Einfluß der chemischen Struktur auf die mechanischen Eigenschaften von modifizierten Polycarbonaten

Beginning with the current theories concerning the solid state structure of bisphenol-A-polycarbonate, the effect of chemical substitution of the bisphenol upon the thermal, mechanical, and dynamic mechanical properties will be discussed in detail. The observed mechanical properties of the various polycarbonates is considerably influenced by their chemical structure. Among all of the polycarbonates, bisphenol-A-polycarbonate is unique, particularly with respect to its low temperature properties. The ductile-to-brittle transition as a function of temperature correlates to the high temperature region of Gamma relaxation (G′′). Any theoretical approach to completely characterize and describe the experimentally observed phenomena must take into consideration as a fundamental parameter the conformational flexibility of the polycarbonate chain.     

Einfluß der mechanischen spannung und der temperatur auf die photooxidation von polyethylen

The tensile stress and temperature effects on the Polyethylene photooxidation kinetics have been investigated. Subjects are light stabilized and not stabilized high density Polyethylene films. The tensile stress used were 10% and 20% of the breaking stress. Temperatures of 50°C, 30°C, 5°C were realized in a chamber for an artificial climate with an irradiation source mercury ark lamp type ??PK-2. The duration of exposure was up to 1500h. The oxidation degree has been appreciated by the carbonyl index determined by means of a IR spectrophotometer. It was established that the photooxidation process rate depends on the temperature as well as on the mechanical stress. At the tensile stress used it was found a decrease of the oxidation rate in comparison with the unloaded samples. The mechanical stress influence was stronger when testing unstabilized Polyethylene.     

Einfluß der Katalysatorstruktur auf die Kinetik der Hydrierung und Isomerisierung

Influence of the Catalyst Structure on the Kinetics of Hydrogenation and Isomerization The selectivity with which an unsaturated oil can be hardened is determined, among other things, by the structure of the catalyst. A catalyst with many narrow pores will generally have a lower selectivity which is caused by transport limitations involving the triglycerides in the catalyst particles. This transport limitation is clearly shown by the distribution of the positional isomers which are formed during the hydrogenation of model substances such as methyl oleate and glyceryl trioleate. We also found that the rate of migration of the double bond strongly depends on the configuration. The migration of the double bond from the trans position proceeds much more rapidly than that from the cis position. The results obtained enable us to draw up a reaction scheme which may serve as a basis for calculating the composition of partially hardened fats while taking into account the structure of the catalyst. This is illustrated with experimental results of hydrogenations of methyl linoleate and glyceryl trilinoleate on various nickel-silica catalysts of different structure.     

Einfluß der Gruppenkomponenten auf die Eigenschaften von Estermontanwachsen

Influence of Group Components on the Properties of Montana Ester Waxes The group of wax esters and hydrocarbons was separated from the refined wax R by means of ion exchange on Wofatit SBW and column chromatography on silica gel. A part of the wax acids obtained was esterified with ethyleneglycol. Twenty wax systems having various compositions were prepared from wax acid glycolester and hydrocarbon group components. The wax systems were investigated for drop point, characteristic values, density, electrostatic properties, penetration, flow point, and flow curve. Furthermore, the formation of water emulsions was studied with these wax systems. Relationships between the composition of group components and definite physical and chemical characteristics were established.     

Einfluß der Glycerid-Verteilung auf die rheologischen Eigenschaften von Fetten

Effect of Glyceride Distribution on the Rheological Properties of Fats Investigations on suppository bases showed that the glyceride distribution influences the rheological properties of fats strongly. The authors presume that the viscosity behaviour is related to the random distribution of glycerides.     

Der Einfluß der Witterung auf die Eigenschaften von Methacrylat-Polymeren

Under atmospheric influence the molecular weight of PMMA decreases. The decrease of the molecular weight depends among other things on M?_v itself, on the content of UV absorbing additives, on the place and on the amount of the radiant energy. As many properties of PMMA in particular the characteristic mechanical values determined in the short time test depend above M _v = 10⁵ only slightly or not at all on the molecular weight, the weathering changes these properties only insignificantly. Properties such as light transmittance, softening point, tensile or flexural strength and moduls of elasticity don't change. The characteristic values for toughness of a material such as impact strength and elongation at rupture show a perceptible decrease. Open air weathering in tropical climate can cause more intense changes of the properties than in Central Europe. If the material has a thickness of 5 mm weathering can result in reversible colour phenomena. Polymers with an UV protection don't show this effect. In case of open air weathering copolymers with acrylonitrile (here AN/MMA = 70/30) show stronger changes of the properties than pure PMMA. Nevertheless they are suited for an outdoor application of many years duration.     

