Search

The mass transfer performance of isopropanol (IPA) absorption by triethylene glycol (TEG) aqueous solution in a spray-bed absorber was investigated, and the mass transfer coefficients predicted by an artificial neural network (ANN) and response surface methodology were compared in this study. The operating variables affecting the mass transfer performance of a spray-bed absorber include the gas and TEG fluxes, concentration of IPA, concentration of TEG aqueous solution, and operating temperature. The experimental results demonstrated that the mass transfer coefficient of a spray-bed absorber increased with increases in gas and liquid fluxes and decreased with increases in concentration of IPA. The Back-Propagation algorithm in the ANN model was selected to predict the mass transfer coefficients of the spray–bed absorption system. Hidden layers with 2, 4 and 6 neurons respectively were set to analyze the effect of the number of neurons on the target value, and then different transfer functions were used to compare the accuracy in predicting mass transfer coefficient. Finally, the influences of the number of hidden layers and different learning rules on the prediction of mass transfer coefficients were examined. The simulated results showed that the average error of the ANN using the TanhAxon transfer function, the Conjugate Gradient learning rule, two hidden layers, and 6 neurons in each hidden layer was within 1%. The results not only verified the successful establishment of the experimental device but also proved the accurate prediction of mass transfer coefficients by the ANN model. [ABSTRACT FROM AUTHOR]

Two series of toughened, semiconductive polyaniline (PANI)/polyurethane (PU)-epoxy (PANI/PU-EPOXY) nanocomposites were prepared using a conducive polymer, PANI, and PU prepolymer-modified-diglycidyl ether of bisphenol A (DGEBA) epoxy. Firs, he PU prepolymer-modified epoxy oligomer was synthesized by a stoichiometric reaction between the terminal isocyanate groups of he PU prepolymer and he pendent hydroxyl groups of he epoxide. PU prepolymers were made either of polyester (polybutylene adipate, PBA) or polyether (polypropylene glycol, PPG) segments. The composites were characterized by thermal, morphological, mechanical, and electrical studies. Impact strength was enhanced 100% in PU (PPG 2000)-modified composites; whereas, only ca. 30-50% increases in impact strength were observed for he other modified composites. In addition, he thermal stability of his composite proved superior o ha of neat epoxy resin, regardless of a PU content a 27.5 w%. Scanning electron microscopy (SEM) morphology study showed hat the spherical PU (PPG 2000) particles (ca. 0.2-0.5 µm) dispersed within the matrix accounts for these extraordinary properties. The conductivity of the composite increased to ca. [10.sup.-9]-[10.sup.-3] S [cm.sup.-1] upon addition of PANI when tested in the frequency range 1 kHz-13 MHz. This study demonstrated a useful way to simultaneously improve the toughness and conductivity of the epoxy composite, thus rendering it suitable for electromagnetic interference and various charge dissipation applications. POLYM. ENG. SCI., 48:345-354, 2008. © 007 Society of Plastics Engineers, INTRODUCTION Among the different types of conducting polymers, polyaniline (PANI) may have the greatest potential for commercial application because of its unique electrochemical properties and environmental stability [1-3]. In addition, [...]

The effect of the ultrasonic/mechanical stirring method (physical treatment) and 3‐glycidoxypropyltrimethoxy silane (GPS, chemical treatment) modifications on the sugarcane fiber (SGF)/epoxy composites was investigated to improve the interfacial interaction between fiber and epoxy resin. An optimum concentration GPS at 2 wt% was found for the best improvement in tensile strength at 40 wt% SGF content based on the evaluation of GPS content, indicating the role of GPS as an effective coupling agent. Overall, the best improvement in tensile strength was observed for GPS‐modified cases, and particularly tensile strength reached up to 32.9 MPa at 50 wt% of fiber content. In addition, three types of Polyurethane (PU)‐modified epoxy with different polyols at various SGFs contents were investigated. In all cases, the tensile strength of SGF/PU‐epoxy cases was higher than that of SGF/epoxy cases due to the relatively lower viscosity of PU‐epoxy to easily wet the SGF surface. In general, impact strength for samples without physical or chemical treatment also ranked the lowest value in most cases. The enhanced interfacial interaction between SGF and epoxy for surface‐modified cases was suggested through the morphology observation, dynamical mechanical analysis, and the onset degradation improvement in thermal stability. [ABSTRACT FROM AUTHOR]

