scholarly journals Colorless and Transparent Copolyimides and Their Nanocomposites: Thermo-Optical Properties, Morphologies, and Gas Permeabilities

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 585 ◽  
Author(s):  
Hyeon Shin ◽  
Young-Je Kwark ◽  
Jin-Hae Chang
Keyword(s):  
Optical Properties ◽  
Coefficient Of Thermal Expansion ◽  
Amic Acid ◽  
Gas Permeation ◽  
Molar Ratio ◽  
Molar Ratios ◽  
Thermal Imidization ◽  
Organically Modified ◽  
Permeation Properties

A series of linear aromatic copolyimides (Co-PIs) were synthesized by reacting 4,4′-biphthalic anhydride (BPA) with various molar contents of 2,2′-bis(trifluoromethyl)benzidine (TFB) and p-xylylenediamine (p-XDA) in N,N′-dimethylacetamide (DMAc). Co-PI films were fabricated by solution casting and thermal imidization with poly(amic acid) (PAA) on glass plates. The thermo-optical properties and gas permeabilities of Co-PI films composed of various molar ratios of p-XDA (0.2–1.0 relative to BPA) were investigated. Thermal properties were observed to deteriorate with increasing p-XDA concentration. However, oxygen-transmission rates (O2TRs) and optical transparencies improved with increasing p-XDA concentration. Co-PI hybrids with a 1:0.2:0.8 molar ratio of BPA:TFB:p-XDA and organically modified hectorite (STN) were prepared by the in situ intercalation method. The morphologies and the thermo-optical and gas permeation properties of the hybrids were examined as functions of STN loading (5–50 wt %). XRD and TEM revealed substantial increases in clay particle agglomeration in the Co-PI hybrid films as the clay loading was increased from 5 to 50 wt %. The coefficient of thermal expansion (CTE) and the O2TR of a Co-PI hybrid film were observed to improve with increasing STN concentration; however, its optical transparency decreased gradually with increasing STN concentration.

Synthesis and properties of low coefficient of thermal expansion copolyimides derived from biphenyltetracarboxylic dianhydride with p-phenylenediamine and 4,4′-oxydialinine

e-Polymers ◽  
2016 ◽  
Vol 16 (4) ◽  
pp. 295-302 ◽  
Author(s):  
Yonglin Lei ◽  
Yuanjie Shu ◽  
Jinhua Peng ◽  
Yongjian Tang ◽  
Jichuan Huo
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Thermomechanical Analysis ◽  
Amic Acid ◽  
Molar Ratio ◽  
Structure And Property ◽  
Property Relations ◽  
Ft Ir ◽  
Biphenyltetracarboxylic Dianhydride

AbstractA series of copolyimides were prepared by thermal imidization of poly(amic acid)s (PAAs) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (a-BPDA), p-phenylenediamine (PDA) and 4,4′-oxydialinine (4,4′-ODA) commonly used for the production of commercial polyimides. The flexible copolyimide films were obtained from that the molar ratio of s-BPDA, a-BPDA, PDA and 4,4′-ODA was 9:1:8:2 (Co-PIs-3), 8:2:9:1 (Co-PIs-5) and 8:2:8:2 (Co-PIs-6). These obtained copolyimide films were characterized by Fourier transform-infrared spectroscopy(FT-IR), wide angle X-ray (WAXD), Thermogravimetric (TG), dynamic mechanical thermal analysis (DMA), thermomechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) and mechanical properties measurement. The results showed that three copolyimides remained semi-crystalline and exhibited high glass transition temperature (Tg), high thermal stability, great ultimate tensile strength and low coefficient of thermal expansion (CTE). The Co-PIs-5 had lower crystallinity, lower CTE, greater elongation at break, higher Tg and thermal stability and the greater dense extent, compared with Co-PIs-3 and Co-PIs-6. Structure and property relations of the prepared polyimides were also briefly discussed. The results revealed that the copolymerization of s-BPDA/PDA with a small number of 4,4′-ODA/a-BPDA was a useful means for enhancing flexibility without sacrificing low CTE.

