Eigenschaften von gelösten und gequollenen Polymethylmethacrylaten in Abhängigkeit von der Struktur

The stereocomplex formation, which is observed after mixing of stereoregular samples of polymethylmethacrylate (PMMA) in various solvents was studied by dielectric and viscosimetric measurements. By means of X-ray wide angle diffraction measurements of mixtures of stereoregular polymers freed from solvent it was found that the stereocomplex consists of crystalline regions. From viscosity measurements of solutions of various tacticity in comparison with swelling properties of crosslinked PMMA it is concluded that the association of isotactic and syndiotactic sequences, which is considered to be the reason for stereocomplex formation, also exists in solutions and gels of atactic PMMA. From the temperature dependence of the reduced specific viscosity, the complex dielectric constant, and the swelling we deduce that the association in microcrystalline regions leads to formation of physical crosslinks, which melt in a certain temperature range. The properties of dilute solutions prepared from mixtures of isotactic and syndiotactic PMMA and toluene can be interpreted by intermolecular association mainly. The anomalies observed in very dilute solutions are explained by intramolecular association. The properties of solutions in which association occurs are dependent on their preliminary thermal treatment and their previous history.     

Die Zusammensetzung tierischer Organ- und Depotfette in Abhängigkeit von der Fütterung II Gas-chromatographische Analyse der Fettsäuren von Kälber- und Rinderfetten

The Composition of Lipids of Animal Organ and Depot Fats in Relation to Feed II: Gas-chromatographic Analysis of Fatty Acids of Calves and Cattle Fats In the milk as well as in the fats of calves and cattle 81 fatty acids were found. The composition of fatty acids of the depot and organ fats of cattle — in winter with stall-feeding and in summer with pasture-feeding — were compared with the winter and summer milk fats. The differences between the fats from the same parts of calves and cattle are discussed.     

Beeinflussung der Waschintensität (WI) in Abhängigkeit von Chemie und Mechanik

Influence of Chemical and Mechanical Factors on the Intensity of Washing Mutual effects of the two significant chemical and mechanical factors that influence the removal of dirt could be studied by treating the fabric in specific manner using a roller-type washing machine, which was developed in author's institute, and a device for measuring the working force. The tests revealed distinctly that intensity of washing is preferably promoted under the action of a solution of washing agent when fibres within the thread are displaced as widely as possible. When the aforesaid conditions are fulfilled, dirt substances from fabrics are suitably dispersed and suspended, which result in optimum washing action.     

Festigkeitsuntersuchungen von Agglomeraten in Abhängigkeit der Herstellungsparameter in Intensivmischern

Granules of ceramic materials are differently stressed by the processes during pelletizing in high shear mixers. This has a major influence on the resulting agglomerate size distribution. The paper presents the results of different mixing tools and impeller speed on the agglomerate strength. Therefor agglomerates have been compounded under certain conditions. Subsequently, their strength has been determined with a single particle breakage equipment.     

Abhängigkeit der thermomechanischen Eigenschaften von vernetzten Methacrylpolymeren von deren Zusammensetzung

The thermomechanical behaviour of crosslinked polymers containing two types of segments: a) monodispersed on the length L₁ (polymethylenglycolphthalate with a side group ? CH₂OR in the ethylene glycol units) and b) polydispersed on the length L?₂ (polymethacrylate and polyacrylonitrile) has been investigated. It was shown that at L₁ = const. the thermomechanical properties of polymers do not depend linearly on L?₂. Polymers with polymethacrylate segments are transparent and homogeneous at arbitrary compositions. Polymers with polyacrylonitrile segments are transparent and homogeneous at a content of acrylonitril units below 60%. After thermal treatment between 200 and 250°C they become paramagnetic, undergo additional crosslinking and improve their heat- and thermostability as a result of chemical changes involving the nitrile groups.     

Abhängigkeit der UV-Absorption binärer Styrol-Copolymerisate von der Länge der Styrolsequenzen

The UV-spectrometer is proposed in the literature as a second detector for gel permeation chromatography, independent of the usual differential refractometer. The intention is to get information on the variation of the chemical composition of styrene copolymers with molecular weight. The present paper disproves the usual assumption that UV-absorption of styrene copolymers is depending only on the concentration of phenyl rings. However, the absorption also depends on the length of the styrene sequences and therefore mostly on the monomer ratio in the copolymer. The UV-spectra of binary styrene copolymers with ecrylonitrile, maleic anhydride and butadiene were measured at different monomer ratios. From the measurements we calculated the molar absorption coefficient of the phenyl ring for different absorption bands. In comparison with homopolystyrene it is shown that both the position and the absorption coefficient of the bands can depend on the sequence length distribution of the copolymers. We suggest this to be caused by dispersion interactions between neighbouring phenyl rings. Consequences for the use of a UV-spectrometer as a detector for gel permeation chromatography are discussed.     

