Frictional Properties of Tablet Lubricants

Some frictional properties of tablet lubricants were determined. The friction coefficients and the adhesion forces of six lubricants were evaluated by the method proposed previously. The ejection force against the radial force for each lubricant yielded a straight line through the origin, so that the adhesion forces of these lubricants were estimated to be almost zero. All lubricants had low friction coefficients when they alone were compressed. The value for metal stearate was the smallest and that for talc was the largest. The affinity of the lubricants to the die wall, another important property of the lubricants, was also determined. After the die wall was conditioned by the tabletings of each lubricant alone, the serial tabletings of lactose granulates in the die were carried out. The increasing rate of ejection force in the conditioned die in a serial tableting was different for every pretreatment of each lubricant. The affinity of magnesium stearate to the die wall surface was superior to that of other lubricants.     

Adhesion of Tablets in a Rotary Tablet Press II. Effects of Blending Time,Running Time,and Lubricant Concentration

Abstract

Of the three essential functions of tablet lubricants, only the true lubricant and glidant properties have been studied in detail by objective means. Only recently has instrumentation which permits the objective measurement of the antiadhesion activity in a rotary tablet press been developed. Using a rotary press instrumented to measure the adhesion of tablets to the lower punch face, this study focuses on the adhesion of tablets in two direct compression systems. At any given compression force, adhesion of microcrystalline cellulose tablets lubricated with magnesium stearate appeared to decrease with increases in blending time or intensity of blending. Over a three-hour running time, adhesion force was found to increase to peak values and then to decline with both microcrystalline cellulose and hydrous lactose lubricated with magnesium stearate. However, ejection forces decreased gradually to apparently limiting values in each case. The adhesion of tablets to the lower punch face appeared to be affected partly by the condition of the tablet - die wall interface. Studies comparing lubricated and unlubricated microcrystalline cellulose suggest two opposing effects on tablet adhesion: (1) enhancing adhesion due to an increased reaction at the lower punch resulting from reduced die wall friction; and, (2) reducing the adhesion of tablets via the “antiadherent” effect. At the lubricant levels studied, stearic acid generally appeared to be less efficient than magnesium stearate in reducing both the adhesion and ejection forces in microcrystalline cellulose blends. However, with hydrous lactose blends, the true lubricant and antiadherent activities of stearic acid appeared to be greater than those of magnesium stearate at the 1.00% level of addition.     

Adhesion of Tablets in a Rotary Tablet Press II. Effects of Blending Time, Running Time, and Lubricant Concentration

Of the three essential functions of tablet lubricants, only the true lubricant and glidant properties have been studied in detail by objective means. Only recently has instrumentation which permits the objective measurement of the antiadhesion activity in a rotary tablet press been developed. Using a rotary press instrumented to measure the adhesion of tablets to the lower punch face, this study focuses on the adhesion of tablets in two direct compression systems. At any given compression force, adhesion of microcrystalline cellulose tablets lubricated with magnesium stearate appeared to decrease with increases in blending time or intensity of blending. Over a three-hour running time, adhesion force was found to increase to peak values and then to decline with both microcrystalline cellulose and hydrous lactose lubricated with magnesium stearate. However, ejection forces decreased gradually to apparently limiting values in each case. The adhesion of tablets to the lower punch face appeared to be affected partly by the condition of the tablet - die wall interface. Studies comparing lubricated and unlubricated microcrystalline cellulose suggest two opposing effects on tablet adhesion: (1) enhancing adhesion due to an increased reaction at the lower punch resulting from reduced die wall friction; and, (2) reducing the adhesion of tablets via the “antiadherent” effect. At the lubricant levels studied, stearic acid generally appeared to be less efficient than magnesium stearate in reducing both the adhesion and ejection forces in microcrystalline cellulose blends. However, with hydrous lactose blends, the true lubricant and antiadherent activities of stearic acid appeared to be greater than those of magnesium stearate at the 1.00% level of addition.     

