Polymers

Research

14 pages, 3310 KiB

Open AccessArticle

Micro and Nano Smart Composite Films Based on Copper-Iodine Coordination Polymer as Thermochromic Biocompatible Sensors

by Javier Conesa-Egea, Alberto Moreno-Vázquez, Vanesa Fernández-Moreira, Yolanda Ballesteros, Milagros Castellanos, Félix Zamora and Pilar Amo-Ochoa

Polymers 2019, 11(6), 1047; https://doi.org/10.3390/polym11061047 - 15 Jun 2019

Cited by 9 | Viewed by 3735

Abstract

Herein is presented the preparation and characterization of a composite material obtained by the combination of nanosheets of a coordination polymer (CP) based on the copper(I)-I double chain with response to temperature and pressure with polylactic acid (PLA) as biodegradable organic matrix. The [...] Read more.

Herein is presented the preparation and characterization of a composite material obtained by the combination of nanosheets of a coordination polymer (CP) based on the copper(I)-I double chain with response to temperature and pressure with polylactic acid (PLA) as biodegradable organic matrix. The new films of composite materials are generated using a simple and low-cost method and can be created with long lateral dimensions and thicknesses ranging from a few microns to a few nanometers. Studies show that the new material maintains the optical response versus the temperature, while the elasticity and flexibility of the PLA totally quenches the response to pressure previously observed for the CP. This new material can act as a reversible sensor at low temperatures, thanks to the flexibility of the copper(I)-iodine chain that conforms the CP. The addition of CP to the PLA matrix reduces the elastic modulus and ultimate elongation of the organic matrix, although it does not reduce its tensile strength. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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12 pages, 4797 KiB

Open AccessArticle

Fabrication of Graphene-Metal Transparent Conductive Nanocomposite Layers for Photoluminescence Enhancement

by Hongyong Huang, Zhiyou Guo, Sitong Feng, Huiqing Sun, Shunyu Yao, Xidu Wang, Dong Lu, Yaohua Zhang and Yuan Li

Polymers 2019, 11(6), 1037; https://doi.org/10.3390/polym11061037 - 11 Jun 2019

Viewed by 2968

Abstract

In this work, the synthesis and characterization ofgraphene-metal nanocomposite, a transparent conductive layer, is examined. This transparent conductive layer is named graphene-Ag-graphene (GAG), which makes full use of the high electron mobility and high conductivity characteristics of graphene, while electromagnetically induced transparency (EIT) [...] Read more.

In this work, the synthesis and characterization ofgraphene-metal nanocomposite, a transparent conductive layer, is examined. This transparent conductive layer is named graphene-Ag-graphene (GAG), which makes full use of the high electron mobility and high conductivity characteristics of graphene, while electromagnetically induced transparency (EIT) is induced by Ag nanoparticles (NPs). The nanocomposite preparation technique delivers three key parts including the transfer of the first layer graphene, spin coating of Ag NPs and transfer of the second layer of graphene. The GAG transparent conductive nanocomposite layer possess a sheet resistance of 16.3 ohm/sq and electron mobility of 14,729 cm²/(v s), which are superior to single-layer graphene or other transparent conductive layers. Moreover, the significant enhancement of photoluminescence can be ascribed to the coupling of the light emitters in multiple quantum wells with the surface plasmon Ag NPs and the EIT effect. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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13 pages, 6337 KiB

Open AccessArticle

Synthesis of Negatively Charged Polyol-Functional PSF Membranes with Good Hydrophilic and Efficient Boron Removal Properties

by Jinbo Jin, Xilan Du, Jie Yu, Shuhao Qin, Min He, Kaizhou Zhang and Jingkui Yang

Polymers 2019, 11(5), 780; https://doi.org/10.3390/polym11050780 - 1 May 2019

Cited by 9 | Viewed by 3488

Abstract

Boron removal remains a major barrier to water purification, it is important to develop a specialized adsorption membrane for boron removal. By means of a simple and effective method, a hydrophilic membrane for boron removal with a polyhydroxy functional group on the surface [...] Read more.

