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.     

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.     

Frictional Properties of Tablet Lubricants

Abstract

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.     

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     

The Tabletting Properties of Dika Fat Lubricant

Abstract

The lubricant property of dika fat, a solid vegetable oil extracted from the kernels of Irvingiaqabonensis var gabonensis and var excelsia was investigated. An instrumented tablet machine (ITM) was used to evaluate the effect of dika fat on the unit ejection force (EJF/A) of a model direct compression formulation. Dika fat, at equivalent concentration levels, performed better than magnesium stearate, stearic acid and a hydrogenated vegetable oil STEROTEX, in reducing EJF/A of tablets compressed from the model direct compression formulation. Dika fat imparted no adverse effect on the hardness, disintegration and dissolution of directly compressed hydrochlorothiazide tablets prepared in this study.     

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.     

The Evaluation of Fine-Particle Hydroxypropylcellulose as a Roller Compaction Binder in Pharmaceutical Applications

In solid dosage manufacturing, roller compaction technology plays an important role in providing cost control and a quality product. The objective of this study was to evaluate the effectiveness of fine-particle hydroxypropylcellulose (HPC) as a dry binder in roller compaction processing. The formula included acetaminophen (APAP), microcrystalline cellulose, fine-particle HPC, croscarmellose sodium, and magnesium stearate. The fine-particle HPC was incorporated into the formula at 4%, 6%, and 8% w/w levels. Three compaction pressures (30, 40, and 50 bars) were used for each formulation. The roller compaction equipment used in this study had a processing capacity of 40 to 80 kg/hr. A tablet compression profile was generated on a rotary tablet press, and compression forces used were 5, 10, 15, 20, and 25 kN. The significant criteria for tablet evaluation were capping, hardness, friability, ejection force, and drug dissolution. As the binder concentration of HPC increased, tablet capping decreased, and tablet friability improved. As the concentration of HPC increased, only slight differences were noted in tablet hardness. All the formulations pass the USP requirement of 80% APAP dissolved within 30 min. Using 8% HPC could eliminate the formula capping problem. The friability results were less than 1% at all compression forces. The minimum tablet ejection forces were found in the formulations prepared under 40 bars compaction pressure. The utility of fine-particle HPC as a roller compaction binder was established. The applicable binder concentrations and roller compaction pressures were found. Using HPC at these binder levels and operating parameters could overcome capping and friability problems and achieve the optimal tablet dosage forms.     

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.     

Detrimental consequences of the Paracetamol tablet elastic relaxation during ejection

Background: It is generally accepted that the tablet elastic relaxation during compaction plays a vital role in undermining the final tablet mechanical integrity. One of the least investigated stages of the compaction process is the ejection stage. Method: This work has successfully monitored the paracetamol tablet dimensional changes during ejection using noncontact dimensional measuring devices. The extent of the tablet damage was physically viewed by examining the presence of cracks on the tablet side surfaces upon complete ejection from the die cavity. Results: Damaged tablets were obtained when the paracetamol tablets exhibited comparatively high elastic relaxation during the ejection stage of the compaction process. Conclusion: Hence, this work presents evidences of the detrimental consequences of the paracetamol tablet elastic relaxation during ejection on its final mechanical integrity..     

Investigation of the tableting behavior of Ibuprofen DC 85 W

The aim of the present study was to investigate the tableting behavior of Ibuprofen DC 85?W with special focus on the tablet disintegration time, the tablet crushing strength, and the sticking tendency to punch surfaces. To simulate production conditions, tableting was conducted on a rotary press, equipped with three compaction stations. An I-optimal design of experiments was used to analyze the influence of the pre-compaction, the intermediate compaction, and the main compaction force on the two responses: tablet disintegration time and crushing strength. It was shown that Ibuprofen DC 85?W showed a good tableting behavior with regard to both responses. The tablet disintegration was considerably affected by the maximum compaction force applied, but was also slightly affected by preceding compaction events. The tablet crushing strength was mainly affected by the maximum applied compaction force independent of the order of these forces. The sticking tendency of Ibuprofen DC 85?W was compared with that two other ibuprofen powder formulations in long-term tableting runs. Compared to the other two formulations, sticking was considerably lower with Ibuprofen DC 85?W. The sticking tendency was not influenced by the addition of an intermediate compaction force, but was remarkably reduced by the choice of the punch tip coating.     