Die Kinetik des Schmelzens und der Kristallisation von Kakaobutter

The Kinetics of Melting and Crystallization of Cocoa Butter Melting is kinetically the reverse of crystallization. It was shown in a previous publication that the kinetics of fat crystallization is the same as that of precipitation from colloids. It is shown in the present paper that the kinetics of melting of solid fat is the same as that of the dispersion of gels. The kinetics of the melting of cocoa butter was investigated by linearization of experimental data from the literature. The linearization shows that the melting is accompanied by crystal transformations, and that the various crystal forms melt in succession.     

Tendenzen in der EG-Umweltschutzgesetzgebung und Auswirkungen auf die chemische Industrie in Deutschland

Trends in the Environmental Legislation of the European Community and their Consequences for the German Chemical Industry. Environmental legislation from the EC has changed considerably in recent years. The directives of the early eighties contained mainly general guidelines and generous limit values. Due to the need for unanimous voting for the decisions stricter thresholds were not achievable. They had relatively small impact on Germany because that country's internal legislation was more stringent. There is now a new trend which gives cause for concern. Many elements of the latest directives do not match the German legal system and lead to stringent conditions. This is due to the fact that they have to be implemented in addition to existing legislation: Much written information and evidence of performance are required, relating to e.g. the installations and the management of the company. As a consequence there will be further complications in the approval procedure for chemical plant.     

Struktur und Eigenschaften von ABS-Polymeren, 13. Einfluß der Polymerisationsbedingungen auf die Struktur von ABS-Polymeren bei der Pfropfung in Emulsion

By grafting styrene-acrylonitrile onto poly(butadiene) latex graft polymers of different structure are synthesized. During the graft reaction the monomer to poly(butadiene) ratio and the conversion were varied and the influence of these variations on the degree of grafting and the molecular weight of grafted chains was studied. By mixing these graft polymers of different graft structure (graft density) with styrene-acrylonitrile-copolymers, ABS-materials are formed with a rubber content of 17.5% by weight. Glass transition temperature (T_g) of the elastomer phase of these ABS materials as well as notched impact values correlate with graft density of the rubber component.     

Einfluß der Metallseifen auf die rheologischen Eigenschaften von lipophilen Grundlagen

Influence of Metallic Soaps on Rheological Properties of Lipophilic Bases Influence of metallic soaps on the rheological properties of lipophilic suppository bases was determined. The investigations revealed that rheological properties of suppository bases are considerably altered by the addition of metallic soaps. Alterations in rheological properties are determined from the ratio of solid to liquid components.     

Der einfluss des zuschlags und der betonfestigkeit auf die spannungs-dehnungs-linie von konstruktivem leichtbeton

The stress-strain-relations of lightweight concrete published so far differ greatly in shape and ultimate strain. In some cases the curves experimentally obtained are similar to those of normal-weight concrete, in other cases they are very stretched compared to normal-weight concrete. The scatter of the measured values of the ultimate strain of lightweight concrete is greater than the scatter found with normal-weight concrete. It could be shown that the shape of the stress-strain-relation of lightweight concrete also depends on ultimate stress as well as on the type of lightweight aggregate. Furthermore the ultimate strain measured under constant rate of strain is obviously influenced by the type of aggregate and by the strength of concrete. An explanation of the deviation from normal-weight concrete is given.     

Über die Auswirkungen von Tensiden auf die Mundschleimhaut

Action of Surfactants on the Mucous Membrane of the Mouth Besides suitable brush and cleaning agents, a definite time is also required for the removal of mucoproteids, that are held rather rigidly on the tooth surface, thus forming matrix for tartar and pigment deposits. Mostly, a layman does not devote this amount of time for dental care. A proper dental care is one of the most important prophylactic measures against caries and paradentopathies. Extensive cytological investigations carried out for several years have shown that certain surfactants at concentrations below 2%, preferably between 1.2 and 1.5%, facilitate the cleansing without impairing the mucous membrane of the mouth.