Boron removal remains a major barrier to water purification, it is important to develop a specialized adsorption membrane for boron removal. By means of a simple and effective method, a hydrophilic membrane for boron removal with a polyhydroxy functional group on the surface was prepared. Firstly, a polysulfone (PSF) membrane was modified by co-depositing polyethyleneimine (PEI) with dopamine (DA) in one-step to produce amine-rich surfaces, then the DA/PEI-functionalized membranes were reacted with glycidol, with the prepared membranes corresponding to PSF-PDA/PEI membranes and PSF-diol membranes. The prepared membranes were characterized by water-uptake, FTIR, (X-ray photoelectron spectroscopy) XPS, (Field emission scanning electron microscope) FESEM, and zeta potential measurements. The hydrophilicity of the membrane was characterized by the static water contact angle (WCA) test. In addition, we systematically studied the impact of initial boron concentration, chelating time, and pH value on boron removal performance. The results showed that the PSF-diol membrane had strong hydrophilicity with a WCA of about 38°. The maximum adsorption capacity of boron appeared to be 1.61 mmol/g within 10 min at a boron concentration of 300 mg/L. Adsorption kinetics showed that saturation adsorption can be achieved in minutes at the initial concentration of 5 mg/L, which is beneficial to a rapid filtration process. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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14 pages, 7548 KiB

Open AccessArticle

Characterization of KH-560-Modified Jute Fabric/Epoxy Laminated Composites: Surface Structure, and Thermal and Mechanical Properties

by Xue Wang, Lihai Wang, Wenwen Ji, Quanling Hao, Guanghui Zhang and Qingkai Meng

Polymers 2019, 11(5), 769; https://doi.org/10.3390/polym11050769 - 1 May 2019

Cited by 29 | Viewed by 4672

Abstract

In this study, jute fabrics were used to reinforce epoxy resin to prepare laminated composites. KH-560 silane coupling agent modification was used to improve the interfacial compatibility between fibers and epoxy. The effects of different immersion times (0 min, 10 min, 30 min, [...] Read more.

In this study, jute fabrics were used to reinforce epoxy resin to prepare laminated composites. KH-560 silane coupling agent modification was used to improve the interfacial compatibility between fibers and epoxy. The effects of different immersion times (0 min, 10 min, 30 min, 60 min, 90 min, and 120 min) on the jute fiber’s element content, crystal structure, and thermal stability, and the mechanical properties of laminated composites were studied. X-ray diffractometry (XRD) analysis showed that the KH-560 modification improved the crystallinity index (CI) and crystallite sizes (CS) of jute fibers. Scanning electron microscopy (SEM) analysis of the tensile fracture surfaces revealed a thick epoxy on the modified pulled fiber surfaces. Fourier transform infrared spectroscopy (FTIR) and energy dispersive spectrometer (EDS) analysis identified the presence of silicon and C–O–Si/Si–O–Si cross-linked structures on the surface of modified jute fibers. These cross-linked structures improved the thermal stability and mechanical properties of the laminated composites. When the immersion time was 60 min, the CI, CS, tensile strength, tensile modulus, flexural strength, and flexural modulus of the modified samples were 42.39%, 3.62 nm, 34.6 ± 1.1 MPa, 2.11 ± 0.12 GPa, 83.7 ± 1.8 MPa, and 4.08 ± 0.12 GPa, respectively, which were better than that of unmodified and other modified composites. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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13 pages, 3351 KiB

Open AccessArticle

Error Analysis in Determination of Density and Temperature of Saline Solution Using Fiber Optic Photoacoustic Transducer Coated with MoS₂-PDMS Composite

by Cheng Li, Jian Liu and Xiao Bin Peng

Polymers 2019, 11(5), 762; https://doi.org/10.3390/polym11050762 - 1 May 2019

Cited by 2 | Viewed by 3083

Abstract

Regarding the ultrasound determination of density-dependent salinity in seawater, a miniature broadband (up to ~12.8 MHz at 6 dB bandwidth) fiber-tip photoacoustic transducer coated with an ~68.32 μm thick MoS₂-polydimethylsiloxane (PDMS) composite was developed for simultaneously measuring the temperature and density [...] Read more.

Regarding the ultrasound determination of density-dependent salinity in seawater, a miniature broadband (up to ~12.8 MHz at 6 dB bandwidth) fiber-tip photoacoustic transducer coated with an ~68.32 μm thick MoS₂-polydimethylsiloxane (PDMS) composite was developed for simultaneously measuring the temperature and density of laboratory saline solutions, along with a piezoelectric transducer (PZT) for ultrasound detection. The two parameters, respectively, ranging 20 °C to 50 °C and from 0.99 g/cm³ to 1.10 g/cm³ were measured and then extracted based on the regressive dependence on the propagation speed and attenuation of the ultrasonic wave. In terms of the established linear regression model and estimated regression characteristic parameters, the calculated temperature and density results, respectively, exhibited the extended uncertainty values of 1 °C and 1.08 × 10⁻³ g/cm³ (k = 2.132), accompanied with an excellent goodness of fit (R² > 0.97) and significance of the binary linear regression (F >> F_0.01). The highly consistent experimental data confirmed the accuracy of our method, thus suggesting the potential of measuring salinity in seawater using compact fiber-optic photo-induced ultrasound scheme. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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15 pages, 5717 KiB

