水性聚氨酯/丙烯酸酯基多维度导电银浆的制备及低温固化特性

采用醇热法制备了纳米银颗粒、纳米银线和微米银片,对其进行多维度配合作为复合导电填料,以水性聚氨酯/丙烯酸脂复合树脂(WPUA)为载体和黏结相,采用搅拌混合法制备了水性树脂基多维度低温固化导电银浆。利用透射电镜、扫描电镜、水接触角测试和电阻测试,研究了不同固化温度对导电银浆成膜后的力学性能、导电性能及亲疏水特性的影响。结果表明,随着固化温度的上升,银浆漆膜的硬度、附着力及耐水性逐渐增加,WPUA基银浆漆膜的硬度在120℃时可达到3H等级,附着力在100℃可达到1等级,水接触角在140℃时可以达到93°;而WPUA银浆漆膜的电阻率随着固化温度的上升,呈现先增加后减小的趋势,在固化温度为160℃时的电阻率为0.19×10^(-3)Ω·cm。文中制备的多维度复合导电银浆在柔性电子印刷领域有着很好的应用前景。

Validity ranges of interfacial wave theories in a two-layer fluid system

In the present paper, we endeavor to accomplish a diagram, which demarcates the validity ranges for interfacial wave theories in a two-layer system, to meet the needs of design in ocean engineering. On the basis of the available solutions of periodic and solitary waves, we propose a guideline as principle to identify the validity regions of the interfacial wave theories in terms of wave period T, wave height H, upper layer thickness dl, and lower layer thick-ness d2, instead of only one parameter-water depth d as in the water surface wave circumstance. The diagram proposed here happens to be Le Mehaute＇s plot for free surface waves if water depth ratio r= d1/d2 approaches to infinity and the upper layer water density p1 to zero. On the contrary, the diagram for water surface waves can be used for two-layer interfacial waves if gravity acceleration g in it is replaced by the reduced gravity defined in this study under the condition of σ=（P2 - Pl）/P2 → 1.0 and r 〉 1.0. In the end, several figures of the validity ranges for various interfacial wavetheories in the two-layer fluid are given and compared with the results for surface waves.

Discoloration mechanism,structures and recent applications of thermochromic materials via different methods:A review

Thermochromic material is a kind of smart material whose color will vary as the result of the phase transition caused by the temperature change. The characteristics of thermochromic materials are the memory functions to the temperature, having great potential applications in aerospace, military, anticounterfeiting technology, construction and other fields. In recent years, many kinds of thermochromic materials have been prepared by different methods and their discoloration mechanisms are various according to published literatures. In this paper, the classification, discoloration mechanism, preparation methods, application fields and development trend of thermochromic materials are reviewed.

Synthesis of fluorescent carbon quantum dots from aqua mesophase pitch and their photocatalytic degradation activity of organic dyes

A synthesis strategy of fluorescent carbon quantum dots(CQDs) with high quantum yield(QY) using aqua mesophase pitch(AMP) as the carbon source has been developed via the hydrothermal method in this study. The hydrothermal temperature and soaking time have important effects on the morphology and QY of CQDs. As-prepared CQDs at 120℃ holding for 24 h(CQDs-120-24) have the uniform size of about 2.8 nm, and the QY can reach 27.6%. The obtained CQDs are successfully modified with ammonia and thionyl chloride, respectively, and they exhibit an excellent photocatalytic performance on degrading rhodamine B(Rh B), methyl blue(MB) and indigo carmine(IC). Importantly, the degradation percentage of N-CQDs on Rh B under natural light for 4 h reaches 97% with the degradation rate constant of 0.02463 min^(-1) and it can maintain 93% after repetitively used 5 times. The results indicate that these as-prepared CQDs have the potential application in degrading organic dyes.

