Struktur und eigenschaften von ABS-polymeren II.. Grenzviskositäts-molekulargewichtsbeziehungen für azeotrope styrol/acrylnitril-copolymerisate

Limiting viscosity numbers of azeotropic copolymers of styrene and acrylonitrile were measured in dimethylformamide (DMF) and in methyl ethyl ketone (MEK). Their weight average molecular weights (10⁴ g/mole ? M_w ? 10⁶ g/mole) were determined by light scattering. The viscosity – molecular weight relationships obtained, are for DMF and for MEK The number average molecular weights were determined by osmotic pressure measurements, and now molecular weight heterogenities were calculated. The homogenity in composition was investigated by light scattering measurements in different solvents. In addition the viscosity-molecular weight relationship for polystyrene in DMF was determined and compared with the relationship for the azeotropic poly (styrene-co-acrylonitriles) and for polyacrylonitrile: On account of the results a possibility is shown for calculating molecular weights of poly (styrene-co-acrylonitrile) of any composition from limiting viscosity numbers and the acrylonitrile contents.     

d-NMR-Untersuchung der behinderten Rotation am -Bindungsinkrement. X. N-substituierte Thiocarbamidsäure-O-phenyl- und S-äthylester

d-N.M.R.-Investigation of the Restricted Rotation at the -Bonding Increment. X. N-Substituted Thiocarbamic acid-O-Phenyl- and S-Ethylesters The free enthalpies of activation of the restricted rotation at the partial -double bond in thiocarbamic acid esters have been determined for (R¹ = methallyl; R² = me, et, iso-pr, cycl. hex; X  S and Y  O C₆H₅ respectively X  O and Y  S C₂H₅). The results have been compared with values, earlier observed for other mono- and dithiocarbamic acid esters, substituted at nitrogen analogously.     

The kinetics and mechanism of the chloride-chlorate reaction

The kinetics of the reaction have been studied at 25°C. in strong acid solution; the effects of acidity, chloride, chlorate and chlorine are reported. A mechanism is postulated to interpret the peculiar features of this reaction as well as the stoichiometry and some of the kinetics of the parallel reaction The mechanism involves HClO₂ and HOCl as intermediates General rate expressions are derived for the formation of chlorine dioxide and chlorine, and the individual rate constants are calculated. An expression is obtained for the relationship between the ratio of chlorine dioxide to chlorine produced and the ratio of chlorate to chloride.     

Drop size distribution in a graesser contactor

An investigation was conducted of drop size distribution in a Graesser contactor, employing five liquid – liquid systems, viz., kerosene/water, benzene/water, xylene/water, hexane/water and n–butyl acetate/water. A 100 mm (4 inch) diameter Graesser contactor was used for this purpose It was found that the drop size distribution in a Graesser contactor obeys the upper – limit distribution expressed as: where A correlation was developed relating the Sauter mean diameter (d₃₂) to other effective groups      

Eine neue Methode zur Bestimmung des Molekulargewichts von Polymeren durch Ultrazentrifugation

The Lamm differential equation (DG) for the ultracentrifuge was solved for the case δc/δt ≠ 0 experimentally. The concentration gradient in the ultracentrifuge cell was determined by measuring the refractive index increment as well as the UV-absorption. Thus by simultaneously determining sedimentation and diffusion coefficient a new method for absolute molecular weight measurement was obtained.     

d-NMR-Untersuchungen der behinderten Rotation am Bindungsinkrement. IX. Behinderte Rotation um partielle Doppelbindungen in kernsubstituierten Phenyl-β-dimethylaminovinyl-thioketonen

d-N.M.R.-Investigations of the Restricted Rotation at the Bonding Increment. IX. Restricted Rotation about Partial Double Bonds in Nucleo-substituted Phenyl-β-dimethylaminovinyl-thioketones Due to resonance stabilization restricted rotations about partial and double bonds have been observed in some substituted phenyl-β-dimethylaminovinyl-thioketones 2. The free enthalpies of activation have been determined by means of d-n.m.r.-spectroscopy in dependence on the properties of the p-phenyl substituents and the solvent. The measured ΔG^≠-values depend on the σ-substituent constants and on the E_T-values of solvent polarity linearly. Substituents with electron-withdrawing properties and solvents with increasing polarity enhance the free enthalpies of activation of the restricted rotation.     

Spin coating behavior of polyimide precursor solutions

Experimental data confirm the utility of the following simple equation in predicting the spin coating behavior of polyimide precursor solutions: in which .     

Polymer swelling 2: A restudy of poly(styrene-co-divinylbenzene) swelling in terms of the cross-link density1

A very convenient and reliable gravimetric method was developed for measuring swelling of poly(styrene-co-divinylbenzene) in particulate form. The method is based on the gravimetric procedure reported earlier² for monitoring liquid uptake by thin (<0.3 mm) microporous composite films, consisting of swellable particulate (80% by weight) enmeshed in poly(tetrafluoroethylene) microfibers (20%). The swellability S (in milliliter of liquid absorbed per gram of polymer in equilibrium with excess liquid) for six sty-co-DVB polymers with crosslink densities ranging from 0.01 to 0.12 was measured in 19 organic liquids. In each study of S as a function of the relationship was given by where is the average number of carbon atoms in the “backbone” of the polystyrene segments between cross-link junction, C is the relative swelling power of the liquid, and is the critical cross-link density above which S is equal to zero.     

