Bonding characteristics by scanning electron microscopy of powders mixed with magnesium stearate

The effect of degree of mixing on the bonding properties of blends of magnesium stearate and tablet excipients is shown to be dependent upon the compression behaviour and bonding mechanism of the excipient studied. Magnesium stearate exercises a maximum effect on excipients such as the starch derivative Amylose V, which undergoes complete plastic deformation without any fragmentation and is bonded by cohesion. The effect on excipients bonded by cold-bonding mechanisms after plastic flow of the crystals, as demonstrated for sodium chloride, is dependent on the extent to which clean, lubricant-free surfaces are formed during compression. The bonding properties of excipients such as dicalcium phosphate dihydrate, which undergo complete fragmentation under pressure, are practically uninfluenced by mixing with magnesium stearate.     

Desaturation of palmitate and stearate by cell-free fractions from soybean cotyledons

Homogenates of cotyledons from immature soybean seeds were fractionated by centrifugation. Cell-free preparations actively desaturated 1-¹⁴C-palmitate and 1-¹⁴C-stearate to produce 9,10-unsaturated acids. The 9-desaturase activity was present mainly in supernatant fractions (22,000 and 105,000 xg). These fractions also desaturated oleate to linoleate and elongated C₁₄, C₁₆ and C₁₈ acids. In view of this versatility of desaturase systems in the soybean, including the 9-desaturase(s) for C₁₄, C₁₆ and C₁₈ saturated acids, there would not seem to be further need to consider a separate plant pathway for biosynthesis of unsaturated fatty acids. Published as Journal Paper No. 3197, AES, Purdue University, Lafayette, Indiana 47907.     

硬脂酸镁改性碳酸钙研究

采用硬脂酸镁对碳酸钙进行表面改性处理,考察了改性剂用量、改性温度、改性时间对粉体改性效果的影响。通过对改性前后碳酸钙粉体的活化度、吸油值、沉降体积以及黏度等性能的测试,从而确定最佳的改性条件。结果表明,最佳的改性工艺条件为：改性剂用量为2%,改性温度为70℃,改性时间为30min。由红外光谱分析可知,硬脂酸镁与碳酸钙之...     

An investigation of magnesium stearate mixing in a V-blender through gamma-ray detection

Magnesium stearate (MgSt) is a widely used powder lubricant in the pharmaceutical industry whose mixing dynamics remain poorly understood. In this work, MgSt was used as a radioactive tracer to investigate its mixing behaviour in a V-blender. MgSt was mixed with a microcrystalline cellulose and spray-dried lactose pre-blend, and a number of samples were then extracted from the powder bed with a core sampler. The amount of lubricant measured in each sample allowed the investigation of the effect of the blender fill volume and rotational speed, the pre-blend composition and the lubricant loading profile on mixing performance. Results indicate that, of these 4 parameters, the rotational speed and the pre-blend composition had the most significant effect on mixing behaviour. Contrary to our expectations, the MgSt loading profile had little effect on mixing performance. Both results indicate the overriding importance of the shear force applied on the powder bed on mixing performance. In a final experiment, the mixing performance of MgSt was compared to that of Sodium Lauryl Sulfate (SLS) at identical fill volumes and rotational speeds. Results show that, in spite of its larger particle size, SLS is more difficult to mix to the other excipients than MgSt.     

The variance-sample size relationship and the effects of magnesium stearate on ordered powder mixtures

The variance-sample size relationship of ordered powder mixture has been investigated. It was confirmed that the mixing variances, especially in micro-     

Electrostatic performance of various lubricant powders in P/M electrostatic die wall lubrication

