Thermotropic polyester carbonates. III. Thermotropic polyester carbonates as self-reinforced plastics

Thermotropic polyester carbonates derived from t-butylhydroquinone, methylhydroquinone, diphenyl terephthalate, and diphenyl carbonate in the molar ratio of 50 : 50 : 55 : 45; 50 : 50 : 57.5 : 5 : 42.5 and 50 : 50 : 60 : 40 can be injection molded successfully from temperatures 10°C below melting to 30–40°C above melting. Normally the best molding temperatures are 10–20°C above melting. If the molding conditions are controlled properly, tensile strengths as high as 1.8 × 10⁴ psi, tensile moduli as high as 7.4 × 10⁵ psi, and flex moduli as high as 1.1 × 10⁶ psi can be obtained.     

HIGH TEMPERATURE LOAD AND FUSION TESTS OF FIRE BRICK FROM THE PACIFIC NORTHWEST IN COMPARISON WITH OTHER WELL-KNOWN FIRE BRICK1

Seventeen samples of fire-clay brick from the Pacific Northwest have been tested with twenty-seven other commercial brands of fire clay, silica, magnesia, chromite, zirconia, diaspore, silicon carbide and crystalline alumina, as well as china clay and crystalline sillimanite products made at the University of Washington. The tests show that the fire-clay brick of the Pacific Northwest vary considerably in quality. According to the high temperature load test, the majority of the local brick are among the upper grades, some are to be classed with the best fire-clay brick and one equal to the best diaspore brick. The brick tested is not the best which can be made from Pacific Northwest materials, for the kaolins in eastern Washington and northwestern Idaho give opportunity for the production of an all-kaolin fire brick. A method is suggested for testing super-refractory materials under load at high temperatures similar to the standard load test for fire clay and silica brick except that the temperatures are measured by cones, and are raised until 10% linear deformation of the brick is obtained. The rate of heating and soaking varies with the brick under test, and the principles learned from the cone fusion test are used in the application of heat. A numerical value, expressing the area under the cone-shrinkage curve, affords an easy method for comparing the high temperature load resistance of various refractories. The brick which are best able to resist deformation at high temperatures are composed of crystalline materials which have developed a recrystallized bond of the same composition. These are crystalline silica, silicon carbide, corundum and sillimanite, and they resist deformation at temperatures close to their melting points. Amorphous materials like fire clay, diaspore, bauxite or even the very refractory crystalline materials lie chromite and periclase, which depend on amorphous silicates for a bond or are contaminated with silicate impurities. will fail with the softening of the bond of the amorphous impurities. The cone fusion of the brick as a whole can not be depended upon to indicate the resistance to load at high temperatures.     

Refractory Castables: II, Some Properties, and Effects of Heat-Treatments

Differential thermal analyses were made and weight losses were determined up to 1000°C. for a domestic and an imported high-alumina hydraulic cement after hydrating. Refractory castables were prepared in the laboratory with these two cements and fire-clay brick and flintclay aggregates. Compressive, transverse, and tensile strengths of these castables were obtained after heating 4,8, and 12 months at 300°C. and at other temperatures up to 1350°C. for shorter periods of time. Sixteen commercial brands of castables were tested for sieve analysis, P.C.E., and flow, on the material "as received". The three types of strengths of the sixteen castables also were determined after treatments at 95% relative humidity and after heating at temperatures up to 1350°C. Some information on porosity and structural and linear changes after the heat-treatments was obtained.     

Application of Sonic Moduli of Elasticity and Rigidity to Testing of Heavy Refractories

The application of A.S.T.M. C 215-51 T (Tentative Method of Test for Fundamental Transverse Frequency of Concrete Specimens for Calculating Young's Modulus of Elasticity) to the nondestructive testing of 1- by 1- by 7-in. laboratory fire-clay specimens and standard 9-in. fire-clay and high-alumina refractory brick is reviewed. Both room-temperature measurements and hot sonic modulus of elasticity measurements to 1700°F. are analyzed. Sonic moduli of elasticity and rigidity are compared with modulus of rupture by a theory of measurements and statistical analysis. The limits of uncertainty of the average of modulus of rupture are shown to be a function of the degree of verification whereas in the case of both sonic moduli they are not. Limits of uncertainty of the average of sonic moduli data are usually of the same order as errors calculated from the precision of measurements. In the case of modulus of rupture of well-vitrified clays, the uncertainty of the average is much greater than calculated error limits. Sonic moduli differentiate statistically between two samples of 60% alumina brick whereas modulus of rupture does not. If Poisson's ratio is assumed to be zero rather than the conventional one-sixth, ratios of sonic modulus of elasticity to rigidity are shown to approximate the theoretical ratio more closely. Effects of nonuniform density to displace normal nodes are illustrated. Hot sonic modulus of elasticity is shown to reflect changes due to crystallographic inversions, deterioration of chemical bond in unfired brick, and development of sintered bond in unfired brick.     