Evaluation of Two New Tablet Lubricants -Sodium Stearyl Fumarate and Glyceryl Behenate. Measurement of Physical Parameters (Compaction,Ejection and Residual Forces) in the Tableting Process and the Effect on the Dissolution Rate

Abstract

A comparison of two new tablet lubricants, sodium stearyl fumarate and glyceryl behenate, was made with magnesium stearate. Physical parameters such as compaction force, ejection force and residual force were investigated and quantified. The effect of these lubricants on a biopharmaceutical parameter such as dissolution rate was also evaluated. The results indicate that where magnesium stearate cannot be used due to problems of compaction, lubrication, stability or for biopharmaceutical reasons, sodium stearyl fumarate should be used as the tablet lubricant of choice, followed by glyceryl behenate as the next alternative     

Evaluation of Two New Tablet Lubricants -Sodium Stearyl Fumarate and Glyceryl Behenate. Measurement of Physical Parameters (Compaction, Ejection and Residual Forces) in the Tableting Process and the Effect on the Dissolution Rate

A comparison of two new tablet lubricants, sodium stearyl fumarate and glyceryl behenate, was made with magnesium stearate. Physical parameters such as compaction force, ejection force and residual force were investigated and quantified. The effect of these lubricants on a biopharmaceutical parameter such as dissolution rate was also evaluated. The results indicate that where magnesium stearate cannot be used due to problems of compaction, lubrication, stability or for biopharmaceutical reasons, sodium stearyl fumarate should be used as the tablet lubricant of choice, followed by glyceryl behenate as the next alternative     

Comparison of Methods for Evaluation of Friction During Tableting

Abstract

The friction between a tablet and the die wall can be evaluated by comparison of the forces on the upper and lower punches, i.e. force ratio (R-value) or force difference (FD, or by measuring the forces on the lower punch immediately before ejection (REF) or during ejection (EJF). These parameters were compared for different materials using an instrumented single-punch press. The compaction load and the dimensions of the compact had an obvious influence on all parameters studied. By correcting for differences in contact area between tablet and the die wall it appears possible to eliminate the influence on FD, REF and EJF from variation in tablet height. Several compaction loads within the range of interest have to be studied to get a complete picture of the behaviour of a tablet granulate. The different parameters did not always give correlating results and EJF appears to give the best prediction of adhesion problems.     

Adhesion of Tablets in a Rotary Tablet Press I. Instrumentation and Preliminary Study of Variables Affecting Adhesion

This study describes instrumentation to Measure the adhesion of tablets to the lower punch face by means of a strain gaged cantilever beam affixed to the feed frame in front of the sweep-off blade. The tablet is detached from the lower punch by striking this blade. The adhesion force is the total force measured by the beam less that due to the momentum of the tablet. Tableting was performed on a Stokes RB-2 press previously instrumented to monitor compression and ejection forces. Generally, the higher the compression force, or the lower the magnesium stearate concentration, the higher the adhesion in three direct compression fillers (compressible sugar, microcrystalline cellulose, lactose). With microcrystalline cellulose (0.1% magnesium stearate), adhesion decreased with Increased tablet thickness or decreased tablet diameter (constant thickness) ac constant compression pressure Simultaneous measurement of ejection forces revealed that differences in true lubricant efficiency did not necessarily reflect differences in adhesion. The ability to distinquish differences in adhesion offers promise in assisting in the rational design of tablet formulations.     

Aspects of the Lubrication Requirements for an Automatic Capsule Filling Machine

Aspects of the lubrication requirements for an automatic capsule filling machine, instrumented to monitor compression and ejection forces, were studied under various filling conditions. Three common capsule fillers (compressible starch, micro-crystalline cellulose, and anhydrous lactose) were filled into No. 1 gelatin capsules. Two main sets of runs were made. The first set was designed to study the influence of powder bed height, piston height and compression force on the ejection forces generated during the filling process. The second set was aimed at comparing lubricant type and levels. It was shown that the ejection force is increased by increasing the powder bed height, piston height and compression force. Compressible starch and micro-crystalline cellulose required relatively low levels of magnesium stearate as compared to anhydrous lactose. The performance of stearic acid and especially magnesium lauryl sulfate compared favorably with magnesium stearate in compressible starch.     

