Lösungsthermodynamik von FeCl2 und NiCl2 in mischschmelzen aus zwei alkalichloriden oder alkali- und erdalkalichlorid

The excess chemical potential (μ^E) and the partial heat of solution of FeCl₂ and NiCl₂ in molten mixtures of chlorides were determined at 820 and 920°C for diluted solutions by emf-measurements with Galvanic cells of the type

An average cationic potential

is defined and used to fix a common ionic radius and distanceparameter

for the mixed solvent. There exist correlations of the type

and the corresponding constants are tabulated.     

Al_2(SO_4)_3/FeCl_3催化合成乙酸异戊酯

以冰乙酸和异戊醇为原料,Al_2(SO_4)_3/FeCl_3为催化剂,对催化合成乙酸异戊酯的条件进行研究。考察催化剂用量、乙酸与异戊醇物质的量比以及反应时间对乙酸酯化率的影响。结果表明,Al_2(SO_4)_3/FeCl_3具有良好的催化活性,在乙酸物质的量为0.1 mol、乙酸与异戊醇物质的量比为1∶4、催化剂用量1.0 g、反应时间2.0 h和带水剂环己烷用量10 m L反应条件下,重复实验3次,平均乙酸酯化率为93.50%。     

Zur kinetik der Vernetzung von Epoxidharzen

The crosslinking of epoxy resins,—phenylglycidylether as a model system as well as monomers and oligomers of diglycidylether of bisphenol A and of hydantoine resins—, with acid anhydride in presence of amine accelerators has been investigated. Experimental methods used were chemical analysis, dilatometry and calorimetry. From the determination of the chemical yield resulted, that crosslinking of epoxy and anhydride is a zero order reaction, but for longer distances of reaction time different rate constants must be used, leading to large differences in the activation energies of the steps of crosslinking. From time dependant deviations of the anhydride conversion yield from stochiometry it was concluded, that at first an intermediate compound originates and the linking of these units in the network determines the second step of crosslinking.     

Die kinetik der verseifung von homo- und copolymerisaten aus vinylestern in dispersion und lösung

A kinetical treatment for the hydrolysis of vinyl acetate polymers with Na-hydroxide (concentration a) in methanol-water (70 : 30) is reported. The decrease of the total concentration of polyvinyl ester (b_g) with time (t) can be described by an equation for a bimolecular reaction, providing a correction for the total concentration of the polymer: ? db_g/dt ? k₂·a·b_g·V where V ? (1 ? D³_i/D³_g). D_g represents the diameter for the spherical polymer coil, whereas D_i is the diameter of the inner sphere that does not take part in the reaction. In the two phase system under consideration the OH ions initially can react with the outer shell of the polymer coil only. After diffusion also ester groups of the inner shells are attacked. The coil is then widened, until V becomes unity. For both, the hydrolysis of the polymer and the monomer, identical reaction rates k₂ and temperature dependence of k₂ were found. V is a function of a₀, and the molecular weight. Neither an unzippering reaction nor a side group induced reaction is considered effective. For the hydrolysis of aqueous dispersions with NaOH or CaO one finds V ? 6 Δ R/D_g, where Δ R ? (D_g ? D_i)/2 ? const ? D_g. A particle size distribution enters the kinetical treatment separately. For several homo- and copolymers from vinyl- acetate, propionate, pivalate, versatate, chloride as well as from ethylene, n- and t-butyl acrylate and styrene k₂ · Δ R has been measured. From this data the effective surface for both pigmented and unpigmented films of latexes can be determined. The energy of activation has been found to be 11 kcal/val in water and 16 kcal/val in methanol-water.     

Zur kinetik und teilchenbildung der fällungspolymerisation von acrylsäure in gegenwart von polystyrol-block-polyethylenoxid-copolymeren

A surfactant system containing polystyrene-block-poly(oxyethylene) and water was used for the free radical precipitation polymerization of acrylic acid in toluene. The use of this stabilizing system makes it possible to produce poly(acrylic acid) dispersions with a particle diameter ranging from 50 to 300 nm and solid contents up to 40 wt.-%, which remain stable for months. The rate of polymerization, which was measured on-line in a reaction calorimeter shows a strong autocatalytic behavior. The maximum of the polymerization rate and the corresponding time of appearance depend strongly on the water content. The influence of the composition of the surfactant (block length), its concentration and the concentration of initiator and monomer on the polymerization rate and the particle diameter were studied. Especially by varying the block length of the copolymer, the number of particles, respectively the particle diameter, can be controlled. To describe the course of the polymerization process, a model based on the theory of homogeneous particle nucleation is suggested. The influence of water on the swelling equilibrium of the poly(acrylic acid) particles is taken into account.     

Zur kinetik der polymerisation von vinylchlorid mit modifizierten ziegler-katalysatoren

The polymerization of vinylchloride in methylcyclohexane with the catalyst system TiCl₄-(C₂H₅)₂Al(OC₂H₅)-p-dioxane has been investigated kinetically. The dependence of the rate of polymerization on the concentration of the catalyst and the monomer followed the equation V_Br=[Kat]_0,53[M]. The overall activation energy was 8,3 kcal/mol. The monomer reactivity ratio of the copolymerization of vinylchloride with styrene coincides with that of a radical mechanism.     

