Lubricant Particle Size Research Articles

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.

Microstructural Characterization of Solid State Reaction Phase Formed During Sintering of Hexagonal Boron Nitride with Iron.

In the development of dry self-lubricating composites, not only solid lubricant particle size and distribution are important, but also the correct selection of the solid lubricant characteristics, which should be stable, i.e. not reactive, during the whole processing. In this work, Fe+9 vol% h-BN composites were produced by uniaxial cold compaction and sintering, for which a reaction between h-BN and iron was detected after sintering at 1,150°C. The reaction phase was characterized by optical and scanning electron microscopy and identified by X-ray diffraction and energy-dispersive X-ray spectroscopy. The newly formed phase had high hardness when compared with the iron matrix. The resulting composites presented a high friction coefficient and high wear.

Tribological studies to analyze the effect of solid lubricant particle size on friction and wear behaviour of Ti-6Al-4V alloy

In modern industry, mechanical parts are subjected to friction and wear, leading to heat generation, which affects the reliability, life and power consumption of machinery. The study of lubricant film formed between various geometric shapes are inherently complicated and interconnected, making it necessary to understand the concepts of tribological phenomena. To overcome the tribological losses due to friction and wear, use of lubricants with high viscosities and lower evaporation makes relative motion between two surfaces very smooth. Advancement in modern tribology has facilitated the use of applying solid lubricants in various industrial applications. Solid lubricants in ample thickness can effectively work under extreme conditions of temperature, loads and speeds. The effectiveness of solid lubricant particles strongly depends on the type of lubricant used in the suspension, solid lubricant particle size, and as well as concentration. In view of this, the present investigation aims to develop MoS2 suspension with different weight fractions and to analyze tribological properties in order to make it suitable for most industrial applications. To characterize the same, an experimental setup has been developed to observe and measure the lubricant film thickness at various particles size and concentrations of solid lubricants. To determine Extreme Pressure (EP) properties of applied solid lubricants, EP test (ASTM D2783) experiments were performed on a four-ball tester. The results obtained from the experiments show the use of the solid lubricant with lesser particle size provide effective thin film thickness in comparison with larger particle size. The results indicate that the optimum particle size and concentration of suspended MoS2 solid lubricants improve the tribological properties with an intended life time of the surfaces.

Influence of nano-level variation of solid lubricant particle size in the machining of AISI 1040 steel

Significant advances have been made in understanding the behaviour of engineering materials when machining at higher cutting conditions from practical and theoretical standpoints. Nano-integrated manufacturing is a subject of immense interest for various sustainable engineered systems. Metal removal processes involves generation of high cutting forces and temperatures. Usage of proper lubricant is an important aspect to reduce forces and temperatures and as a whole to improve total cutting phenomena. The present investigation analyses a green, petroleum-free lubricant that is produced by mixing two environmentally benign components – canola oil and nano crystalline boric acid. To study the influence of variation of nano-level boric acid particle size and its weight percentage on the performance of proposed green particulate fluid lubricant (GPFL), various turning tests were conducted on AISI 1040 steel using tungsten carbide inserts. Variations in cutting forces, tool temperatures and surface roughness are studied. The experimental results reveal that increase of cutting forces as well as the tool temperatures with the decrease in the boric acid particle size. The surface quality of the machined surface is reduced as the solid lubricant particle size is reduced in the nano-level.

Studies on the Behaviour of the Green Particulate Fluid Lubricant in Its Nano Regime when Machining AISI 1040 Steel

Significant advances, both practical and theoretical, have been made in understanding the behaviour of engineering materials when machining at higher cutting conditions. Nano-integrated manufacturing is a subject of immense interest for various sustainable engineered systems. Metal removal processes involve the generation of high cutting forces and temperatures. The use of proper lubricant to reduce forces and temperatures and to improve total cutting phenomena overall is an important aspect. The present investigation analysed a green, petroleum-free lubricant that is produced by mixing two environmentally benign components, canola oil and nano-crystalline boric acid. To study the influence of variation of nano-level boric acid particle size and its weight percentage on the performance of the proposed green particulate fluid lubricant, various turning tests were conducted on AISI 1040 steel using tungsten carbide inserts. Variations in cutting forces, tool temperatures and surface roughness were studied. The experimental results revealed that both cutting forces and tool temperatures increased as the boric acid particle size decreased. The surface quality of the machined surface was reduced as the solid lubricant particle size was reduced to the nano-level. Interestingly, reductions in both cutting force and tool temperature were observed as the boric acid weight percentage decreased, tending towards the pure canola oil-based machining results. The surface quality of the machined surface was also improved as the volume fraction of boric acid was decreased.

Surface model and tool-wear prediction model for solid lubricant-assisted turning

Mathematical models for surface roughness and tool wear are developed through regression analysis of the experimental data collected from machining. Different particle sizes and flowrates of solid lubricants are employed in the study. Experimental results show a significant effect of solid lubricant particle size and flowrate on surface roughness and tool wear. Decrease in the particle size resulted in reduced tool wear and surface finish improvement. Various machining parameters such as cutting forces, tool wear, and surface roughness improved with an increase in the flowrate of solid lubricant up to a certain level and remained constant at higher flowrates. To estimate the effect of solid lubricants on machining, exponential models are proposed in the present work to predict tool wear and surface roughness as a function of solid lubricant particle size, flowrate, machining time, and cutting force. Predicted values obtained from the developed model and experimental results are compared, and error<10 per cent is observed.

SOME OBSERVATIONS ON THE EFFECT OF LUBRICATION ON THE CRUSHING STRENGTH OF TABLETS.

Abstract The effect of mean compaction pressure, base particle size, lubricant particle size, and lubricant concentration, on crushing strength of tablets has been determined for crystalline aspirin, hexamine, sucrose and sodium chloride, and simple granulations of sucrose and of hexamine. Magnesium stearate powder was used as a lubricant. The lubricant decreased the strength of all tablets, the reduction being greatest for the crystalline materials. Variation of lubricant particle size had no effect on strength, and the behaviour of the granulations was not predictable from the characteristics of the crystalline materials. The results are compared with those of other workers.