Effect of temperature and solvent composition on the unperturbed dimensions of polystyrene

Several procedures have been used to establish and verify the unperturbed state of polystyrene in 1-chlorodecane (θ = 6.2° C) and 3-methyl cyclohexanol (θ = 98.4° C) as well as in other single solvents having 6.2° < θ < 98.4°. At each θ-temperature for a single solvent, the unperturbed state for a binary solvent was established in mixtures of 1-chlorodecane and 3-methyl cyclohexanol of varying composition. Viscometric measurements showed that neither the nature of the solvent nor the temperature affects the unperturbed chain dimensions appreciably. On the other hand, the unperturbed mean square radius of gyration measured directly by light scattering exhibits a definite decrease with increase in temperature, which accords qualitatively with the conformational energy calculations of Flory and co-workers.     

Temperature dependence of unperturbed dimension and interaction parameters of polyester resin in solvents

The flow behaviour of a polyester in various solvents was studied at temperatures ranging from 10 to 80°C. The practical data obtained from the temperature dependence of limiting viscosity number [η] were used to calculate unperturbed dimensions and interaction parameters of the polyester resin in poor, moderate and good solvents. The data provided information regarding conformational transitions in the polymer chains in terms of exothermic or endothermic local ordering of solvents on resin segments and their fixation on polymer coils. The temperature dependence of unperturbed dimensions K_e, Flory–Huggins interaction parameter χ₁₂, the second virial coefficient A₂, entropy parameter U₁, enthalpy parameter K₁, and viscosity expansion factor α_n, has been used to estimate the solvent quality for the resin.     

Substituted poly(silylenemethylene)s with short range interactions that induce a preference for the same local conformation in unperturbed atactic, isotactic, and syndiotactic chains

A rotational isomeric state model has been developed for the poly(silylenemethylenes) with repeating sequence [Si(CH₃)R-CH₂]_x, R=-O(CH₂)_NOC₆H₄C₆H₅. The model incorporates all first- and second-order interactions, as well as higher order interactions that are mandatory in some of the conformations. Chains with all possible stereochemical sequences prefer a local conformation that is a run of trans states at the C-Si bonds in the backbone. This preference arises from an attractive second-order interaction of the first methylene group in the side-chain bonded to chain atom i with the silicon atoms indexed i±2. Unperturbed chains have larger dimensions than the simpler chain in which R is merely a methyl group. The temperature coefficients of the unperturbed dimensions are large and negative. The preference of unperturbed atactic, isotactic, and syndiotactic chains for the same local conformation may contribute to the facile formation of smectic phases by the presumably atactic chain, as reported by Park et al. [Macromolecules 35 (2002) 2776].     

Mathematical models of the thermal decomposition of coal: 2. Specific heats and heats of reaction

Published data on the specific heat of coal and coke have been analysed and have been used to define a model which predicts the specific heat of coal during thermal decomposition. The Einstein model is used to describe the variation of specific heat with temperature and the effect of composition is determined by assuming that the vibrational energy at any temperature is the same for each atom. A new explanation for the endothermic reactions below 650 °C reported by previous workers is proposed as a consequence of the unexpectedly high specific heats predicted in this region using the above model. The exothermic reactions occurring at high temperatures appear to be attributable to the evolution of methane.     

Self- and mutual-diffusion coefficients in the dodecane/polystyrene system

The self-diffusion coefficient of dodecane in cross-linked polystyrene was measured using pulsed gradient spin echo nuclear magnetic resonance (PGSE–NMR) spectroscopy. The concentration and temperature dependence of the diffusion coefficient was analyzed by the Fujita and Vrentas–Duda models. Parameters describing the Fujita model were determined from fitting of diffusion data to the PVT behavior of the system. Parameters describing the Vrentas–Duda model were determined from the analysis of the viscosity of dodecane, the viscoelastic relaxation properties, and the glass transition temperature of polystyrene as well as from the diffusion coefficient of the system, measured from independent experiments. Both the Fujita and Vrentas–Duda models described well the concentration and temperature dependence of the diffusion coefficient. Mutual diffusion coefficients were determined from these results. © 1994 John Wiley & Sons, Inc.     

