Lubricant Concentration Research Articles

Fast dentification of overlapping fluorescence spectra of oil species based on LDA and two-dimensional convolutional neural network

Although most petroleum oil species can be identified by their fluorescence spectra, overlapping fluorescence spectra make identification difficult. This study aims to address the issue that fluorescence spectroscopy is ineffective in identifying overlapping oil species. In this study, an equivalent model of overlapping oil species with fluorescence spectra was established. The linear discriminant analysis (LDA)-assisted machine learning (ML) algorithms K nearest neighbor (KNN), decision tree (DT), and random forest (RF) improved the identification of fluorescent spectrally overlapping oil species for diesel-lubricant oils. The identification accuracies of two-dimensional convolutional neural network (2DCNN), LDA combined with the ML algorithms effectively all 100 %. Furthermore, Partial Least Squares Regression (PLSR) algorithm, Support Vector Regression (SVR) algorithm, DT regression algorithm, and RF regression algorithm were also used to identify the lubricant concentration in diesel-lubricant oils. The coefficient of determination of the DT was 1, and the root-mean-square error was 0, which identified the concentration of lubricant oils in them accurately and without error.

Low ice adhesion on soft surfaces: Elasticity or lubrication effects?

HypothesisSoft materials are promising candidates for designing passive de-icing systems. It is unclear whether low adhesion on soft surfaces is due to elasticity or lubrication, and how these properties affect the ice detachment mechanism. This study presents a systematic analysis of ice adhesion on soft materials with different lubricant content to better understand the underpinning interaction. ExperimentsThe wetting and mechanical properties of soft polydimethylsiloxane with different lubricant content were thoroughly characterized by contact angle, AFM indentation, and rheology measurements. The collected information was used to understand the relationship with the ice adhesion results, obtained by using different ice block sizes. FindingsThree different de-icing mechanisms were identified: (i) single detachment occurs when small ice blocks are considered, and the ice completely detaches in a single event. In the case of larger ice blocks, the reattachment of the ice block is promoted by either: (ii) stick–slip or, (iii) interfacial slippage, depending on the lubricant content.It was confirmed that the ice adhesion strength not only depends on material properties but also on experimental conditions, such as the ice dimensions. Moreover, differently than on hard surfaces, where wetting primarily determines the icephobic performance, also elasticity and lubrication should be considered on soft surfaces.

Experimental Study on the Impact of Lubricant on the Performance of Gravity-Assisted Separated Heat Pipe

Gravity-assisted separation heat pipes (GSHPs) are extensively utilized in telecommunications base stations and data centers. To ensure year-round cooling, integrating GSHPs directly with a vapor compression refrigeration system is a viable solution. It is unavoidable that the refrigeration system’s lubricant will infiltrate the heat pipe loop, thereby affecting its thermal performance. This paper examines the performance of a GSHP, which features a water-cooled plate heat exchanger as the condenser and a finned-tube heat exchanger as the evaporator, when the working fluid (R134a) is contaminated with a lubricant (POE, Emkarate RL-46H). The findings are compared with those from a system free of lubricant. The experimental outcomes indicate that the presence of lubricant degrades the heat transfer efficiency, particularly when the filling ratio is adequate and no significant superheat is observed at the evaporator’s outlet. This results in a 3.86% increase in heat transfer resistance. When the charge of the working fluid is suboptimal, the average heat transfer resistance remains relatively constant at a 3% lubricant concentration yet increases to approximately 5.27% at a 4–6% lubricant concentration, and further to 12.32% at a 9% lubricant concentration. Concurrently, as the lubricant concentration fluctuates between 3% and 9%, the oil circulation ratio (OCR) varies from 0.02% to 0.11%.

Formulation, Optimization, and Evaluation of Ezetimibe for Chronotherapeutic Drug Delivery using Compression-Coating Technology