Electrostatic die wall lubrication is an advanced lubrication technique in the production of machinery parts of powder metallurgy. Electrostatic performance of lubricants is one of key factors for successful operation. Among electrostatic parameters, the charge-to-mass ratio of dry lubricant powders has been considered to be the most critical factor to make good adhesion between the dry lubricant powders and the inner die wall. This paper investigates electrostatic performances and potential dependences of the charge-to-mass ratios of various single lubricants and lubricant mixtures, such as zinc stearate, W-special wax, EBS wax, graphite and h-boron nitride, and some combinations of these single lubricants. The experimental results indicate that not all of the single lubricants can properly be charged by electrostatic charging. Zinc stearate, h-BN and EBS wax can easily be charged and the charge-to-mass ratios can be obtained up to the proper value (0.2 μC/g) high enough for die wall lubrication practice. For lubricant mixtures, wax combinations show satisfactory electrostatic response and both conducting and insulating lubricant powder additions influence the electrostatic performance of the mixtures significantly. Mechanism of charging is discussed and a quantitative estimation of the ratio is given. Processing variables influencing the charge-to-mass ratios are also discussed.     

Synthesis and sintering of cordierite sol-gel powders based on different magnesium salts

The effect of the nature of the magnesium salt on synthesis and sintering of cordierite powders made by the sol-gel method was established. The phase composition of the powder and behavior of the material in sintering are a function of the calcination temperature of the xerogels.     

Studies on the behaviour of chromium (iii) soaps. I. Spectrophotometry of chromium stearate and palmitate in nonaqueous solutions

Studies on the spectrophotometry of chromium stearate and chromium palmitate in benzene, toluene, xylene, carbon tetrachloride and pyridine solvents provide evidence for the existence of complex ion formation. It has been found that this property can be applied successfully for the estimation of chromium in the concn range 1 to 11 mM/liter at 425 and 580 mμ. The method can be employed for the higher concn (> 11 m M/liter) range also but the Beer-Lambert’s law is applicable only at 425 mμ.     

Studies on the behaviour of chromium (iii) soaps. II. Solubility and viscometric studies with chromium stearate and palmitate in nonaqueous solutions

The colloid chemical behaviour of the chromium stearate and palmitate in nonaqueous solutions have been investigated by solubility and viscometric methods. Chromium stearate and palmitate form no micellar aggregate in pyrindine but aggregate into micelles in benzene, toluene, xylene and carbon tetrachloride in the concn range of ca. 0.7–1.5×10⁻² mole/liter. Viscometric studies can be utilized in estimating the concn of the metal soaps in fairly concd solution: 0.822–27.431 g/liter.     

High-pressure phase equilibrium measurements and thermodynamic modeling for the systems involving CO2, ethyl esters (oleate,stearate, palmitate) and acetone

The aim of this work was to study the phase behavior of systems involving carbon dioxide (CO₂), fatty acid ethyl esters (ethyl oleate, ethyl stearate and ethyl palmitate) and acetone at high pressures. The phase behavior involving these components is an important step regarding the design and optimization of industrial processes based on supercritical conditions, such as biodiesel production and fatty esters fractionation involving supercritical and/or pressurized solvents. In addition, supercritical CO₂ can offer an interesting alternative for glycerol separation in water-free biodiesel purification processes. The binary systems investigated in this work were CO₂ + ethyl oleate, and CO₂ + ethyl stearate and these were compared with the CO₂ + ethyl palmitate system. The ternary CO₂ + ethyl palmitate + acetone was also investigated at two different ethyl palmitate to acetone molar ratios of (1:1) and (1:3). The static synthetic method using a variable-volume view cell was employed to obtain the experimental data in the temperature range of 303.15–353.15 K. Vapor–liquid (VL), liquid–liquid (LL) and vapor–liquid–liquid (VLL) phase transitions were observed in these systems. In the binary systems, the solubility increased with the presence of unsaturation and decreased with the number of carbon atoms in the fatty ester chain. Addition of acetone as well as ethanol eliminated the liquid–liquid immiscibility and reduced the pressure transitions, therefore increasing the solubility of the ester in supercritical CO₂. The experimental data sets for the binary and ternary systems were successfully modeled using the Peng–Robinson equation of state with the classical van der Waals quadratic mixing rule (PR-vdW2) and Wong-Sandler (PR-WS) mixing rule. Both models showed good performance in the phase equilibrium correlations and in predictions for the binary and ternary systems.     

