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The strength of the wet granule is due to surface tension of the liquid and capillary forces These forces are responsible for initial agglomeration of the wet powder. GRANULATION:-it is a pharmaceutical process tha converts a mixture of powders,which have poor cohesion ,into aggregates capable of compaction 4 Slide 5: 5 IMPORTANCE OF GRANULATION : The major reason for granulating the powdered starting material in the manufacture of tablets and granules are to: To improve the flow properties so that, the mass uniformity of the dose. To prevent segregation of ingredients in the mixture. To improve the compression characteristics of the mixture. To reduce the environmental hazards for the working personnel due to dust formation from toxic materials. To reduce the bulk volume of voluminous powders and make them more convenient for storage and transport. To improve the appearance of the product.(4) The granules being heavier do not blow out of the die and do not clog the lower punch. Drugs with a lose dose (<50mg) are prepared by direct compression but high dose drugs (>50mg)require method of granulation. 6 IMPORTANCE OF GRANULATION BASIC CHARACTERISTICS OF GRANULES : Granules ready for compression must have two characteristics Fluidity Compressibility Fluidity:-here it refers to flow property or uniform flow of granules through hopper ,into and through the frame and into the dies. Compressibility:- here it refers to property of granules to form a stable, compact mass when pressure is applied 7 BASIC CHARACTERISTICS OF GRANULES GRANULATION PROCESSS : The standard methods frequently used today in tablet mannufacturing are granulation and direct compression Granulation technique includes wet granulation and dry granulation/slugging methods wherein binders are added in solution/suspension form and in dry form respectively In Direct Compression, binders possessing direct compressibility characteristics are used. 8 GRANULATION PROCESSS CLASSIFICATION OF BINDERS : 9 CLASSIFICATION OF BINDERS GRANULE GROWTH MECHANISMS : The proposed granulation mechanism can be divided into three stages 1.Nucleation 2. Transition 3.Ball growth 10 GRANULE GROWTH MECHANISMS Slide 11: 1.Nucleation: The granulation starts with adhesion among particles due to liquid bridges and the formation of agglomerates at capillary state. These structures may act as nucleus for successive enlargement of granules. 2. Transition: Nuclei can grow in two possible ways: either single particles can be added to the nuclei by pendular bridges, or two or more nuclei may combine. The combined nuclei will be reshaped by the agitation of the bed. This stage is characterized by the presence of a large number of small granules with a fairly wide size distribution. If the size distribution is not excessively large, this point represents a suitable end point for granules used in capsule and tablet manufacture 11 Slide 12: 3.Ball growth: Further granule growth produces large, spherical granules and the mean particle size of the granulating system will increase with time. If agitation is continued, granule coalescence will continue and produce an unusable, overmassed system, although this is dependent upon the amount of liquid added and the properties of the material being granulated. The four possible mechanisms of ball growth are a) Crushing and layering: b) Coalescence: c) Abrasion transfer: d) Layering: 12 Slide 13: a) Crushing and layering: Granules break into fragments that adhere to other granules, forming a layer of material over the surviving granule. b) Coalescence: Two or more granules join to form a larger granule. c) Abrasion transfer Agitation of the granule bed leads to the attrition of material from granules. This abraded material adheres to other granules, increasing their size. 13 Slide 14: d) Layering: When a second batch of powder mix is added to a bed of granules the powder will adhere to the granules, forming a layer over the surface and increasing the granule size. This mechanism is only relevant to the production of layered granules using spheronizing equipment. Using the slower processes, such as the planetary mixer, there is usually sufficient time to stop the process before overmassing occurs. With faster granulation equipment the duration of granulation can only be used as a control parameter when the formulation is such that granule growth is slow and takes place at a fairly uniform rate. J In many cases, however, the transition from a non-granulated to an overmassed system is very rapid, and monitoring equipment is necessary to stop the granulation at a predetermined point, known as granulation end-point control. 14 BALL GROWTH MECHANISM : 15 BALL GROWTH MECHANISM GRANULAR PROPERTIES OF POWDER : DERIVED PROPERTIES OF POWDER Any properties which are derived from fundamental property are called as derived properties of the powder Fundamental property being size, shape and size distribution of the particle was dealt previously 16 GRANULAR PROPERTIES OF POWDER VOLUME : (a)TRUE VOLUME :- VP True volume of the powder is the volume of the particles itself ,it does not include the inter particle space(voids) and intra particle space (represented by pores and crevices) volume (b)GRANULE VOLUME:-Vg It is the volume of the powder and volume of intra particle space and does not include volume of interspace particle For non porous powder true volume and granular volume are the same (c)BULK VOLUME :-Vb It is the volume of the powder and volume of inter particle space and intra particle space. 