Determination of flow properties of powders

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Published on November 29, 2012

Author: pharma.keerthi

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PowerPoint Presentation: FLOW PROPERTIES OF POWDERS & ITS DETERMINATION Seminar submitted during I M.Pharmacy (pharmaceutics) I  Semester Course By J.Keerthi Priya , B.Pharm. Under the supervision of Dr.S.A.Azeez , M.Pharm. PGDM.Ph.D. Professor & Principal April– 2012 SIMS college of pharmacy, Mangaldas Nagar, Guntur. FLOW RATE : : FLOW RATE : Mass of a substance that passes through a given surface per unit time. Represented by g/sec. Knowledge of flow properties of a powder or bulk is necessary to design bulk solid handling equipment so that no flow problems (flow obstruction, segregation, irregular flow, flooding, etc )occur . 10/04/2012 SIMS college of pharmacy 2 IMPORTANCE OF FLOW RATE IN THE MANUFACTURING OF TABLETS AND CAPSULES[1]: IMPORTANCE OF FLOW RATE IN THE MANUFACTURING OF TABLETS AND CAPSULES [1] No content uniformity No dose precision Irregular flow of powder from the hopper Tablets with non uniform weights 10/04/2012 SIMS college of pharmacy 3 Flow properties[1]: Flow properties [1] It is a mechanical property Bulk powders are similar to non-Newtonian liquids due to their plastic flow and sometimes dilatancy. Particles are influenced by attractive forces (vary in degrees). Pharmaceutical powders may be broadly classified into Free flowing and Cohesive or sticky or non free flowing 10/04/2012 SIMS college of pharmacy 4 Factors influencing flow properties[3]: Factors influencing f low properties [3] Particle size Particle shape Porosity Density of bulk powder Moisture content 10/04/2012 SIMS college of pharmacy 5 Particle size[3]: Particle size [3] Particles below 10µm in size possess attractive forces ( Vander Waals , electrostatic and surface tension forces) between them , owing to cohesion of particles. Thus poor flow properties. As the particle size increases the flow of powders increases i.e., free flowing. This is due to gravitational force on the diameter of particle. Relationship between gravitational force and diameter is given by g α d 3 Appropriate blend of coarse and fine particles improves the flow properties 10/04/2012 SIMS college of pharmacy 6 Particle nature[1]: Particle nature [1] Nature of particle Effect on flow property Smooth surface Increase the flow property Rough surface Poor flow due to friction Flat and elongated particle Gives high porosity and low flow property high density & low porosity Good flow property 10/04/2012 SIMS college of pharmacy 7 POROSITY[3]: POROSITY [3] Porosity or voids ( ):- Ratio of void volume to the bulk volume of the packing. Porosity or voids ( ) = = 10/04/2012 SIMS college of pharmacy 8 volumes Definitions True volume Volume of powder itself Granule volume Volume of powder + voids (inter particle spaces ) Bulk volume Volume of powder + volume of intra particle space+ voids Void volume Bulk volume – true volume ( Vb - Vp) PowerPoint Presentation: Two ideal packing arrangements that influence porosity Closest or rhombohydral Most open, loosest or cubic packing. Cubic arrangement Closest or rhombohydral 9 Low porosity ( ) =26% High porosity ( ) =48% PowerPoint Presentation: Porosity is frequently expressed in per cent. Per cent , It can also be represented in terms of density Per cent , 10/04/2012 SIMS college of pharmacy 10 Density of bulk powder[3]: Density of bulk powder [3] Bulk density ( ) = Bulk volume : Volume of powder + volume of intra particle space+ voids Bulk density decreases with decrease in particle size 10/04/2012 SIMS college of pharmacy 11 Moisture content [3]: Moisture content [3] The higher the moisture content the greater the risk of cohesion and adhesion. Moisture content can be reduced by drying. 10/04/2012 SIMS college of pharmacy 12 Flow properties can be improved by [3]: Flow properties can be improved by [3] Powder processes into granules of spherical shape. Choosing optimum size of granules (400 to 800 um). Incorporating optimum amount of fines (about 15% w/w) Incorporating optimum concentration of lubricants ( magnesium stearate , talc etc.,) 10/04/2012 SIMS college of pharmacy 13 Determination of flow properties[3]: Determination of flow properties [3] For free flowing particles Angle of repose Compressibility index Dispersibility Flow through an orifice For cohesive particles Shear cell method 10/04/2012 SIMS college of pharmacy 14 Angle of repose[1][3][6]: Used to measure frictional forces in a loose powder It is the maximum angle possible between the surface of a pile of powder and the horizontal plane. If more material is added to the pile, it slides down the sides until the mutual friction of the particles , producing a surface at an angle θ ,in equilibrium with the gravitational force. Angle of repose [1][3][6] 10/04/2012 SIMS college of pharmacy 15 PowerPoint Presentation: The tangent of angle of repose is equal to the coefficient of friction , µ , between the particles. Tan θ = µ Hence the rougher and more irregular the surface of the particle the higher the angle of repose. Angle of repose can be calculated by θ = tan -1 Where = height of the pile =radius of the base of the pile θ = angle of repose 10/04/2012 SIMS college of pharmacy 16 PowerPoint Presentation: Alternatively , When opposite sides of a pile are measured, Cos θ = Or θ = Cos -1 Where D = diameter of the base and = the opposite sides of the pile The lower the angle of repose the better the flow properties. 