Objectives: The purpose of the present study was to Formulation, optimization and evaluation of drug for chronotherapeutic drug delivery using compression coating technology for hypercholesterolemia. Material and Methods: The drug delivery system was designed to deliver the drug at a time when it could be needed for the most in the early morning (4 to 6 a.m.) for patients in case of hypercholesterolemia. The pulsatile concept was applied to the dosage form by having a lag phase followed by an immediate release. The prepared system consisted of two parts: a core tablet containing the active ingredient and fracture outer shell with delay-release polymer having diffusion characteristics. Solid dispersion was carried out by screening of betacyclodextrin, Polyvinyl pyrrolidone (PVP K30), and HPMC using three different drug complex ratios 1:1, 1:2, and 1:3 by a solvent evaporation method through spray dryer. The immediate-release core tablet (IRCT) was prepared by using a superdisintegrant with active ingredients. Screening of IRCT was carried out by pre and post compression parameters, disintegration time and an in-vitro dissolution study. The pulsatile release tablet (PRT) of optimized IRCT was made by Glyceryl Behenate and Dibasic Calcium Phosphate. Optimization of polymer concentration of PRT was carried out by pre and post-compression parameters, pulsatile lag time, and an in-vitro dissolution study. A 32 factorial design was employed to optimize the PRT. The design consisted of two dependent variables R1, and R2 independent variables X1 and X2. The two independent formulation variables selected for the study including Concentration of coating polymer and Concentration of lubricant. The dependent variables are Lag Time and Thickness. Results: XRD, DSC and FTIR spectra showed that solid dispersion was formed by the drug and PVP K30 complex. IRCT batch RR1 containing 22mg croscarmellose sodium to achieve good 30sec disintegration time and 98.34% drug release at the end of 20 minutes of Ezetimibe respectively. PRT formulation DR6 showed good pre and post-compression parameters with a satisfactory drug release of 98.34% for Ezetimibe respectively with a lag time of 6 hours. The 32 factorial design was used for the optimization of PRT parameters. A total of 9 experiments were performed for two factors at three levels each. The optimized batch showed 98.27% DR for Ezetimibe in 6.2 hrs (within 20 min after lag time) with pulsatile lag time up to 6.0 hrs and thickness of 5.10 kp. Conclusion: It was concluded that tablet within the tablet, pulsatile drug delivery of Ezetimibe (BCS class-II drugs) was successfully formulated with the advantage of enhanced solubility, and pulsatile release behavior and had an added benefit of suitable for chronopharmacotherapy of diseases that show circadian rhythms in their pathophysiology.

Withdrawn: Low ice adhesion on soft surfaces: Elasticity or lubrication effects?

HypothesisSoft materials are promising candidates for designing passive de-icing systems. It is unclear whether low adhesion on soft surfaces is due to elasticity or lubrication, and how these properties affect the ice detachment mechanism. This study presents a systematic analysis of ice adhesion on soft materials with different lubricant content to better understand the underpinning interaction. ExperimentsThe wetting and mechanical properties of soft polydimethylsiloxane with different lubricant content were thoroughly characterized by contact angle, indentation, and rheology measurements. The collected information was used to understand the relationship with the ice adhesion results, obtained by using different ice block sizes. FindingsThree different de-icing mechanisms were identified: (i) single detachment occurs when small ice blocks are considered, and the ice completely detaches in a single event. In the case of larger ice blocks, the reattachment of the ice block is promoted by either: (ii) stick–slip or, (iii) interfacial slippage, depending on the lubricant content.It was confirmed that the ice adhesion strength is not a material property, since it depends on the ice block size. As such, differently than on hard surfaces, where wetting primarily determines the icephobic performance, also elasticity and lubrication need to be considered on soft surfaces.

Selection of Various Indications of Tempering Lubricant Concentration Reuse in the Wet Rolling Process

ABSTRACTDiscarded tempering lubricants retained significant reuse potential, making their recycling a vital step in reducing resource wastage and wastewater treatment costs in the strip steel industry. Hence, developing an accurate, rapid evaluation indicator for recycled fluid concentration was essential for facilitating this process. Research showed that among common evaluation indicators for metal fluids, three—electrical conductivity, refractive index and total base number (TBN)—due to their high linear correlation with tempering lubricant concentration (R2 > 0.995), could be utilised to monitor the dynamic changes in the concentration of tempering lubricants. Subsequent experiments on reused tempering lubricants revealed that electrical conductivity, significantly altered by iron powder (7%–24% variance), and refractive index, impacted by hydraulic oil (3% deviation), highlighted contaminant challenges; yet, filtration effectively mitigated iron powder's effect on TBN. Finally, A 17‐day reused tempering lubricants simulation demonstrated consistent effectiveness of the three indicators in monitoring the need to update tempering lubricant concentration. However, in terms of sensitivity, precision, and particularly stability and relative mean deviation, the TBN concentration evaluation indicator outperformed, with TBN (3.38%) < Refractive Index (7.92%) < Electrical Conductivity (11.05%). This indicates the TBN method's superior stability over conductivity and refractive index methods, with its accuracy deviation below 2%, making it a stable, simple and reliable metric worthy of broader adoption.