Open AccessArticle

Enhancing the Interfacial Strength of Carbon Fiber/Poly(ether ether ketone) Hybrid Composites by Plasma Treatments

by Chunrui Lu, Si Qiu, Xue Lu, Jian Wang, Lin Xiao, Ting Zheng, Xiaodong Wang and Dongxing Zhang

Polymers 2019, 11(5), 753; https://doi.org/10.3390/polym11050753 - 28 Apr 2019

Cited by 49 | Viewed by 5012

Abstract

As a promising alternative to traditional prepreg, carbon fiber/poly(ether ether ketone) (CF/PEEK) hybrid composites have attracted wide public interest for their flexibility and conformability. However, modification methods focused on the hybrid premix have not been previously studied. In the present work, the interfacial [...] Read more.

As a promising alternative to traditional prepreg, carbon fiber/poly(ether ether ketone) (CF/PEEK) hybrid composites have attracted wide public interest for their flexibility and conformability. However, modification methods focused on the hybrid premix have not been previously studied. In the present work, the interfacial strength of the hybrid composite was improved by treating the carbon and PEEK fibers together in a radiofrequency (RF) plasma containing one of the following gases to achieve surface activation: air, Ar, or Ar–air. After plasma treatment, the increased roughness of CF and the grafted chemical groups of CFs and PEEK fibers were propitious to the mechanical interlocking and interfacial strength. Significant interfacial shear strength (IFSS) enhancement was achieved after Ar 1 min, air 1 min plasma treatment. This study offers an alternative method for improving the interfacial properties of CF/PEEK composites by focusing on the boundary layer and modifying and controlling the fiber–matrix interface. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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13 pages, 4024 KiB

Open AccessArticle

Structure and Flame-Retardant Actions of Rigid Polyurethane Foams with Expandable Graphite

by Yongjun Chen, Yuanfang Luo, Xiaohui Guo, Lijuan Chen, Tiwen Xu and Demin Jia

Polymers 2019, 11(4), 686; https://doi.org/10.3390/polym11040686 - 16 Apr 2019

Cited by 31 | Viewed by 4525

Abstract

In this paper, rigid polyurethane foams that were filled with expandable graphite (RPUF/EG) composites were prepared by the liquid blending method, and then the structure and flame retardancy performance of materials were investigated through optical microscope, scanning electron microscope, limit oxygen index, cone [...] Read more.

In this paper, rigid polyurethane foams that were filled with expandable graphite (RPUF/EG) composites were prepared by the liquid blending method, and then the structure and flame retardancy performance of materials were investigated through optical microscope, scanning electron microscope, limit oxygen index, cone calorimeter, thermogravimetric analysis coupled to fourier transform infrared spectrum, and X-ray photoelectron spectroscopy. The results showed that a large number of EG could be good to the exhibition of flame retardancy of RPUF, where the optimal material was found at loading 15 phr EG that showed an increased limit oxygen index value and a decreased calorific or fuming value. TGA coupled FTIR and XPS revealed that EG could disassembled before RPUF under heating treatment, and it could form a pyknotic and enahnced residual carbon layer on RPUF surface after the fire, which restricted the transfer of gas, like oxygen or heat into PU matrix, finally resulting in the promotion of flame retardancy of RPUF. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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9 pages, 5131 KiB

Open AccessArticle

Structure and Mechanical Performance of Poly(vinyl Alcohol) Nanocomposite by Incorporating Graphitic Carbon Nitride Nanosheets

by Shaojian He, Jiaqi Wang, Mengxia Yu, Yang Xue, Jianbin Hu and Jun Lin

Polymers 2019, 11(4), 610; https://doi.org/10.3390/polym11040610 - 3 Apr 2019

Cited by 22 | Viewed by 4769

Abstract

Owing to the high aspect ratio, the two-dimensional (2D) inorganic nanofillers have attracted extensive interest in the field of polymer reinforcement. In this work, graphitic carbon nitride (g-C₃N₄) nanosheets were obtained via thermal condensation of melamine and were then [...] Read more.