To achieve a sustainable bioeconomy, various bioderived additives have been developed to produce biocomposites, but only a handful of research on biocomposites focuses on the effect of bioderived additives on interpenetrating polymer networks (IPNs). This study is aimed at understanding the interaction between bioadditives and interpenetrating polymer networks and is the first study to build the relationship between bioadditive ratio and damping factor based on dynamic mechanical analysis. The IPNs were prepolymerized in bulk by isocyanate and poly(oxypropylene) polyol (PPG) with two different molecular weights (PPG 700 and PPG 1000), and then, they were grafted with bisphenol A diglycidyl ether epoxy. The bioadditives were prepared from agricultural waste, sugarcane bagasse, and the effect of the coupling agent 3-glycidoxypropyltrimethoxysilane on a bioadditive surface was also discussed in this study. The results show that modified bioadditives have significant enhancement on tensile strength and tensile modulus of polyurethane-grafted epoxy resin interpenetrating polymer networks (PU(PPG)-EP graft-IPNs). However, the enhancement is not from a strong covalent bond between matrix and additives, that is, due to the well-dispersed bioadditives which provide stiff segments. The static and dynamic mechanical performance, water absorption ratio, and morphology of the (PU(PPG)-EP graft-IPNs) elastomers were also thoroughly discussed in this study. [ABSTRACT FROM AUTHOR]

Rare studies have investigated on the 2‐way shape memory crosslinked blends with multiple shape memory behavior up to date. To consider the merit of commercial cost‐competitive crystalline polymers, ethylene vinyl‐acetate copolymer (EVA)/polycaprolactone (PCL) blends (60/40 and 30/70) were peroxide‐cured to form the 2‐way multi‐shape memory crosslinked blends using a melt‐blending method. Both resins were selected to have a similar controlled crosslinking degree, which allowed us to distinctly evaluate their actuation contributions from the cooling‐induced elongation (crystallization) and from the entropy‐driven elongation during cooling process, respectively. In the 2‐way process for the 60/40 system, 2 respective peaks contributed from the cooling‐induced crystallization of EVA and PCL in the cooling curves based on the strain derivate rates at various temperatures were observed. After the cooling process under the loading stress of 150 kPa, the 2‐step heating‐induced contraction process with increasing temperature started at 54.1°C above the melting temperature of PCL at 52.3°C and EVA at 78.3°C, demonstrating 2‐way multi‐shape memory behavior. The multi‐step behavior was more prominent at higher PCL composition and higher load for the 30/70 system. It was found that the entropy‐driven contribution to the overall actuation magnitude increased with increasing nominal loads due to the increased orientation of molecular networks in the blends. The current approach offers numerous possibilities in preparing 2‐way multi‐shape memory crosslinked blends. [ABSTRACT FROM AUTHOR]

The comparison on the NaOH and 3-glycidoxypropyltrimethoxy silane (GPS) modifications on the rice husk/epoxy composites was made to improve the interfacial interaction between epoxy resin and rice husk. An optimum concentration of NaOH at 6 wt% or GPS at 10 wt% was found based on the highest performance of mechanical properties at 70 wt% rice husk content. As for the effect of rice husk content, the maximum reinforcing effect was found at 50 and 70 wt% of rice husk with NaOH and GPS treatment, respectively. This was attributed to the increased surface roughness after NaOH modification and silane interaction to enhance the interfacial reaction of rice husk for stronger adhesion, as evidenced by the morphology observation. The highest reinforcement and thermal stability was observed for GPS-modified cases. Silane treatment gave the lowest glass transition temperatures for the investigated cases due to the flexible alkyl group. For the water absorption property, GPS-modified cases conferred the lowest level in comparison with that in both unmodified and NaOH modified composites. This was mainly attributed to that the hydrophilic hydroxyl groups were reduced through the reaction of silanol/epoxy groups on GPS and hydroxyl groups on the rice husk, which again echoed the significance of silane surface treatment. POLYM. COMPOS., 38:1992-2000, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