High temperature tribological behaviors of the D-gun sprayed CrFeNiAl0.3Ti0.3-Ag-(Ba,Ca)F2 high entropy alloy matrix self-lubricating coatings

In this work, the detonation spraying approach was implemented to successfully create high-performance CrFeNiAl0.3Ti0.3 high-entropy alloy (HEA) matrix coatings with the incorporation of Ag and (Ca, Ba)F2 eutectic solid lubricants. The microstructure, mechanical and high-temperature tribological performance of this coating were investigated. It was found that the dense lamellar structures and the fine grains resulted in the self-lubricating coating of CrFeNiAl0.3Ti0.3 with a considerable hardness of above 454 HV and a significant good bond strength of above 54 MPa. By adjusting the incorporation content of Ag and (Ca, Ba)F2 solid lubricants with 10 wt%, the composite coating exhibited satisfactory tribological performance from 25 °C to 800 °C, which displays the low friction coefficient of 0.32 ∼ 0.59 and the wear rate of 3.34 ∼ 16.71 × 10−5 mm3/Nm. Especially at 800 °C, an oxide-containing glaze layer formed on the worn surface of the coating, effectively enhancing the tribological performance of the self-lubricating coating.

Modeling and prediction of tribological properties of copper/aluminum-graphite self-lubricating composites using machine learning algorithms

The tribological properties of self-lubricating composites are influenced by many variables and complex mechanisms. Data-driven methods, including machine learning (ML) algorithms, can yield a better comprehensive understanding of complex problems under the influence of multiple parameters, typically for how tribological performances and material properties correlate. Correlation of friction coefficients and wear rates of copper/aluminum-graphite (Cu/Al-graphite) self-lubricating composites with their inherent material properties (composition, lubricant content, particle size, processing process, and interfacial bonding strength) and the variables related to the testing method (normal load, sliding speed, and sliding distance) were analyzed using traditional approaches, followed by modeling and prediction of tribological properties through five different ML algorithms, namely support vector machine (SVM), K-Nearest neighbor (KNN), random forest (RF), eXtreme gradient boosting (XGBoost), and least-squares boosting (LSBoost), based on the tribology experimental data. Results demonstrated that ML models could satisfactorily predict friction coefficient and wear rate from the material properties and testing method variables data. Herein, the LSBoost model based on the integrated learning algorithm presented the best prediction performance for friction coefficients and wear rates, with R2 of 0.9219 and 0.9243, respectively. Feature importance analysis also revealed that the content of graphite and the hardness of the matrix have the greatest influence on the friction coefficients, and the normal load, the content of graphite, and the hardness of the matrix influence the wear rates the most.

Synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve tribological properties of M50 bearing steel with microporous channels

Purpose This paper aims to study the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 to improve the tribological properties of M50 bearing steel with microporous channels. Design/methodology/approach M50 matrix self-lubricating composites (MMSC) were designed and prepared by filling Sn–Ag–Cu and MXene–Ti3C2 in the microporous channels of M50 bearing steel. The tribology performance testing of as-prepared samples was executed with a multifunction tribometer. The optimum hole size and lubricant content, as well as self-lubricating mechanism of MMSC, were studied. Findings The tribological properties of MMSC are strongly dependent on the synergistic lubrication effect of MXene–Ti3C2 and Sn–Ag–Cu. When the hole size of microchannel is 1 mm and the content of MXene–Ti3C2 in mixed lubricant is 4 wt.%, MMSC shows the lowest friction coefficient and wear rate. The Sn–Ag–Cu and MXene–Ti3C2 are extruded from the microporous channels and spread to the friction interface, and a relatively complete lubricating film is formed at the friction interface. Meanwhile, the synergistic lubrication of Sn–Ag–Cu and MXene–Ti3C2 can improve the stability of the lubricating film, thus the excellent tribological property of MMSC is obtained. Originality/value The results help in deep understanding of the synergistic lubrication effects of Sn–Ag–Cu and MXene–Ti3C2 on the tribological properties of M50 bearing steel. This work also provides a useful reference for the tribological design of mechanical components by combining surface texture with solid lubrication. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0381/

Influence of GNPs solid lubricant on the fabrication of Cu/SS304L composite micro channels

The different solution-processed concentrations of graphene solid lubricant (0 – 30 mg/mL) were applied on the surface of copper/stainless steel 304 L composite foils. A variable trend of rolling force occurs, with a first falling and then rising trend and the lowest rolling force was obtained at 25 mg/mL for 3.82 kN. Besides, the height of ridges and aspect ratio were improved with an increased solution-processed concentration. On the valley surfaces, the GNPs filled up the cracks, flattened the grooves and eliminated the micro scratches. This indicates the self-repairing and self-polishing mechanisms of GNPs in the micro rolling process. The sliding and exfoliation of GNPs also contributed to the reduced roughness and improved quality of the sample surfaces.