Die Beständigkeit von Einbrennlackierungen im UV-Licht in Abhängigkeit vom Vernetzungsgrad

Stability of Stoved Paints in UV-Light as a Function of the Degree of Cross-Linkage Degree of cross-linkage and UV-stability of stoved and pigmented paints based on saturated hydroxy-containing polyester resins were investigated. The degree of cross-linkage of the coatings was measured by determining the hardness as such, hardness after exposure to xylene, and by infrared estimation of the hydroxyl group. The hardness and the IR method enable determination of the degree of polyester-triazine resin cross-linkage, whereas the solvent method indicates the extent of triazine-resin cross-linkage. The effect of temperature on polyester cross-linkage and on triazine resin cross-linkage is reported and the influence of both the reactions on mechanical properties of the coatings is recorded. The UV-stability of the coatings with respect to retention of gloss and yellowing was determined. Gloss retention is improved with increasing degree of cross-linkage, whereas the stability against yellowing initially decreases with increased content of triazine-resin up to a minimum, whereafter an increase in stability against yellowing is observed with increase in triazine-resin cross-linkage. Relationships between yellowing stability and cross-linkage reaction were obtained from the effect of stoving temperature on the yellowing curve.     

Montage von Chemieanlagen — Vorbereitung und Durchführung

Construction of chemical plant – preparation and execution . The construction of chemical production plant must be carried out observing all factors necessary for reliability. Furthermore, it should be performed as rapidly as possible to minimize erection costs and to ensure that the plant comes on stream by the desired date. To meet these demands, large construction projects require careful preparation such as model construction, production of isometric drawings, estimates of material and labour requirements just as much as good organization of the construction site. Chemical companies with engineering departments mainly constructing plant for their own requirements and which, unlike engineering companies, do not have to pay attention to the individual wishes of their customers, are usually able to work more uniformly and effectively, and with less expenditure on coordination.     

Die Ausnutzung von Gesamtfettsäuren und Calcium von gesunden Säuglingen im 1. Lebensvierteljahr in Abhängigkeit vom Fettsäuren-Gehalt und von der Fettsäuren-Zusammensetzung in Milchmischungen

Utilization of Mixed Fatty Acids and Calcium by Healthy Sucklings in the First Quarter Year of Their Life in Relation to the Fatty Acid Content and the Fatty Acid Composition of the Milk Mixtures The daily utilization of calcium and mixed fatty acids by 43 healthy sucklings from 4^th till 90^th day of their life is reported. The sucklings received the usual cow milk mixtures with different fat contents and varying fatty acid compositions. It is shown that the calcium utilization by the new-borns and young sucklings is, even on feeding with mother's milk, lower than in the later infant age. Furthermore, a statistically proved relationship is shown to exist between the level of fat content as well as the fatty acid spectrum of the feed and the calcium utilization.     

Die abhängigkeit der Ah-Kapazität von Leclanché-trockenbatterien von der Zellenbelastung und Zellengeometrie

An attempt is made to show that a definite relation exists between the ampere-hours capacity of Leclanché cells, their discharge current strength and their cell geometry which is satisfactorily represented by the formula

Ah = Ah_max{1 - exp [-K₀(4πhRa)^1/2]}

Résumé

On essaye de démontrer qu'une relation simple existe entre la capacité en Ah d'éléments Lechlanché et du courant de décharge ainsi que de la géométrie de la cellule, qui est représentée d'une manière satisfaisante par la formule

Ah = Ah_max{1 - exp [-K₀(4πhRa)^1/2]}     

Untersuchungen zur Freisetzungsgeschwindigkeit von Salicylsäure aus Salbenschichten, 2. Die Abhängigkeit der Freisetzungsgeschwindigkeit von rheologischen Parametern und der Löslichkeit in Kohlenwasserstoffgemischen und anderen Salbengrundlagen

Studies on the Rate of Liberation of Salicylic Acid from Ointment Layers, 2. Dependence of Rate of Liberation on Rheological Parameters and Solubility in Hydrocarbon Mixtures and Other Ointment Bases Influences of solubility, HLB-value and selected rheological parameters on the liberation of salicylic acid from ointment layers were investigated. Simple and multifactorial correlation calculations show that the solubility of salicylic acid in the ointment layer is the most importent factor, whereas the rheological parameters have a detectable effect, only when ointments of similar chemical composition are compared. Moreover, the HLB-value has no significant effect and the interface tension of ointment/water is only of minor significance.