SECONDARY EXPANSION OF HIGH-ALUMINA REFRACTORIES*

Several mixtures of raw and calcined diaspore and bauxite with raw and calcined fire clays were prepared and fired at 2700°F. Specimens were refired at higher temperatures, and the linear changes were determined. Bodies composed of high-alumina grog and fire clay expand in the refire, whereas specimens of fire-clay grog that are bonded with ground raw diaspore exhibit shrinkage. The cause of the secondary expansion and shrinkage of these bodies is discussed.     

SPALLING AND LOSS IN COMPRESSIVE STRENGTH OF FIRE BRICK1

A preliminary report of the loss of compressive strength when fireclay brick from the Pacific Northwest were subjected to a series of heat treatments to 1350° and 1250°C. It illustrates some of the variations of heat treatment in the manufacturer's kilns and the differences between the high siliceous type of fire brick and the vitrifying clay type with lower free silica content. It is possible that a satisfactory spalling test may be developed in this direction.     

OUTLINE OF REFRACTORY REQUIREMENTS FOR THE IRON AND STEEL INDUSTRY1

One of the greatest obstacles to the development of better refractories for the iron and steel industry has been the failure of the iron and steel men to give refractory manufacturers accurate detailed analysis of chemical, physical and thermal conditions to which the refractories are to be subjected. This paper summarizes briefly some of the conditions to be encountered in the major processes. Blast furnace refractories may be divided according to requirements as follows: Hearth and Bosh brick should withstand the scouring action of molten iron and acid slag at temperatures around 1800°C. Inwall brick should be impervious to hot, reducing gases, should resist the sand blast action of the from particles of ore carried by the gas, should have a low coefficient of thermal expansion and should possess sufficient compressive strength to support the weight of the upper part of the furnace. Top brick should be as dense and resistant to abrasion as possible. Downcomer, Dustcatcher and Gas Line brick should be dense and resist sand blast action of gas heavily laden by particles of charge. Hot Blast Main and Bustle Pipe brick should be of low heat conductivity. Hot Blast Stove brick should not vitrify at 900°C, should have maximum capacity for absorbing and giving off heat, and be of high compressive strength. The by-product coke oven is becoming a big factor in the refractory fields and has major requirements as follows: Canals and Ovens require brick of high thermal conductivity which will resist sudden changes in temperature and will not be affected by reducing gases at high temperatures. Checker brick should have great capacity for absorbing heat. Bessemer converters require brick resistant to slag at temperatures from 1600° to 1700°C, the nature of the slag being determined by whether the process is acid or basic. Requirements for open hearth furnaces are as follows: Roof brick (both acid and basic furnaces) must not only be capable of maintaining an arch but should withstand as much as possible the action of iron oxides at temperatures of 1800°C. Checker brick (both acid and basic furnaces) should possess a maximum capacity for absorbing and giving off heat, and a minimum chemical affinity for oxides from charge. Ports (both acid and basic) must withstand the action of slag splashes, also direct action of flame. The hearth of the furnace consists of several courses of brick (acid or basic depending on the process) upon which is built the hearth proper by means of many layers of crushed refractory of the same nature. This crushed material must frit together at high temperatures without excessive softening.     

Curing stresses in an epoxy polymer

Curing stresses in sheets of an epoxy polymer cured at 80°C, 120°C, and 135°C have been determined using the layer removal procedure. Tensile stresses were found to be present in the interior and compressive stresses near to the surface in all samples. Very low stresses were found to be present in material cured at 80°C, with a maximum compressive stress level close to 0.5 MN/m² and a maximum tensile stress close to 0.25 MN/m². Higher stress magnitudes were obtained when using higher curing temperatures, with values of more than 1 MN/m² (compressive) and 0.6 MN/m² (tensile) recorded for specimens cured at 135°C.     