Comparison of Methods for Evaluation of Friction During Tableting

The friction between a tablet and the die wall can be evaluated by comparison of the forces on the upper and lower punches, i.e. force ratio (R-value) or force difference (FD, or by measuring the forces on the lower punch immediately before ejection (REF) or during ejection (EJF). These parameters were compared for different materials using an instrumented single-punch press. The compaction load and the dimensions of the compact had an obvious influence on all parameters studied. By correcting for differences in contact area between tablet and the die wall it appears possible to eliminate the influence on FD, REF and EJF from variation in tablet height. Several compaction loads within the range of interest have to be studied to get a complete picture of the behaviour of a tablet granulate. The different parameters did not always give correlating results and EJF appears to give the best prediction of adhesion problems.     

Bonding and tribological properties of perfluorinated lubricantsand hydrogenated amorphous carbon films

Molecular properties of perfluorinated lubricants and amorphous carbon films relevant to the tribological performance of hard disk drives have been measured. The bonding of water and model perfluorinated lubricants to amorphous carbon surfaces has been studied by thermal desorption spectroscopy. Binding energies consistent with a physisorbed state are found for each of these small molecules. Binding energies are found to increase with increasing molecular weight and polarity of the adsorbate as well as increasing surface free energy of the carbon film. Adhesion forces and coefficients of friction have been measured with atomic force microscopy at hydrogenated amorphous carbon surfaces as a function of hydrogen content. An increase in both adhesion and friction forces is observed with increasing hydrogen contents and is attributed to changes in the surface free energy of the carbon films     

Effectiveness of Lubricants and Lubmcation Mechanism in Tablet Technology

Abstract

A method for quantitative evaluation of the effectiveness of the lubricant used in tablet technology has been recentey proposed by the authors It was based on the ejection force determination expressed as relationship between the force on the lower punch and the time (ejection curve).

The proposed methodology allows now quantitative analysis of the tablet ejection, considering that the lot of the parameters linked to the conditionning, tooling and operative procedure that can negatively affect the measurement, were optimized During the methodology development, series of ejection curves, relative to different type of diluent and a variety of lubricants, were collected Certain relationship between the form of ejection curve and the capacity of lubricant to reduce frictions was observed.

Starting from these observations, the aim of this work was to analyze quantitatively the ejection curves obtained with the proposed methodology, in order to have a measure of the effectiveness of the lubricant in the formulation. The ejection curve must be considered as an effective means for this type of analysis, mainly because its pattern modifies according to formulative parameters such as compression force and lubricant amount.

Moreover, the product of ejection peak value and area under the ejection curve gives a dependent parameter that appears to be very sensitive to the conditions affecting tablet manufacturing in terms of lubrication Because of its informative quality, this lubrication index could be profitably be used in the optimisation procedures for formula preparation.     

The Influence of the Zinc Phosphate Coating on the coefficient of friction when cold heading AISI 1018 steel wire

A Waterbury-Farrel cold heading machine was instrumented so that the total force and frictional force could be recorded during the first blow operation of AISI 1018 steel wire and the efficiency of various lubricants, including zinc phosphate, was evaluated. Zinc phosphate and other bonded lubricants did not offer any distinct advantage in reducing the coefficient of friction between the wire and the central bore of the first blow punch whereas a low cost liquid lubricant, SAE 30 oil, used either alone on bare wire or with bonded lubricants proved to be the most effective. It is suggested that a low cost liquid lubricant, such as SAE 30 oil, used on bare wire has both economic and operational advantages under conditions where no extrusion is carried out during the first blow.     

Should Magnesium Stearate be Assessed in the Formulation of Solid Dosage Forms by Weight or by Surface Area ?

Abstract

Three batches of magnesium stearate differing in morphology, particle size, bulk density and specific surface area were compared in the preparation of Pyrazinamide direct compression tablets. When the lubricants were used in the same amount they gave rise to tablets differing in hardness, disintegration and dissolution. When they were used in such amounts to develop equivalent lubricating areas, the final characteristics of the tablets were almost identical. A direct correlation was found between lubricating areas and ejection force.     