The Effect of Microcrystalline Cellulose-CaHPO4 Mixtures in Different Volume Ratios on the Compaction and Structural-Mechanical Properties of Tablets.

Using microcrystalline cellulose (MCC) with plastic behaviour and calcium phosphate anhydrous (CaHPO4) with brittle behaviour under compaction is very popular in the pharmaceutical industry for achieving desirable structural-mechanical properties of tablet formulations. Thus, mixtures of specific grades of MCC and CaHPO4 were tested in volume proportions of 100-0, 75-25, 50-50, 25-75, and 0-100 at a constant weight-by-weight concentration of sodium stearyl fumarate lubricant, utilizing a state-of-the-art benchtop compaction simulator (STYL'One Nano). Tablet formulations were prepared at 100, 150, 250, 350, 450, and 500 MPa, and characterized by tabletability profile, ejection force profile, proportion-tensile strength relationship, proportion-porosity relationship, pressure-displacement, and elastic recovery profiles, as well as by in-/out-of-die Heckel plots and yield pressures. Interestingly, the 25-75 formulation demonstrated a two-stage out-of-die Heckel plot and was additionally investigated with X-ray micro-computed tomography (µCT). By post-processing the µCT data, the degree of brittle CaHPO4 particles falling apart, along with the increasing compression pressure, was quantified by means of the surface area to volume (S/V) ratio. For the 25-75 formulation, the first stage (up to 150 MPa) and second stage (above the 150 MPa) of the out-of-die Heckel plot could be attributed to predominant MCC and CaHPO4 deformation, respectively.

Highly Concentrated Electrolyte Superlubricants Enhanced by Interfacial Water Competition Around Chemically Active MgO Additives.

The low concentration of water-based lubricants and the high chemical inertness of the additives involved are often regarded as basic norms in the design of liquid lubricants. Herein, a novel liquid superlubricant of an aqueous solution containing a relatively high concentration of salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), is reported for the first time, and the superlubricity stability and load-bearing capacity of the optimized system (MgO0.10/LiTFSI10) are effectively strengthened by the addition of only trace (0.10 wt %) water-chemically active MgO additives. It demonstrates higher applicable loads, lower COF (∼0.004), and stability relative to the base solution. Only a trace amount of MgO additive is needed for the superlubricity, which makes up for the cost and environmental deficiencies of LiTFSI10. The weak interaction region between free water and the outer-layer water of Li+ hydration shells becomes a possible ultralow shear resistance sliding interface; the Mg(OH)2 layer, generated by the reaction of MgO with water, further creates additional weakly interacting interfaces, leading to the formation of an asymmetric contact between the clusters/particles within the hydrodynamic film by moderating the competition between interfacial water and free water, thus achieving high load-bearing macroscopic superlubricity. This study deepens the contribution of electrolyte concentration to ionic hydration and superlubricity due to the low shear slip layer formed by interfacial water competition with water-activated solid additives, providing new insights into the next generation of high load-bearing water-based liquid superlubricity systems.

Clarification of the Effect of Surface Energy on Tribological Behavior of Two-Phase Lubricant Using Reflectance Spectroscopy and Hydrodynamic Analysis

Recently, a new type of lubricant called two-phase lubricants has been developed to realize a high viscosity index. Two-phase lubricants are mixtures of two different lubricants, realizing low viscosity even at low temperatures due to the temperature dependence of the solubility of the lubricant molecules. In the present paper, the effect of surface energy on the tribological behavior of the two-phase lubricant is clarified using in situ observation with reflection spectroscopy. Sliding surfaces with high hydrogen-bonding terms in the surface energy components attracted high-polar lubricants, resulting in reduced friction. Analysis of the theoretical friction coefficient using Couette flow assumption revealed an important design concept of two-phase lubricants: the concentration of high viscosity lubricants on solid surfaces develops a viscosity distribution in the oil film, resulting in reduced friction.

