Effects of NCO/OH Ratio and Reactive Diluent Type on the Adhesion Strength of Polyurethane Methacrylates for Cord/Rubber Composites

A series of dual curable polyurethane methacrylate-based oligomers were synthesized by changing the NCO:OH ratio and then were included in adhesive formulations using trimethylolpropane trimethacrylate and tricyclodecane dimethanol diacrylate (TCDDA) as reactive diluents. The effects of NCO:OH ratio and reactive diluent type on the structural properties of UV-cured free films and adhesion properties between polyester cord/rubber surfaces were studied. The highest adhesion strength of the 103?N?cm^?1 was obtained when the NCO:OH ratio was set as 4 and the TCDDA was used as a reactive diluent.     

The effects of chelation on the adhesion of two different root canal sealers

Objective: This study aims to evaluate alterations in the root canal dentin after irrigation with EDTA, HEBP, and Chitosan in order to determine the push-out bond strengths of the different root canal sealers on altered dentin surfaces. Materials And Methods: Crowns of 70 maxillary single-rooted teeth were removed to obtain a standardized length of 16 mm. The canals were instrumented using rotary files and the step back technique. The master apical file used in this study was #40. The subgroups were determined based on the chelation agent and the material of the root canal sealer that was used (17% EDTA, 18% HEPB, 0.2% Chitosan, Well Root ST (WRST) or AH Plus). Three slices with 1 mm thickness were cut from the root thirds of each tooth and subjected to a push-out test. The data (MPa) were analyzed using a one-way ANOVA and a Duncan’s multiple comparison test at a level of α = 0.05. Finally, scanning electron microscope (SEM) photographs were taken. Results: Groups that used WRST exhibited significantly higher push-out bond strength values in all subgroups independent of the irrigant that was used (ANOVA, p < 0.05). Group 1 showed higher push-out bond strength than the other AH Plus subgroups. Conclusion: The EDTA improved the push-out bond strength of the AH Plus. The WRST root canal sealer had the highest push-out bond strength and did not depend on the irrigant used.     

Channel Estimation for Realistic Indoor Optical Wireless Communication in ACO-OFDM Systems

Terahertz wave has attracted wide attention for its great transparency, low photon energy and high imaging resolution. Experiments were performed to explore the basic application of continuous terahertz wave. Some articles for daily use were chosen and sealed as samples and detected by the continuous-wave terahertz imaging system. Then a foam specimen was made with inclusions placed in it and detected by the system. The experimental results demonstrate that the system can detect and image the shapes and locations of the samples and inclusions correctly, though the air hole defect in the foam specimen is difficult to identify. The different colors indicating the strength of the reflected signal help to distinguish the different materials. The work paves the way for our future research and application of continuous terahertz wave.     

Tetrakis(alkylthio)-substituted lutetium bisphthalocyanines for sensing NO2 and O3

In this study, the nitrogen dioxide (NO₂) and ozone (O₃) sensing properties of a series bis[tetrakis(alkylthio) phthalocyaninato] lutetium(III) complexes [(C_nH_2n+1S)₄Pc]₂Lu(III) (n = 6, 10, 16) are investigated as a function of concentration in the temperature range between 25 °C and 150 °C. The concentration ranges were 1–10 ppm for NO₂, and 50 ppb–1 ppm for O₃. The response time and the sensor response to NO₂ are measured for approximately 1 min and 100% ppm⁻¹, respectively, for compound 1 at room temperature. At room temperature, all compounds are in the solid phase. The response time decreases to a few seconds with increasing operation temperature to 150 °C. At this temperature, all compounds are in the liquid crystal phase. The fastest response to oxidizing gases is observed at the liquid crystal phase of the Pcs. It has also been observed that the response time and the sensor response depend on the alkyl chain lengths of the Pcs. The doping effect of oxygen has been determined under high purity nitrogen N₂ flow, after exposure to dry air, at a different period of time and after annealing. It has been found that the conductivities of [(C_nH_2n+1S)₄Pc]₂Lu(III) thin films increased after exposure to dry air and the conduction mechanism also changed from ohmic behavior to space-charge-limited conduction.     

