Synthesis, Characterization and Surface Properties of Cross-linked Polyurethane Dispersions Modified by Organosiloxane

A series of cross-linked polyether-polyester polyurethane dispersions modified with organosiloxane were prepared based on hydroxyl-terminated polydimethylsiloxane (HTPS) as hydrophobic component and 3-aminopropyl-triethoxysilane (APTS) as cross-linker as well as a bridge between polyurethane (PU) and polysiloxane (PSIL). It was discovered that polydimethylsiloxane segments were incorporated into PU chains chemically and organosiloxane was preferentially oriented toward the surface layer of the film by making a comparison of attenuated total reflection (ATR) spectra between the copolymer and the blend of PU and PSIL, which was further confirmed by investigation of electron spectroscopy for chemical analysis (ESCA). The relationships between surface properties of the film formed from polyurethane dispersion and organosiloxane content were also studied. The results showed that water contact angle of the film increased with the increase of organosiloxane content. Interestingly, it was also found that water contact angle of PUS film increased firstly and then decreased when film-forming temperature varied from 25℃ to 55℃.     

疏水性聚酯薄膜的制备及表面形貌分析

利用NaOH溶液化学刻蚀聚酯薄膜成功制得疏水性薄膜.研究了聚酯在碱性溶液中发生水解反应时外界条件对刻蚀结果的影响规律,分析了外界化学条件引起表面微观物理形貌的变化及其所对应的表面特性.结果表明,薄膜经pH为12的碱液在40℃下超声刻蚀5 min左右,并用无水乙醇浸泡,可达到与水接触角120°以上的疏水效果.     

Electrical conductivity of poly(vinyl alcohol)/carbon nanotube multilayer thin films: Influence of sodium polystyrene sulfonate mediated carbon nanotube dispersion

This investigation was aimed to enhance the dispersibility of multi-walled carbon nanotubes (MWCNT) using sodium polystyrene sulfonate (Na-PSS) polyelectrolyte. Subsequently, electrically conducting, multi-layer thin films are prepared utilizing layer by layer assembly method with poly(vinyl alcohol) as a host matrix. The highest extent of MWCNT dispersion was observed in MWCNT:Na-PSS ratio of 1:9 (wt/wt), which was estimated from UV-Vis spectroscopic analysis. Zeta potential measurements of Na-PSS modified MWCNT dispersion showed large negative potentials ranging from −52 to −64 mV in the most stable pH range of 4 to 10, suggesting the colloidal stability is due to the long-range repulsive nature of electrostatic interactions from negatively charged sulfonate groups. Complementary molecular dynamics simulations showed that adsorption of Na-PSS imparts a large negative potential to the carbon nanotube surface, which increases with an increase in Na-PSS concentration. The multi-layer thin film of (1:9) MWCNT:Na-PSS exhibited a DC electrical conductivity of 2.96 × 10² S/m.     

Novel composites of copper nanowire/PVDF with superior dielectric properties

Novel copper nanowires (CuNWs)/poly(vinylidene fluoride) (PVDF) nanocomposites with high dielectric permittivity (ε′) and low dielectric loss (ε″) were prepared by a precipitation technique followed by melt compression. Their dielectric properties over the broadband frequency range, i.e. 10¹–10⁶ Hz, were compared with multi-walled carbon nanotubes (MWCNT)/PVDF nanocomposites prepared by the same technique. It was observed that the CuNWs/PVDF nanocomposites had higher dielectric permittivity, lower dielectric loss and thus significantly lower dissipation factor (tan δ) than the MWCNT/PVDF nanocomposites at room temperature. This behavior was ascribed to a higher conductivity of the fresh core of the CuNWs relative to the MWCNT, which provided the composites with a higher amount of mobile charge carriers participating in the interfacial polarization. Moreover, the presence of oxide layers on the CuNWs surfaces diminished the conductive network formation leading to a low dielectric loss.     