The use of molten magnesium chloride in the preparation of crystalline ceramic powders

The interaction of molten MgCl₂ with various oxides and oxide minerals is described. Whithin several hours, at temperatures of 700–1100°C, components such as oxides of Fe, K, Ca and — under proper conditions — Ti are largely converted into the corresponding chlorides, the more volatile of which evaporate, the others being extracted into the liquid phase. By proper choice of stoichiometry, crystalline cordlerite, forsterite, enstatite and spinal could be prepared; they contained a total < 0.2% of oxides of Na, K, Ca and Fe, and their average-diameter range was usually 1–10 μm (or larger for forsterite). The preparation of other microcrystalline powders in molten MgCl₂ is briefly discussed.     

Hot pressing of bimodal alumina powders with magnesium aluminosilicate (MAS) addition

High quality alumina ceramics were fabricated by hot-pressed sintering using bimodal alumina with superfine component as raw material and magnesium aluminosilicate (MAS) glass as sintering aid. Densification behavior, microstructure evolution and mechanical properties of alumina were investigated from 1300 °C to 1450 °C. The bimodal alumina powders were sintered to 99.8% of the theoretical value at 1400 °C and a comparative dense microstructure with a few plate-like abnormal grains was observed. With increase of sintering temperature up to 1450 °C, many fine matrix grains were consumed and quite a few abnormal grains impinged upon each other. For the alumina ceramics hot-pressed from bimodal alumina with 30 wt.% superfine component, optimal mechanical properties were obtained at 1400 °C. The bending strength and fracture toughness were 522 MPa and 5.0 MPa m^1/2, respectively.     

Study of the behaviour of magnesium stearate with different specific surface areas on the surface of particles during mixing

The behaviour of two types of magnesium stearate with different specific surface areas on granule particles was examined. The magnesium stearate concentration was measured with an energy-dispersive X-ray fluorescence analyser. Different measurement procedures were used to investigate the properties of the two types of magnesium stearate when using different blending times and rotation speeds. Correlations were found between the specific surface area of the magnesium stearate, the blending time, the rotation speed and the specific surface free energy of the excipients. If magnesium stearate has a high specific surface area it shows higher adhesion work and is able to create a very thin homogeneous layer on the surface of the particles. Magnesium concentration was detected with the energy-dispersive X-ray fluorescence analyser. Based on the X-ray investigation the optimum blending time and rotation speed can be determined.     

硬脂酸稀土和硬脂酸钙对PVC热稳定特性的比较研究

为有助于加深对稀土热稳定剂的认识,尝试以CaSt2为参照,并以LaSt3为代表,比较研究了硬脂酸稀土对PVC的热稳定特性,并探讨了有关的原理。结果表明:(1)硬脂酸稀土的热稳定特性与CaSt2相似;(2)LaSt3/ZnSt2和环氧大豆油(ESO)的并用效果与CaSt2/ZnSt2相当,但与季戊四醇(PET)和二苯甲酰甲烷(DBM)的并用效果与CaSt2/ZnSt2相比略有逊色;(3)LaSt3/ZnSt2和PET、DBM的并用效果不如CaSt2/ZnSt2的原因可能在于,与Ca2 相比,La3 能更强烈地与Zn2 竞争和PET和DBM形成配合物,从而使后两者的作用更不能得到充分发挥。     

乙二醇硬脂酸酯的合成

以对氨基苯磺酸为催化剂催化合成乙二醇硬脂酸酯。研究了酯化反应时间、醇酸摩尔比、反应温度、催化剂用量等对产品收率的影响。结果表明,最佳反应条件为:n(醇)∶n(酸)=1.3∶1,催化剂的用量为2.0 g,控温135℃,反应时间为3 h,酯收率可达92.6%。