Mechanistic transformations involving living and controlled/living polymerization methods

This review is prepared on the occasion of the 50th anniversary of the historic discovery of living anionic polymerization by Michael Szwarc. This process enabled preparation, with good control of polymer architecture, of well-defined polymers such as block and graft copolymers, star polymers, macrocycles, and functional polymers. Transformation reactions provide a facile route to synthesis of block copolymers that cannot be made by a single polymerization mode. A variety of transformation reactions involving step-growth, conventional and controlled free radical, cationic, anionic, group transfer, activated monomer Ziegler–Natta and metathesis reactions are known. In this article, transformation reactions involving living and controlled/living polymerization methods are reviewed. Other possibilities of combining different polymerization methods namely, macromonomer technique, coupling reactions, dual polymerizations and click chemistry are described. Preparation of star and miktoarm-star block copolymers by using mechanistic transformations is also presented.     

Correlation of ternary liquid--liquid equilibrium data using neural network-based activity coefficient model

Liquid--liquid equilibrium (LLE) data are important in chemical industry for the design of separation equipments, and it is troublesome to determine experimentally. In this paper, a new method for correlation of ternary LLE data is presented. The method is implemented by using a combined structure that uses genetic algorithm (GA)--trained neural network (NN). NN coefficients that satisfy the criterion of equilibrium were obtained by using GA. At the training phase, experimental concentration data and corresponding activity coefficients were used as input and output, respectively. At the test phase, trained NN was used to correlate the whole experimental data by giving only one initial value. Calculated results were compared with the experimental data, and very low root-mean-square deviation error values are obtained between experimental and calculated data. By using this model tie-line and solubility curve data of LLE can be obtained with only a few experimental data.     

Air oxidation of aqueous cyanides in a countercurrent fixed bed reactor

This study was conducted to discuss the removal of cyanides from water by air oxidation. Experiments were carried out in a countercurrent fixed bed reactor for three different values of temperature, concentration, gas and liquid flow rates. It was operated at pH 12 by using delrin (formaldehyde polymer) as packing material. Effects of some operating parameters on the conversion were studied, and it was observed that the conversion percent increased by increasing temperature and decreasing gas and liquid flow rates. Effect of concentration was not steady. A conversion of 89% was achieved under optimum conditions while it ranges from 44 to 79% at room temperature.     

Synthesis and characterization of UV-curable dual hybrid oligomers based on epoxy acrylate containing pendant alkoxysilane groups

This work involves the synthesis of novel hybrid oligomers based on a UV-curable epoxy acrylate resin (EA). The EA resin was modified with various amount of 3-isocyanatopropyl trimethoxysilane (IPTMS) coupling agent. The modification percentage of the hybrid oligomer was varied from 0 to 50 wt.%. UV-curable, hard and transparent organic–inorganic hybrid coatings were prepared on Plexiglas substrates and their characterization was performed by the analyses of various properties such as hardness, gloss, tape adhesion test and stress–strain test. Results from the mechanical measurements show that the properties of hybrid coatings improve with the increase in modification ratio. The thermal behavior of coatings was also evaluated. It is observed that the thermal stability of epoxy acrylate coatings is enhanced with incorporation of siloxane. Gas chromatography/mass spectrometry analyses showed that the initial weight loss obtained in thermogravimetric analysis is due to the degradation products of the photoinitator and the acrylic acid moiety of acrylic monomers.     

A generalized sample preparation method by incorporation of metal–organic compounds into polymers for electroless metallization

Polymer metallization is important for several applications but triggering of electroless deposition is problematic. A simple and inexpensive method to prepare the polymers for initiating the electroless copper deposition is successfully applied to Liquid Crystal Polymer and Polyethylene Terephthalate. The samples are prepared by incorporation of a small amount (<0.5 wt%) of metal–organic compounds (palladium, nickel, or copper acetates) in the molten polymers. During blending, the polymers are held at sufficiently high temperatures to thermally decompose the acetates, yielding the metallic particles (Pd, Ni, or Cu) which are used as the activators. After surface preparation, copper is deposited on polymers in an electroless bath including formaldehyde as reducer. The influence of bath parameters (temperature, composition) and the nature of activators is investigated. This method can be extended to other polymers by finding an appropriate polymer/metal–organic couple. It is also demonstrated that cheaper Ni or Cu can substitute expensive Pd.