Oxidative Degradation and Kinetics of Trichloroethylene by Thermally Activated Persulfate

2014 ◽  
Vol 675-677 ◽  
pp. 547-550
Author(s):  
Jun Jie Yue ◽  
Xiao Qiao Zhu ◽  
Yu Ting Wang ◽  
Yu Qin Zhang ◽  
Li Zhao ◽  
...  
Keyword(s):  
Oxidative Degradation ◽  
Chemical Oxidation ◽  
Molar Ratio ◽  
Pseudo First Order Reaction ◽  
In Situ Chemical Oxidation ◽  
First Order ◽  
Molar Ratios ◽  
Thermally Activated ◽  
Kinetics Of

In situ chemical oxidation with persulfate (PS) anion (S2O82-) is a viable technique for remediation of groundwater contaminants such as trichloroethylene (TCE). This laboratory study investigated the use of the oxidant sodium PS for the chemical oxidation of TCE at different conditions to determine the influence of temperature, pH, and the PS/TCE molar ratio. Experiments revealed that higher temperatures, lower pH, and higher PS/TCE molar ratios were to the benefit of TCE oxidation by PS. By investigating the reaction kinetics, the degradations of contaminant can be described by use of pseudo-first-order reaction. At the temperatures ranging from 25°C to 40°C, the activation energy for the degradation of TCE was determined to be 85.04 KJ/mol.

Tuning the pore sizes of novel silica membranes for improved gas permeation properties via an in situ reaction between NH3 and Si–H groups

2015 ◽  
Vol 51 (13) ◽  
pp. 2551-2554 ◽  
Author(s):  
Masakoto Kanezashi ◽  
Rui Matsugasako ◽  
Hiromasa Tawarayama ◽  
Hiroki Nagasawa ◽  
Tomohisa Yoshioka ◽  
...  
Keyword(s):  
High Temperatures ◽  
Gas Permeation ◽  
Silica Membranes ◽  
Pore Sizes ◽  
In Situ Reaction ◽  
Permeation Properties

The tuning of pore sizes in triethoxysilane (TRIES)-derived membranes via an in situ reaction between NH3 and Si–H groups at high temperatures.

scholarly journals Quantitative in Situ X-ray Diffraction Analysis of Early Hydration of Belite-Calcium Sulfoaluminate Cement at Various Defined Temperatures

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 297
Author(s):  
Maruša Borštnar ◽  
Christian L. Lengauer ◽  
Sabina Dolenec
Keyword(s):  
Calcium Sulfate ◽  
Elevated Temperatures ◽  
Cement Clinker ◽  
Molar Ratio ◽  
Phase Assemblage ◽  
Early Hydration ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Molar Ratios

The influence of temperature on the early hydration of belite-calcium sulfoaluminate cements with two different calcium sulfate to calcium sulfoaluminate molar ratios was investigated. The phase composition and phase assemblage development of cements prepared using molar ratios of 1 and 2.5 were studied at 25, 40 and 60 °C by in situ X-ray powder diffraction. The Rietveld refinement method was used for quantification. The degree of hydration after 24 h was highest at ambient temperatures, but early hydration was significantly accelerated at elevated temperatures. These differences were more noticeable when we increased the temperature from 25 °C to 40 °C, than it was increased from 40 °C to 60 °C. The amount of calcium sulfate added controls the amount of the precipitated ettringite, namely, the amount of ettringite increased in the cement with a higher molar ratio. The results showed that temperature also affects full width at half maximum of ettringite peaks, which indicates a decrease in crystallite size of ettringite at elevated temperatures due to faster precipitation of ettringite. When using a calcium sulfate to calcium sulfoaluminate molar ratio of 1, higher d-values of ettringite peaks were observed at elevated temperatures, suggesting that more ions were released from the cement clinker at elevated temperatures, allowing a higher ion uptake in the ettringite structure. At a molar ratio of 2.5, less clinker is available in the cement, therefore these differences were not observed.

Concurrent In Situ Formation of Ag / Ag2S Nanoparticles in Polymer Matrix by Facile Polymer-Inorganic Solid State Reaction

2009 ◽  
Vol 5 ◽  
pp. 143-152
Author(s):  
Sujata Waghmare ◽  
Manish Shinde ◽  
Ramkrishna Gholap ◽  
N. Koteswara Rao ◽  
Ranjit R. Hawaldar ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Solid State Reaction ◽  
Polymer Network ◽  
Morphological Features ◽  
Molar Ratio ◽  
Simultaneous Occurrence ◽  
Metallic Silver ◽  
Molar Ratios

