The influence of polycaprolactone content on the surface properties of polyurethane networks

The aim of this work was to examine the influence of polycaprolactone (PCL) as a soft segment (SS) on the surface properties of polyurethane networks (PUNs). Five PUNs with different SS content (from 10 to 50 wt%) were prepared using Boltorn® aliphatic hyperbranched polyester of the second pseudo generation and isophorone diisocyanate as components of hard segments. The structure, hydrophobicity, wettability, and swelling behavior of these PUNs were investigated. Primarily, the obtained results showed that properties of prepared PUNs strongly depend on the content of SS that is, PCL. It has been established that the increase of SS content reduced the degree of hydrogen bonding in PUNs. Also, the increase of the SS content in PUNs induced appearance of more pronounced microphase separated morphology, better hydrophobicity and non-wetting with diiodomethane. Simultaneously, the increase of the SS content led to the decrease of contact angles with formamide, and surface free energy of the prepared PUNs. These PUNs show good surface properties that are required for their potential application such as coatings.     

Crystallization of Zirconium-Rich PLZT Thin Films Below 500°C

The general problem of processing zirconium-rich lead-lanthanum-zirconate-titanate (PLZT) thin films at the commonly used temperatures between 600 and 650 C is lead-oxide loss, leading to the formation of a non-ferroelectric, surface pyrochlore-type phase. To avoid lead-oxide losses due to sublimation and/or the interaction of the film with the substrate, it is desirable that the annealing temperatures are as low as possible. Our goal was to study and prepare perovskite PLZT 9.5/65/35 (Pb 0.858 La 0.095 Zr 0.65 Ti 0.35 O 3 ) thin films below 500 C. At 400 C the growth of the perovskite phase follows the parabolic law typical of diffusion controlled processes. During prolonged annealing growth continues until the limiting stoichiometry of the perovskite phase with regard to the PbO is reached. We conclude that, even at this low temperature the amount of PbO in the film is the critical factor in the crystallization of the perovskite phase.     

Water‐soluble/dispersible carbazole‐containing random and block copolymers by nitroxide‐mediated radical polymerisation

A series of carbazole‐containing water‐dispersible poly(acrylic acid)‐b‐(9‐(4‐vinylbenzyl)‐9H‐carbazole) block copolymers (poly(AA)‐b‐poly(VBK)) and water‐soluble poly(methacrylic acid‐ran‐(9‐(4‐vinylbenzyl)‐9H‐carbazole)) (poly(MAA‐ran‐VBK)) random copolymers were synthesised in a controlled manner (i.e. low polydispersities $(\overline {M_{{\rm w}} } /\overline {M_{n} } < 1.3)$ by nitroxide‐mediated polymerisation (NMP) using an SG1‐based alkoxyamine initiator, BlocBuilder. Poly(AA)‐b‐poly(VBK) block copolymers were most easily accessed by using poly(AA) in its protected form as the macroinitiator for the 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) block. Controlled polymerisation of MAA was accomplished using an excess of 10 mol.% SG1 relative to BlocBuilder with VBK as controlling co‐monomer (initial molar feed content f_VBK,0 = 0.03–0.20) in dimethylformamide at 80°C. Poly(MAA‐ran‐VBK) copolymers with a final VBK molar composition of F_VBK < 0.30 resulted in water‐soluble copolymers. In addition, as macroinitiators, poly(MAA‐ran‐VBK)s were sufficiently pseudo‐living to reinitiate a second batch of monomer (90 mol.% methyl methacrylate with styrene) in organic solvent and by ab initio, surfactant‐free emulsion polymerisation. In both cases, low polydispersity, amphiphilic block copolymers resulted $(\overline {M_{{\rm w}} } /\overline {M_{{\rm n}} } < 1.3)$ . © 2012 Canadian Society for Chemical Engineering     

ON THE SIMULTANEOUS EFFECT OF BEAM DEFLECTION AND THERMAL LENSING PHENOMENA IN PHOTOTHERMAL SPECTROMETRY

Abstract

A general model that accounts for a combined effect of thermal lensing and photothermal beam deflection was derived. The model enables the estimation of contributions to the measured photothermal signal from each of the two phenomena. Experimental parameters such as modulation frequency, the pump beam diameter, and the position of detector can be optimized using this model in order to minimize the unwanted effects of misalignment or laser pointing instability, and to improve the accuracy of thermal lens and photothermal beam deflection spectrometry.     

Perspectives of atmospheric reference leaks calibration by gravimetric method

The measurement of freon (mainly R134a) leaks is an important task of metrology. The paper deals with the study of the possibilities of improvement of gravimetric traceability method for the permeation secondary standards of atmospheric freon leaks. Their leak rates are different under atmospheric and vacuum conditions; only the first one is interesting for practical use. Moreover, the desirable steady state after changing the conditions is achieved only after certain relaxation time. This complicates the correction of the buoyancy influence, which causes the uncertainty increase. The leak rates of a typical secondary standard of this kind under atmospheric and vacuum conditions are compared, the needed relaxation times searched and some possibilities of further improvement discussed.     

气动乳化液自动配比仪的设计

提出了气动乳化液自动配比仪的构想,该配比仪以井下压风为动力,利用综合控制器(PLC)作为控制单元,实现乳化液浓度的自动配比。其配液方式可分为自动调节和人工调节两种。该装置不仅能够更好地实现乳化液的全封闭式管理,保持乳化液系统的清洁,降低液压支架液压元件的损坏,也大大减少了乳化油的浪费。     

An economic model for the appraisal and selection of energy supply system

Economic evaluation of different energy supply systems (district or local heating by natural gas) in Serbia is considered in this paper. According to variety of Serbian settlements (in density, size and layout of buildings) model which has ability to represent their different characteristics is formed. Model is based on identification of smaller urban areas with identical or similar characteristics and their representations with one of predefined nominal urban areas. For various nominal urban areas preferred type of energy supply system was selected. Obtained results formed matrix of preferred type of energy supply system (district or local heating) for different urban structures. This models’ matrix could be simple and useful tool for initial decision about energy supply system.     

Investigation on thermal radiation spectra of coal ash deposits

This paper deals with thermal radiation properties of ash deposits on a pulverized coal boiler of an electric power plant. Normal emittance spectra in the 2.5–25 μm interval, and total normal emittance, were measured on 4 kinds of ash layers of a mm magnitude order thickness, at 560 → 1460 → 560 K in heating and cooling. It was found that ash powder layers are opaque for infrared radiation. The emittance increases with ash radiation wavelength and temperature. Ash powder is sintered and fused above 1200 K. The emittance of the sintered layer is above that of the unsintered layer. The authors propose, and explain by an example, correlating the experimentally obtained emittance spectra of ash deposits with a continuous curve, the formula of which defines the dependence of emittance on wavelength and temperature, i.e. ε = ε(λ,Т). Use of this formula, with parameter values determined by the proposed methodology, may greatly simplify the practical application of the experimentally determined emittances in the thermal design of existing and new steam boiler furnaces.