Mikrozelluläre Polymerfilme durch Phasentrennung während der Filmbildung und ihre Eigenschaften

Microcellular films from solutions of vinylchloride-vinylacetate copolymers, cellulose nitrate and chlorinated rubber have been prepared by phase formation and separation during the process of film formation. The dependence of deformational properties of these films from the solvent composition has been discussed on the basis of their morphological structure and the interaction between the chain segments. The decrease of intrinsic viscosity with increasing amounts of non-solvent indicates a preferred adsorption of the good solvent by the copolymers. The rheological behaviour of this copolymer in concentrated solutions of solvent/nonsolvent mixtures indicates a strong influence of the special dissolution procedure, which may be explained by different ratios of intra-and intermolecular interactions of the copolymer chains.     

Die mechanisch-chemische degradation von polymeren bei der verarbeitungstemperatur

There is a number of questions that remains unanswered by the literature regarding mechano-chemical degradation of plastics at the temperatures of processing. The investigations described here were carried out to determine the degree to which different polymers are degraded at the temperatures of processing under the influence of mechanical forces and to determine the relationship between melt viscosity and degree of degradation, as well as to understand the mechanism and the kinetics of degradation.     

Neutral-atom electron binding energies from relaxed-orbital relativistic Hartree-Fock-Slater calculations 2 ≤ Z ≤ 106

Electron binding energies in neutral atoms have been calculated relativistically, with the requirement of complete relaxation. Hartree-Fock-Slater wavefunctions served as zeroth-order eigenfunctions to compute the expectation of the total Hamiltonian. A first-order correction to the local approximation was thus included. Quantum-electrodynamic corrections were made. For all elements with atomic numbers 2 ≤ Z ≤ 106, the following quantities are listed: total energies, electron kinetic energies, electron-nucleus potential energies, electron-electron potential energies consisting of electrostatic and Breit interaction (magnetic and retardation) terms, and vacuum polarization energies. Binding energies including relaxation are listed for all electrons in all atoms with 2 ≤ Z ≤ 106. A self-energy correction is included for the 1s, 2s, and $\text{2p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ levels. Results for selected atoms are compared with energies calculated by other methods and with experimental values.     

Zur kenntnis der vernetzenden copolymerisation

Styrene has been copolymerised with 0,02–2,0 mol % of I to various conversions. Hydrolysis in an acidic solution of 2,4-dinitrophenylhydrazine leads to a degradation of the crosslinked polymer into the primary chains. The sites of the crosslinks are indicated in the primary chains in the form of 2,4-dinitrophenylhydrazone groups. These groups are quantitatively determined by photometry. This investigation showed an equal reactivity of the two doublebonds of I with styrene: r₁₂ = 0,22; r₁₃ = 0,27. In the case of nearly total conversion of the monomers (av. 96%), both doublebonds of I are quantitatively converted (no steric hinderance or ?shielding”?). Investigations of the gelpoint conditions yielded in crosslink-efficiencies from 30 to 40%. It could be demonstrated that the possibility of cyclopolymerisation is to be excluded from the interpretation of this effect. The low value of the crosslink-efficiency is caused by the formation of large rings which contain I and styrene as well.     

Über die Härtungsreaktion von Phenol-Formaldehyd-Harzen I

Investigating the viscosity of a phenol formaldehyde resin, the rate equation for the curing process of the resin has been determined. According to the measurements the equation is as follows: Using of the integrated form of this equation the rate constants of the curing process relating to different temperatures as well as the value of the activation energy have been determined.     

Alterung des polybutadies bei anwesenheit von metallverbindungen

In the ageing of industrial polybutadienes the effect of decomposition products of ZIEGLER–NATTA catalysts could not be distinguished from other Important factors. However, the additional introduction of Co, Ti or Ni compounds (components of the ZIEGLER-NATTA catalysts) has influenced the oxidation process. The effect of different acetylacetonates (Ti, Co, Ni, V, Al, Cc, Mn, Cu) on the oxidation of purified polybutadiene in presence or in absence of an antioxidant has further been studied. The apparent activation energies of oxidation have been estimated and possible mechanismus of the actions of metal compounds in the oxidation of polybutadiene have been proposed.     

Strukturuntersuchungen an cellulosefasern verschiedenen verstreckungsgrades mittels IR-reflexionsspektroskopie und deuteriumaustausch

Successive drawing of regenerated cellulosic fibers increases the molecular orientation of the polymer chains and is widely used for improving the tensile properties of fibers. A new technique for the measurement of plane polarized IR-spectra of deuterated cellulosic fibers with the help of FMIR-reflection attachment is reported. The dichroism of the crystalline OH-stretching vibration is related to the molecular orientation in dependence of the extent of stretching of the cellulosic fibers. Various methods for the determination of the degree of crystallinity in cellulosic fibers are discussed.     

Über die synthese von organischen polymergelen mit einheitlicher maschenweite

Surprisingly because of a strong steric hindrance of the α-methyl group no gel is formed after terminating a bifunctional living poly-(α-methylstyrene) with CH₃SiC1₃, SiC1₄, (PNCl₂)₃ or pentamethyl-1,3,5-trichlorotrisilmethylene. However, gelation can be achieved by means of anionic polymerization of poly-(α-methylstyrene) molecules with two unsaturated end groups. These may be introduced by coupling reactions of living poly-(α-methylstyrene) with methacryloyl chloride, acryloyl chloride or p-vinylphenyl-dimethylchlorosilane. The essential parameters governing the degree of interlacing were investigated at star-shaped polymers which were formed by chain termination of monofunctional living poly-(α-methylstyrene), with the above mentioned unsaturated halogen derivatives and under similar reaction conditions. By determination of the number of branchings it can be shown, that homogeneous networks can only be synthesized with p-vinylphenyl-dimethylchlorosilane as an interlacing reagent for living poly-(α-methylstyrene). A gel, which was obtained under these conditions, behaves in GPC like a network of narrow pore size distribution : The upper and the lower exclusion limits are so close together, that by their means polymer mixtures can even be separated, when their average molecular weights differ only by a factor of 2. Starting from p-isopropenylphenyl-dimethylchlorosilane, we synthesized the corresponding H-Si-derivative and found that it can be polymerized by Na-naphthalene at ?78 °C in tetrahydrofuran. Thereby living polymers of predictable average molecular weight are obtained, having a reactive and variable H—Si-function in each and every monomer unit.     

Defect studies of gap crystals pulled from non-stoichiometric melts: I. Growth related defect analysis

Using the liquid encapsulation Czochralski technique it has recentlybeen demonstrated that GaP crystals can be pulled from a melt which contains as little as 10 atom percent phosphorus in gallium solution. This marked deviation from stoichiometry significantly influences the nature of the defects in the resulting crystals. In the present report we have characterized the defects in GaP crystals pulled from non-stoichiometric melts by means of chemical etching and X-ray topographic techniques. Melt compositions of 36, 30, 20 and 10 a/o were studied. It is shown that, although twinning, gallium inclusions, and growth boundaries have all been observed, crystals can be grown which are free of these defects, and also have dislocation densities near zero over large portions of the crystal. The results are presented in individual sections illustrating the various crystallographic aspects of each type of defect. Interactions which exist between these different defects and their relation to the non-stoichiometric crystal growth conditions are discussed.