Ultradrawing of polystyrene by solid-state coextrusion: Shear-induced crystallization in isotactic polystyrene

Polystyrene with a 60% isotactic dyad content (iPS) was subjected to two-stage solid-state coextrusion at 124 and 160°C. It was shown that only shear-induced crystallization occurred with the amount of crystallinity strongly dependent on draw ratio. The steep increase in crystallinity from 0 to 29% is accompanied by a marked increase in the absolute total birefringence from 0 to 30 × 10^?3 and the tensile properties, from 2.5 GPa to 4.5 GPa, giving strong evidence for the necessity of a crystalline phase to achieve higher tensile moduli. Wide-angle X-ray scattering showed a higher crystal orientation for the extrudate produced at 124°C than for the one produced at 160°C. Thermal shrinkage experiments support a partial dissipation of orientation after extrusion at 160°C and on reextrusion in general. Electron microscopy revealed a fibrous nature for the solid-state coextrudates produced at both temperatures.     

Microstructure characterization and compressive performance of 3D needle-punched C/C–SiC composites fabricated by gaseous silicon infiltration

3D needle-punched C/C-SiC composites were fabricated from carbon fiber reinforced carbon (C/C) preforms, with densities of 1.05?g/cm³ and 1.28?g/cm³, by the gaseous silicon infiltration (GSI) method at fabrication temperatures from 1500?°C to 1800?°C. The compressive strengths and elastic moduli in transverse direction are larger than those measured under longitudinal compression except that samples fabricated from 1.28?g/cm³ density exhibit lower elastic moduli in transverse direction than in longitudinal direction. The compressive strength and modulus increase with fabrication temperature at 1500?°C and 1600?°C, and then decrease with higher fabrication temperature. Samples fabricated from the lower density C/C preforms have greater compressive strength and modulus. X-ray tomography was applied before and after the mechanical tests to characterize the microstructure and damage patterns, and the results indicated that for C/C-SiC composites fabricated at 1700?°C from 1.28?g/cm³ density C/C preform the matrix has a volume fraction (vol%) of 36.9%, and the initial intra-bundle cracks (0.6?vol%) display a space crossing structure while the inter-bundle pores (6.0?vol%) are special irregularly distributed.     

MASS TRANSFER AND DIFFUSION COEFFICIENT DETERMINATION IN THE WET AND DRY SALTING OF MEAT

ABSTRACT

Dehydrated salted meat is widely used in Brazil as a very important source of animal protein. The main objective of this kind of processing is water removal. initially by osmotic pressure changes and then by drying, resulting in a product with intermediate moisture levels.

In this work, mass transfer and salt diffusion in pieces of meat submitted to wet and dry salting were studied. Slabs of beef m. trapezius with an infinite plate geometry were salted in a NaCl saturated solution or in a dry salt bed, at two temperatures (10 and 20°C) and different time exposures (120 min and 96 hours). Equilibration studies were extended up to six days.

It was observed that water loss increased with salt uptake, for increasing periods of times. At 20°C the moisture loss was higher than it was at 10°C in both salting processes. On the other hand, the kinetics of salt uptake and moisture loss were of greater importance in the process of dry salting than in that of wet salting.

The salt diffusion coefficient for wet salting was 0.26 × 10^?10m²/s at20°C and 0.25 × 10^?10 m²/s at 10°C and for the dry salting the values were 19.37 × 10^?10 m²/s at 20°C and 17.21 × 10^?10 m²/s at 10°C.     

Optimisation and Evaluation of La0.6Sr0.4CoO3 – δ Cathode for Intermediate Temperature Solid Oxide Fuel Cells

In this work, La_0.6Sr_0.4CoO_{3 – δ}/Ce_{1 – x}Gd_xO_{2 – δ} (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700 °C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (R_p) of 0.11 Ω cm² at 700 °C is obtained for the cathode containing 30 wt.‐% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950 °C; the corresponding R_p of 0.24 Ω cm² at 600 °C and 0.06 Ω cm² at 700 °C are achieved, respectively. An YSZ‐based anode‐supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950 °C. The cell with an active electrode area of 4 × 4 cm² exhibits the maximum power density of 0.42 W cm^–2 at 650 °C and 0.54 W cm^–2 at 700 °C. More than 300 h operating at 650 °C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application.     