Oxidation of thiols in gas-liquid systems. I. Reaction in the absence of added metal catalysts

Studies have been made of the kinetics of the reaction with oxygen of several simple aliphatic and aromatic thiols in alkaline solution and in the absence of added metal catalysts. The results have been shown to be markedly affected by trace amounts of impurities, and the kinetics of the reaction have been measured under conditions of the minimum impurity levels obtainable. Under these conditions in the early stages of reaction, the rate law with, for example, ethanethiol has been found to be: which after ≈ 10–30% of reaction changes approximately to: Values of the energies of activation and pre-exponential factors for the oxidation of ethanethiol have been determined and investigations have been made of the effect on the reaction kinetics of the efficient removal, and of the addition of trace quantities of metals.     

Transferts thermiques entre un serpentin et des fluides newtoniens ou non—newtoniens agités par une turbine à pales inclinées dans une cuve

The present work deals with the heat transfer from a hélicoïdal worm to newtonian or non-newtonian liquids, which and stirred by a 4 pitched blade-turbine in a cylindrical tank. The effective viscosity of the pseudoplastic liquids is determined by the Metzner-Otto model combined with the Ellis rheological equation. The heat transfer in the newtonian fluids in a turbulent system is most precisely represented by the following equations: (a) (b) In the case of non-newtonian fluids and of downward pumping, the following equation enables to obtain a very precise evaluation of the heat-transfer coefficient in a transitional flow.      

Catalytic oxidation of benzene to maleic anhydride in a continuous stirred tank reactor

The kinetics of the vapor phase oxidation of benzene has been studied over an industrial catalyst in a continuous stirred tank reactor in the temperature range from 280 to 430°C and at atmospheric pressure. The products obtained are maleic anhydride, carbon oxides and water. The rate of the overall reaction (disappearance of benzene) is represented by the following expression based upon a steady state adsorption model The rate of formation of maleic anhydride is correlated by the equation which allows for a homogeneous depletion of maleic anhydride. The rate constants k_B, k_O, k_2(g) were found to follow Arrhenius behavior.      

Synthesis of alternating polyamide esters by melt and solution polycondensations of N,N′-Di(6-hydroxycaproyl) diamines and N-6-hydroxycaproyl aminoalcohol with terephthalic and adipic dimethyl esters and dichlorides

Alternating polyamide esters of structures A and B were obtained by melt polymerization of dimethyl adipate and terephthalate or by solution polymerization of adipoyl and terephthaloyl chlorides, with N,N′-di(6-hydroxycaproyl)diamines and an N-6-hydroxycaproyl aminoalcohol: where R₁ is selected from dimethylene, hexamethylene, and p-phenylene radicals, and R₂ is selected from tetramethylene or p-phenyl radical. Polyamide esters of structure A′ were also prepared: Average values of melting points of the resulting polyamide esters were dependent on the starting diacid derivatives, amide diols, and methods of polymerizations as follows: where CPZ, CHD, CED, and CPPD are N,N′-di(6-hydroxycaproy1)-, each in this order: piperazine, hexamethylenediamine, ethylenediamine, and p-phenylenediamine. ECA is N-(2-hydroxyethyl)6-hydroxycaproamide. For a given polyamide ester obtained from the same starting materials and by the same method of polymerization, the melting points increased with inherent viscosities. Polyamide esters of high molecular weight were obtained from CHD with both adipic and terepbthalic derivatives both by melt and solution polymerizations. Polymerizations of the other amide diols gave lower molecular weights. Solution polymerization gave colorless or light-colored polymers, while melt polymerization gave deeper-colored polymers.     

d-NMR-Untersuchung der behinderten Rotation am -Bindungsinkrement. III. N-substituierte Carbamid- und Thiocarbamidsäure-O-äthylester

d-N.M.R.-Investigation of the Restricted Rotation at the -Bonding Increment III. N-Substituted Carbamic and Thiocarbamic Acid O-Ethyl Esters At low temperature the n.m.r.-spectra of some N-substituted carbamic and thiobarbamic acid O-ethyl esters show two signals for each of the different proton groups. These have been assigned to the syn and the anti form by using Eu(fod)₃ as a shift reagent. The thermodynamic parameters ΔG≠ for the restricted rotation about the -bonding have been determined by the method of SHANAN -ATIDI and BAR -ELI . The results are discussed with regard to the tendency of the heteroatoms to form double bonds and the steric and conjugative effects of substituents, respectively.     