Comparison of thermal techniques for glass transition measurements of polystyrene and cross-linked acrylic polyurethane films

There are few quantitative comparisons in the literature between glass transitions (T_g) measured by differential scanning calorimetry (DSC) and by dynamic mechanical analysis (DMA). Also, in the case of DMA, two different operational definitions have been used to obtain the glass transition, namely, the loss modulus (E″) and damping (tan δ) peak temperatures. We propose a new DMA definition of T_g and demonstrate that it agrees with DSC T_g measurements within ±2°C for both thermoplastic polystyrene and thermoset cross-linked acrylic polyurethane films with measurable tan δ peaks. The glass transitions for a single polystyrene standard and several cross-linked acrylic polyurethane films were measured by DSC. Additionally, E″ and tan δ peak temperatures were measured by DMA as a function of frequency and temperature. Empirically, it was determined that the average of the E″ and tan δ peak temperatures measured at 1 rad/s oscillation frequency corresponds to the glass transition measured by the ASTM E1356 DSC test method. © 1994 John Wiley & Sons, Inc.     

The distribution of soap in the polymerization system for preparation of carboxylated polystyrene latexes

The distribution of soap in the polymerization system for preparation of carboxylated polystyrene latexes has been investigated. The critical micelle concentration (CMC) for sodium dodecyl sulfate (SDS) in the polymerization system was determined by surface tension measurement to be 0.173 mmole/l. The solubility of styrene (St) in the aqueous phase of the polymerization system was determined by NMR measurement to be 4.52 mmole/l. It was confirmed by NMR measurement that at the concentration of SDS higher than the CMC, St is solubilized in the interior of the SDS micelles, and the concentration of solubilized St is almost proportional to the concentration of micellar SDS. From this relationship, the number and radius of SDS micelles containing solubilized St can be determined.     

Comparison of methods for the detection of cocontinuity in poly(ethylene oxide)/polystyrene blends

Four methods for detecting cocontinuity in a poly(ethylene oxide)/polystyrene (PEO/PS) system are compared: scanning electron microscopy (SEM) with image analysis, solvent extraction, electrical conductivity measurements, and rheological measurements. Measurements of the amounts of interfacial area using a novel image analysis method showed that the interfacial area reached local maxima at the boundaries of the region of cocontinuity. Solvent extraction experiments allowed the region of cocontinuity to be characterized based on the ability of the blends to maintain their shape during extraction and measurements of the degree of continuity of the PEO phase. Electrical conductivity measurements were modeled using percolation theory to estimate the minimum PEO concentration required to form a continuous phase. Rheological measurements showed that the elastic modulus measured at low frequencies reached local maxima at the boundaries of the region of cocontinuity. SEM with image analysis and solvent extraction provide the most quantitative information about the blend morphology and are the most powerful methods for characterizing the region of cocontinuity. Polym. Eng. Sci. 44:714–727, 2004. © 2004 Society of Plastics Engineers.     

The compatibility of the polystyrene/acrylonitrile-butadiene-styrene grafted copolymer system

Summary The study of polystyrene (PS)/acrylonitrile-butadiene-styrene (ABS) grafted copolymer/cyclohexanone or methylene chloride system compatibility both in concentrated solutions and solid state has been carried out by phase separation, viscosimetrical measurements and thermal behaviour.Having in view the obtained data it has been ascertained that the systems present different degrees of compatibility depending on the mixtures composition. At higher temperatures, the compatibility of the components is changed.     

Evaluation of portable dilution system for aerosol measurement from stationary and mobile combustion sources