17 VOLUME DENSITY : (a)True density:- True density is the density of material itself True density= weight of the powder/ True volume of the powder Volume occupied by voids and intra particle pores are not included in this measure 18 DENSITY True densities of some pharmaceutically important powders : 19 True densities of some pharmaceutically important powders Slide 20: (b)Granular density:- ρg Granular density is the weight of the granule by granular volume of the powder It is mathematically written as Granule density=granule weight/granule volume 20 Slide 21: (c)Bulk density:-ρb Bulk density is the mass of the powder by the bulk volume of the powder Mathematically written as Bulk density=mass of the powder/bulk volume of the powder Bulk density depends on particle size distribution, shape, cohesiveness of the particles Determination is by tapping method 21 : Comparision of bulk densitiy and true density of the powder APPLICATION OF BULK DENSITY Used to check the uniformity of bulk chemicals container size for a dosage form depends on the bulk density. 22 POROSITY : Porosity is the total space present in a collection of a powder , Void volume=bulk volume-true volume Porosity(ε)=void volume/bulk volume =Vb-Vp /Vb =1-VP/Vb porosity is frequently expressed in percent ε=Vb –Vp/Vb ×100 Intra particle porosity (ε)particle (ε)particle=Vg-Vp /Vg =1-VP/Vg Inter space porosity (ε)interspace (ε)interspace =Vb-Vg/V b =1-Vg/Vb 23 POROSITY Slide 24: In a collection of powder the porosity depends on the type of packing (a)closed packing or rhombohedral packing (b)open or cuboidal packing If the powder consists of isodiametric particles(spherical partical) and if the packing is open type the theoretical porosity is 48% and for the closed packing, it is 26%. But in practical situation,only a mixture of these two porosity is possible and the porosity is around 30% or above. 24 Slide 25: Usually the powder consists of different size particles and Porosity may go Below (minimum) 26% As smaller particles fill the void spaces between larger particles. Above (maximum) 48% If the powder contains floccules or aggregates which lead to formation of bridges and arches in the packing. 25 Slide 26: 26 APPLICATIONS OF POROSITY : Porosity influences the rate of disintegration and dissolution. Higher the porosity , faster the rate of dissolution Adsorption of any materials depends on the porosity of solid. Porosity gives an idea about the type of packing between the particles inturn decides the type of the container to be selected. 27 APPLICATIONS OF POROSITY FLOW PROPERTIES OF POWDER : Content uniformity and dose presicion of the tablet dosage form is achived only by good flow properties (a)processing of powder into granules of spherical shape. (b)choosing optimum size of granules around 400µm to 800µm . (c)incorporating optimum amount fines,about 15% w/w. (d)inclusion of lubricants such as magnesium stearate,talc. 28 FLOW PROPERTIES OF POWDER FLOW CHARACTERISTICS OF POWDERS OR GRANULES : ANGLE OF REPOSE:- Angle of repose is the maximum angle possible between the surface of the pile of the powder and the horizontal plane By definition, Tanθ = h/r Where, θ=angle of repose h=height of the r=radius of the of the base of pile 29 FLOW CHARACTERISTICS OF POWDERS OR GRANULES Slide 30: 30 RELATIONSHIP BETWEEN ANGLE OF REPOSE AND POWDER FLOW : 31 RELATIONSHIP BETWEEN ANGLE OF REPOSE AND POWDER FLOW FACTORS AFFECTING ANGLE OF REPOSE : MOISTURE EFFECT OF SIZE AND SHAPE EFFECT OF FINE EFFECT OF GLIDANT AND LUBRICANT APPLICATIONS OF ANGLE OF REPOSE Angle of repose actually measures the frictional forces between the particle which is given as tanθ=µ. Angle of repose measure the flow of powder or granules which helps in compressing the granules for the tablets, filling of capsule and also removal from the container. 32 FACTORS AFFECTING ANGLE OF REPOSE ANGLE OF REPOSE OF SOME SOME PHARMACEUTICAL EXCIPENTS : 33 ANGLE OF REPOSE OF SOME SOME PHARMACEUTICAL EXCIPENTS DISPERSIBILITY/DUSTINESS : Dispersibility of the powder is the ability of a material to flow or pour easily over a plane Dipersibilty(%) = powder weight in the watch glass ×100 Intial weight of the sample Any loss of the powder during the fall is the result of dispersion calculated using the above relation Lycopodium spores shows the greatest dispersibility and arbitrarily assigned 100% dustabilty Dustability:- Talcum powder---57% Potato starch-----27% Charcoal(fine)----23% 34 DISPERSIBILITY/DUSTINESS DISPERSIBILITY APPARATUS : 35 DISPERSIBILITY APPARATUS CARR’S CONSOLIDATION INDEX:- : Carr’s consolidation index= 1 - Bulk density ×100 Tappeddensity Carr’s index gives measure of flow property of the powders or granules. 36 CARR’S CONSOLIDATION INDEX:- GRADING OF THE POWDERS BASED ON THEIR FLOW PROPERTIES ACCORDING TO CARR’S INDEX : 37 GRADING OF THE POWDERS BASED ON THEIR FLOW PROPERTIES ACCORDING TO CARR’S INDEX Slide 38: REFERENCE 1. Theory and practise of industrial pharmacy,3rd edition, lachman,L., liebermanH.A. & kanig,J.L , Lea & febier 1986. 2. Physical pharmacy, 3rd edition,Alfred martin.,James sawbric., arthur cammarata, K.M.Vargese company, 1983. 3. Text book of physical pharmaceutics C.V.Subramanyam. 4. Physical pharmaceutics,1stedition, Dr.Shymala Bhaskaran.,Birla publication pvt.Ltd.2006. 5. www.pharmpedia.com 38 Slide 39: ? 39 Slide 40: THANK YOU 40 You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.