Press Chamber Coating as External Lubrication for High Speed Rotary Presses: Lubricant Spray Rate Optimization

ABSTRACT

Lubrication of the tooling (punches and dies) is necessary to produce tablets. The most commonly used lubricant is magnesium stearate. Adding and blending magnesium stearate to the tablet mass often has negative effects on the properties of the compressed tablets (e.g., decreasing the tensile strength of the tablet). To avoid these negative effects, external lubrication systems were developed. This study investigated the functionality and the influence of a new press chamber coating system called the PKB II. The major difference between the PKB II and previous systems is its ability to spray a mixture of powdered magnesium stearate and air directly onto the punches and dies which was determined to allow the running of the rotor at higher speeds. The data showed a clear correlation between the spray rate of the lubricant and the concentration of the magnesium stearate per tablet. The PKB II was designed to allow for adjustments, in order to optimize the spray rate, by using the ejection force. The concentration of magnesium stearate was reduced to approximately 0.04% per tablet, using the PKB II. Additionally, the most common negative effects, such as the decrease in tablet tensile strength, were avoided by using this system.     

The Effect of Magnesium Stearate Admixing in Different Types of Laboratory and Industrial Mixers on Tablet Crushing Strength

Abstract

It is generally known that hydrophobic lubricants such as magnesium stearate can have a strong negative effect on the binding properties of directly compressible filler-binders. It was found that the decrease in binding forces is not only dependent on the tablet ingredients and the lubricant concentration used, but especially on the mixing time and mixing procedure. Most studies were performed, however with small laboratory scale mixers. In order to evaluate the effect of magnesium stearate admixing in different types of laboratory-scale and industrial mixers, the decrease in crushing strength was measured for a test formulation during mixing with the lubricant in different mixers. The formula used consisted of 90% a-lactose monohydrate 100 mesh, 9.5% microcrystalline cellulose and 0.5% magnesium stearate. The mixers used were two laboratory scale mixers: a 2 litre Turbula mixer and a 13 litre cubic mixer and five production scale mixers: a 45 litre drum mixer, 90 litre, 200 litre and 900 litre planetary mixers and a 1.000 litre V-shaped mixer, respectively. For the test formulation used, it was found that the effect of lubricant admixing on tablet crushing strength was strongly dependent on type, size and rotation speed of the mixer used.

When operated at the same rotation speed, the decrease in crushing strength was much faster for the large industrial mixers than for the small laboratory mixers. These differences were explained by differences in shear forces during the mixing process and the efficiency of the mixing procedure.

For the industrial mixers the decrease of the tablet crushing strength as an effect of lubricant admixing was mainly determined by the rotation speed and only to a small extent by the type and size of the apparatus. Moreover no effect of load could be observed between the mutual industrial mixers used.

For a prediction of the effect of lubricant admixing on tablet crushing strength in large mixers, efficient laboratory mixers, operating at high rotation speeds can be used. For this purpose a 2 litre Turbula mixer is a valuable tool in preformulation work.     

The Effect of Lubricants on the Properties of Chloroquine Phosphate Tablets

Abstract

The properties of tablets prepared from different size fractions of chloroquine phosphate granules using different lubricants were evaluated. Lubricants used were magnesium stearate, stearic acid and talc, tablet properties studied include weight variation, crushing strength, friability and disintegration time

The effects obtained were largely dependent on the type and concentration of lubricant. Generally, as granule size increased, tablets were found to show increased weight variation, decreased hardness and increased friability. With tablets containing talc as lubricant, disintegration time was shown to decrease with increase in granule size.

There appears to be an optimum lubricant concentration for the compression of different granule size fractions.     