Preparation and characterization of Cr- and Fe-pillared bentonites by using CrCl3, FeCl3, Cr(acac)3 and Fe(acac)3 as precursors

Four pillared bentonites (Cr-PILB, Cr(acac)₃-PILB, Fe-PILB and Fe(acac)₃-PILB were prepared and characterized by X-ray diffraction (XRD), nitrogen sorption measurements and thermogravimetric (TG) analysis. The surface acidities of the samples and their structures were also investigated in the gas phase adsorption data of pyridine by the aid of FT-IR spectroscopic techniques. The XRD data and FT-IR spectra of the samples reflected mainly the structure of bentonite. The nitrogen adsorption–desorption isotherms of the samples were Type II shaped and showed in general mesoporous structures with pore openings of 4 nm. Two steps mass losses were observed in the TGA thermograms of B, Cr-PILB and Fe-PILB, while three steps mass losses were detected in the case of Cr(acac)₃-PILB and Fe(acac)₃-PILB. IR study by the adsorption of pyridine on the samples showed both Lewis and Brönsted acid sites on their surfaces.     

Modified carbonization of polyacrylonitrile by incorporation of FeCl2 and Fe(NO3)3—pore structure

The structure and texture of the pyrolysis product was modified by the incorporation of FeCl₂ or Fe(NO₃)₃ into polyacrylonitrile (PAN). The additives were added to a PAN solution in dimethylformamide. The incorporation of FeCl₂ and Fe(NO₃)₃ into PAN was found to result in carbons with a smaller interlayer spacing than the carbon derived from pure PAN, as well as a larger crystallite size and a larger volume of micropores with a radius of ca. 1.8 nm. FeCl₂ was more effective than Fe(NO₃)₃ in the modification of the carbonization behavior of PAN.     

Vorgehensmodell zur Standardisierung und Klassenbildung von Modulen in der Anlagenplanung

The process industry faces the challenges of intensified, global competition with increasing market dynamics. Modular, transformable production concepts promise a better adaption to these in the dimensions of throughput, product mix, and production location. To support the planning and engineering process of plants, a module definition with accompanying intensive and extensive parameters is given on the one hand. On the other hand, a procedure model is developed which classifies and standardizes modules for plants. This is demonstrated for a generic case study.     

Der einfluss des verhältnisses der stöchiometrischen mengen von FeCl2 zum pyromellitsäuredianhydrid während der synthese von eisenpolyphthalocyaninen auf dessen elektrochemische aktivität in der kathodenreduktion von sauerstoff

The influence of the ratio of FeCl₂ to pyromellitic dianhydride on the electrochemical activity of iron polyphthalocyanine in the reaction of oxygen reduction, was investigated. It was stated that the increase of this ratio leads to the increase of the electrochemical activity which is probably the result of different share of free polyphthalocyanine and iron polyphthalocyanine in the catalyst. It was stated that the vacuum heating leads to the increase of electrochemical activity. This effect may be explained by the cross-linking of polyphthalocyanine with the support via the surface compounds.     

Planung und Auswertung von Ringversuchen zur Ermittlung der Wiederholbarkeit und Vergleichbarkeit

Planning and Evaluation of Collaborative Tests for the Determination of Repeatability and Reproducibility The aim of collaborative tests is to determine the precision of analytical methods. Repeating measurements in a certain laboratory variances of results appear. If measurements of the same kind are repeated in different laboratories on a certain material, the variance of the results is still higher, according to experience. These two kinds of variances are called “repeatability” and “reproducibility” respectively. Rules are stated, by which collaborative studies may be planned in order to determine the two kinds of variances; among them a rule for the necessary number of participants and analyses. Then, a simple and clear method is described, by which the repeatability and reproducibility can be calculated. The method operates without the presumption of normality, that otherwise is often needed for statistical evaluations. The method is explained by an example.     

Reverse ATRP of acrylonitrile with diethyl 2,3-dicyano-2,3-diphenyl succinate/FeCl3/iminodiacetic acid

The reverse atom transfer radical polymerization (RATRP) technique using FeCl₃/iminodiacetic acid (IMA) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexa-substituted ethane thermal initiator, diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS), was firstly used as the initiator in this iron-based RATRP system. The polymerization in N,N-dimethylformamide not only shows the best control of molecular weight and its distribution but also provides rather rapid reaction rate with the ratio of [AN]:[DCDPS]:[FeCl₃]:[IMA] at 500:1:2:4. The rate of polymerization increases with increasing the polymerization temperature and the apparent activation energy was calculated to be 49.9 kJ mol⁻¹. The polymers obtained were end-functionalized by chlorine atom, and they were used as macroinitiators to proceed the chain extension polymerization in the presence of FeCl₂/IMA catalyst system via a conventional ATRP process. The resultant polyacrylonitrile fibers were obtained with the fineness at 1.16 dtex and the tenacity at 6.01cN dtex⁻¹.     

Anwendung der FMIR-Technik zur infrarotspektroskopischem Identifizierung von beschechteten Folien und Papieren

The high efficiency of FMIR-technique by infrared investigations of coated foils, papers and cartons is shown in some examples. In this method the surface of the sample to be investigated which is pressed on both sides of a KRS-5 crystal is scanned repeatedly by the IR-beam. This investigation shows that the reflectance technique yields spectra of higher quality (= resolution + band depth) than the traditional transmittance technique. Moreover the procedure of pressing can be omitted in the investigation of lacquered foils or foils with a smooth surface before recording the spectra. This proved to be necessary according to our results we received by the FMIR investigation of coated papers. Often better spectra of foils are obtained if a FMIR-erystal with 15 reflections is used (angle of incidence 60°). The FMIR-method has the great advantage of simplicity and speed.