One commercial type of fumed silica modified with methoxy polyethylene glycol (mPEG) plasticizer was incorporated into polylactic acid (PLA) biobased polymer to improve its performance. The modification on silica was confirmed through Fourier transform infrared spectra, nuclear magnetic resonance, and TGA assessments. The grafting percentage of mPEG onto silica was about 19.8 wt %. Transmission electron microscope revealed a similar degree of dispersion for control silica and modified silica-filled PLA nanocomposites. Not much difference in the glass transition temperatures at various silica contents was found for PLA/control silica systems from the differential scanning calorimetry measurement, but the glass transition temperature of PLA/modified silica nanocomposite at 10 phr of modified silica showed up to 11°C decrement. It was suggested that the mPEG plasticizer efficiently plasticized the PLA matrix through the enhanced segmental mobility of PLA chains. Young's modulus of PLA was about 2133 ± 53 MPa, and the value for the nanocomposite increased to 2547 ± 54 MPa at 10 of phr control silica mainly due to the reinforcing effect from nanoparticles. For modified silica, Young's modulus decreased at various silica contents. The elongation at break for modified silica-filled cases was higher than that of control silica-filled cases. These results were attributed to the plasticizing effect of surface modifier. Optical transmittance for pristine PLA was generally in a similar order as PLA/control silica and modified silica cases at various silica contents. The results agreed with the morphology observation as well. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Segmented polyurethane (SPU) materials based on different soft-segment component (PPG, PTMO and PBA) and various length of soft-segment (molecular weight of PBA: 500, 700 and 1000) were synthesized in this research. The soft-segment components were synthesized from polyether-polyols (PPG and PTMO) or from polyester-polyol (PBA). The physical properties and structure characterization of the synthesized SPUs were fully investigated using differential scanning calorimetry (DSC) analysis, and stress-strain measurements. Blood compatibility was evaluated with the platelet adhesion ratio (PAR) and the morphological observation for adhering platelets. Our results showed that the physical properties and blood compatibility of SPUs were closely related to its composition, which was controlled by (1) the types of the soft-segment component employed and (2) the length of soft segments. Polyether-polyol-based SPUs exhibited greater phase separations, poorer tensile strengths, and better blood compatibility, compared with polyester-polyol-based SPUs. SPUs with shorter soft-segment component exhibited greater phase mixing, higher tensile strength, but lower blood compatibility of SPUs, as compared with its counterparts with longer soft-segment component. [ABSTRACT FROM AUTHOR]