Owing to the high aspect ratio, the two-dimensional (2D) inorganic nanofillers have attracted extensive interest in the field of polymer reinforcement. In this work, graphitic carbon nitride (g-C₃N₄) nanosheets were obtained via thermal condensation of melamine and were then ultrasonically exfoliated in water, which was confirmed by atomic force microscopy (AFM) and TEM. Poly(vinyl alcohol) (PVA)/g-C₃N₄ nanocomposites were achieved by solution casting using water as the solvent. The structure and mechanical performance of PVA/g-C₃N₄ nanocomposites were studied. It was found that the g-C₃N₄ nanosheets were well dispersed in the PVA matrix. The introduction of g-C₃N₄ nanosheets increased the glass transition temperature and crystallinity of the nanocomposites, leading to the improved mechanical performance. Compared with the pure PVA, the PVA/g-C₃N₄ nanocomposite with 0.50 wt% g-C₃N₄ nanosheets showed ~70.7% enhancement in tensile strength, up from 51.2 MPa to 87.4 MPa. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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14 pages, 5646 KiB

Open AccessArticle

Influence of MoS₂ Nanosheet Size on Performance of Drilling Mud

by Sung Hyun Hong, Hae Jin Jo, Min-Ju Choi, Ho Won Jang, Young Ju Kim, Wook Ryol Hwang and Soo Young Kim

Polymers 2019, 11(2), 321; https://doi.org/10.3390/polym11020321 - 13 Feb 2019

Cited by 17 | Viewed by 4027

Abstract

Water-based drilling mud (WBM) is a non-Newtonian fluid that has a variety of applications such as in transporting cuttings during drilling, protecting the borehole, and cooling the drill bit. With the development of nano-technology, various nanoparticles have been synthesized and have been added [...] Read more.

Water-based drilling mud (WBM) is a non-Newtonian fluid that has a variety of applications such as in transporting cuttings during drilling, protecting the borehole, and cooling the drill bit. With the development of nano-technology, various nanoparticles have been synthesized and have been added to WBM to improve its performance. Shear thinning is the most important factor in drilling mud and this attribute can be improved when two-dimensional particles are added. MoS₂ nanoparticles, which represent a typical two-dimensional material, are easy to synthesize in large quantities and have a high thermal conductivity and low coefficient of friction. Since the two-dimensional structure, thermal conductivity, and low coefficient of friction of MoS₂ would improve the performance of WBM, we experimented with MoS₂ nanosheets as an additive, under optimal conditions, using various samples each with uniform sizes and thicknesses of nanosheets. A large amount of MoS₂ nanosheets was synthesized, sorted by thickness and diameter, and added to drilling mud. The diameter of MoS₂ was divided into a small diameter group (about 100–400 nm) and a big diameter group (about 300–650 nm), and the thickness was divided into 1–2 nm and 5–10 nm groups. Experimental results showed that when MoS₂ is added to WBM, shear thinning occurs more strongly. In addition, the addition of MoS₂ with a thickness of 1–2 nm and a diameter of 300–650 nm resulted in the highest increase in viscosity and thermal conductivity of WBM. As a result, we experimentally confirmed that MoS₂ can be used as an additive to increase the thermal conductivity and viscosity of WBM and to make shear thinning phenomenon more. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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13 pages, 2586 KiB

Open AccessArticle

Hydrophobicity of Polyacrylate Emulsion Film Enhanced by Introduction of Nano-SiO₂ and Fluorine

by Tao Xu, Qiangqiang Xiao, Jiayu Chen, Li Li, Xiongjun Yang, Lifang Liu, Wenhui Yuan, Bingjian Zhang and Huijun Wu

Polymers 2019, 11(2), 255; https://doi.org/10.3390/polym11020255 - 3 Feb 2019

Cited by 17 | Viewed by 4791

Abstract

This study proposes to utilize modified Nano-SiO₂/fluorinated polyacrylate emulsion that was synthesized with a semi-continuous starved seed emulsion polymerization to improve the hydrophobicity, thermal stability, and UV-Vis absorption of polyacrylate emulsion film. To verify the proposed method, a series inspection had [...] Read more.

