SOLVENT QUALITY AND SOLUTION BEHAVIOR OF NYLON 12

The refractive index increment,dynamic and static laser light scattering,intrinsic viscosity[η]and Huggins constant(K_H)of nylon 12 have been measured in m-cresol and sulphuric acid/water system at 10-60℃.The intrinsic viscosity,R_H,R_g,A_2,and(~2)~(1/2)(calculated from viscosity data)and"a"values of nylon 12 are found to be higher in m-cresol than in sulphuric acid.All these parameters decrease with the increase in water contents in sulphuric acid.The refractive index increment,K_H and activation energy show an opposite trend to that of[η].The intrinsic viscosity,R_H,R_g,A_2, and(~2)~(1/2) have maximum values around 30-40℃in sulphuric acid/water system,whereas in m-cresol they fall at about 20℃.It has been concluded that the variation in size,interaction parameter(second virial coefficient),[η]and K_H of the polymer solutions with the alteration in solvent composition and temperature are the out come of change in thermodynamic quality of solvents,selective adsorption,hydrogen bonding and conformational transitions.It has also been concluded that the increase in temperature first enhances the quality of the solvent,encourages hydrogen bonding and specific adsorption, and then deteriorates,bringing conformational transitions in the polymer molecules.However,the addition of water to sulphuric acid continuously deteriorates the solvent quality.This characteristic of the solvent system brings conformational changes in the polymer especially at low temperatures.     

The phase diagram and supercooling conditions for the Ca(NO3)2−CaCl2−H2O system

The liquidus temperature and induction periods were measured for crystallization in a system of calcium nitrate, calcium chloride, and water over a concentration range of 5–20 mole% Ca(II), i.e., R=4–18 [R=moles H₂O/moles Ca(II)] and y_cl=0–1 [y_cl=moles Cl^–/moles (NO ₃ ^– +Cl^–)]. A ternary phase diagram was constructed, and qualitative dependences of the supercooling at which the solution began to crystallize on the system composition were found. A wide range of stability toward crystallization was found for solutions withR=4–10 and y_cl=0–0.7 The relationships between the system stability toward crystallization and the viscosity, glass-transition temperature, and the liquidus temperature are discussed.     

Change of water structure by solvents and polymers

Viscosity measurements have been made of water-solvent and water-polymer solutions in a temperature range of 20–60 centigrades. A medium structure temperatureT ₀ was calculated from the Vogel-equation. Water has a structure temperature of 140–150 K, its decrease indicates structure breakage, an increase structure promotion. Pyridine, dioxane, dimethylformamide and urea are structure breakers. This is explained by a shift of the equilibrium — bonded water molecules — nonbonded — to the right. Acetone shows hydrophobic bonding in the same concentration range of 0–10 mole % as the normal alcohols. They are quasifree liquids-structure temperature zero-in the pure state. This is explained by hydrogen bridged dimer formation with the exception of tert-butanol. Its 3 methylgroups sterically prevent dimer formation and cause structuring. Adding urea to methanol-water solutions breaks water structure according to urea concentration but extends the hydrophobic bonding maximum over the whole diagram. Glucose-water solutions have a minimum in the structure temperature diagram. Its left side indicates waterstructure breakage, its right side formation of a new structure forced upon water by the sugar. The equilibrium can be formulated: Waterlike bonded-nonbonded-hetero (solvent)-like bonded, Ribose also shows this minimum but after a short range of heterobondedness the structure is completely broken to nonbondedness.The polymers dextrane and polyvinylpyrrolidone are strong waterstructure breakers. Dextrane much stronger than PVP, it breaks to nonbondedness while PVP maintains a certain structuring, perhaps indicating heterobonding at higher concentrations. Polyacrylamide is a strong structurebreaker. It resembles urea in this sense. Perhaps the solvationwater structure of the NH₂ groups is very different from pure waterstructure. Polyacrylicacid breaks waterstructure completely, if sodiumchloride is added waterstructure is rebuilt again. The only waterstructure promoting polymer is natural gelatine. Perhaps this structure is different from pure water or the watermolecule equilibrium is shifted towards bondedness. The structure temperatures of pure polyethyleneglycoles show a minimum with increasing molecular weight. The high structure temperature of the small chains is explained by long chain assoziates formation through hydrogen bridging. This liquid of long assoziate chains is structured and has a high structure temperature. With increasing molecular weight ringformation instead of linear assoziation becomes possible. These neutral rings form a free liquid. Long chains again have a linear structure and the structure temperature increases at higher molecular weights. Existence of linear chain assoziation of low molecular PEGs is proved with their breakage by adding the chain terminating methanol.Dedicated to Prof. Dr. F. H. Müller.Herrn Chemotechniker D. Ziegler möchte ich für die sorgfältige Durchführung der Messungen sehr danken.Dem Verband der Chemischen Industrie danke ich sehr für die Ermöglichung der Arbeit.     

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.