The glass transition temperatures, Tg, and thermal effects of polymerization, Att, have been determined for five epoxy adhesives of unknown composition. From the trends AHvs./tcure it has been possible to attain a phenomenologieal kinetic order of the polymerization rate at 100 ~ through an iterative calculation procedure. For most of the investigated adhesives there are reasons (double peak of polymerization and double Tg signal) to assume that they are graft copolymers.Studies on epoxy materials, prepregs and adhesives have been greatly developed in view of their important technical applications: specially devised investigations have been reported on their elastic properties, thermal expansion, strains associated with the polymerization process, etc. [1,2].Qualitative and quantitative chemical analysis is in any case essential in the research into such materials: as a rule it requires an extremely refined instrumentation, allowing the separation and recognition of the individual components within a number of compounds accompanying the main epoxy bulk [3,4].As typical investigations, differential thermal analysis (DTA) and/or differential scanning calorimetry (DSC) have been employed either to evaluate the thermal effect accompanying the polymerization or to check the glass transition temperature, Tg [5][6][7][8][9][10].In the present work quantitative DTA determinations were carried out for different adhesives behaving as thermosets, in order to establish: i) the thermal effect accompanying the polymerization, ii) the phenomenologieal kinetics of the cure process, iii) the correlation curve between the degree of polimerization, ~, and Tg. The compositions of these materials are only partially known, but their main ingredients are bisphenol, epichlorhydrine, Novolac, tetraglycidylmethylene dianiline, nitrilerubber, etc., depending on the particular resin. ExperimentalThe storage temperature of the prepolymer tapes was about -18 ~ From tight rolls of such tapes small soft cylinders of prepolymer (dia. ,,~ 3 mm, length ,-~ 3 mm) were rapidly cut, weighed (the usual weight was about 50 mg), sealed in silver DTA pans at room temperature and again cooled down to -18 ~

Electrical conductivities and densities of molten (Na—Tl)NO3 mixtures have been measured in the temperature range between 192°C and 400°C. At all compositions the specific conductivities appear to be linear functions of the temperature. While the equivalent conductivities of the mixtures deviate negatively from additivity, the apparent activation energies ΔΕ (from the relation Λ =Λ0 · exp(—ΔE/R T) exhibit positive deviations from additivity. This behavior is similar to that of other univalent binary systems with a common anion and seems to indicate that the polarization of the nitrate ion due to different cation sizes is the main cause of the additional hindrance to the electrical transport in mixtures.

Emf measurements on suitable solid galvanic cells have been carried out to investigate the thermodynamics of solid solutions of Li2O in normalNiO . It was shown that in the range of the dilute solutions [0.15–7 a/o (atomic per cent) Li] α—Li2SO4 is useful as an intermediate electrolyte. The following cell was operated normalPt/normalNiO,Li2Ofalse(x2false)//α—Li2SO4//normalNiO,Li2Ofalse(x1false)/normalPt at temperatures between 570° and 800°C. Results show that the mixture is ideal to 1.5 a/o Li. Deviations from ideality at higher concentrations can be described with purely configurational energy terms.

Abstract. The application of a dual-sector high-resolution mass spectrometer (HRMS) to the detection of several CF3-containing compounds in Earth's atmosphere is described. By this technique, the contents of air samples collected in remote areas surrounding Bozeman, Montana, are introduced to the HRMS by gas chromatography (GC) while the HRMS is tuned to the exact masses of the ions expected in the electron impact ionization of each compound. By the analysis procedure developed here, the mass scale of the instrument is continuously recalibrated during the analysis so that any level of mass resolution that is required for the complete separation of hydrocarbon-based from halocarbon-based ions of the same nominal mass can be selected. Owing to the unusually large ion optic system of the mass spectrometer, high ion throughput to the detector is maintained even when higher levels of mass resolution are selected. By this technique, the sensitive detection of CF 4 (CFC-14), CF3C1 (CFC-13), CHF 3 (HFC-23), CF3CF2C1 (CFC-115), CF3Br (halon-1301), and CF 3CH2F (HFC-134a) in background air samples is demonstrated using essentially all of the major ions that appear in the electron impact mass spectrum of each compound. Most of these compounds are thought to be present in background air at the low parts-per-trillion by volume level. This is one of only two reports, to date, of CHF 3 presence in background air. A potential source of this compound is suggested by additional measurements provided here.

The dielectric constant of monoclinic zirconia and of lime-zirconia (up to a CaO content of 20% mole) has been measured at 25 °C by the powder method. For pure Z r02 the D.C. is 13.5, while for lime-zirconia a non linear dependence on the CaO content has been observed in the measured range, with a maximum at about 14% mole CaO. The results are discussed, in the light of the authors previous density data for the same systems, in terms of the width of the homo geneity range of the solid solutions. In tro d u c tio nThus, the questions of the dielectric constant of A large scattering exists within the literature values of the dielectric constant of pure Z r0 2 (11 < e < 2 8 ), measurements having been made mostly on thermal or anodic films and only in very few cases on bulk material. In particular, H a r r o p and Wanklyn 1 gave a value of 22 + 3 obtained on little single crystals 2, while C ox 3 reported a value of 11 + 1 for thermal and anodic films. Such strong discrepancies might be accounted for, among other factors, by the influence of the morphology of the samples and of the experimental methods, as it was recognized by the same authors 1> 3.As for lime-zirconia, K r ö g e r 4 quoted a value of 12.5, while emphasizing that the dielectric constant of such system had not been systematically investi gated as a function of lime concentration. From data reported by H a r r o p and W a n k l y n 1 on calcia-and magnesia-stabilized zirconia, it might be inferred that the dielectric constant in these cases is practically insensitive to quite large changes in com position. This would be somewhat surprising, if one considers, e. g., that V a n V e s s e m 5 showed the di electric constants of NaCl + NaBr and KJ + KBr solid solutions to be strongly in excess over the additive values. pure zirconia and of lime-zirconia are still open to further investigation. The latter presents some in teresting theoretical connections with the defect solid state of solid solutions or, at least, with the equi librium phase diagram of the system Z r0 2 -CaO. Moreover, to our knowledge, no other research has been carried out after that of Van Vessem on the dielectric constant of solid solutions of ionic solids.In this paper, the results of dielectric constant measurements, by the powder method, on pure Z r0 2 and some Z r0 2 + CaO solid solutions in the com position range 8 -f-20 mole % CaO are reported. Although the powder method suffers from a largely approxim ate theoretical treatment, it turns out con venient since it allows the use of finely ground pow ders instead of large and flat slabs of single crystals or large size pressed pellets, being at the same time free from the errors involved in the film method.T h e P o w d e r M ethod By this method one determines the apparent di electric constant of the heterogeneous system form ed with the investigated solid, in powdered form, and a gaseous phase (or the vacuum ). The pre-