10/04/2012 SIMS college of pharmacy 17 PowerPoint Presentation: Effect of lubricants and fines on the granule flow properties.. Decrease in particle size leads to higher angle of repose Lubricants at low concentration decrease the angle of repose and at high concentration enhance the angle of repose. Fines (pass through 100 mesh) increase the angle of repose. 10/04/2012 SIMS college of pharmacy 18 Angle of repose: Angle of repose Angle of repose Flow property <25 excellent 25-30 good 30-40 passable >40 very poor 10/04/2012 SIMS college of pharmacy 19 Carr’s consolidation index[3]: Carr’s consolidation index [3] This property known as compressibility. It relates with flow rate, cohesiveness & particle size. 10/04/2012 SIMS college of pharmacy 20 PowerPoint Presentation: Calculated from powder density. . Consolidation index = x 100 Or Consolidation index = x 100 Where initial density ( ) = ratio of mass of powder to the initial volume = g/cc tapped density ( ) = ratio of mass of power to the tapped volume = g/cc W = mass of the powder = volume occupied by certain mass of powder = volume occupied by the same mass of the powder after standard tapping 10/04/2012 SIMS college of pharmacy 21 PowerPoint Presentation: 10/04/2012 SIMS college of pharmacy 22 Consolidation index (%) Flow 5-15 Excellent 12-16 good *18-21 fair to passable *23-25 poor 33-38 very poor >40 very very poor Grading of the powders for their flow properties according to Carr Index Hausner′s Ratio[8]: Hausner′s Ratio [8] It is a number or indication that is correlated to the flowability of a powder or granular material . It is named for the engineer Henry H. Hausner. The Hausner ratio is calculated by the formula H = Where H = Hausner’s ratio = tapped density = initial density 10/04/2012 SIMS college of pharmacy 23 PowerPoint Presentation: The Hausner ratio (H) is related to the Carr’s index (C), by the formula Where C = Carr’s index A Hausner′s ratio of < 1.25 ( 20% Carr's) good flow. > 1.5( 33% Carr's) poor flow. Flowability of powders owing 1.5 > H >1.25 can be enhanced by the addition of glidants. The equipment required to perform the Carr’s index and Hausner ratio is relatively cheap and the technique is easy . 10/04/2012 SIMS college of pharmacy 24 PowerPoint Presentation: 10/04/2012 SIMS college of pharmacy 25 Scale of flowability [7] Dispersibility[3]: Dispersibility [3] It is the ability of a material to flow or pour easily over a plane. Dispersibility, dustiness, & flowability are inter- related term . Dispersibility (%) = X 100 10/04/2012 SIMS college of pharmacy 26 Dispersibility apparatus:- A hallow cylinder (330 x 102 mm) through which material is Drop from a height of 610 mm above the glass watch (diameter 102 mm). Flow through an orifice[7]: Flow through an orifice [7] Measuring the ability and the time taken for a powder to flow through an orifice of known size. The flow rate through an orifice is generally measured as the mass per time flowing from any of a number of types of containers(cylinder or funnel or hopper). Factors that effect powder that flow through the orifice other than powder characteristics shape and material employed in the construction of the powder container the diameter height of the powder bed and the shape of the orifice concerned. 10/04/2012 SIMS college of pharmacy 27 PowerPoint Presentation: 10/04/2012 SIMS college of pharmacy 28 Flow through an orifice (funnel) [4] Flow through an orifice (cylinder) [4] Requirements of the flow through apparatus[7]: Requirements of the flow through apparatus [7] The height of the powder bed (the ‘head’) is much greater than that of the orifice The diameter of the opening is greater than 6 times the diameter of the particles and The diameter of the cylinder is greater than 2 times the diameter of the opening then any difference in results brought about by either powder bed or orifice can be considered negligible. 10/04/2012 SIMS college of pharmacy 29 PowerPoint Presentation: Equation given by Jones and Pipel [2] 1/n where W = flow rate = Particle density g = Gravity = Orifice diameter A and n = constants 10/04/2012 SIMS college of pharmacy 30 Shear cell method[7]: Shear cell method [7] Used extensively in the pharmaceutical materials. From this method a wide variety of parameters can be obtained, they are Yield loci The angle of internal friction the unconfined yield strength The tensile strength Flow factor etc., 10/04/2012 SIMS college of pharmacy 31 Basic modes of shear cell[6]: Basic modes of shear cell [6] Cylindrical Annular Plate type All the 3 have lower stationary base and the upper movable portion The powder bed is placed in between them and the force necessary to shear the powder bed by moving the upper ring is determined 10/04/2012 SIMS college of pharmacy 32 Annular (ring) type Reference : Reference MARTIN’S PHYSICAL PHARMACY AND PHARMACEUTICAL SCIENCES 5 TH EDITION Theory and practice of industrial pharmacy by LEON LACHMAN HERBERT A. LIEBERMAN JOSEPH L. KANIG 3 RD edition TEXTBOOK OF PHYSICAL PHARMACEUTICS C.V.S. SUBRAHMANYAM http://www.antech.ie/flotestbep.shtml http://www.freemantech.co.uk/en/powder-flow-and-powder-behavior.html http://www.dietmar-schulze.de/grdle1.pdf http://pharmacopeia.cn/v29240/usp29nf24s0_c1174.html http://en.wikipedia.org/wiki/Hausner_ratio 10/04/2012 SIMS college of pharmacy 33 Any query: Any query 10/04/2012 SIMS college of pharmacy 34 PowerPoint Presentation: 10/04/2012 SIMS college of pharmacy 35

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