This study proposes to utilize modified Nano-SiO₂/fluorinated polyacrylate emulsion that was synthesized with a semi-continuous starved seed emulsion polymerization to improve the hydrophobicity, thermal stability, and UV-Vis absorption of polyacrylate emulsion film. To verify the proposed method, a series inspection had been conducted to investigate the features of the emulsion film. The morphological analysis indicated that Nano-SiO₂ was surrounded by a silane molecule after modification, which can efficiently prevent silica nanoparticles from aggregating. Fourier transform infrared spectra confirmed that modified SiO₂ and dodecafluoroheptyl methacrylate (DFMA) were successfully introduced to the copolymer latex. The particle size of latex increased with the introduction of modified Nano-SiO₂ and DFMA. UV-Vis absorption spectra revealed that modified silicon nanoparticles can improve the ultraviolet shielding effect obviously. X-ray photoelectron spectroscopy illustrated that the film–air interface was richer in fluorine than film section and the glass side. The contact angle of modified Nano-SiO₂/fluorinated polyacrylate emulsion containing 3 wt % DFMA was 112°, slightly lower than double that of polyacrylate emulsion, indicating composite emulsion films possess better hydrophobicity. These results suggest that introducing modified Nano-SiO₂ and fluorine into polyacrylate emulsion can significantly enhance the thermal stability of emulsion films. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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17 pages, 5082 KiB

Open AccessArticle

Effect of Flank Rotation on the Photovoltaic Properties of Dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene-Based Narrow Band Gap Copolymers

by Mingjing Zhang, Liangjian Zhu, Pengzhi Guo, Xunchang Wang, Junfeng Tong, Xiaofang Zhang, Yongjian Jia, Renqiang Yang, Yangjun Xia and Chenglong Wang

Polymers 2019, 11(2), 239; https://doi.org/10.3390/polym11020239 - 1 Feb 2019

Cited by 6 | Viewed by 3065

Abstract

Side chain engineering has been an effective approach to modulate the solution processability, optoelectronic properties and miscibility of conjugated polymers (CPs) for organic/polymeric photovoltaic cells (PVCs). As compared with the most commonly used method of introducing alkyl chains, the employment of alkyl-substituted aryl [...] Read more.

Side chain engineering has been an effective approach to modulate the solution processability, optoelectronic properties and miscibility of conjugated polymers (CPs) for organic/polymeric photovoltaic cells (PVCs). As compared with the most commonly used method of introducing alkyl chains, the employment of alkyl-substituted aryl flanks would provide two-dimensional (2-D) CPs having solution processability alongside additional merits like deepened highest occupied molecular orbital (HOMO) energy levels, increased absorption coefficient and charger transporting, etc. In this paper, the triple C≡C bond was used as conjugated linker to decrease the steric hindrance between the flanks of 4,5-didecylthien-2-yl (T) and dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (DTBDT) core. In addition, an alternating CP derived from 4,5-didecylthien-2-yl-ethynyl (TE) flanked DTBDT, and 4,9-bis(4-octylthien-2-yl) naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole (DTNT), named as PDTBDT-TE-DTNT, was synthesized and characterized. As compared with the controlled PDTBDT-T-DTNT, which was derived from 4,5-didecylthien-2-yl flanked DTBDT and DTNT, the results for exciton dissociation probability, density functional theory (DFT), time-resolved photoluminescence (PL) measurements, etc., revealed that the lower steric hindrance between TE and DTBDT might lead to the easier rotation of the TE flanks, thus contributing to the decrease of the exciton lifetime and dissociation probability, finally suppressing the short-circuit current density (J_SC), etc., of the photovoltaic devices from PDTBDT-TE-DTNT. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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14 pages, 3104 KiB

Open AccessEditor’s ChoiceArticle

Design and Compressive Behavior of a Photosensitive Resin-Based 2-D Lattice Structure with Variable Cross-Section Core

by Shuai Li, Jiankun Qin, Bing Wang, Tengteng Zheng and Yingcheng Hu

Polymers 2019, 11(1), 186; https://doi.org/10.3390/polym11010186 - 21 Jan 2019

Cited by 34 | Viewed by 5105

Abstract

This paper designed and manufactured photosensitive resin-based 2-D lattice structures with different types of variable cross-section cores by stereolithography 3D printing technology (SLA 3DP). An analytical model was employed to predict the structural compressive response and failure types. A theoretical calculation was performed [...] Read more.

This paper designed and manufactured photosensitive resin-based 2-D lattice structures with different types of variable cross-section cores by stereolithography 3D printing technology (SLA 3DP). An analytical model was employed to predict the structural compressive response and failure types. A theoretical calculation was performed to obtain the most efficient material utilization of the 2-D lattice core. A flatwise compressive experiment was performed to verify the theoretical conclusions. A comparison of theoretical and experimental results showed good agreement for structural compressive response. Results from the analytical model and experiments showed that when the 2-D lattice core was designed so that R/r = 1.167 (R and r represent the core radius at the ends and in the middle), the material utilization of the 2-D lattice core improved by 13.227%, 19.068%, and 22.143% when n = 1, n = 2, and n = 3 (n represents the highest power of the core cross-section function). Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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9 pages, 2945 KiB

