Porosity

pharmaceutics

1. GURUNANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND TECHNOLOGY

2. PROPERTIES OF POWDER (P0R0SITY ) PRESENTED BY Sumel Ashique . Roll No-80 Sumit Saha . Roll No-81 Supratim Das. Roll No-82 B.pharm,2 nd yr,3 rd sem,Sec -B

3. CONTENTS . . . Porosity and its evaluation tests True Density Bulk Density Numerical problems and solutions Bulkiness Flow properties of powders Factors affecting on flow properties

4. Porosity: The porosity or voids is defined as the ratio of the void volume to bulk volume. (V B P )/ V b =1- V p / V b Void volume = V b – V p Porosity is expressed in percent , Vb =Bulk volume Vp =True volume  

5. Problems: A sample of calcium oxide powder with a true density of 3.203 and weighing 131.3 gm was found to have a bulk volume of 82cm 3 when placed in a 100 ml graduated cylinder .calculate the porosity . The volume of the particle is (131.3g /3.203gcm -3 ) =41cm 3 =( v b - v p )/ v b =(82-41)/ 82 = 0.5 =50  

6. Densities of Powders: It is defined as the mass per unit volume . Types of density: There are three types of densities based on the determination method : True Density. Bulk Density. Granule Density .

7. True Density ( : Defined as the volume of the pores and voids within the sample . Bulk Density ( b ) Defined as the volume of all of the pores within the sample. Granule Density( g ) Defined as the ratio of the mas of the granular powder and granule volume .  

8. Bulkiness: The reciprocal of bulk density is known as the bulkiness or specific bulk volume. It increases with a decreases in particle size. It may get reduced since the smaller particles may shift between the larger ones .

9. Flow properties: Flow properties of powder is in an important parameter in the production of pharmaceutical dosage forms . It may be free flowing or may have poor flow. Reasons of poor flow: Cohesiveness between particles due to van der waals , electrostatic forces. Adhesion between the particles and the container wall. Friction between particles .

10. Test to evaluate the flow ability of a powder Carrs Compressibility Index: A volume of powder is filled into a graduated glass cylinder and repeatedly tapped a known duration.The volume of powder after tapping is measured . Carrs Index ( Tapped density- Bulk density Bulk density =Weight/bulk volume Tapped density=Weight/ true volume  

11. Relationship between powder flowability and compressibility:   Flow Description Compressibility Excellent flow 5-15 Good 16-18 Fair 19-21 Poor 22-35 Very poor 36-40 Extremely poor  

12. Hausner Ratio: H.ratio =Tapped density / Bulk density It is related to inter particle friction. Values less than 1.25 indicates good flow ( coarse spheres) and greater than 1. 5 indicates poor flow .( flakes) Between 1.25 and 1.5 added glidant normally improves flow. 1.5 added glidant does not improve flow.  

13. Factors affecting the flow properties of powders Particle size distribution : the average particle size improves the flow properties due to reduction in the cohesive forces. Particle shape and texture : spherical particles have better flow ability as compared to irregular particles. Surface forces : Reduction of electrostatic charges can improve powder flow ability .Drying of particles will reduce the cohesiveness and . Addition of fines : presence of small portion of fines in a powder may improve the flow properties. Flow activators :  

14. REFFERENCE… Micromeritics and powder Rheology ;Physical Pharmacy; S.P Agarwal , Rajesh Khanna ; page no-38,39,40,.41,42,43,44,45;CBS publishers; Second edition.

15. THANKING YOU. . .