恒热流条件下亲疏水表面液滴蒸发特性

以恒热流方式结合高速摄影技术同步观察记录3 μl的小液滴在不同亲疏水表面的蒸发过程。通过一系列的对比实验观察记录了不同亲疏水表面液滴蒸发时接触角、接触直径、蒸发时间等的动态特性。从实验分析中可以看出亲水表面液滴蒸发速率比疏水表面上液滴蒸发速率快,并且随着热通量的增大,液滴蒸发速率增大。在恒热流条件下亲疏水表面液滴蒸发以CCR模式为主,在蒸发后期呈现混合蒸发模式,全程未出现CCA模式。     

CdS-TiO2/MWCNTs光催化剂的制备、结构表征及性能

采用溶胶-凝胶法,以多壁碳纳米管为载体制备了CdS和TiO₂复合的双组分负载型半导体光催化剂。以挥发性有机污染物VOCs中的甲苯去除率作为光催化剂活性指标,通过正交实验,确定了光催化剂的最佳制备条件。结果表明,光催化剂的最佳制备条件为： 活性组元n(TiO₂)∶n(CdS)＝1∶0.02,加入水的体积分数为5%,载体多壁碳纳米管的质量分数2%, 450 ℃焙烧2 h。采用透射电镜TEM对催化剂结构进行了表征,通过BET测试分析了催化剂比表面积和孔径分布,运用X射线衍射分析了催化剂的晶型特征,利用紫外-可见吸收光谱检测了催化剂的光吸收能力和光吸收值。     

Study of crater structure formation on the surface of biaxially oriented polypropylene film

Biaxially oriented polypropylene (BOPP) film accounts for a large amount of polypropylene since it is well suited for food packaging films or industrial films, because of its high performance in terms of mechanical and optical properties. Recently machine speed has been increasing to obtain higher production rate and film thickness has become thinner to reduce the environmental load. To meet the demands, many researchers have been investigating stretchability of PP by connecting the stretching force at the yield point and crystalline structure. Many other studies have been conducted regarding the surface structure of BOPP. Although there were some cases that crater‐like film surface roughness was formed on BOPP films, the formation mechanism of craters has not been clarified. In this report, new hypothesis of the crater‐like film surface roughness formation mechanism is proposed by observing the transformation of crater from sheet to BOPP film and by investigating the relationship between the stress–strain curve and surface roughness change. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Steady‐shear rheology properties of polydimethylsiloxane (PDMS) colloids as a new contrast agent for nuclear magnetic resonance imaging

This work investigated the toxicity, the nuclear magnetic resonance (NMR) spectra, the NMR imaging, and the steady‐rheology properties concerning polydimethylsiloxane (PDMS) colloids. These experiments illustrate low toxicity, strong NMR signal intensity, as well as clear images, and render the colloids the potential application as contrast agent for gastrointestinal NMR imaging. The steady‐shear rheology data are fitted very well by the model τ = τ₀ + AÝ^m. According to the theory of Princen and Kiss, 12 we found the yield stresses (τ₀) of the colloids are proportional to φ^1/3/D in 0.72 ≦ φ ≦ 0.81. Based on the model and the definition of the capillary number Ca = τ/(σ/R), a linear relationship between log(D) and m was discovered if the assumptions that 2Ca σ/A and Ý_eff are constants are satisfied. We also proved these assumptions are rational in the investigated range 0.62 ≦ φ ≦ 0.81. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1888–1896, 2002     

POM/MWNTs-PEG复合材料的制备和结晶性能研究

采用原子转移自由基聚合的方法将聚乙二醇（PEG）接枝到多壁碳纳米管（MWNTs）上,然后利用平板硫化机制备出聚甲醛（POM）/MWNTs-PEG复合材料。利用扫描电子显微镜、透射电子显微镜、红外光谱和热重分析对MWNTs-PEG进行表征。通过差式扫描量热仪研究了该复合材料结晶行为的变化,用Jeziorny法和Mo法对其进行非等温结晶动力学分析。结果表明,PEG均匀接枝到MWNTs上;MWNTs-PEG的加入具有异相成核的作用,使POM结晶温度向高温区移动,结晶速率提高,半结晶时间缩短;结晶速率常数值增加,F(T)值降低;有效结晶活化能降低;MWNTs-PEG最终起到促进POM结晶的作用。     

Synthesis of hybrid polyaniline/carbon nanotube nanocomposites by dynamic interfacial inverse emulsion polymerization under sonication