Open AccessArticle

Dynamic Optics with Transparency and Color Changes under Ambient Conditions

by Yejia Jiang, Songshan Zeng, Yu Yao, Shiyu Xu, Qiaonan Dong, Pingxu Chen, Zhaofeng Wang, Monica Zhang, Mengting Zhu, Gefan Xu, Huidan Zeng and Luyi Sun

Polymers 2019, 11(1), 103; https://doi.org/10.3390/polym11010103 - 9 Jan 2019

Cited by 25 | Viewed by 5771

Abstract

Mechanochromic materials have recently received tremendous attention because of their potential applications in humanoid robots, smart windows, strain sensors, anti-counterfeit tags, etc. However, improvements in device design are highly desired for practical implementation in a broader working environment with a high stability. In [...] Read more.

Mechanochromic materials have recently received tremendous attention because of their potential applications in humanoid robots, smart windows, strain sensors, anti-counterfeit tags, etc. However, improvements in device design are highly desired for practical implementation in a broader working environment with a high stability. In this article, a novel and robust mechanochromism was designed and fabricated via a facile method. Silica nanoparticles (NPs) that serve as a trigger of color switch were embedded in elastomer to form a bi-layer hybrid film. Upon stretching under ambient conditions, the hybrid film can change color as well as transparency. Furthermore, it demonstrates excellent reversibility and reproducibility and is promising for widespread application. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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14 pages, 4178 KiB

Open AccessArticle

Mechanically Enhanced Electrical Conductivity of Polydimethylsiloxane-Based Composites by a Hot Embossing Process

by Xiaolong Gao, Yao Huang, Xiaoxiang He, Xiaojing Fan, Ying Liu, Hong Xu, Daming Wu and Chaoying Wan

Polymers 2019, 11(1), 56; https://doi.org/10.3390/polym11010056 - 2 Jan 2019

Cited by 20 | Viewed by 5654

Abstract

Electrically conductive polymer composites are in high demand for modern technologies, however, the intrinsic brittleness of conducting conjugated polymers and the moderate electrical conductivity of engineering polymer/carbon composites have highly constrained their applications. In this work, super high electrical conductive polymer composites were [...] Read more.

Electrically conductive polymer composites are in high demand for modern technologies, however, the intrinsic brittleness of conducting conjugated polymers and the moderate electrical conductivity of engineering polymer/carbon composites have highly constrained their applications. In this work, super high electrical conductive polymer composites were produced by a novel hot embossing design. The polydimethylsiloxane (PDMS) composites containing short carbon fiber (SCF) exhibited an electrical percolation threshold at 0.45 wt % and reached a saturated electrical conductivity of 49 S/m at 8 wt % of SCF. When reducing the sample thickness from 1.0 to 0.1 mm by the hot embossing process, a compression-induced percolation threshold occurred at 0.3 wt %, while the electrical conductivity was further enhanced to 378 S/m at 8 wt % SCF. Furthermore, the addition of a second nanofiller of 1 wt %, such as carbon nanotube or conducting carbon black, further increased the electrical conductivity of the PDMS/SCF (8 wt %) composites to 909 S/m and 657 S/m, respectively. The synergy of the densified conducting filler network by the mechanical compression and the hierarchical micro-/nano-scale filler approach has realized super high electrically conductive, yet mechanically flexible, polymer composites for modern flexible electronics applications. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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16 pages, 11904 KiB

Open AccessArticle

The Optimization of Process Parameters and Characterization of High-Performance CF/PEEK Composites Prepared by Flexible CF/PEEK Plain Weave Fabrics

by Chunrui Lu, Nuo Xu, Ting Zheng, Xin Zhang, Hanxiong Lv, Xue Lu, Lin Xiao and Dongxing Zhang

Polymers 2019, 11(1), 53; https://doi.org/10.3390/polym11010053 - 31 Dec 2018

Cited by 43 | Viewed by 6247

Abstract

Continuous carbon fiber (CF)-reinforced poly (ether ether ketone) (PEEK) composites have excellent mechanical properties, but their processing techniques are limited. Therefore, we promoted a braiding method based on the hybrid fiber method by hot-compacting CF/PEEK plain weave fabrics to solve the problem of [...] Read more.