Effect of particle size on the dispersion behavior of magnesium stearate blended with microcrystalline cellulose

The majority of tablets manufactured contain lubricants to reduce friction during ejection. However, especially for plastically deforming materials, e.g., microcrystalline cellulose (MCC), the internal addition of lubricants is known to reduce tablet tensile strength. This reduction is caused by the surface coverage by lubricant particles, the extent of which depends on both process and formulation parameters. Previously published models to predict the lubrication effect on mechanical strength do not account for changes in the excipient particle size. In this study, the impact of both lubricant concentration and mixing time on the tensile strength of tablets consisting of three different grades of MCC and four grades of magnesium stearate (MgSt) was evaluated. By taking into account the particle size of the applied excipients, a unifying relationship between the theoretically estimated surface coverage and compactibility reduction was identified. Evaluating the dispersion kinetics of MgSt as a function of time reveals a substantial impact of the initial surface coverage on the dispersion rate, while the minimal tensile strength was found to be comparable for the majority of formulations. In summary, the presented work extends the knowledge of lubricant dispersion and facilitates the reduction of necessary experiments during the development of new tablet formulations.

Advancing tablet lubrication: A systematic comparison of feed frame lubrication and internal lubrication

For the continuous manufacturing of tablets, internal lubrication is often utilized. Here, lubricant is added to a pre-blend in an additional blending step. However, over-lubrication may occur, with a negative impact on the tablet quality. This study consequently focuses on the systematic comparison of internal lubrication to an alternative, named feed frame lubrication. This method represents a new lubrication type, where the lubricant is fed into the feed frame without prior blending.A design of experiments with shear number and lubricant content as factors was used. Target properties were tensile strength, disintegration time and contact angle. Based on the data, multiple linear regression models were created and optimized using backward stepwise regression.Feed frame lubrication exhibited similar or even improved tablet properties compared to internal lubrication. The tablets turned out to be harder with decreased disintegration times. Finally, feed frame lubrication reduces the need for an additional blending step.

Extraction of biodiesel from pomelo peel and investigation of its efficiency as a lubricant in water-based drilling fluid

Abstract Reducing friction between drill string and wellbore wall is one of the key functions of drilling fluid which may result from tight holes, key seats, differential sticking, or cutting build up along the drill string. However due to growing environmental concerns, biodegradable lubricants which are also cost-efficient are appreciated and mandated in many countries. This study discusses the performance analysis of biodegradable biodiesel produced from pomelo peels and Petroleum-based lube oil as drilling fluid lubricants. The test samples comprise 700 mL of water + 10 % bentonite + 3 % barite + 0.25 % CaCO3 + 0.25 % KOH + 1 % CMC + lubricant. Two sets of lubricants were utilized to prepare 10 samples of drilling fluid, one set with petroleum-based lubricant and other with biodiesel. Essential oil was extracted from pomelo peel with the help of the Clevenger apparatus. The oil was then converted to biodiesel through the process of transesterification. Biodiesel properties were tested for the ASTM standards. Both sets of drilling fluid samples were tested for their rheological, filtration and lubricating properties and from the results obtained it can be concluded that both type of lubricating agents have almost negligible impact on rheological and filtration loss properties. However, the lubricity coefficient values drastically decreased as we increased the lubricant content, which is an indication that biodiesel extracted from pomelo peel acts as a better lubricant. The values of the lubricity coefficient for biodiesel based drilling fluid also fell well within the advised range (<0.30). We can therefore draw the conclusion that biodiesel made from pomelo peel can replace petroleum-based lubricants while also lowering the environmental concerns related to lubricants.

Effects of different factors on the friction and wear mechanical properties of titanium alloy materials with cortical bones at near service conditions.

The artificial joint is one of the most effective methods to treat joint injuries. The service performance of artificial joints is gradually weakened because of the wear of artificial joints in actual service. In order to obtain the potential failure mechanism of the artificial joint in actual service, the study was carried out with the multiple factors that affect the service performance of the artificial joint. The experimental study was carried out on the change rule of mechanical behavior of the contact interface between the artificial joint of titanium alloy and cortical bone. The multi-factor is compression load, contact load, friction velocity, and lubrication environment, respectively. The results indicate that the friction coefficient, wear mass, and wear coefficient of Ti-6A1-4V titanium alloy decreased with the increasing of the compression load. The friction rate and the friction coefficient of Ti-6A1-4V titanium alloy decreased with the increasing of the contact load. The wear mass and friction coefficient of Ti-6A1-4V titanium alloy increased with the increasing of contact load. The lubrication effect is better with the increasing of lubricant concentration. Based on the observation of the SEM, the wear type influenced by compression load and friction rate is mainly abrasive wear and oxidation wear. The wear type influenced by contact load is mainly abrasive wear and adhesive wear. The wear type influenced by lubricants is mainly oxidation wear. When wear mass and wear coefficient are used as the criteria for evaluating friction and wear, the order of influential factors to friction and wear of Ti-6Al-4V titanium alloy plate is friction rate, compression load, contact load, and lubricant concentration. This research can provide a theoretical reference for the optimal manufacture of the artificial joint of titanium alloy and optimal rules of safe service conditions.