On the processing properties and friction behaviours during compaction of powder mixtures

ABSTRACT

Iron-based powder mixtures were prepared by dry and wet mixing method. The friction properties during compaction were tested by measuring the internal and external friction coefficient. The test results showed that the wet mixing process could realise the homogeneity of lubricant and improve the processing properties of the powder mixtures. With 0.6 wt-% lubricants, wet mixing powder mixtures have a flow rate of 29.6 s/50?g, an apparent density of 3.18?g?cm^–3, a repose angle of 35.5°, and the friction coefficient during the compaction is 0.223. An equation to calculate the total (both internal and external) friction forces during the compaction process is proposed, and then the factors influencing the friction coefficient during compaction were quantitatively analysed.     

Comparative Tableting Properties of Sixteen Microcrystalline Celluloses

Abstract

The tableting characteristics of sixteen NF grade microcrystalline celluloses produced by seven manufacturers were investigated. Nine samples were type 1 celluloses (fine powders) and seven corresponded to type 2 celluloses (coarse powders). Some samples were second batches of the same products. The powders were examined for their moisture content, particle-size distribution, for their true, bulk and tap densities and for their flow properties. The effect of adding a lubricant with a low friction coefficient (0.5% magnesium stearate) on the packing and flow properties was evaluated.

Basic compression studies were made on an instrumented eccentric tableting machine at an axial pressure of 100 MPa. The work of compression and the elastic recovery of the compacts were determined, as well as many friction parameters. The tabletability of the powders was assessed by measuring the diametral crushing force of the compacts.

In a second set of experiment, we examined the effect on the compactability of the powders of adding 0.5% magnesium stearate.

Weight variations of lubricated tablets were studied on a high speed rotary machine. In these runs, the force required to prepare tablets of a given mechanical strength was monitored. The uniformity of dimensions, the friability and the disintegration time of the tablets were also checked.

Great differences in packing and tableting properties and in sensitivity to the addition of a lubricant were generally observed between products from the various manufacturers. In contrast, lot-to-lot variability was quite acceptable.     

Compaction of homogeneous (Mn,Zn)-ferrite potcores

The compaction of thin-walled potcore compacts (height 10 mm, diameter 15 mm, wall thickness 1 mm) with a high homogeneity is analysed. High homogeneity implies that the density is uniform throughout the compact. In order to attain this goal, internal and external friction are minimized while the mode of pressing and pressing velocity are optimized. Internal friction refers to friction between the powder particles, which is influenced by the particle size distribution and additives. The use of five different additives is evaluated. External friction relates to the friction between the powder and the die wall, which is influenced by the relative hardness of the die wall and lubricants. The effects of three different coatings and a lubricant on friction with the die wall have been investigated. The homogeneity of compacts with complicated shapes is affected by the formation of large local density gradients, which lead to differential shrinkage during sintering. By characterizing the shape of sintered products, it is shown that the inhomogeneity in compacts is reduced by optimizing the pressing mode and the pressing velocity. This improves the variation of the diameter over the height of the sintered potcores from 3 to 1.0%     

轮缘固体润滑剂对轮轨减摩及损伤性能影响

用MMS-2A滚动摩擦磨损试验机完成试验工作,对比干态和3种不同固体润滑剂作用工况,分析干态和3种不同固体润滑剂作用后的轮轨摩擦性能和固体润滑剂的有效作用时间,探究固体润滑剂对轮轨摩擦性能的影响;分析不同工况下轮轨表面磨损量和表面裂纹,同时对裂纹的长度、角度、深度进行统计,分析固体润滑剂作用对轮轨损伤性能影响。结果表明:固体润滑剂具备减摩润滑作用,其中1号效果最佳,将干态下的摩擦系数0.5降低到0.2左右;固体润滑剂通过降低接触界面的摩擦系数减小轮轨界面的切向摩擦力,降低轮轨表面的磨损量,其中固体润滑剂1降低车轮和钢轨的磨损量最大,分别降低95.3%和97.1%;固体润滑剂主要通过抑制疲劳裂纹的长度来抑制轮轨疲劳裂纹的生长和扩展,通过正应力挤压作用使轮轨表面疲劳裂纹开口紧闭,缓解裂纹根部分支现象,有效抑制轮轨疲劳裂纹生长与扩展行为.