Induction periods in the polymerization of lactams initiated with carboxylic acids in an anhydrous medium

The polymerizations of capro-, enantho-, capryl- and laurolactam were investigated. It was found that polymerization initiated with aliphatic carboxylic acids proceeds prevailingly via addition of the lactam group to the carboxyl group. In the case of capro-, enantho- and capryllactam, addition of the lactam group to the forming primary amino groups also becomes operative with increasing extent of polymerization. Determination of the content of free initiator during caprolactam polymerization showed that incorporation of the initiator ended approximately at the end of the induction period. The induction period of caprolactam polymerization initiated with lauric or caproic acid is longer than for N-caproyl-6-aminocaproic acid as initiator. The acceleration of polymerization is due to the fact that addition of the first caprolactam molecule to the initiating carboxylic acid proceeds considerably more slowly than addition of the second and further molecules.     

Spherical harmonics and cartesian tensor scalar product expansions of the distribution function

On the basis of the expansion of the distribution function in a sum of the spherical harmonics, the distribution functionf(v, r, t) is expanded in a series of scalar products of two Cartesian tensors term by term, i.e. The tensors and ^(l) (l=2, 3) are constructed in dependence on the spherical harmonic expansion coefficients (the tensors and ^(l) (l=0, 1) have been constructed by Jancel and Kahan [3]). On the basis of the knowledge of the analytic form off ₂ andf ₃ the equations forf ₁ f ₂ andf ₃ for the case of the Boltzmann's equation are determined.Technická 2, Praha 6, Czechoslovakia.     

Zur Temperaturabhängigkeit der Rechteckigkeits-Koeffizienten der Mangan-Magnesium-Ferrite

Ohne Zusammenfassung

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Abschließend danken wir der Kollegin A. Hadincová für die mit Sorgfalt durchgeführten Messungen.     

Phonon thermal conductivity of amorphous selenium doped by germanium

The thermal conductivity of the amorphous semiconducting system Se-Ge in the temperature range of 100 to 300°K was measured. The Debye model was used for the analysis of the experimental values and the calculated mean free path of phonons was related to the size of the basic structure units of the selenium glass. The shift of the thermal conductivity of amorphous selenium doped with germanium was explained by means of the increase of the velocity of sound observed together with the occurrence of the covalent bond Se-Ge between the basic structure units of the studied amorphous system.