Continuous carbon fiber (CF)-reinforced poly (ether ether ketone) (PEEK) composites have excellent mechanical properties, but their processing techniques are limited. Therefore, we promoted a braiding method based on the hybrid fiber method by hot-compacting CF/PEEK plain weave fabrics to solve the problem of difficult wetting between CF and PEEK. Four parameters—melting temperature, molding pressure, crystallization temperature and the resin contents—were investigated for optimized fabrication. After studying the melting range, thermal stability and the contact angle of PEEK under different temperatures, the melting temperature was set at 370 °C. An ultra-depth-of-field 3D microscope was adopted to investigate the effects of molding pressure in the melting stage. The tensile strength or modulus along and perpendicular to the carbon fiber direction and crystallinity under different crystallization temperatures were analyzed. As a result, the sample crystalized at 300 °C showed an excellent tensile properties and crystallinity. The increased mass ratio of PEEK ranging from 50.45% to 59.07% allowed for much stronger interfacial strength; however, the higher resin content can lead to the dispersion of CFs, loss of resin and the formation of defects during processing. Finally, the optimal resin mass content was 59.07%, with a tensile strength of 738.36 ± 14.49 MPa and a flexural strength of 659.68 ± 57.53 MPa. This paper studied the optimized processing parameters to obtain better properties from CF/PEEK plain weave fabrics and to further broaden the specific applications of CF/PEEK composites, demonstrating a new direction for its fabrication. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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12 pages, 2577 KiB

Open AccessArticle

MoSe₂-GO/rGO Composite Catalyst for Hydrogen Evolution Reaction

by Wenwu Guo, Quyet Van Le, Amirhossein Hasani, Tae Hyung Lee, Ho Won Jang, Zhengtang Luo and Soo Young Kim

Polymers 2018, 10(12), 1309; https://doi.org/10.3390/polym10121309 - 27 Nov 2018

Cited by 38 | Viewed by 6624

Abstract

There has been considerable research to engineer composites of transition metal dichalcogenides with other materials to improve their catalytic performance. In this work, we present a modified solution-processed method for the formation of molybdenum selenide (MoSe₂) nanosheets and a facile method [...] Read more.

There has been considerable research to engineer composites of transition metal dichalcogenides with other materials to improve their catalytic performance. In this work, we present a modified solution-processed method for the formation of molybdenum selenide (MoSe₂) nanosheets and a facile method of structuring composites with graphene oxide (GO) or reduced graphene oxide (rGO) at different ratios to prevent aggregation of the MoSe₂ nanosheets and hence improve their electrocatalytic hydrogen evolution reaction performance. The prepared GO, rGO, and MoSe₂ nanosheets were characterized by X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The electrocatalytic performance results showed that the pure MoSe₂ nanosheets exhibited a somewhat high Tafel slope of 80 mV/dec, whereas the MoSe₂-GO and MoSe₂-rGO composites showed lower Tafel slopes of 57 and 67 mV/dec at ratios of 6:4 and 4:6, respectively. We attribute the improved catalytic effects to the better contact and faster carrier transfer between the edge of MoSe₂ and the electrode due to the addition of GO or rGO. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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21 pages, 7153 KiB

Open AccessArticle

Preparation and Properties of SBS-g-GOs-Modified Asphalt Based on a Thiol-ene Click Reaction in a Bituminous Environment

by Jing Li, Meizhao Han, Yaseen Muhammad, Yu Liu, Zhibin Su, Jing Yang, Song Yang and Shaochan Duan

Polymers 2018, 10(11), 1264; https://doi.org/10.3390/polym10111264 - 13 Nov 2018

Cited by 40 | Viewed by 5707

Abstract

Styrene-butadiene styrene graphene oxide nanoplatelets (SBS-g-GOs)-modified asphalt was prepared by reacting thiolated GOs (GOs-SH) with SBS in asphalt using a thiol-ene click reaction. The temperature resistance and mechanical properties of asphalts were analyzed by dynamic shear rheology (DSR) and multiple-stress creep-recovery (MSCR) tests, [...] Read more.

Styrene-butadiene styrene graphene oxide nanoplatelets (SBS-g-GOs)-modified asphalt was prepared by reacting thiolated GOs (GOs-SH) with SBS in asphalt using a thiol-ene click reaction. The temperature resistance and mechanical properties of asphalts were analyzed by dynamic shear rheology (DSR) and multiple-stress creep-recovery (MSCR) tests, which revealed that an optimum amount of GOs-SH (0.02%) can effectively improve the low temperature and anti-rutting performance of SBS asphalt. Segregation experiments showed that SBS-g-GOs possessed good stability and dispersion in base asphalt. Fluorescence microscopy results revealed that the addition of GOs-SH promoted the formation of SBS network structure. Textural and morphological characterization of GOs-SH and SBS were achieved by Fourier transform infra-red (FT-IR) spectroscopy, energy-dispersive X-ray spectroscopy (EDX), atomic-force microscopy (AFM), X-ray diffraction (XRD), and scanning electron microscopy (SEM), while surface chemical composition was tested by X-ray photoelectron spectroscopy (XPS). Based on textural characterization data, a suitable reaction mechanism was proposed that involved the preferential reaction between GOs-SH and 1,2 C=C of SBS. The currently designed GOs-SH incorporated asphalt via thiol-ene click reaction provides new ideas for the preparation of modified asphalt with enhanced mechanical properties for target-oriented applications. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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15 pages, 8112 KiB

