Physical Stability Properties Research Articles

Some of the Properties of Three-layer Particleboard Panels Made from Under-utilized Species in Oklahoma

The objective of this study is to determine some of the properties of experimental three-layer particleboard panels made from osage orange (Maclura pomifera) and eastern redcedar (Juniperus virginiana L.), which are considered as invasive under-utilized species in Oklahoma. Static bending, internal bond strength, thickness swelling, and surface roughness characteristics of experimental panels made from particles of two species and their half and half mix are investigated. Whole-tree chipped material is used to manufacture experimental panels. The samples are tested for their mechanical strength and physical stability properties according to the procedures defined by ASTM D-1037. The modulus of elasticity of the panels made from eastern redcedar is 16.6 and 15.5% higher than the ones made from osage orange and mixed particles, respectively. Overall mechanical properties of the panels are not statistically different from each other at the 95% confidence level. Thickness swelling of the samples range from 17.4 to 23.2% as a result of 2- and 24-h water soaking tests. All panels yield adequate bending strength, stiffness, and thickness swelling. Surface characteristics of the samples are also evaluated employing a stylus type equipment. Two parameters, average roughness (Ra) and maximum roughness (Rmax) are used as indicators and it has been found that all the specimens have a relatively rough surface as substrate for typical overlaying applications.

Parenteral water/oil emulsions containing hydrophilic compounds with enhanced in vivo retention: formulation, rheological characterisation and study of in vivo fate using whole body gamma-scintigraphy

The preparation and characterization of parenteral water-in-oil (w/o) emulsions with a potential for sustained release of hydrophilic drugs was described with emphasis on rheological behaviour and spreading phenomenon after intramuscular (i.m.) injection in rabbit thigh muscle. Both steady state and dynamic rheological parameters were investigated showing Newtonian behaviour at low fraction of disperse phase ratio as opposed to viscoelastic and pseudoplastic behaviour at high fraction of disperse phase. Disappearance and spreading behaviour of hydrophilic radioactive markers, aprotinin (6512 g/mol) and pertechnetate (193 g/mol) entrapped in w/o emulsions from an i.m. injection site was studied by whole body gamma-scintigraphy. The retention of entrapped aprotinin 24 h postinjection was 83±5% for a low spreading emulsion and 76±6% for a high spreading emulsion. The corresponding values for pertechnetate were 50±11 and 23±2%, respectively. The relatively long retention times were suggested to be related to the good physical stability properties of the present emulsions. It was concluded that the presented w/o emulsions are promising vehicles for sustained release of hydrophilic drugs from an i.m. injection site.

Production of brined soft cheese from frozen ultrafiltered sheep's milk. Part 1. Physicochemical, microbiological and physical stability properties of concentrates

Some physicochemical, microbiological and physical stability changes in sheep's milk as a result of its concentration by ultrafiltration (UF) and long-term deep-frozen storage were studied. Skim milk was concentrated by UF to 19.37, 23.40 or 26.49% total solids (TS), mixed with cream to obtain recombined UF concentrates with 30.40, 33.95 or 36.90% TS, respectively, and then frozen and stored at −20 °C for up to 6 months. With the exception of highly concentrated milks frozen for 6 months, no significant differences in lipolysis (acid degree value) and fat oxidation (peroxide value) were observed between the control milk and the UF milk concentrates stored frozen for up to 6 months. The UF process resulted in significant increases in the bacterial and coliform counts in sheep's milk, which decreased during the frozen storage. The UF concentrates exhibited good protein stability throughout frozen storage, except for one obtained from milk to which 0.5% NaCl was added before UF, which destabilized after 2 months frozen storage.

Rheological prediction of the physical stability of concentrated dispersions containing particulates

A dynamic rheological technique is presented that can be used for the prediction of physical stability of concentrated dispersions containing particulates, as well as product development and quality control. Typical physical evaluation frequently requires weeks or months before an assessment can be made. By using dynamic rheology, the prediction of physical stability can often be accomplished in less than three (3) hours. The dynamic or oscillatory rheology technique is performed in two parts. First, a strain sweep test (frequency constant, strain variable) defines the linear viscoelastic range (LVR). Second, frequency scans (from 0.01 to 5.0 Hz) are performed at various temperatures, from 5 to 49°C (40–120°F). It is critical that the frequency scans are performed in the LVR. Dynamic rheology measurements yield data on the elastic (G′) and viscous (G″) moduli. Plotting the elastic to viscous moduli ratio as a function of frequency and temperature generates a 3‐D surface which is a “fingerprint” of the dispersion’s colloidal stability. The G′/G″ ratios correlate well with observed physical stability properties. A volume index or a simple mean/variance calculation can be used to assign a value to the graphical 3‐D representations.

Prediction of Infiltration of Water into Aggregated Clay Soil Samples

The physical properties—stability, water retention, diffusivity and conductivity—relevant to the study of infiltration into aggregated media were measured for four aggregate sizes: 2.38–2.00 mm; 1.168–0.840 mm; 0.417–0.295 mm; 0.105–0.053 mm referred to in the study as sizes 1, 2, 3, and 4. There were < 15, 5, and 4% aggregate breakdown of sizes 1, 2, and 3 during infiltration. These media were considered stable to infiltration. The large volume changes (swelling and shrinking) which result from wetting and drying aggregates of sizes 4 and the nature of the hysteresis curves suggest that aggregate rear-rangement rather than breakdown may be dominant. The release of water in two distinct steps and the several thousand-fold decrease in conductivity at the moisture content of these two steps, particularly for sizes 1 and 2 suggest that these media can be described as well-aggregated, i.e. having a discontinuity of pore sizes. The hysteresis in moisture retention, equilibrium moisture retention curves, and the changes in moisture retention with time were measured for confined and unconfined samples of the aggregates. Wetting and drying diffusivities and conductivities of confined and unconfined samples were also measured and used in the prediction of horizontal and vertical infiltration under zero and small negative pressures into columns of each of the four aggregate sizes using the diffusion equation. Diffusivities and conductivities were larger on wetting than on drying and generally larger in unconfined than in confined samples. Horizontal and vertical infiltration were reasonably well predicted when water infiltrated under negative pressure and the diffusivities and conductivities used were calculated from infiltration profiles developed under the same water tension. Predictions of infiltration under zero pressure were generally not as successful. For these media, the values of water tension, diffusivity and conductivity at any water content depend on the rate of wetting. The values to be used in the prediction of infiltration must therefore be measured for times of wetting which correspond to the duration of infiltration. The classical diffusion equation can be used to predict infiltration into aggregated claysoils if the correct diffusivities and conductivities are used.

Stability of alumino silicate refractories to aluminum alloys

A comparative study was made of the stability of commercial aluminosilicate refractories in aluminum melts. All of the studied refractories (containing from 32 to 62% Al2O3) react with liquid aluminum alloys. Of the studied refractories, fireclay brick for blast furnaces (GOST 1598-53, class A) have the best stability. The thermal stability, the stability of physical properties, and the chemical stability of fireclay brick for blast furnaces are better than those of high-alumina brick, and the cost is less. Studies must be made to try to find refractories that combine stability to the chemical action of aluminum alloys with a high resistance to the shock of the charge and the variations in temperature.