This study presents the emission factor of PM_2.5, elemental carbon (EC), organic carbon (OC), and water-soluble ions for biomass-fired-induced downdraft gasifier and light duty diesel vehicle (LDDV). A portable dilution system (PDS) developed for on-field measurement of aerosol and their precursors from combustion sources were used for quenching of aerosol at near-atmospheric condition before collection on filters. PDS consists of a heated duct and particle sampling probe, dilution tunnel, zero air assembly, and a power supply unit. PDS was evaluated under controlled conditions in laboratory for gasifier cookstove and LDDV over wide range of dilution ratios to understand the effect of dilution on mixing, particle formation, and loss. The invariability in CO₂, recorded along the length and at radial distances of cross-section of dilution tunnel, confirmed the rapid and homogenous mixing inside the dilution tunnel. The particle loss and nucleation inside the dilution tunnel accounted for 6–20% at different dilution ratios (30:1–90:1). PM_2.5 emission factors for wood combustion in gasifier cookstove showed mild decrease (13%) with increasing dilution ratio from 75:1 to 108:1. However, a considerable decrease of 37% (221–139 mg km^?1) was observed for LDDV with increase in dilution ratio from 39:1 to 144:1. Similar decrease in particulate organic carbon emission rates were observed indicating scarcity of sorptive organics, and insufficient residence time for condensation limited the particle formation from vapor phase organic compounds at high dilution ratios.

© 2016 American Association for Aerosol Research     

同阴离子双盐体系分离过程图解法综合

氯化钾是我国化肥生产的重要原料,包含氯化钾的无机盐体系的分离过程综合研究具有重要理论意义和应用价值。以NaCl-KCl-H₂O体系为例,提出了一种同阴离子双盐体系分离过程的综合方法。该方法是通过分析同阴离子双盐体系的固液平衡关系,在温度的影响和同离子效应的基础上建立的。其利用图解法直接从相图中寻找可行的分离工艺流程,设计过程简便易行。分别给出NaCl-KCl-H₂O体系的两个和MgCl₂-KCl-H₂O体系的一个过程综合案例,并给出了相应的工艺流程。     

On the compatibility of polystyrene/acrylonitrile-butadiene-g-styrene copolymer/solvent system

Summary Influence of the temperature on the compatibility of the polystyrene / AB-g-S graft copolymer / cyclohexanone have been studied by light scattering and viscosity measurement. It was established that the compatibility of components is changed in the temperature range where the conformational transitions take place.     

Determination of infinite dilution diffusion and activity coefficients of solvents in polystyrene by inverse gas chromatography on a capillary column

Infinite dilution activity and diffusion coefficients of several solvents in polystyrene have been measured by inverse gas chromatographic on a capillary column for temperatures between 110 and 170°C. Chromatographic data have been treated according to Khan's model, evaluating the contribution to the peak broadening due to radial and axial molecular diffusion in the mobile phase, radial diffusion in the stationary phase, and interfacial mass transfer resistance. Four capillary columns have been prepared with coating thickness ranging from 0.5 to 3.3 microns in order to determine the minimum thickness necessary to obtain reliable measurements of the diffusion coefficient of the solvent in the polymer in every possible experimental condition. Our experimental data are in considerable agreement with the data already available in the literature, obtained by static and chromatographic methods. © 1994 John Wiley & Sons, Inc.     

Specific heats of the solid-state phases of trimargarin and tristearin

Differential scanning calorimetry is used to obtain specific heats of the α, β′₂, β′₁ and β phases of trimargarin and tristearin in the temperature range from 190–350 K. Unequal specific heats are observed for β′ phases of the 2 lipids in contrast to nearly coincident values for their respective α and β phases. These results are discussed on the basis of odd vs even chain length triglycerides.     

乙烯装置稀释蒸汽发生器及急冷油系统改进

乙烯装置稀释蒸汽发生器是回收循环急冷油热量和发生稀释蒸汽(DS)，保证该系统热平衡的主要设备。天津乙烯装置在生产运行中出现了稀释蒸汽发生器热量回收减少，DS发生量减少，裂解汽油干点上升，装置无法正常运行。笔者针对暴露出问题进行综合分析，找出原因并对稀释蒸汽发生器和急冷油系统进行改进，改进后取得了明显效果。     

硝酸配稀系统及含NO_x尾气处理系统的设计

某厂采用一套设备稀释98%的浓硝酸,配制65%、40%和25%等浓度的稀硝酸,硝酸配稀时产生的尾气对环境造成污染,且危害工人健康。本系统采用带夹套的配酸贮槽来减少NOx的生成,同时用尿素溶液作还原剂吸收NOx;采用引射式吸收器作为吸收设备,使NOx反应生成的CO2和N2可直接排放,处理后的NOx含量在(100~300)×10-6之间,符合大气污染物综合排放标准(GB16297-1996)的要求,企业也实现了清洁生产。