Experimental Analysis of Crystallinity and Mechanical Properties for Fused Filament Printed Polyetherketone Composites

The objective of this article is to examine the impacts of molybdenum disulphide (MoS2) and graphite-filled (Gr) polyetheretherketone (PEEK) composites that have been fabricated through 3D printing on their mechanical properties and crystallinity. Seven samples and thirty-five dog bones were produced using different filament strands to conduct the analysis. Before extrusion into filaments, the solid lubricants, MoS2, and graphite were uniformly dispersed within the PEEK through mechanical blending. At a concentration of 10 wt.%, the PEEK/MoS2 composites exhibited the highest tensile strength, measuring approximately 104 MPa, while the PEEK/Gr composites displayed the lowest tensile strength at the same concentration, approximately 36 MPa. In addition, the PEEK/MoS2 composites demonstrated better elongation, approximately 4.7%, compared to the PEEK/Gr composites, which exhibited approximately 2.3% elongation. X-ray diffraction (XRD) data revealed that neither MoS2 nor graphite significantly interacted with the PEEK matrix. The degree of crystallinity, as determined by density matrices, indicated that the printed PEEK composites possessed a higher level of crystallinity, approximately 62% at a concentration of 5 wt.%, than the calculated values. This suggests that the filament-making and 3D printing processes had an annealing effect. The significance of solid lubricant content and dispersion in shaping the mechanical properties and crystal formation of 3D-printed PEEK composites is emphasized in this study. Furthermore, this research provides valuable insights for optimizing PEEK-based materials for various applications.

Investigation of Dispersion Kinetics of Particulate Lubricants and their Effect on the Mechanical Strength of MCC Tablets

IntroductionTablets are commonly produced by internally adding particulate lubricants, which are known to possibly lower the mechanical strength of tablets. This reduction is caused by the coverage of matrix forming components by lubricant particles, resulting in decreased interparticulate interactions. The known incompatibilities with some active compounds of the predominantly used lubricant, magnesium stearate, call for the in-depth characterization of alternative lubricants.PurposeInvestigation of the dispersion behavior of five commonly applied pharmaceutical lubricants by mathematically modeling the dispersion kinetics for short and extended mixing times.MethodsThe dispersion behavior of five different pharmaceutical lubricants were examined by systematically varying lubricant concentration and mixing time of binary formulations and evaluating the kinetic of tensile strength reduction by theoretically estimating the surface coverage based on particle sizes.ResultsFor short mixing times, a unifying relationship between compactibility reduction and theoretical surface coverage was identified. Subsequently, for extended mixing times, distinct differences in the shear strength and dispersion kinetics of the investigated lubricants were found.ConclusionsThe lubricant particle size controls the tensile strength reduction if short mixing times are applied. For extended mixing times, the investigated lubricants can be divided into two groups in terms of dispersion kinetics. Possible underlying reasons are discussed in detail in order to enhance the general understanding of lubricant dispersions in tablet formulations.

Effect of Compaction Pressure on the Enzymatic Activity of Pancreatin in Directly Compressible Formulations.

Tableting of biomolecules is a challenging formulation phase due to their sensitivity to various process parameters, such as compression pressure, process dynamics, or the temperature generated. In the present study, pancreatin was employed as a model enzyme mixture, which was formulated in tablet form utilizing the synergistic effects of brittle and plastic excipients (dibasic calcium phosphate and microcrystalline cellulose, respectively). The effect of varying compaction pressure and lubricant concentration on the generated temperature and enzymatic activity was evaluated. The tablets were analyzed for pancreatin content and the activity of two enzymes (protease and amylase) using pharmacopoeial tests. This study indicated that the formulations proposed here allow tableting over a wide range of compaction pressures without adversely affecting pancreatin content and its enzymatic activity.