Anthraquinone derivatives as organic stabilizers for rigid poly(vinyl chloride) against photo-degradation

Anthraquinone derivatives have been prepared and investigated as photo-stabilizers for rigid PVC by measuring the extent of weight loss (%), the amount of gel formation as well as the intrinsic viscosity of the soluble fractions of the degraded polymer. The results indicated a reasonable stabilizing effect of these derivatives compared with UV-commercially used stabilizers. A synergistic effect is achieved when the anthraquinone derivatives are mixed with UV-absorbers in a weight ratio of 75% of investigated organic stabilizer and 25% of reference stabilizer.A probable radical mechanism is proposed to account for the stabilizing action of the organic investigated materials.     

Analysis of entry flow to determine elongation flow properties revisited

The minimisation technique proposed by Binding (J. Non-Newtonian Fluid Mech., 27 (1988) 173) was used in our Generalised Engineering Bernoulli Equation framework to relate the entry pressure and stress power. We arrived at a final result similar to Binding's using assumed kinematics. Through subsequent assumptions to the kinematics we finally arrive at a result exactly equivalent to Cogswell's technique (Trans. Soc. Rheol., 16 (1972) 383). Thus, these two techniques are related in this general framework. The techniques were used to predict elongation flow properties of a polymer melt and polymer solution. The results for the polymer melt clearly show Cogswell's technique is adequate at high elongation rates. All these techniques require minimisation of the stress power with respect to the flow volume and discussion is given as to the validity of this minimisation technique. In addition, the approximate variational technique we propose gives clears limits as to when a technique, such as Cogswell's, can be applied.     

Experimental Research on NO2 Viscosity and Absorption for (1-Ethyl-3-methylimidazolium Trifluoroacetate + Triethanolamine) Binary Mixtures

The viscosity (9.34–405.92 mPa·s) and absorption capacity (0.4394–1.0562 g·g⁻¹) of (1-ethyl-3-methylidazolium trifluoroacetate + triethanolamine) binary blends atmospheric pressure in the temperature range of 303.15–343.15 K and at different mole fractions of [EMIM] [TFA] have been carried out. The molar fraction of [EMIM] [TFA] dependence of the viscosity and absorption capacity was demonstrated. The addition of a small amount of [EMIM] [TFA] into TEA led to rapidly decreased rates of binary blends’ viscosity and absorption capacity. However, the viscosity and absorption of binary blends did not decrease significantly when [EMIM] [TFA] was increased to a specific value. Compared with the molar fraction of the solution, the temperature had no obvious effect on viscosity and absorption capacity. By modeling and optimizing the ratio of viscosity and absorption capacity of ([EMIM] [TFA] + TEA), it is proven that when the mole fraction of [EMIM] [TFA] is 0.58, ([EMIM] [TFA] + TEA) has the best viscosity and absorption capacity at the same time. In addition, at 303.15 K, ([EMIM] [TFA] + TEA) was absorbed and desorbed six times, the absorption slightly decreased, and the desorption increased.     

A note on second‐order finite‐difference schemes on uniform meshes for advection‐‐diffusion equations

An artificial‐viscosity finite‐difference scheme is introduced for stabilizing the solutions of advection‐diffusion equations. Although only the linear one‐dimensional case is discussed, the method is easily susceptible to generalization. Some theory and comparisons with other well‐known schemes are carried out. The aim is, however, to explain the construction of the method, rather than considering sophisticated applications. © 1999 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 15: 581–588, 1999     

Viscous behavior of linear and three‐branch alkanes: Linking the equilibrium and transport theories

A new model for zero‐shear viscosity, η, is proposed. The model combines the Simha–Somcynsky (SS) statistical thermodynamic theory of liquids with the Eyring Significant Structure (ESS) transport theory. Using the new model, a successful linearization of the experimental viscosity vs. hole fraction data was obtained. A comparison between the new model and Utracki's relation, ln η = a₀ + a₁/(h + a₂) was also made. The former was found to be more successful for both linear and nonlinear structures, provided that an appropriate choice of the degrees of freedom of normal and activated states was made. The proportionality constant of the activation energy and transmission coefficient were also calculated for each species. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 879–887, 1999     