Synthesis of waterborne polyurethane using snow as dispersant:Structures and properties controlled by polyols utilization

waterborne polyurethane (WPU) dispersions have gained attention towards environm entally-friendly synthesis. In this article, a series of waterborne polyurethane em ulsions was successfully synthesized and extensively characterized in terms of thermal, mechanical properties, hydrophilic behavior and morphology. Snowwas chosen as dispersant instead of comm only used water. Preparation param eters such as intrinsic properties and molecular weight of polyols were discussed systematically. A chain structure was confirmed by Fourier transform infrared (FT-IR) spectroscopy. when com paring the nature of the polyols (PPG, PEG and PNA, 2000g/mol) of this study, as-synthesized polyether waterborne polyurethane provided higher solid content, viscosity and water-resistance. However, polyester waterborne polyurethane perform ed differently and it exhibited higher therm al stability and crystallinity. When com paring the samples (WPU-N210, WPU-N220, WPU-N230 and WPU-N240) with different molecular weight of the same polyol (PPG) used as soft segment, the emulsion WPU-N220 with molecular weight of 2000g/mol PPG provided the highest solid content and lowest viscosity. It was observed th at particle size was uniform and highly dispersed for all sam ples from TEM images. Therm ogravim etric, differential scanning calorim etry (DSC) and X-ray diffraction results dem onstrated that the emulsion WPU-N230 with m olecular weight of 3000 g/mol PPG possessed higher therm al stability and crystallinity than the other samples. The reason was that the Tg and thermal stability were increased with increasing molecular weight. when molecular weight increased, the arrangem ent of soft segm ent became more regular and so did the regularity of the molecular chains. This work demonstrated that different polyols as soft segment applied could lead to great differences in the structure and property of the resulting WPU.

Preparation and Characterization of Mesophase Pitch via Co-Carbonization of Waste Polyethylene/Petroleum Pitch

The low-cost petroleum pitch and waste polyethylene （WPE） were used as raw materials to prepare the mesophase pitch by co-carbonization method and the forming mechanization of mesophase pitch was also investigated. Polarized microscopy, softening point, Fourier transform infrared spectroscopy （FTIR） and thermogravimetric analysis （TGA） were used to characterize and analyze the properties and struc- ture of the mesophase pitch. The results showed that the carbonization yield of the modified pitch was high when 1-2 wt% WPE was added and the property of mesophase pitch （MP1-450-4 and MP2-450-4） prepared by thermal polymerization was excellent. Moreover, when the treatment temperature was above 420 ~C, the mesophase development of the modified pitch may be entire and 100% streamline texture mesophase can form. During the co-carbonization of WPEJpetroleum pitch, a large number of naphthenic structures and methylene bridges may be generated, which can improve the properties of the obtained mesophase pitch.

A controllable soft-templating approach to synthesize mesoporous carbon microspheres derived from d-xylose via hydrothermal method

Highly dispersed carbon microspheres(CMSs)derived from D-xylose were successfully synthesized under hydrothermal conditions and followed by further carbonization,in which F127 was used as a soft template.As-synthesized products were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),flourier transform infrared spectroscopy(FT-IR),thermal gravimetric(TG)and X-ray diffraction(XRD).The results showed that the morphology and structure of the CMSs prominently depended on the stirring speed during hydrothermal reaction.The resultant CMSs principally had non-porous structure without stirring and had a very smooth surface.When the stirring speed increased to 200 rpm,the synthesized mesoporous carbon microspheres at 220?C for 24 h(CMSs-5)had a uniform size distribution of 1–1.4μm and a specific surface area of 452 m^2/g.Nevertheless,with further increasing to 400 rpm,as-fabricated carbon products were mostly amorphous with a low degree of sphericity.Results demonstrated that the diameter of the products decreased with the increase of stirring speed.Furthermore,the sphericity product yield of CMSs reduced with the increase of stirring speed.XRD result showed that all the obtained samples contained partial graphite phase.In addition,a formation mechanism was proposed that involved polymerization product as the precursors for microsphere formation.The controllable and green strategy may provide a great convenience to study properties and applications of carbon microspheres.

Recent Advances in Synthesis of Waterborne Polyurethane and Their Application in Water-based Ink:A Review

Over the last few years, waterborne polyurethane （WPU） was applied to various fibers, adhesives, primers for metals, caulking materials, emulsion polymerization media, paint additives, defoamers, associate thickeners, pigment pastes, textile dyes and biomaterials, resulting in the increasing enthu- siasm of researchers to design and synthesize novel WPU with unique properties. Thus, various processes and raw materials have been developed to prepare WPU. This review gives an overview on the de- velopments of WPU mainly derived from novel polyols, analyzes the potential application in water-based inks and presents the probable future research area about water-based inks. Notably, the poly（e-cap- rolactone） and poly（lactic acid） are the versatile materials used in WPU synthesis and supply the po- tential special performance for preparing WPU. Meanwhile, addition-fragmentation chain transfer （RAFT） polymerization and atom transfer radical polymerization （ATRP） processes provide an opportu- nity to control the chain sequence of WPU and obtain products with the desired performance.