Hydrogen Permeation Properties and Hydrothermal Stability of Sol–Gel‐Derived Amorphous Silica Membranes Fabricated at High Temperatures

The sol–gel method was applied to the fabrication of amorphous silica membranes for use in hydrogen separation at high temperatures. The effects of fabrication temperature on the hydrogen permeation properties and the hydrothermal stability of amorphous silica membranes were evaluated. A thin continuous silica separation layer (thickness = <300 nm) was successfully formed on the top of a deposited colloidal silica layer in a porous glass support. After heat treatment at 800°C for an amorphous silica membrane fabricated at 550°C, however, it was quite difficult to distinguish the active separation layer from the deposited colloidal silica layer in a porous glass support, due to the adhesion of colloidal silica caused by sintering at high temperatures. The amorphous silica membranes fabricated at 700°C were relatively stable under steam atmosphere (500°C, steam = 70 kPa), and showed steady He and H₂ permeance values of 4.0 × 10^?7 and 1.0 × 10^?7 mol·m^?2·s^?1·Pa^?1 with H₂/CH₄ and H₂/H₂O permeance ratios of ~110 and 22, respectively. The permeance ratios of H₂/H₂O for membranes fired at 700°C increased drastically over the range of He/H₂ permeance ratios by factors of ~3–4, and showed a value of ~30, which was higher than those fired at 500°C. Less permeation of water vapor through amorphous silica membranes fabricated at high temperatures can be ascribed to the dense amorphous silica structure caused by the condensation reaction of silanol groups.     

Effects of time and temperature on the tension-tension fatigue behavior of short fiber reinforced polyamides

To support the fatigue design of the cyclically stressed plastics parts, such as automotive under-the-hood and exterior components, we analyzed the short-term and long-term mechanical performance (tensile strength, fatigue strength, and fatigue life) of short glass fiber reinforced polyamides PA 6 and PA 66. Comprehensive tension-tension fatigue tests were conducted with reference to the latest ASTM, ISO, and Japanese industrial standards for plastics, at temperatures from −40°C to 121°C, on materials aged at 121°C for 0, 100, 500, and 1000 h. Tests were conducted at a loading frequency f = 5 Hz, stress ratio R = 0.1, and in a wide range of cycles to failure from 2 × 10³ to 2 × 10⁶. Without aging and for both PA 6 and PA 66, the highest fatigue strength or fatigue life was found at −40°C; it decreased significantly at 23°C, and decreased further at 121°C. The fatigue strength of PA 6 was found to be higher than that of PA 66 at −40°C, but the reverse was seen at 23°C. At 121°C, the fatigue strengths of PA 6 and PA 66 were virtually the same. Aging at 121°C improved the tensile strength of PA 6 and PA 66 as aging time increased from 100 to 1000 h, and this process seemed to be more influential for PA 6.     

THE RELATIVE MAGNITUDE OF RADIATION AND CONVECTION HEATING IN A MUFFLE KILN1

Rates of Heating by Convection and by Radiation in a Muffle Kiln, 38°×18°× 36° high, were each determined for temperatures from 350° to 800°C from measurements with a steady flow water calorimeter whose surface was first gold plated and then covered with a mixture of platinum black and lamp black. Taking the reflecting powers as 91 and 4 per cent, respectively, for the two surfaces, the radiation heating increases approximately according to the Stefan-Boltzmann fourth power law, while the convection heating comes out proportional to the temperature difference between calorimeter and muffle; that is, C=γ(T-t) where γ= 2.34×10⁻⁴ gm. cal./cm.² sec. The ratio of convection to radiation decreases from about .40 at 350° to .10 at 800°C, so that for the higher temperatures the convection heating may be neglected in rough computations of the rate of heating in such a kiln.     

Effect of MgO calcination temperature on the reaction products and kinetics of MgO–SiO2–H2O system

MgO-based binders have been widely studied for decades. Recently, the MgO–SiO₂–H₂O system was developed as a novel construction material, however, its reaction mechanism remains unclear. This paper investigated the reaction products and kinetics of MgO/silica fume (SF) pastes with MgO calcinated at different temperatures. The results indicate that MgO presented larger grain size after calcination at higher temperature. Mg(OH)₂ and magnesium silicate hydrate (M–S–H) gel were formed when using MgO calcined at 850, 950, and 1050°C. However, only M–S–H gel was formed when using MgO calcined at 1450°C. The reaction kinetics of MgO could be described using α = 1 − e^−k*t. The reaction rate of MgO increased with decreasing calcination temperature, increasing SF dosage, and the addition of sodium hexametaphosphate. Only M–S–H gel was formed when the reaction rate of MgO was below the demarcation line (about 0.250 × 10⁻⁶ s⁻¹), and the corresponding demarcation area was around 14 days.     

