The creep of kevlar-29 fibers

Single Kevlar-29 fibers have been subjected to creep loading over a temperature range of 23 to 400°C for which the applied load was 50 percent that of tensile strength at each temperature considered and also subjected to a range of loads at 23°C. It has been shown that strain expressed as a logarithmic function of time describes the experimental results obtained. Up to 70 percent of breaking load, a primary creep mechanism dominates and at higher loads a secondary creep process becomes increasingly important.     

Tensile strength of polyurethane exposed to nitrogen dioxide

Polyurethane prepared from tetramethylene glycol and diisocyanate was exposed in the form of films to small pressures of NO₂ and to NO₂ plus air. Tensile strength was measured as a function of exposure time and temperature with an apparatus especially constructed for the purpose of measuring mechanical properties in different environmental “atmospheres.”     

Preparation of Titanium Nitride/Alumina Laminate Composites

A preparation route for TiN/Al₂O₃ laminate composites has been described. A water-based process using Al₂O₃ and TiN slurries with solids contents of 40 and 35 vol%, respectively, was used to make TiN and Al₂O₃ tapes. The removal of the binder was monitored by weight-loss measurements in a thermogravimetry unit. Bodies composed of Al₂O₃ and TiN tapes were densified at temperatures of 1400° and 1500°C using the Spark Plasma Sintering^® (SPS) technique. Densities of >98% of the theoretical densities were approached. Crack-free and almost fully densified TiN/Al₂O₃ compacts were prepared by heating the burned-out green bodies to the final sintering temperature (1500°C) at a rate of 100°C/min, and with a holding time of 5–10 min, under a pressure of 75 MPa. The microstructures of the obtained compacts were studied using scanning electron microscopy. Grain sizes in the sintered Al₂O₃ and TiN compacts were similar to those of the precursor powders. Hardness and indentation fracture toughness were measured at room temperature, and the monolithic compacts as well as the laminate composites exhibited anisotropic mechanical behavior; i.e., the cracks propagated much more easily in a direction parallel to the laminas than perpendicular to them.     

Hydrothermal products of the C3MS2-C12A7-MgO system

The autoclave products of reduced steel-slag of an electronic furnace mainly containing C₃MS₂ phase were detected. The hydrothermal products of this slag included calcio-chondrodite, brucite, and hydrogarnet phases. When suitable (CaO + MgO)/SiO₂ molar ratios were chosen, C₃MS₂ can react with SiO₂ to produce calcium silicate hydrates tobermorite, xonotlite, gyrolite, and truscottite phases with different saturated water vapor pressures. The phase brucite was present along with tobermorite, whereas phases Mg-xonotlite, Mg-gyrolite, and Mg-truscottite can rarely coexist with brucite. Hydrogarnet phase disappeared when Mg-truscottite was formed.     

A new batch solvent-extraction pilot plant

Summary and Conclusions A new improved batch solvent extraction plant and its versatility of design have been described. Data have been given on the cost and initial test operations. The performance of the plant has been tested, and its value as a research tool has been demonstrated by the production of free gossypol and meals low in gossypol for use in research. Simplicity of operation is borne out by the fact that only one operator is needed. A limited number of detail drawings of the plant are available on written request from the Southern Regional Research Laboratory. Presented at the fall meeting, American Oil Chemists’ Society, Nov. 2–4, 1953, in Chicago, Ill. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Irradiation of poly(vinyl chloride) with H2 plasma. II

Poly(vinyl chloride) films blended with plasticizers, stabilizers, and fillers are irradiated with a beam of H₂ plasma. The polymer partially loses its solubility in cyclohexanone. The viscosity of the soluble part decreases in the initial stages and then increases on further irradiation. Crosslinking was followed by dehydrochlorination and discoloration of the polymer. The electrical conductivity was measured as a function of the irradiation dose and time. The plasticizers enhanced the action of plasma while the stabilizers and fillers reduced it.     

Tensile behavior of glass fiber-reinforced acetal polymer

The tensile stress-strain behavior of glass fiber-reinforced polyacetal resin was investigated for various fiber concentrations, fiber length distributions, and finishing agents. The polyacetal fiber blends change considerably in strength and elongation at break when treated with ammonium chloride, but otherwise similar specimens still follow a common stress-strain curve to a point shortly before failure. As the mean fiber length decreases, the modulus and tensile strength fall, but the elongation at break remains almost unchanged. The observed tensile behavior is discussed in terms of a simplified model, which assigns the fibers to two categories: a fraction α parallel to the applied load, and the remainder distributed in a plane perpendicular to the load axis. By fitting this model to the stress-strain curves, two other constants of each system are derived: a length-dependent efficiency factor β for parallel fibers, whose magnitude agrees with the predictions of Rosen and his co-workers, and a factor γ which expresses the constraint of the matrix resin by the “transverse” fibers. The behavior of γ is consistent with Tsai's theory of the transverse modulus of laminates, if a reasonable amount of fiber–fiber contact is assumed. In terms of this model, possible interpretations of the behavior under repeated loading and the mechanism of tensile failure are presented.     

The electrochemistry of nitrate-amide melts: Reactions of nickel and copper in nitrate-amide melts

Copper and nickel may be electrodeposited from their ions in solution in nitrate-amide melts at room temperature. In the ammonium nitrate-acetamide-urea melt at 23°C, the reduction to the metal competes with the corrosion reaction at low rates and with the reduction of the ammonium and nitrate ions of the melt at high current densities. Two distinct types of nickel complexes are found in solution. The nickel complex formed by the corrosion reaction is bound by at least one ammonia ligand. Nickel complexes formed by dissolving the halide in the melt show evidence of coordination by less strongly bounding ligands, probably by amides. Similarly, the visible spectra of copper chloride in solution suggest that the cupric ions are coordinated primarily by amides. The copper corrosion reaction produces a complex with a spectra distinctly different from that of cupric chloride in solution. The shift in absorption maxima suggests that the copper complex formed by the corrosion reaction has at least one ammonia ligand in the coordination sphere.     

High oxide ion conduction in sintered oxides of the system Bi2O3-Y2O3

The ionic conduction in sintered Bi₂O₂-Y₂O₃ was investigated by measuring the conductivity and the emf of an oxygen concentration cell using the specimen tablet as electrolyte. The face centred cubic phase in this system was found to show high oxide ion conduction accompanied by a little electronic conduction when exposed to air. This phase was stable with a composition of 25 ～ 43 mol % Y₂O₃ over a wide range of temperatures, and the oxide ion conductivity increased with decrease in Y₂O₃. The conductivities of (Bi₂O₃)_0.75 (Y₂O₃)_0.25 were 1.6×10^?1 Ω^?1 cm^?1 at 700°C and 1.2×10^?2 Ω^?1 cm^?1 at 500°C values which are many times higher than those of stabilized zirconia (ZrO₂)_0.90(Y₂O₃)_0.10 at corresponding temperatures. Specimens containing less than 25 mol % Y₂O₃ showed a phase transition at 700 ～ 580°C and the conductivities decreased remarkably below these temperatures. High oxide ion conduction in the fcc phase is attributed to the migration of oxide ion vacancies which were present in an appreciable amount.