This article describes an ultrasonically assisted in situ interfacial dynamic inverse emulsion polymerization process of aniline in the presence of multiwalled carbon nanotubes (MWNT) in chloroform. During polymerization, MWNT are coated with polyaniline (PANI) forming a core‐shell structure of nanowires, as evidenced by cryogenic transmission electron microscopy. Thermogravimetric analysis curves and conversion measurements provided important knowledge regarding the unique polymerization method. Scanning electron microscopy images and surface resistivity imply that PANI/MWNTs are characterized by a structural synergistic effect. The PANI coating of MWNT leads to a remarkable improvement in separation and dispersion of MWNT in chloroform, which otherwise would rapidly coagulate and settle. The presented interfacial dynamic polymerization process is very fast, reaching 82% conversion within 5 min of sonication and produces stable clear dispersions of doped PANI in chloroform. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication of a model cellulose surface from straw with an aqueous sodium hydroxide/thiourea solution

Model cellulose surfaces were prepared with both microcrystalline cellulose and cellulose isolated from wheat straw with different molecular weights. A sodium hydroxide/thiourea aqueous solution, instead of any organic solvents, worked as the solvent for dissolving cellulose, and model cellulose films were prepared by a two‐step method: first, the cellulose solution was deposited onto the surface of the substrate with the spin‐coating method, and second, the as‐prepared film was washed with deionized water to remove the impurities and was formed with a flattened surface. Atomic force microscopy was used to measure the morphology, surface roughness, and thickness of the cellulose thin films. X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectrometry were used to characterize the surface chemical information of the films. The results revealed that model cellulose surfaces could form from both kinds of cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

细菌纤维素/碳纳米管/MnO2复合超级电容器电极

基于细菌纤维素(BC)的三维多孔及柔性支架结构和碳纳米管(MWCNT)的优良导电性,构筑起BC/MWCNT自支撑导电基底。其中,二者通过氢键紧密结合,协同赋予复合基底优良的电导率和机械性能。然后将二氧化锰(MnO₂)电沉积在该基底上,构建了一种新型的BC/MWCNT/MnO₂薄膜电极。BC/MWCNT复合膜的多孔结构、电解质吸收特性及蜂窝状活性MnO₂纳米片的桥连结构,赋予其出色的电化学性能(在1 mA cm_-2^{的电流密度下},其面积比电容和质量比电容分别达到1.17 F cm_-2^和200 F g_-1⁾和显著的循环稳定性(在20 mA cm_-2^{的电流密度下进行}10000次循环后,其比电容保留率稳定在96%)。这种无粘合剂的薄膜电极制备简便且成本低廉,在开发柔性储能器件方面具有巨大潜力。关键词：细菌纤维素(BC);碳纳米管(MWCNT);二氧化锰(MnO₂);膜电极;电化学性能中图分类号：TQ630 文献标识码： A 文章编号：1003-5214 (2020) 01-0000-00     

Compounding of MWCNTs with PS in a Twin‐Screw Extruder with Varying Process Parameters: Morphology,Interfacial Behavior,Thermal Stability,Rheology, and Volume Resistivity

1, 2, 3, 5, and 7.5 wt% MWCNTs are incorporated into PS in a twin‐screw extruder at varying speeds, throughputs and extruder barrel temperatures. Increased SME at enhanced processing speeds seems to have the single largest effect in enhancing dispersion. A relative evaluation of PS/MWCNT interactions indicate an interfacial layer growth of 24% for 2 wt% MWCNT at 1100 rpm compared to 18% growth at 500 rpm. Raman analysis does not show an MWCNT peak shift but a constant increase in FWHM is observed irrespective of the MWCNT content. A significant enhancement of thermal stability occurs up to 2 wt% MWCNT loading while 1–2 wt% shows the rheological threshold. The volume resistivity decreases dramatically in a 2 wt% sample processed at 1100 rpm compared to those processed at 500 rpm.

     

碳纳米管负载铂-二氧化钌纳米颗粒催化剂的制备及表征

以多壁碳纳米管(MWNTs)为载体,采用化学还原法制备了多壁碳纳米管负载的铂-二氧化钌纳米颗粒催化剂(Pt-RuO2/MWNTs),并利用透射电镜(TEM)、电化学法等技术对该催化剂形貌和电化学性质进行了表征。结果表明,大小约为4～5nm的金属纳米颗粒均匀地分散在碳纳米管上,同时考察了该催化剂在铁氰化钾溶液中的循环伏安行为以及对该催化剂进行了电化学阻抗分析。     

Formation of Ziegler-type catalytic systems on the surface of multi-walled carbon nanotubes for the production of composite materials by in situ polymerization