The development of flexible electronics requires the patterning of conductive and active semiconductor films. Although inorganic materials such as indium tin oxide and metal nanoparticles have high conductivity and transparency, their poor interfacial adhesion with organic layers, lack of flexibility, high weight and high capital costs are drawbacks. In contrast, organic conducting polymers have great potential for use in commercial flexible electronic applications because of their low production costs, environmental stability and acceptable conductivities. A UV-curable photoresist containing hydroxyl groups was prepared from a mixture of a photoinitiator, epoxy-acrylate resin, hydroxyethyl methacrylate and tripropylene glycol diacrylate. Patterns having line widths/spaces of 100/100 µm and 10/5 µm were fabricated on a poly(ethylene terephthalate) (PET) substrate using lithography techniques. (3-Methyl-3,4-dihydro-2 H-thieno[3,4-b]dioxepin-3-yl)methanol (ProDOT-OH) was self-synthesized through urethane linkages onto the surface of the patterned photoresist on the PET film, which was then dipped into a solution of another monomer, 3-thienylethoxybutanesulfonate (TEBS), and initiator and polymerized in situ to form conductive poly(ProDOT-OH- co-TEBS) films covering the surface of the patterned resist. The optimal conductivity of the poly(ProDOT-OH- co-TEBS) films was ca 90 S cm−1 with an optical transparency of ca 70%. A new bottom-up technique has been developed for the preparation of patterned organic transparent conductive films: self-synthesis of the monomer using urethane-forming reactions and subsequent in situ polymerization. The conductivity of the films can be controlled by the polymerization reaction time and the resolution of the pattern. These conductive patterned films might be applicable to the manufacture of industrial touch panels or chemical/biological sensors. Copyright © 2009 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article discusses a study which examined a bottom-up technique in preparing transparent conductive films of polyaniline (PANI). Particular focus is given to the formulation of a photoresist that consists of an acrylate-endcapped urethane oligomer, acrylic acid and a photoinitiator. Results of the study showed an interaction between the carboxylic acid units of photoresist's surface and the aniline monomer units which led to the formation of anilinium complexes.

Based on 187 galaxy clusters identified from the photometric redshifts of galaxies in the Cosmic Evolution Survey (COSMOS) field(Wen & Han 2011), cluster galaxies brighter than MV = -20.5 are classified into four categories according to their best-fitting templates of the spectral energy distributions (SEDs) provided by Ilbert et al. (2009): early-type (including elliptical and lenticular) galaxies (E+S0), spiral galaxies (S), irregular galaxies (Irr), and starbursts (SB). The fractions of these four SED types are presented as the functions of redshift in Figure 1. Fraction of each category varies remarkably with cluster redshift: fractions of normal galaxies (E+S0+S+Irr) tend to decrease with redshift, whilst the starburst proportion tends to increase with redshift. For the normal galaxies, there exists a sequence for the decreasing slopes of morphological fractions. Majority of the galaxies in high-redshift clusters (z > 1.0) are experiencing strong star-formation activities, which leads to a very high proportion of starburst. [ABSTRACT FROM PUBLISHER]

Abstract: In this study, we prepared nanocomposites of multi-walled carbon nanotubes (MWCNTs) and low-energy-bandgap conjugated polymers incorporating 3,4-alkoxythiophene monomers. Poly(3,4-dihexyloxythiophene) (PDHOT) and poly(3,4-dimethoxythiophene-co-3,4-dihexyloxythiophene) [P(DMOT-co-DHOT)] have relatively low-energy-bandgaps (ca. 1.38 and 1.34eV, respectively), determined from the onsets of absorbances in their UV–Vis spectra, because of the electron-donating effects of their alkoxy groups. MWCNTs have poor solubility in common organic solvents; after surface modification with alkyl side chains using the Tour reaction, however, the p-hexylaniline modified MWCNT derivative (MWCNT-HA) was readily dispersed in CHCl3 and could be mixed with the low bandgap polymers. Scanning electron microscopy images revealed that MWCNT-HA was dispersed well in each polythiophene derivative; only a few MWCNT-HA bundles could be observed at a high MWCNT-HA content (≧20wt.%). The electrical conductivities of the MWCNTs/PDHOT composites were dependent on their MWCNT content, reaching 16S/cm at 30wt.% MWCNT-HA. We suspect that the two hexyloxy chains of PDHOT enhanced its solubility and allowed it to wrap around the surfaces of the MWCNTs more readily. [Copyright &y& Elsevier]

In this paper a new technique is proposed for the fabrication of two-dimensional (2D) and three-dimensional (3D) photonic crystals using monodisperse polystyrene microspheres as the templates. In addition, the approaches toward the creation of their corresponding inversed structures are described. The inversed structures were prepared by subjecting an introduced silica source to a sol-gel process; programmed heating was then performed to remove the template without spoiling the inversed structures. Utilizing these approaches, 2D and 3D photonic crystals and their highly ordered inversed hexagonal multilayer or monolayer structures were obtained on the substrate.