Open AccessArticle

Preparation and Hydrogen Storage Characteristics of Surfactant-Modified Graphene

by Tao Xu, Jiayu Chen, Wenhui Yuan, Baoqing Li, Li Li, Huijun Wu and Xiaoqing Zhou

Polymers 2018, 10(11), 1220; https://doi.org/10.3390/polym10111220 - 2 Nov 2018

Cited by 7 | Viewed by 3380

Abstract

As the depletion of traditional fossil fuels and environmental pollution become serious problems for human society, researchers are actively looking for renewable energy sources. Since hydrogen energy is considered a clean, efficient, and renewable alternative energy source, it is regarded as the most [...] Read more.

As the depletion of traditional fossil fuels and environmental pollution become serious problems for human society, researchers are actively looking for renewable energy sources. Since hydrogen energy is considered a clean, efficient, and renewable alternative energy source, it is regarded as the most promising option. In this context, how to store hydrogen safely and efficiently has become the major challenge that hinders the actual application. To fill this gap, this paper proposes to utilize surfactant-modified graphene for hydrogen storage. Through a modified Hummers’ method and ultrasonic stripping, this study proposes to prepare graphene from graphite oxide with NaBH₄. The surfactant sodium dodecyl benzene sulfonate (SDBS) was used as a dispersant during the reduction process to produce dispersion-stabilized graphene suspensions. Then, to investigate the characteristics of the graphene suspensions, X-ray diffraction (XRD), SEM, TEM, Fourier transform infrared (FT-IR), Raman, XPS, TG, and N₂ adsorption–desorption tests were conducted. Finally, analytical models for hydrogen adsorption were investigated with Langmuir and Freundlich fittings. The results show that the application of SDBS can effectively reduce the agglomeration among graphene monolayers and increase the specific surface area of graphene, and that the adsorption behavior is consistent with the Freundlich adsorption model, and is a physical process. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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12 pages, 3102 KiB

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Inorganic and Organic Hybrid Nanoparticles as Multifunctional Crosslinkers for Rubber Vulcanization with High-Filler Rubber Interaction

by Lijuan Chen, Xiaohui Guo, Yuanfang Luo, Zhixin Jia, Yongjun Chen and Demin Jia

Polymers 2018, 10(10), 1138; https://doi.org/10.3390/polym10101138 - 12 Oct 2018

Cited by 13 | Viewed by 4045

Abstract

Improving the interfacial interaction between rubber and silica nanoparticles, and simultaneously reducing free sulfur and preventing migration and volatilization of a rubber vulcanizing agent, commercial sulfur compound aliphatic ether polysulfide (VA-7) was chemically attached to the silica surface to obtain a functionalized nanoparticle [...] Read more.

Improving the interfacial interaction between rubber and silica nanoparticles, and simultaneously reducing free sulfur and preventing migration and volatilization of a rubber vulcanizing agent, commercial sulfur compound aliphatic ether polysulfide (VA-7) was chemically attached to the silica surface to obtain a functionalized nanoparticle (silica-s-VA7). Functional nanoparticles can not only effectively crosslink rubber without sulfur as a novel vulcanizator, but are also evenly dispersed in the rubber matrix and improve the dispersion of the remaining pristine silica as an interfacial compatibilizer. In addition, the thicker immobilized polymer layer and prominent crosslinking density of SBR nanocomposites simultaneously demonstrate that the novel vulcanizing agent silica-s-VA7 gives rise to significant improvement on the rubber–filler interfacial adhesion on account of the covalent linkages of organic and inorganic interfaces between elastomer and nanofillers. We envisage that this strategy may provide a new avenue to implement high-efficiency design for a multifunctional rubber-vulcanizing agent through an organic and inorganic hybridization mechanism. Full article

(This article belongs to the Special Issue 2D Polymers and Composites: Preparation, Characterization and Application)

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