Struktur und Eigenschaften von ABS-Polymeren. XII. Oxydativer Abbau von Polybutadien-Pfropfpolymeren aus ABS; Vergleich verschiedener Abbaumethoden

Polybutadiene graft polymers are characterized by first degrading polybutadiene under mild oxidation conditions with tert-butylhydroperoxide and OsO₄ at 110°C for 30 min is p-dichlorbenzene and then degrading it in a second step with periodic acid at room temperature. This degradation method is compared with a degradation procedure with KMnO₄ and a degradation with tert-butylhydroperoxide and OsO₄ in toluene and benzene at different temperatures and for different degradation times. It could be shown, that the described degradation method fully degrades polybutadiene without changing the chain length of the grafted styrene-acrylonitrile-copolymer chains.     

Vergleich von herkömmlichen und reacetylierten Chitosanen hinsichtlich ihrer Flockungseigenschaften

Since for some years chitosan is in the focus of biologically orientated research. It has a huge number of advantages compared to synthetic products. In this work the chitosan was reacetylated and afterwards characterized. Reacetylated chitosan dissolves in deionized water without any additives and shows good flocculation properties. Furthermore the properties of flocculation were compared to commercial chitosan. Molar mass, pH value, and the salinity in the system have great influence on position and width of the flocculation window.     

Chromatographischer und spektroskopischer Vergleich des Autoxidationsprozesses von Öl- und Elaidinsäure

Chromatographic and Spectroscopic Comparison of the Autoxidation Process of Oleic and Elaidic Acid The autoxidation process of cis-9-octadecenoic and trans-9-octadecenoic acid was studied using thin-layer chromatography, gasliquid chromatography, nuclear magnetic resonance spectroscopy and infra-red spectroscopy. On the basis of results obtained and by comparison with the “classical methods”, such as the course of peroxide value, and changes in acid value and iodine value, a scheme has been proposed to characterize the initial phase of the autoxidation process of oleic and elaidic acids.     

Durch Wasserstoffperoxid ausgelöste Ringverengung von Aminohydroxy-hexahydrobenzoxazolcarbonsäureamid zu Amino-cyclopentanspirooxazolinon

A Ring Contraction Induced by Hydrogenperoxide 2-Amino-7a-carbamoyl-3a-hydroxy-3a,4,5,6,7,7a-hexahydro-benzoxazole ( 1 ) and hydrogenperoxide rearrange to 2′-amino-cyclopentanespiro-5′-oxazolin-4′-one ( 5 ). 5 and aniline hydrochloride form the phenylaminoderivative 6 , 5 and 2,5-dichlorophenylhydrazine hydrochloride form the 2,5-dichlorophenylhydrazinederivative 7 . 5 and hydrochloric acid afford cyclopentanespiro-5′-oxazolidin-2′,4′-dione ( 8 ). Hydrolysis of 5 or 8 furnish 1-hydroxy-cyclopentane-carboxylic acid ( 9 ).     

Autoxidationsverhalten von Tritetradecylglycerinäther im Vergleich zu Trimyristin und Kokosöl

Autoxidation Behaviour of Tritetradecyl Glycerol Ether in Comparison with Glyceryl Myristate and Coconut Oil Tritetradecyl glycerol ether is considerably less stable towards atmospheric oxygen than glyceryl myristate and coconut oil: During the storage of tritetradecyl glycerol ether at 60°C up to 96 hours, the peroxide value increases continuously after an incubation time. Under the same conditions, the peroxide value of a reference sample containing 500 ppm of α-tocopherol did not increase. Upon heating to 180°C the tritetradecyl glycerol ether is degraded much more rapidly than glyceryl myristate and coconut oil. Chiefly polar reaction products are being formed, according to liquid and gel permeation chromatography presumably mono- and dialkyl glycerol ethers, tetradecanal, tetradecanol and further compounds not yet identified. The reaction products, in part, possess a higher molecular weight than the original compound. The resolution of the reaction products by liquid chromatography is described.     