We herein report the feasibility of polymer-inorganic solid-state reaction route for simultaneous in situ generation of Ag & Ag2S nanostructures in polymer network wherein an engineering thermoplastic, polyphenylene sulphide (PPS), itself acts as a chalcogen source as well as a stabilizing matrix for the resultant nanoproducts. Typical solid-state reaction was accomplished by simply heating the physical admixture of the two reactants i.e. AgNO3 and PPS by varying molar ratios mainly 1:1, 1:5, 1:15, 1:20, at the crystalline melting temperature (285 °C) of PPS. The synthesized nanoparticles were characterized by various physico-chemical techniques like X-ray Diffractometry, Scanning Electron Microscopy equipped with EDAX, Transmission Electron Microscopy and UV-Visible spectroscopy. The prima facie observations suggest the effective formation and subsequent entrapment of mainly nanocrystalline metallic silver (fcc) in PPS matrix for all the molar ratios chosen for the reaction. Additionally, simultaneous occurrence of nanocrystalline Ag2S (monoclinic phase) is also noticed in case of heated admixture of AgNO3: PPS with equimolar ratio. The TEM analysis reveals nanoscale polydispersity (5nm to 70nm) and prevalence of mainly spherical morphological features in all the cases with occasional indications of triangular and hexagonal morphological features depending upon the reaction molar ratio.

Transport in Polyiodide Networks of a Self-Assembled Lithium Iodide Battery

2008 ◽  
Vol 1126 ◽  
Author(s):  
William M. Yourey ◽  
Lawrence Weinstein ◽  
Glenn G. Amatucci
Keyword(s):  
Energy Density ◽  
Electronic Conductivity ◽  
Ex Situ ◽  
Molar Ratio ◽  
Mems Devices ◽  
Lithium Iodide ◽  
3 Dimensional ◽  
Molar Ratios ◽  
High Electronic Conductivity

AbstractAs MEMS devices for biomedical and other applications continue to develop and decrease in dimensions, the demand for power supplies with the appropriate size and energy density continues to grow. Although energy density is an important factor, one of the most crucial factors is the ability to fabricate cells in a variety of shapes so to enable the greatest design flexibility when fabricating a device. Recently our group has introduced an electrochemically self formed battery to grant a path towards the greatest flexibility. In short, a nanocomposite of an alkali halide such as lithium iodide is placed between current collectors and polarized thereby creating a lithium anode and polyiodide cathode in-situ. As with primary lithium-iodine cells the transport within the cathode is a complex mechanism involving the Li+, I-, and e- all within the polyiodide network. After our recent work on in-situ EIS evaluation of the technology, we have launched on an effort to greater understand the limiting transport mechanisms in the positive electrode as a function of polyiodide network development. An in-depth characterization study was performed on the LiI-I2-PVP-H20 at various molar ratios to understand the structural and conductivity changes that take place during formation of the cell A combination of AC impedance and DC polarization studies were used for the impedance characterization in conjunction with blocking electrode methodology for separating the conductivity into its electronic and ionic portions. Also, FTIR and Raman were used to structurally characterize the samples for both the polyiodide formation and the interaction between the polyiodides and polyvinylpyrrolidone (PVP). Being non conjugated, PVP was chosen as it does not intrinsically contribute to the conductivity of the composite but does induce the formation of polyiodide species. As different molar ratio composites are prepared, the concentration of different polyiodide species (I3-, I5-, In-) within the composite change and affect the overall conductivity. A 3-dimensional plot of composite conductivity reveals a high electronic conductivity ridge for samples containing either LiI anhydrous or monohydrate at a constant I2 to PVP ratio. These 3-dimensional plots also allow us to correlate represent in an ex-situ format the electronic and ionic conductivity of the cathode/electrolyte at various depths of discharge.

