Kunststoffe in der Milchwirtschaft — eine kritische Studie,V. Mitteilung: Zur Reinigung und Desinfektion von Kunststoffoberflächen 2. Teil: Hygienische Beschaffenheit von Kunststoffoberflächen und ihre Folgen

Plastics in the Milk Industry — A Critical Study, V. Communication: Cleansing and Disinfection of Plastic Surfaces 2nd Part: Hygienic State of Plastic Surfaces and Their Consequences Plastic articles, meant for repeated use in direct contact with food-stuffs can permanently establish themselves, only if success is achieved in maintaining plastic appliances and parts clean and germ-free without much difficulty. Because in some respects the properties of the plastics deviate from those of hitherto employed materials of construction, the former set specific requirements on cleansing agents and cleansing processes. The cleansing solutions for the plastics must be physico-chemically more effective, in order to overcome the strong adhesion of fatty impurities. Since it is basically doubtful, whether polyolefines without adverse effects can at all be employed for repeated use in direct contact with fat-containing milk products, intensive trials should be made with plastics having lower affinity for fat.     

Kunststoffe in der Milchwirtschaft - eine kritische Studie II. Mitteilung: Lebensmitteltechnologisch bedeutsame Eigenschaften von Kunststoffen,Teil 1

Plastics in the Dairy Industry - A Critical Study II: Food Technologically Significant Properties of Plastics, Part 1 Plastics represent a group of extremely manifold and unusually formable working materials. Producers and manufacturers have learnt to vary the properties of plastic products by special methods and to supply the market with different types of the same plastic material exactly fitted to specific purposes. Chemical, physical, and biological properties as well as manufacture and aging of plastics are discussed. Particular consideration is given to the application of plastics, which is of special interest to the food technologist.     

Kunststoffe in der Milchwirtschaft — eine kritische Studie IV. Mitteilung: Folgen der chemischen Beschaffenheit und Wärmeleitfähigkeit von Kunststoffen

Plastics in the Dairy Industry — A Critical Study IV: Effects Resulting from the Chemical Composition and Thermal Conductivity of Plastics During direct contact between plastics and food-stuffs, interactions among the two may occur. The low molecular weight components escaping from the plastics can adversely affect the organoleptic properties; in a few cases, interference with the path of microbiological processes were also observed. Conversely, edible materials can impair the mechanical properties of some plastics and accelerate their aging process. As a result of their low thermal conductivity, the plastics retard heat exchange between surrounding and the food-stuffs. Therefore, the kryotechnique has to be adapted such that an effective cooling of milk in plastic containers is achieved. Similarly, the wide-spread use of plastics has altered the technique and the pre-requisites for the manufacture of some products of the milk industry.     

Kunststoffe in der Milchwirtschaft - eine kritische Studie I. Mitteilung: Problemstellung und gesetzliche Vorschriften

Plastics in the Dairy Industry: A Critical Study I: Related Problems and Legal Specifications Since many years plastics are widely used in many technical sectors as well as for medical and agricultural purposes. In dairying there are wrapping materials, containers, utensils and machinery equipment made from plastics which come in contact with milk and dairy products. The food regulations in connection with special dairy laws is dealing with these applications. The consequences of these legal regulations for control and application of plastics are discussed especially in regard to the responsibility of dairy factories.     

Kunststoffe in der Milchwirtschaft - eine kritische Studie III. Mitteilung: Verhalten verpackter Milchprodukte in Abhängigkeit von den Dichteeigenschaften von Kunststoff-Folien

Plastics in Dairy Industry - A Critical Study III: Behaviour of the Packed Milk Products in Relation to the Impervious Properties of Plastic Films The storage stability of many milk products depends decisively on the choice of a suitable packing material as well as proper packing. The prerequisite for this choice is as far as possible an exact knowledge of the critical external influences and their points of attack on the foodstuffs. Therefore it is shown, as to how, according to present knowledge, uptake and liberation of water vapour, carbon dioxide, oxygen and aroma affect the quality of milk products. The optical transparency of the plastic packings is of special interest in connection with the oxidative changes. For an effective protection of milk products by a packing with adequate impervious properties, a combination of foils must often be employed.     

Phasengrenzflächen in Blasenströmungen — Teil 2: Großblasen und Pfropfen

In the first part of this article an equation was derived for calculation of the specific interfacial are and the size distribution of bubbles in bubble flow. However, its application is limited to gas contents lower than 12%. At higher gas contents, large bubbles and gas plugs occur in the field of flow. These have a very low interfacial area per unit volume compared to small bubbles. Since large bubbles and gas plugs contain a large proportion of the gas in the flow, the overall interfacial area is reduced. In the present contribution, the gas content above which large bubbles and gas plugs occur is calculated. The results are subjected to experimental testing for vertical pipe flow. In addition, the volume fraction of the larger bubbles is calculated and the results verified experimentally by measurements in bubble columns. Subsequently, the specific enterfacial area with and without large bubbles is calculated for high gas contents. The results are in agreement with values measured for bubble columns and column plates.     