Microstructure characterization and thermal properties of the waste-styrene-butadiene-rubber (WSBR)-modified petroleum-based mesophase asphalt

In this work, waste-styrene-butadiene-rubber(WSBR)-modified petroleum-based mesophase asphalt was prepared through a co-carbonization process. The influence of contents of WSBR and carbonization temperature on the properties of mesophase asphalt was investigated. The chemical constituents,microstructure and thermal property of the samples were characterized. The results show that using WSBR as modifier can significantly promote the formation of mesophase. When the temperature is constant, the addition of WSBR results in more optically anisotropic crystal structure in the samples, and a better thermal stability. When the content of WSBR is invariable, with increasing temperature, the content of anisotropic structure in mesophase asphalt becomes higher and more uniform. The thermal stability of the samples is the best when WSBR content is 10 wt%.

Preparation and characterization of organic pigments and their fluorescence properties depending on bulk structure

Fluorescent pigments, based on the optical or electrooptical properties of dyes, are the main component in fluorescent coatings and inks. In this study, three kinds of dyes（Rhodamine B, Light Green SF Yellowish, Coumarin） with four different ratios（2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%） were employed as luminophor,and the melamine-formaldehyde（MF） resin was used as curing resin to prepare fluorescent pigments in different color. Fourier transform infrared spectroscopy and X-ray diffractometry were carried out to analyze the structure of the fluorescent pigments. Scanning electron microscopy and particle size distribution were used to present the morphology of fluorescent pigments. UV–vis and fluorescence spectrum were used to demonstrate the optical properties. It can be concluded that, coumarin pigments possessed consecutive structure in MF resin while rhodamine B might be the best for the preparation of printing inks among the three kinds of dyes from the view of particle size. The TG results presented that all the pigments showed good thermal stability, which might possess potential application in high speed printing industry.

Structure, mechanical and thermal properties of BMI/E-44/CNTs ternary composites via amination method

Multi-walled carbon nanotubes（CNTs） were modified by an amination treatment with hexamethylenediamine（HMD）, and then bismaleimide（BMI）/epoxy（E-44）/CNTs ternary composites were prepared using modified CNTs as the reinforcement via a simple mixing and curing molding method. The results show that the surfaces of CNTs are grafted polymer with the thickness of 3 nm and the dispersity of surface grafted carbon nanotubes（SG-CNTs） in the resin composites can be improved. The prepared composites contain C-C, C-N, C=O and-COOH groups and can keep a smooth surface. In addition, the composites have the flexural strength of 152 MPa, the tensile strength of 73 MPa and the impact strength of 87 k J m^（-2）,respectively, when the weight ratio of BMI to E-44 is 1：8 and the content of SG-CNTs is 2 wt%. However,the thermal stability of the composites with SG-CNTs is a little lower than that of the composites without SG-CNTs.

A facile synthesis of supported amorphous iron oxide with high performance for Cr(Ⅵ) removal from aqueous solution under visible light irradiation

A series of supported iron oxide nanoparticles were prepared by impregnation with Fe(NO_3)_3 supported on TiO_2,followed by low-temperature calcination. Scanning electron microscopy(SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), UV–vis diffuse reflectance spectra and BET have been used to characterize the samples. These iron oxide-impregnated TiO_2 were examined for photocatalytic reduction of Cr(Ⅵ). The experiments demonstrated that Cr(Ⅵ) in aqueous solution was more efficiently reduced using Fe_2O_3/TiO_2 heterogeneous photocatalysts than either pure Fe_2O_3 or TiO_2 under visible light irradiation. All TiO_2 supported samples were somewhat active for visible light photoreduction. With an optimal mole ratio of 0.05-Fe/Ti, the highest rate of Cr(Ⅵ) reduction was achieved under the experimental conditions. We also compared the photoreactivity of TiO_2 supported iron oxide samples with that supported on Al_2O_3 and ZrO_2. It can be noted that iron oxide nanoparticles deposited on high surface area supports to increase the solid-liquid contact area renders it considerably more active. Noticeably,iron oxide cluster size and dispersion are important parameters in synthesizing active, supported Iron oxide nanoparticles. In addition, the interaction between iron oxide and TiO_2 was proposed as the source of photoactivity for Cr(Ⅵ) reduction.