Polymerisation von Vinylchlorid bei Atmosphärendruck 1. Polymerisationssysteme zur Herstellung von U-PVC

A method for polymerization of vinylchloride (VC) at atmospheric pressure is described, in which the gaseous monomer is polymerized with K₂S₂O₈ as an initiator at 45°C to 60°C. The amount of the polymer formed (so-called U-PVC) as a function of the reaction time depends on the rate of monomer flow. The reaction rate increases with higher initiator concentration as well as with increasing temperature. It is also possible to initiate the polymerization with the redox-system K₂S₂O₈/Na₂SO₃/Cu²⁺ within the range of 0°C to 20°C. By means of transmission electronmicroscopic (TEM) investigations the particle size and particle size distribution as a function of polymerization time and temperature was determined.     

Methoden zur Herstellung und Charakterisierung von Kunststoffen mit verbesserter Blutverträglichkeit

Tubings of different internal diameter (ID) were prepared from 10 different polymers (CPE, EPDM, ETFE, EVA, LDPE, PP, PTFE, PUR, PVC and Silicone):

• tubings of 4–5 mm ID for in vitro- and ex vivo-blood compatibility tests with human blood,
• tubings of 0.3–0.4 mm ID for ex vivo-evaluations for blood compatibility via measuring the bleeding time after introduction of the tubing into the ear vein of rabbits.

The tubings were surface modified by grafting with N-vinyl-N-methyl acetamide (VIMA). For both the original and the grafted tubing correlations were established between the physical characterization (degree of grafting, critical surface tension, ESCA, FT-ATR-IR, SEM) and the in vitro and the ex vivo blood compatibility tests. The in vitro blood compatibility tests consist of an incubation of 4–5 mm tubing with citrated human blood and subsequent determinations of clotting parameters. The human ex vivo blood compatibility tests were performed on human arm veins followed by investigation of the internal surface of the tubing. The results could be correlated with the in vitro tests with human blood. A comparison with conventional tubing on the market (PVC and Silicone) as a standard shows, that PTFE/VIMA, LDPE/VIMA, PUR and EVA have better blood compatibility properties than the standard whereas untreated PTFE and LDPE are ranked below the standard.     

Herstellung von metallischen Nanopartikeln in einem asymmetrischen Dielectric Barrier Discharge‐Plasma bei Atmosphärendruck

This paper focuses on the production of metal nanoparticles in a dielectric barrier discharge (DBD) reactor at atmospheric pressure. In the developed reactor only one electrode is provided with a dielectric (alumina), while the point‐shaped counter electrode is not covered and is accessible to the filamentary discharges (asymmetrical DBD). The metallic particles are formed from the material of the open counter electrode, on which the filamentary discharges lead to the formation of craters. A high number of larger nanoparticles (with diameter of some tens of nanometers) are observed in the cold reactor at the beginning of the discharges. After the achievement of the thermal equilibrium in the reactor mainly very small metallic nanoparticles are produced with constant size and number concentration. The produced metallic particles in thermal equilibrium are crystalline and not agglomerated. The mean diameter of the produced particles is about 4 nm. For given operating conditions of the reactor (fixed electrode gap and gas flow rate) the electrode material has almost no influence on the size of the produced particles, but it determines the number concentration.     

Optische Methoden zur Charakterisierung von hochpolymeren Fasern. 2. Kennzeichnung von Oberflächen durch Specklemeßmethoden.

The surface roughness of textile materials is of great influence on textile processing and practical applications. Speckle-techniques are common for integral, contactless, and non-destructive characterization of metallic surfaces. The scope of this work was to apply the analysis of the contrast of the speckle patterns and the dichromatic speckle correlation to measurements of the roughness of polymer surfaces. For this purpose it was of importance to study the influence of the optical properties of the polymer samples on the characteristics of the speckle field. Methods for measurements on filaments, yarns, and fabrics are discussed.     

Chemische und physikalische Vorgänge bei der Herstellung von Polyurethan-Weichschaumstoffen

The kinetics of foam formation are observed by IR-spectroscopy. The formation of polyurethane and polyurea occurs simultaneously, the transition from the dissolved to the crystalline urea being chronologically measurable. The difference between hotcure and cold-cure (HR) foam is explained. NCO-linking reactions cannot be detected by IR-spectroscopy. Using a foam with a density of 26 kg/m³, a quantitative study of foam formation was made, using chemical methods of analysis. Gas yield and time of curing are determined.     

Optische Methoden zur Charakterisierung von hochpolymeren Fasern. 1. Methodik der Interferenzmikroskopie

Density and orientation describe, besides other characteristics, the structure of high polymers. They can be obtained as a function of the radius by measurement of the refraction index of the fibre. The influence of refraction of light on the obtained index of refraction n(r) is demonstrated by an optical model of the fibre. For fibres having a radius R < 30 μm and changes in the refraction index < 0.02 the influence of refraction is less than ± 0.0002 and therefore of no significance for most textile fibres. Important is the exact adaption of the refraction index of the embeding medium to the margin of the fibre. The computed index at the margin of the fibre takes always the refraction index of the embeding medium. An incorrect adaption can be traced up to 0.2·R into the fibre. A spline function used for the approximation of the relative displacement of interference fringes gives the opportunity to calculate extreme variations in refractive index, this is demonstrated using hollow fibres filled with paraffin-oil. Using a HeNe-laser interference-holographie became possible.     

Künstliche Atmosphären bei der Herstellung von Arznei- und Lebensmitteln,Farben und Lacken sowie anderen Produkten

Artificial Atmospheres in the Manufacture of Drugs, Foods, Colours, Paints and Others Products Application and construction of gas generators meant for producing artificial atmospheres, which prevent fire and explosion in factory plants and enable the processes to be carried out in the absence of air are reported.     

Bestimmung der Temperaturabhängigkeit der Inhibierungsperiode und der Radikalbildungskonstante von AIBN bei der Polymerisation von Methylmethacrylat

The dependence on temperature of the specific reaction rate quotient of the inhibition period has been determined as by dilatometric measurement of the inhibition period caused by dissolved oxygen, and by the initial rate of the methyl methacrylata polymerisation, using azoisobutyronitrile (AIBN) aa initiator. In the examined concentration range the initial polymerisation rate and the reciprocal of the inhibition period are strictly proportional to the root of the initiator concentration, the yield of free initiator radicals is thus independent of the initiator concentration. It is, therefore, possible to determine the radical forming constant k_R of AIBN represented by the equation The fraction of the radicals recombining in the cage can be determined from k_R and the decomposition constant k_z; at 60°C for example it amounts to 24%. This value corresponds very well to the value obtained by the gas-chromatographic investigation of the recombination products by VOGT and DULOG.