glycol

by Ziheng Zhang, Jun Li, Linlin Ma, Xingxing Yang, Bin Fei, Polly H. M. Leung and Xiaoming Tao

Polymers 2020, 12(11), 2735; https://doi.org/10.3390/polym12112735 - 18 Nov 2020

Cited by 8 | Viewed by 2783

Abstract

Extended from our previous finding that poly (3-hydroxybutyrate) (PHB) oligomer is an effective antimicrobial agent against gram-positive bacteria, gram-negative bacteria, fungi and multi-drug resistant bacteria, this work investigates the effect of polyethylene glycol (PEG) on the antimicrobial effect of PHB oligomer. To investigate [...] Read more.

Extended from our previous finding that poly (3-hydroxybutyrate) (PHB) oligomer is an effective antimicrobial agent against gram-positive bacteria, gram-negative bacteria, fungi and multi-drug resistant bacteria, this work investigates the effect of polyethylene glycol (PEG) on the antimicrobial effect of PHB oligomer. To investigate and explain this promoting phenomenon, three hypothetic mechanisms were proposed, that is, generation of new antimicrobial components, degradation of PHB macromolecules and dissolution/dispersion of PHB oligomer by PEG. With a series of systematic experiments and characterizations of high-performance liquid chromatography–mass spectrometry (HPLC-MS), it was deducted that PEG promotes the antimicrobial effect of PHB oligomer synergistically through dissolution/dispersion, owing to its amphipathy, which improves the hydrophilicity of PHB oligomer. Full article

(This article belongs to the Special Issue Progress in Polymer Research: From Sustainable Materials to Biomedical Application)

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