THERMAL EXPANSION OF SILICA BRICK AND MORTARS1

Thermal expansion from 20 to 950°C and physical data of silica brick from various producing districts in the United States and Europe are presented. The variations in thermal expansion of brick from various parts of kilns are given for plants in the United States. The magnitude of variation of the thermal expansion of silica brick is quite small, the expansion ranging between 1.15% and 1.30% at the highest point of expansion. The expansion of the silica mortars varied between 1.30 to 1.52% depending upon variations in clay, quartzite, and bats. The variations in thermal expansion of silica mortars from various producing plants are also shown. Data on the effect of size of grain, clay content, and P.C.E. on the thermal expansion of mortars are given. An extensive bibliography on thermal expansion of silica brick appears with the paper.     

Synthesis of cardo containing asymmetric poly(ether‐naphthalimide‐phthalimide)s

A series of cardo based asymmetric polyimides containing bulky rigid naphthalimide and phthalimide groups were prepared from asymmetric monomer bishaloimide and bisphenols by solution polycondensation. Bishalo(naphthalimide‐phthalimide) monomers containing different terminal leaving groups (Cl, F, NO₂) were synthesized, and the reactivity difference of these monomers was compared for the successful synthesis of polyimides. The inherent viscosities of the polyimides were in the range 0.51 ? 0.60 dL g^?1 in N ‐methyl‐2‐pyrrolidone at 30 °C. These polyimides demonstrated good organosolubility and mechanical properties with tensile strengths of 93 ? 120 MPa, tensile moduli of 3.5 ? 5.3 GPa and elongations at break of 2.8% ? 4.3%. The polyimides showed high glass transition temperatures (T _g) ranging from 330 to 363 °C. The 10% weight loss (T _10%) of asymmetric polyimides reached 436 ? 500 °C in nitrogen and 417 ? 476 °C in air. The water uptake of the polyimides was in the range 0.35% ? 0.72%. © 2017 Society of Chemical Industry     

Reaction Between K2O and Al2O3-SiO2 Refractories as Related to Blast-Furnace Linings

An examination was conducted to determine the mechanism of peeling of fire-clay brick in the low-temperature region of a blast furnace where 3 to 10% K₂O is the principal contaminant. In laboratory tests, as-received high-duty and superduty fire-clay brick and 70% alumina brick treated with KCl-K₂CO₃ mixtures showed no peeling at a temperature of 1600°F. Cracks were found in high-duty brick that were treated with KCN at 1500°F. under partially reducing conditions. X-ray diffraction studies of mixtures of crushed brick and K₂CO₃ indicated the formation of leucite (K₂O.Al₂O₃.4SiO₂) and kaliophilite (K₂O.-Al₂O₃.2SiO₂) at temperatures below 1700°F. These latter data, confirmed by specimens from used blast-furnace linings, showed that silica is the first constituent attacked by alkali. Since the formation of leucite and kaliophilite in fire-clay brick is the probable cause of peeling, the increased reaction of silica, in a dense Al₂O₃.SiO₂ refractory of higher silica content than fire-clay brick, should confine the alkali attack to the surface of the brick in low-temperature applications.     

Temperature effects of silane coupling on moisture treated silica surface

Moisture and temperature effects were investigated on silica/(triethoxysilylpropyl) disulfide (TESPD)/carbon black (CB)/S‐SBR compounds with respect to processability, vulcanization characteristics, physical properties, and alcohol residues. The moisture‐treated compounds exhibited lower rates of viscous heat generation during mixing, lower discharging temperatures (drop temperatures), lower Mooney viscosities, shorter cure times (T_c‐90), higher torque rises (M_H ? M_L), less heat build ups (HBU), and equal or less alcohol residues than the control. As the drop temperatures of the compound were increased, decreased temperature differences between mixer sensor (set drop) and real (proven) temperatures, increased the scorch times (T_s‐2), decreased the cure times (T_c‐90), increased the tensile moduli, and decreased the alcohol residues remaining in the compound. The higher temperature drop compounds (160 and 176°C) exhibited no reversion behavior; however, the lower temperature (120 and 140°C) drop compounds exhibited marching behavior. The treatment of moisture on the silica surface influenced the hydrolysis reaction to the silane and improved coupling on the silica surface. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95:623–633, 2005