Thermal diffusivity of polymers by the flash method

We have adopted the flash method to the measurement of thermal diffusivity α of polymers in the temperature range 100–400K. The pulsed radiant energy from a flash tube is applied to the ‘front’ side of a suspended sample disc, and α is deduced from the exponential decay time constant of the subsequent transient temperature difference between the ‘front’ and the ‘back’ side, while correction against radiation loss is made by measuring the much longer decay time of the back-side temperature. Calibration runs on polycarbonate (PC) samples of several thicknesses show that the method is quick, precise and fairly accurate, and the results obtained are in reasonable agreement with previous determinations. We have also carried out measurements on polyoxymethylene (POM), poly (vinylidene fluoride) (PVF₂) and poly (ethylene terephthalate) (PET) and computed their thermal conductivities. Results on POM and PVF₂, which are semicrystalline, are analysed in the framework of several two-phase models, and the effect of crystallization (produced by annealing) on the glass transition behaviour of PET has also been studied.     

Phosphate-bonded refractory coatings

Conclusions A study of the adhesion and cohesion strength of refractory coatings based on oxides of titanium, zirconium, hafnium, silicon; nitrides of hafnium, boron, silicon; mullite, magnesia spinel, zirconates of calcium, barium, strontium; disulfide and disilicide of molybdenum, and calcium titanate, using phosphate bonds, established the optimum compositions for the coatings for the following alloys: 1Kh18N9T, Él-703, ÉP-99, VT-9, OT-4, ÉI-961, Br.Kh08 bronzes, molybdenum and graphite.Results are given for the working temperatures, shear strengths, and thermal-shock resistance of the coatings and also the electric conductivity and temperature conductivity of some compositions. The refractory coatings with phosphate bonds that were developed are recommended for use in high-temperature installations in the temperature range 1000–1800°C.Translated from Ogneupory, No. 4, pp. 50–54, April, 1973.     

Properties of bioriented nylon 6 films related to film production technology

Four production steps, extrusion, blowing, stabilization, and finishing, are involved in the manufacture of biorented nylon 6 films. The films obtained after each step were studied by wide‐angle diffraction X‐rays, IR analysis, and density measurements. Orientation in the amorphous phase was evaluated by thermal retraction. Free volume was investigated by positron annihilation spectroscopy. Mechanical properties were tested by tensile tests, and permeability was tested with isopiestic permeameters. Quenching, after extrusion, generated an unstable γ crystalline phase and an amorphous phase. Blowing transformed the unstable γ phase into the thermodynamically stable α phase and increased the chain orientation; stabilization increased α phase crystals, favored hydrogen bond formation and, therefore, the mechanical properties, leaving unchanged the chain orientation; the final treatment increased the mechanical properties. The film permeabilities to O₂, N₂, and CO₂ were practically unchanged after each production step; this result may be explained by considering that the nanoholes, present in the films and responsible for the diffusion inside the polymer, maintained practically constant their radius, whereas their number concentration decreased slowly after thermomechanical treatments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 559–571, 2002     

Protective coatings as a means of improving heat resistance of the refractory lining for extra-furnace steelmaking facilities

Protective coatings based on metallic aluminum are developed that can be used to improve the resistance of the refractory lining for extra-furnace steelmaking facilities. By sintering a slurry sprayed on the refractory surface, a heat-resistant gas-impermeable coating containing -corundum is formed.__________Translated from Novye Ogneupory, No. 10, pp. 61 – 63, October, 2004.     

INVESTIGATION OF THE USE OF LASER-DOPPLER VELOCIMETRY IN TWO-PHASE BUBBLY FLOWS

Understanding the dynamic phenomena of viability loss of shear sensitive cells and bubble breakage and coalescence within airlift reactors requires knowledge of local, liquid-phase hydrodynamics. The laser-Doppler velocimeter (LDV) is a non-invasive instrument which may be used to obtain this information. Experimental procedures and software were developed to detect and measure Doppler bursts in two-phase flow in a split-cylinder airlift reactor. Off-line analysis of the data indicated a detection rate approximately one order of magnitude greater than that observed using an available commercial frequency tracker. Approximately 400 to 500 observations are needed for the ensemble mean to characterize the local mean velocity to within ±5% for a superficial gas velocity of 10.4 cm/s, the highest superficial gas velocity used in these studies. The limitations, prospects, and signal-processing options for LDV in this application are also discussed     

Guayule seedling response to nitrogen fertilizers

Slow growth and high seedling mortality limit direct seeding establishment of guayule (Parthenium argentatum G.). This study was conducted to assess seedling growth enhancement by the addition of different rates and forms of N fertilizers and Ca salts. Experiments were conducted in a greenhouse with cultivar 593 under both surface and subirrigated conditions using water low in salts (salinity of 0.8 dSm^–1, SAR of 5.0 and 10 mg Ca L^–1). Under surface-irrigated conditions, seedling height and fresh plant weight increased with N application to the irrigation water to 70 mg L^–1. The best seedling growth was observed when (NH₄)₂SO₄ was added in combination with CaCl₂ or CaSO₄. Progressively less growth was observed by addition of (NH₄)₂SO₄ alone, CO(NH₂)₂ plus CaSO₄, CO(NH₂)₂ alone and Ca(NO₃)₂. When seedlings were subirrigated, however, the best growth was observed with Ca(NO₃)₂. Intermediate growth was obtained with (NH₄)₂SO₄ plus CaSO₄ and lowest growth rates with (NH₄)₂SO₄ alone. These differential responses may be explained by the differences in leaching and volatile characteristics of the N forms. Growth enhancement from N and Ca additions increased with time with significant increases 45 days after seeding. Nitrogen application with Ca may be effective amendment in promoting subsequent growth of direct seeded guayule.     

Channel-collapse effect examined with laboratory equipment and by two-dimensional calculation

Combustion, Explosion, and Shock Waves -