Structure Studies on 6a-Thiathiophthenes and Related Compounds

The results from structure studies on 6a-thiathiophthenes show that different substituent groups perturb the bonding in the three-sulphur sequence to different degrees. Both equal and unequal S? S bonds occur in symmetrically as well as in unsymmetrically substituted derivatives. The specific effect of methyl and phenyl substituents on the sulphur-sulphur bonding may be described by the results from CNDO/2 calculations on mono-methyl and mono-phenyl substituted 6a-thiathiophthenes. Molecular packing and intermolecular close contacts also seem to affect the S? S bonding. The structures of equally substituted 6a-thiathiophthene analogues with and show, when compared with the equivalent 6a-thiathiophthene, that and cause a pronounced change in the S? S bonding, while the perturbation caused by is negligible. In symmetrical 6a-thiathiophthene analogues with and , the average bond length in the linear three-atom sequence is 9 – 12% longer than the respective single bond.     

The molecular weight average obtained by combining quasielastic light-scattering and intrinsic viscosity measurements

For “monodisperse”, randomly coiled macromolecules, we find that the molecular weight, intrinsic viscosity, and diffusion coefficient are accurately related by This equation holds for denatured proteins in 6M GuHCl(aq) as well as for narrow polystyrene fractions in tetrahydrofuran. For a Schulz distribution of molecular weights, the weight measured from combining diffusion and viscosity data is closely approximated by These equations are verified with measurements of wide molecular distributions of polystyrene in toluene and data from the literature. These relations provide a rapid, nondestructive method to determine a well-specified molecular weight average of small quantities of polymers in a wide diversity of solvents using quasielastic light scattering techniques to evaluate polymer diffusion coefficients.     

A modified correlation to predict the minimum velocity required to elutriate solids from a liquid-fluidized bed

The consideration of sphericity of solids for the prediction of u_me gives rise to some improvement of the correlation proposed earlier by the author. In the absence of wall-effect, the following correlation is obtained: which gives a standard deviation of ± 16.3% for 138 different experiments as against ± 21.6% for 134 runs by the correlation reported earlier. The ranges of the various groups are      

A corresponding states treatment of saturated density,surface tension and capillary constant of cryogenic liquids and refrigerants

Using a new set of energy (kT) and length (σ) parameters, a corresponding states treatment is applied to the calculation of some thermophysical properties in a generalised non-dimensional form. The saturated density is well represented by the following equation: for all the liquids studied here. The surface tension correlations are $ \gamma _r^* = 2.055\left({1.219 - T_r^*} \right)^{1.240} $ for cryogenic fluids and hydrocarbons and $ \gamma _r^* = 2.322\left({1.228 - T_r^* } \right)^{1.244}$ for refrigerants. An interpretation of the index in the density equation and the constants in the surface tension equations is given. Using these correlations, an equation is also proposed for the capillary constant.     

Momentum and heat transfer characteristics of liquid-liquid dispersions in turbulent flow

The momentum and heat transfer characteristics of unstable, liquid-liquid dispersions flowing turbulently in a circular tube were investigated. Two mineral oils, a light oil with viscosity of 15 centipoise, and a heavy oil with viscosity of 200 centipoise were used as the dispersed phase while the continuous phase was tap water. At room temperature only, the relative fluidity of the dispersion follows the relation At Reynolds numbers above 60,000 the heat transfer coefficients of all dispersions studied follow the relation where the Prandtl number is that of the continuous phase and the Reynolds number is based upon the viscosity of the dispersion. All properties are evaluated at the film temperature.     

The apparent rate constant model for kinetics of radical chain copolymerization: Chemical-controlled process

In this article the kinetics of chemical-controlled radical-chain copolymerization have been reduced to pseudohomopolymerization kinetics by introducing the apparent rate constants, The methods for the determinations of the values of the apparent rate constants, mode of termination, and the methods for the calculation of molecular weights and distributions are proposed. The data required for these determinations and calculations are simply obtained by the usual steady-state method. According to the traditional kinetics along with the definitions of the apparent rate constants, these apparent rate constants as functions of traditional rate constants, monomer compositions, and copolymer compositions are derived. Further utilizing the theoretical expressions obtained, we show that the apparent rate constants are the general rate constants for both radical chain homo- and copolymerizations. The bulk radical copolymerizations of methyl methacrylate and styrene at various monomer feed compositions at 60°C are used to test the proposed model. The empirical apparent rate constants obtained are described well, by the following expressions, and and the mode of termination on the combination termination is where K and K denote the apparent rate constants of propagation and termination, respectively. The term f₁(= 1 ? f₂) stands for the mole fraction of styrene in the monomer solution fed. F₁ is the copolymer composition produced at f₁. β is the mode of termination.     

Prediction of steady-state dispersion height in the disengaging section of an extraction column from batch settling data

The decay of a dense dispersion formed under calm conditions is given by Experiments in a batch vessel with different liquid-liquid systems and initial drop diameters show that the dimensionless constant K is equal to 26,000. This agrees with the value previously determined from the variation in steady-state dispersion height with throughput in spray columns, the analogous equation being The results can thus be used to predict the height of the dispersion formed in the disengaging section of extraction columns.