Rheology of polydimethylsiloxane swollen with supercritical carbon dioxide

Viscosity curves were measured for polydimethyl siloxane (PDMS) melts swollen with dissolved carbon dioxide at 50 and 80°C for shear rates ranging from 40 to 2300 s⁻¹, and for carbon dioxide contents ranging from 0 to 21 wt %. The measurements were performed with a capillary extrusion rheometer modified for sealed, high-pressure operation to prevent degassing of the melt during extrusion. The concentration-dependent viscosity curves for these systems are self-similar in shape, exhibiting low-shear rate Newtonian plateau regions followed by shear-thinning “power-law” regions. Considerable reduction of viscosity is observed as the carbon dioxide content is increased. Classical viscoelastic scaling methods, employing a composition-dependent shift factor to scale both viscosity and shear rate, were used to reduce the viscosity data to a master curve at each temperature. The dependence of the shift factors on polymer chain density and free volume were investigated by comparing the shift factors for PDMS-CO₂ systems to those obtained by iso-free volume dilutions of high molecular weight PDMS. This comparison suggests that the free volume added to PDMS upon swelling with dissolved carbon dioxide is the predominant mechanism for viscosity reduction in those systems. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 523–534, 1997     

A rheological and morphological study of a copolyester liquid crystal/polypropylene blend system

The effects of composition and shear rate on the rheology and morphology of blends of LC–3000, a thermotropic liquid crystalline polymer consisting of 60/40 of hydroxybenzoic acid and poly(ethylene terephthalate), with polypropylene were studied. It was found that the rheological properties depend in a complex manner on composition and applied shear. Both positive and negative deviations from the log-additivity rule were observed at low shear rates. Significant viscosity reduction was measured when the dispersed phase was a nematic TLCP. The accompanying microstructural transitions were characterized a posteriori, and it was found that the state of dispersion of the TLCP phase also influences the viscosity reduction phenomenon. A nematic, fibrillar TLCP phase shows a viscosity reduction of the order of fourfold with respect to the viscosity of the matrix. Another important finding was that the stability of these fibers would not be expected from work on other non-TLCP-containing immiscible blends. This suggests that the unique rheology of the TLCP minor phase is relevant to the formation of stable fibers. © 1996 John Wiley & Sons, Inc.     

一种新型的荧光探针及其在表面活性剂溶液胶束形成过程中的应用

近年来,具有分子内共扼的电荷转移化合物用作荧光探针来研究微环境的特性得到较大的发展,由Lout坛Law等提出的p-N,N一二烷基氨基爷叉丙二睛类化合物,其吸收光谱,特别是荧光光谱具有强烈的溶剂极性依赖性,即荧光光谱的峰值波长依赖于所处环境的极性,并有良好的线性关系。     

一种具有高分辨率特性的人工粘性法

八十年代发展起来的全变差不增格式在激波计算中所显示的卓越特性使其在气体力学问题的求解中得到广泛的应用。但全变差不增格式的一个缺点是计算量较大。本文提出了一种具有高分辨率特性的人工粘性方法,既保持了全变差不增格式的激波分辨率高的优点,又具有人工粘性法计算量较少的优点。     

On the dimensions of species participating in the growth of ammonium oxalate monohydrate crystals from viscosity data of concentrated aqueous solutions

The experimental data of the temperature and concentration dependence of viscosity of concentrated aqueous ammonium oxalate solutions are analysed using the hole theory of liquids and Einstein's model of viscosity. Analysis of the data revealed that the dimensions of the species participating in the growth of ammonium oxalate monohydrate crystals are 3‐5 times larger than the dimensions of individual NH₄⁺ and C₂O₄^2‐ ions composing them. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)