The peculiarity of formation of Ziegler-type catalytic systems prepared using organoaluminum (AlR₃) and organomagnesium (MgR₂) on the surface of multi-walled carbon nanotubes (MWCNTs) was revealed. We have found first AlR₃ and MgR₂ interact with different sites on MWCNT surface. It was demonstrated by IR spectroscopy that organoaluminum compounds were immobilized on the hydroxyl-containing groups on MWCNT surface. Organomagnesium compounds were immobilized on the topological structural defects of MWCNTs; hydroxyl-containing groups were not required for their immobilization. Further interaction between TiCl₄ and organomagnesium compound immobilized on the MWCNT surface yielded a catalyst containing titanium and magnesium chlorides (an analogue of the known titanium–magnesium catalysts), which exhibits an enhanced activity in ethylene polymerization. The effect of polymerization conditions on molecular weight characteristics of polyethylene in the MWCNT/PE composite material produced by in situ polymerization over the catalyst immobilized on the MWCNT surface was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48212.     

Raman microspectroscopic investigations of polymer nanocomposites: evaluation of physical and biophysical properties

Abstract

The studied nanocomposite membranes were produced from PCL, and contained identical amounts of carbon nano-additives: MWCNTs/MWCNTs-f, CNFs/CNFs-f. The wettability measurements proved to be not sufficient to distinguish materials features. The Raman micro-spectroscopy was selected to uncover interaction at the carbon particle – polymer matrix interphase. Analyzing the interaction of carbon nanoparticles with the polymer matrix, one can see the specificity and the different nature of this interaction, depending on the type of nanoparticle and on its functionalization, which results in material properties. This conclusion was also confirmed by the clear colonization of the human U-2 OS cells on tested nanomaterials.     

In situ cross‐linked‐PDMS/BPPO membrane for the recovery of butanol by pervaporation

In this study, an in situ crosslinked polydimethylsiloxane/brominated polyphenylene oxide (c‐PDMS/BPPO) membrane on ceramic tube has been prepared for the recovery of butanol by pervaporation. A series of BPPO with different bromide‐substituted ratio were firstly synthesized through Wohl–Ziegler reaction. BPPO and PDMS were sequentially assembled and in situ crosslinked to form the final c‐PDMS/BPPO membrane. The results of solid‐state NMR and Differential Scanning Calorimeter demonstrated that the c‐PDMS/BPPO copolymer has a crosslinking structure and the SEM result proved the coverage of ceramic tube by copolymer layer. The effects of preparation conditions including dipping time and bromide‐substituted ratio of BPPO on the membrane performance were studied. The pervaporation experiments of butanol–water mixture indicated that the c‐PDMS/BPPO membrane exhibited an acceptable flux of 220 g·m^?2·h^?1 and high separation factor of 35 towards butanol, when the bromide‐substituted ratio was 34 wt % and the dipping time was 1.33 h. Moreover, the c‐PDMS/BPPO membrane performed excellent stability in an about 200 h continuous butanol recovery, as compared to the PDMS membrane. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40004.     

Facile preparation and properties of polyvinylidene fluoride dielectric nanocomposites via phase morphology control and incorporation of multiwalled carbon nanotubes conductive fillers

A novel PVDF dielectric nanocomposite was achieved by controlling phase morphology and incorporating conductive fillers simultaneously, and the mechanical, thermal, dielectric properties of the resultant dielectric nanocomposites were investigated. Mechanical analysis showed that incorporation of modified MWCNTs (MWCNTs-COOH) in the PVDF nanocomposites resulted in significant improvements on the tensile strength (T_s) and elasticity modulus (E_m). When the filler content was 12 wt%, the T_s of MWCNTs-COOH/PVDF could reach 64.6 MPa. XRD test showed that the addition of MWCNTs-COOH and MWCNTs promoted the formation of β-phase of PVDF. DMA analysis showed that the glass-transition temperature of the PVDF nanocomposites slightly increases on loading of original MWCNTs and this effect was more pronounced on loading MWCNTs-COOH. The dielectric property analysis showed that the original MWCNTs were more likely to form local conductive networks in the PVDF matrix, promoting the electron displacement polarization, and improving the dielectric constant. When the contents of MWCNTs was 12 wt%, the percolation threshold was obtained and the dielectric constant (ε′) reached 286, which was 36 times of pure PVDF. Our work provides a simple way to fabricate polymer blends with excellent dielectric performances, good mechanical properties as well as good processing capability but low cost. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48463.