Gas transport properties of polyimide membranes based on triphenylamine unit

2016 ◽  
Vol 30 (1) ◽  
pp. 100-108 ◽  
Author(s):  
Guangliang Song ◽  
Lina Wang ◽  
Dandan Liu ◽  
Jianan Yao ◽  
Yiming Cao
Keyword(s):  
Transport Properties ◽  
Diffusion Coefficients ◽  
Gas Transport ◽  
Nitrogen Atmosphere ◽  
Gas Permeation ◽  
Gas Transport Properties ◽  
Thermal Imidization ◽  
Backbone Structure ◽  
Solubility Coefficients ◽  
Permeation Properties

A series of polyimide (PI) membranes were prepared based on three triphenylamine-based diamines, namely 4,4′-diaminotriphenylamine, 4,4′-diamino-3′′,5′′-dimethyltriphenylamine, and 4,4′-diamino-3′′,5′′-ditrifluoromethyltriphenylamine, via thermal imidization procedure. The PI membranes displayed good thermal properties, with glass transition temperatures of 279–341°C and 5% weight loss temperatures above 515°C under a nitrogen atmosphere. The gas permeation properties of the membranes were investigated and interpreted from the viewpoint of the PI backbone structure. The gas permeation coefficients increased as the substituent pendant groups at the 3′′,5′′ positions of the triphenylamine varied from –H to –CH3 and –CF3, and the permselectivity of gas pairs (including hydrogen/nitrogen (N2), oxygen/N2, carbon dioxide (CO2)/N2, and CO2/methane) decreased in this order. The diffusion coefficients and solubility coefficients were calculated, and the results revealed the variation of the substituted triphenylamine units principally influenced the diffusion coefficients, indicating that the substituted triphenylamine affected the gas transport properties by “diffusivity-controlled” modification.

Optimal mechanical and gas permeation properties of polypropylene-organically modified montmorillonite (PP-OMMT) nanocomposites

2014 ◽  
Vol 34 (6) ◽  
pp. 501-509 ◽  
Author(s):  
Youssef Al Herz ◽  
Chandra Mouli R. Madhuranthakam ◽  
Ali Elkamel ◽  
Vikas Mittal
Keyword(s):  
Regression Models ◽  
Primary Objective ◽  
Gas Permeation ◽  
Objective Functions ◽  
Modified Montmorillonite ◽  
Organically Modified Montmorillonite ◽  
Organically Modified ◽  
The Cost ◽  
Permeation Properties

Abstract This article focuses on obtaining optimal mechanical properties of polypropylene-organically modified montmorillonite (PP-OMMT) nanocomposites for different objectives using simulations. The primary objective was to minimize the cost of the PP-OMMT nanocomposites. The other aim was to obtain specific desired properties of the nanocomposite (irrespective of the nanocomposite cost). The later simulation results are useful in designing products where quality of the nanocomposite cannot be compromised (while the cost of the PP-OMMT is secondary). The properties that were optimized include Young’s modulus and oxygen permeation. Regression models were obtained and used to predict these properties as functions of corresponding compositions of the composites. Further, optimization procedures were simulated using these models along with other constraints and objective functions. All simulations were programmed using MATLAB version 7.10.0 (R2010a).

Preparation, Characterization and Desulfurization of the Supported Nickel Phosphide Catalysts

2016 ◽  
pp. 431-458
Author(s):  
Zhoujun Wang ◽  
Pingyi Wu ◽  
Ling Lan ◽  
Shengfu Ji
Keyword(s):  
Active Sites ◽  
Mesoporous Molecular Sieve ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Infrared Spectrometry ◽  
Nickel Phosphide ◽  
Molar Ratios ◽  
Diffuse Reflectance Infrared ◽  
Catalytic Performances

Hydrodesulfurization (HDS) is an important technology to produce clean fuels, in which the nickel phosphide catalysts exhibit excellent catalytic performances. In this work, a series of NixP/SBA-15 catalysts with various P/Ni molar ratios were prepared using the mesoporous molecular sieve SBA-15 as the support. The structure and surface properties of the catalysts were characterized by X-ray diffraction (XRD), N2 sorption analysis, transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), and in situ diffuse reflectance infrared Fourier transfer spectroscopy (DRIFTS). The catalytic performances for the HDS of dibenzothiophene (DBT) were evaluated. The results demonstrated that the NixP/SBA-15 catalysts possessed high specific surface area and the mesoporous structures, which benefited the elimination of the internal diffusion limitation in the HDS reactions. Both Ni2P and Ni12P5 phases showed catalytic activity in HDS reactions while Ni2P was more active. The optimal P/Ni molar ratio was about 0.75. The DBT conversion can reach 95.8% under the reaction condition of pressure at 3.0 MPa, H2:oil=600, WHSV at 26.7 h-1, and temperature at 340oC. In situ DRIFTS spectra indicated that the coordinative unsaturated Nid+ (0<d<1) species on the catalysts surface were the active sites for the HDS of DBT.

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