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     

Effect of Stearic Acid Particle Size on Surface Characteristics of Film-Coated Tablets

Abstract

Raw material specifications are vital for many excipients used in the manufacture of tablets. Stearic acid powder is widely used in the pharmaceutical industry as a tablet lubricant. This study shows that the variation in particle size of stearic acid not only affects die wall lubrication properties (ejection force) but also affects surface characteristics of film-coated tablets. A coarser grade of stearic acid can dislodge from tablet surfaces during the film-coating process leaving pit marks, whereas a finer grade of stearic acid (less than 100 mesh) results in film-coated tablets having very smooth surfaces. The mechanism of pitting on the tablet surface is described. A specification for stearic acid particle size to overcome this problem is suggested.     

The Tabletting Properties of Dika Fat Lubricant

The lubricant property of dika fat, a solid vegetable oil extracted from the kernels of Irvingiaqabonensis var gabonensis and var excelsia was investigated. An instrumented tablet machine (ITM) was used to evaluate the effect of dika fat on the unit ejection force (EJF/A) of a model direct compression formulation. Dika fat, at equivalent concentration levels, performed better than magnesium stearate, stearic acid and a hydrogenated vegetable oil STEROTEX, in reducing EJF/A of tablets compressed from the model direct compression formulation. Dika fat imparted no adverse effect on the hardness, disintegration and dissolution of directly compressed hydrochlorothiazide tablets prepared in this study.     

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.     

Effectiveness of Lubricants and Lubmcation Mechanism in Tablet Technology

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.     

Instrumented Tablet Press Studies on the Effect of Some Formulation and Processing Variables on the Compaction Process

Abstract

Using an instrumented tablet press, compression force-time measurements were used to evaluate the effects of formulation and processing variables on the compaction process. The effects of tablet press speed, punch size, depth of upper punch penetration (into the die), and the setting of the overload spring mechanism were studied. The effects of tablet weight, particle size and amount of lubrication were also studied. Several direct compression materials which are believed to compact by different mechanisms were used in the study. The results indicate the sensitivity of the area under the compression force-time curve and the Area/Height ratio. Some of the changes seen in the area and A/H ratio were those which would be expected from a relatively simple model of compaction/compression. The results clearly show the usefulness of the instrumented tablet press as an analytical tool in the development of tablet formulations, the evaluation of processing requirements, and the remedy of tablet production problems.     

Determination of a Relationship Between Force-Displacement and Force-Time Compression Curves

A series of experiments were conducted to evaluate and compare force-displacement and force-time compression curves. A Stokes B-2 sixteen station rotary tablet press was instrumented with piezoelectric transducers to monitor compression and ejection forces (in addition to punch proximity) and interfaced with a microcomputer. Processing and material variables were examined for their effects on the direct parameters (ie. height and area) and derived parameters (ie. area:height ratio and maximum s1ope:height ratio) of the force-time compression curve. Upper punch displacement was estimated and force-displacement curves were plotted. The force-time curve was then divided into three segments pertaining to the three stages of upper punch movement: compression, relaxation, and decompression. The “relaxation” stage was defined as the portion of the compression force-time curve corresponding to the interval when the upper punch displacement was held constant. The total, net and elastic works of compaction were calculated and their relationships with the areas of the individual phases of the force-time compression curve were examined. It appears that the area under the cornpression force-time curve can be related satisfactorily to the work of compaction.     

Axial to Radial Pressure Transmission of Tablet Excipients using a Novel Instrumented Die

Abstract

A die instrumented with four piezoelectric force transducers was developed for use on the Rutgers Integrated Compaction Research System. It was calibrated and characterized using high density polyethylene as the calibrating material. Results showed that the radial response measured by the four die wall transducers was dependent upon the thickness of the compact being compressed and its location within the die. These two factors were incorporated into the calibration constant which converted the die wall response from voltage units into pressure units. Sample compaction profiles showing axial to radial pressure transmission of selected materials of interest in tableting were generated using this die.