Zur copolymerisation von α-methylstyrol und butadien. V. Bestimmung der chemischen heterogenität durch gelchromatographie

The distribution function of the compositional heterogeneity of copolymers from α-methyl styrene and butadiene has been determined from gel permeation chromatography by detection of refractive index and ultraviolet absorption.     

Photovernetzung von Siliconen. VII. Zum Einfluß der Siliconkette – eine kinetische Studie

Photocrosslinking of Silicones. VII. The Influence of the Silicone Backbone – a Kinetic Study The photo-induced radical crosslinking of silicone containing pendant acrylate groups was investigated by nanosecond flash photolysis and photocalorimetry. From the results of the flash photolysis is inferred that the photochemically formed benzoyl radicals react with the acrylate groups of the system. A possible H-abstraction from the methyl groups of the silicone backbone was not observed. The silicone backbone functions only as an internal solvent. Calorimetric measurements with model systems support these results. The polymerization process is inhibited by oxygen. From calorimetric results is inferred that oxygen both inhibits and terminates the polymerization process. Due to their high oxygen solubility the silicone units increase the oxygen influence on the crosslinking. The calorimetric measurements shows also that a direct bond between silicone backbone and the acrylate group reduces the oxygen influence. Also, in absence of oxygen a direct bonded acrylate group accelerates the polymerization rate.     

Stand der Simulation von heterogen‐gaskatalytischen Reaktionsabläufen in Festbettrohrreaktoren — Teil 1

This contribution analyses the state of the art in two parts. Based on general quasi‐homogeneous and heterogeneous reactor models, their benefits and disadvantages as well as simplification options are discussed, taking into consideration catalyst deactivation. Further on, the article focuses on the issue of model trimming for industrial applications. A distinction is made between process rationalisation and the development of new processes. In process rationalisation, models can be tested/adjusted on the basis of meas ured values from industrial reactors. This is not feasible when developing new processes. Thus, the major factors influencing the reliability of prediction, such as model assumptions, initial and boundary conditions, mathematical and computation restrictions, chemical kinetics, thermal and mass transport as well as flow distribution, are analysed first. Eventually, this contribution proposes ways of model trimming and resolving problems of scale transfer.     

Polyreaktionen an pigmentoberflächen. IV. Mitteilung: Polymerisation von n-carboxy-α-aminosäureanhydriden auf der oberfläche von siliciumdioxid

Silica with covalent bound amino-phenyl groups on its surface is used as initiating agent for the polymerization of N-carboxy-α-amino-acid anhydrides (NCAs). The polymerization rate of the amino-phenyl silica initiated polymerization is about three times faster than the polymerization rate of the polymerization initiated by the comparable low molecular compound p-toluidine (propagation rate constant for the polymerization of L-leucine NCA initiated by amino-phenyl silica in dioxane at 15°C: k = 1,8 · 10^?2 1 · mol^?1 · sec^?1). Both reactions show similar conversion-time curves, which are determined by the slow initiation step. By the reaction of amino-phenyl silica with NCAs, silica polypeptides are obtained with an unextractable polymer content from 20 to 85%, while by adsorption only a little amount of polypeptide (about 5%) is irreversibly bound to the silica surface. With a good solvent, the graft polymer is separable into a soluble and an insoluble silica-polypeptide, but not into silica and polypeptide. These facts and the reaction mechanism indicate a covalent bond between silica and polypeptide.     

Zur Synthese von Polyfluoralkylestern der Fluorsulfonyl-difluoressigsäure und der α-Trifluormethylfluoressigsäure

On the Synthesis of Polyfluoroalkylesters of Fluorosulfonyl-difluoroacetic Acid and α-Trifluoromethylfluoroacetic Acid .     

Die copolymerisation von styrol und α-methylstyrol mit hilfe von alkyllithium-verbindungen. 1. Mitteilung: Untersuchung der Copolymerisation von Styrol und α-Methylstyrol mit n-Butyllithium als Initiator und Hexamethylphosphorsäuretriamid als Beschleuniger

The amount of α-methylstyrene incorporated into the copolymer with styrene depends on the amount of hexamethylphosphoramide (HMPA) employed. It increases with increasing HMPA concentrations. Using an equimolar monomer mixture copolymers with α-methylstyrene contents of almost 50% can be obtained; decreasing butyllithium concentrations at a constant ratio of HMPA to n-butyllithium yield copolymers with decreasing α-methylstyrene contents, while at a constant HMPA concentration but decreasing n-butyllithium concentrations copolymers with constant α-methylstyrene contents are obtained.