Vergleich einiger Methoden zur Bestimmung des Oxiran-Sauerstoffgehalts von Ölen und Fetten

Comparison of a Few Methods for the Determination of Oxirane Oxygen Content of Oils and Fats The accuracy and reproducibility of four methods were compared by multiple determinations of oxirane oxygen contents of 9,10-epoxystearic acid, alone or in conjunction with varnish grade linseed oil, of epoxidized oil, as well as of heat treated oxidized oil. Besides the direct method employing HBr/glacial acetic acid three indirect procedures were tested. The differences amongst the above methods lie in titrating agents and end point indication. Especially with regard to attainable accuracy the method employed by the author involving potentiometric end point indication is distinctly advantageous as compared to coloured indicators. None of the methods tested is applicable for the determination of oxirane oxygen content at a level < 0.01%.     

Ausbildung von Verfahrens-Ingenieuren und Vergleich von Abschlüssen innerhalb der EG

Education of chemical engineers and comparison of qualifications within the European Community. The present survey compares and contrasts the various structures of engineering education, and especially of chemical engineering education, in the member countries of the European Community (EC). Each of the different education systems within the EC has its advantages and disadvantages and none of the systems is definitely superior to others. Each system is largely the product of national pecularities and should be seen in the light of the specific cultural background. This often impedes a complete transfer of single elements from one system to another. Proven principles of other education system should, however, serve much more than has been the case in past as a guideline for reforms in our country. Possible steps in this direction are discussed.     

Vergleich des Triglyceridmusters von Humanmilch und Säuglingsnahrungen

Comparison between the triglyceride Patterns of Human Milk and Infant Milk Formulae Human milk contains less triglycerides with saturated fatty acids than the three infant milk formulae analysed but has a higher content of triglycerides with two unsaturated fatty acids. The patterns of the major triglycerides are compared. In human milk, palmitic acid is preferably located in position 2 favourable to digestability, whereas in the infant milk formulae it is mostly distributed over positions 1 and 3.     

Untersuchungen zum Abbau von PVC-Folien durch Wärme und Licht

The degradation of films of copolymers of vinyl chloride and carbon monoxide or oxygen by heat and light was investigated. With increasing carbonyl content the instability increases. The thermal degradation is accelerated by oxygen, the photodegradation is retarded. Due to the influence of light polyene sequences are formed on the surface layers of the polymer film. Therefore the lower layers are not damaged.     

Über das Lagerverhalten von Kartoffelchips bei Belichtung und im Dunkeln I Analyse der durch Licht ausgelösten Veränderungen des Röstöls

Storage Behavior of Potato Chips Exposed to Light and in the Dark I: Analysis of Alterations of the Frying Oil Caused by Light Two aspects should be considered in evaluating potato chips produced commercially: quality control within the production plant at the time of manufacture, and detection of alterations on storage during the period of circulation. Currently, these products are packaged without taking protective measures to eliminate light and atmospheric oxygen. The investigations in the first part of this study were therefore devoted towards the determination of the action of these two parameters on the oxidation of the frying oil. Since the fat content of such products is as high as 45%, one might assume that the state of oxidation of the fat determines the quality of the entire product. Based on the kinetics of peroxide formation and oxygen uptake it is shown that the light sensitivity of refined peanut oil increases with increasing thermal stress in the frying equipment. A common consideration of the oxygen uptake as measured physically, the peroxide formation, the absorption at 232 nm, and the carbonyle content gives a deep insight into the course of the reaction. Due to the tocopherols present in the oil conjugated hydroperoxides are predominantly formed in a wide region of the oxidative process. The parallel reaction of peroxide decomposition, which yields carbonyls having intense taste, occurs to such a small extent that methods suitable for routine analysis are unable to differentiate the samples. Addition of antioxidants was found to be of little use for the quality retention under the action of light. Exact knowledge of the storage behavior might enable to draw consequences for the practice. For example, one might use a packaging, which not only fulfils the technical requirements but also justifies economic considerations.